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  Subjects -> BIOLOGY (Total: 2618 journals)
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    - ZOOLOGY (121 journals)

ZOOLOGY (121 journals)                  1 2     

Acta Herpetologica     Open Access   (Followers: 4)
Acta Theriologica     Full-text available via subscription   (Followers: 6)
Acta Zoologica     Hybrid Journal   (Followers: 3)
Acta zoológica mexicana     Open Access  
African Invertebrates     Open Access  
African Journal of Herpetology     Full-text available via subscription   (Followers: 1)
African Zoology     Open Access   (Followers: 6)
animal     Hybrid Journal   (Followers: 3)
Animal Behaviour     Hybrid Journal   (Followers: 229)
Animal Biology     Hybrid Journal   (Followers: 8)
Animal Biology & Animal Husbandry     Open Access   (Followers: 5)
Animal Biotelemetry     Open Access   (Followers: 2)
Animal Genetics     Hybrid Journal   (Followers: 8)
Animal Migration     Open Access   (Followers: 1)
Animal Studies Journal     Open Access   (Followers: 4)
Annales UMCS, Zootechnica     Open Access   (Followers: 1)
Annales Zoologici     Full-text available via subscription  
Annales Zoologici Fennici     Open Access  
Annals of Animal Science     Open Access   (Followers: 2)
Annual Review of Animal Biosciences     Full-text available via subscription   (Followers: 4)
Anthropozoologica     Full-text available via subscription   (Followers: 4)
Anthrozoos : A Multidisciplinary Journal of The Interactions of People & Animals     Full-text available via subscription   (Followers: 7)
Applied Animal Behaviour Science     Hybrid Journal   (Followers: 11)
Applied Entomology and Zoology     Partially Free   (Followers: 3)
Aquatic Mammals     Full-text available via subscription   (Followers: 4)
Aquatic Sciences     Hybrid Journal   (Followers: 11)
Asian Journal of Animal and Veterinary Advances     Open Access   (Followers: 5)
Australian Journal of Zoology     Hybrid Journal   (Followers: 1)
Bioacoustics : The International Journal of Animal Sound and its Recording     Partially Free   (Followers: 2)
Bird Conservation International     Hybrid Journal   (Followers: 14)
Bird Study     Full-text available via subscription   (Followers: 12)
Brazilian Journal of Veterinary Research and Animal Science     Open Access   (Followers: 6)
British Birds     Full-text available via subscription   (Followers: 8)
Bulletin of the Museum of Comparative Zoology     Full-text available via subscription   (Followers: 3)
Canadian Journal of Animal Science     Full-text available via subscription   (Followers: 5)
Canadian Journal of Zoology     Full-text available via subscription   (Followers: 12)
Contributions to Zoology     Open Access   (Followers: 3)
Der Zoologische Garten     Full-text available via subscription   (Followers: 2)
Ecology of Freshwater Fish     Hybrid Journal   (Followers: 15)
Edentata     Open Access  
European Journal of Taxonomy     Open Access   (Followers: 2)
Euscorpius     Open Access  
EvoDevo     Open Access   (Followers: 1)
Fieldiana Zoology     Full-text available via subscription   (Followers: 2)
Fish and Fisheries     Hybrid Journal   (Followers: 27)
Frontiers in Zoology     Open Access   (Followers: 7)
Graellsia     Open Access  
Hystrix, the Italian Journal of Mammalogy     Open Access  
i-Perception     Open Access   (Followers: 3)
Iheringia. Série Zoologia     Open Access  
In Vitro Cellular & Developmental Biology - Animal     Hybrid Journal   (Followers: 1)
Integrative Zoology     Hybrid Journal  
International Journal of Odonatology     Hybrid Journal   (Followers: 1)
International Journal of Zoological Research     Open Access   (Followers: 2)
International Journal of Zoology     Open Access   (Followers: 2)
International Zoo Yearbook     Hybrid Journal   (Followers: 1)
Invertebrate Reproduction & Development     Hybrid Journal   (Followers: 2)
ISRN Zoology     Open Access  
Italian Journal of Animal Science     Open Access   (Followers: 2)
Italian Journal of Zoology     Hybrid Journal   (Followers: 2)
Journal of Agrobiology     Open Access   (Followers: 2)
Journal of Animal Ecology     Hybrid Journal   (Followers: 28)
Journal of Animal Physiology and Animal Nutrition     Hybrid Journal   (Followers: 5)
Journal of Apicultural Science     Open Access  
Journal of Applied Animal Research     Hybrid Journal  
Journal of Basic & Applied Zoology : Physiology     Open Access  
Journal of Experimental Zoology Part A: Ecological Genetics and Physiology     Hybrid Journal   (Followers: 2)
Journal of Experimental Zoology Part B : Molecular and Developmental Evolution     Hybrid Journal  
Journal of Freshwater Ecology     Hybrid Journal   (Followers: 10)
Journal of Insects     Open Access  
Journal of Venomous Animals and Toxins     Open Access   (Followers: 3)
Journal of Venomous Animals and Toxins including Tropical Diseases     Open Access  
Journal of Wildlife Management     Hybrid Journal   (Followers: 25)
Journal of Zoo and Aquarium Research     Open Access   (Followers: 1)
Journal of Zoological Systematics and Evolutionary Research     Hybrid Journal   (Followers: 5)
Journal of Zoology     Hybrid Journal   (Followers: 9)
Laboratory Animals     Hybrid Journal   (Followers: 11)
Mammalia     Full-text available via subscription   (Followers: 7)
Marine Ecology Progress Series MEPS     Full-text available via subscription   (Followers: 10)
Mastozoología Neotropical     Open Access  
Memorias de la Conferencia Interna en Medicina y Aprovechamiento de Fauna Silvestre, Exótica y no Convencional     Open Access  
Neotropical Primates     Open Access  
New Zealand Journal of Zoology     Hybrid Journal  
Papéis Avulsos de Zoologia     Open Access   (Followers: 1)
Parasite     Open Access   (Followers: 5)
Physiological and Biochemical Zoology     Full-text available via subscription   (Followers: 5)
Polish Journal of Entomology     Open Access   (Followers: 2)
Protist Genomics     Open Access  
Research in Zoology     Open Access   (Followers: 1)
Revista Brasileira de Zoologia     Open Access  
Revista de Biología Marina y Oceanografía     Open Access   (Followers: 1)
Revista de Zoologia     Open Access   (Followers: 1)
Revista del Museo Argentino de Ciencias Naturales     Open Access  
Russian Journal of Herpetology     Full-text available via subscription   (Followers: 1)
Scientific Journal of Animal Science     Open Access   (Followers: 3)
Scientific Journal of Zoology     Open Access   (Followers: 2)
SHILAP Revista de Lepidopterologia     Open Access   (Followers: 2)
Skeletal Muscle     Open Access   (Followers: 2)
Sri Lanka Journal of Aquatic Sciences     Open Access  
Travaux du Muséum National d’Histoire Naturelle “Grigore Antipa”     Open Access  

        1 2     

Journal Cover Journal of Animal Ecology
   Journal TOC RSS feeds Export to Zotero [30 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 0021-8790 - ISSN (Online) 1365-2656
     Published by John Wiley and Sons Homepage  [1604 journals]   [SJR: 2.606]   [H-I: 94]
  • Moving on with foraging theory: incorporating movement decisions into the
           functional response of a gregarious shorebird
    • Authors: Jan A. Gils; Matthijs Geest, Brecht De Meulenaer, Hanneke Gillis, Theunis Piersma, Eelke O. Folmer
      Pages: n/a - n/a
      Abstract: 1.Models relating intake rate to food abundance and competitor densities (generalized functional response models) can predict forager distributions and movements between patches, but we lack understanding of how distributions and small‐scale movements by the foragers themselves affect intake rates. 2.Using a state‐of‐the‐art approach based on continuous‐time Markov chain dynamics, we add realism to classic functional response models by acknowledging that the chances to encounter food and competitors are influenced by movement decisions, and, vice versa, that movement decisions are influenced by these encounters. 3.We used a multi‐state modelling framework to construct a stochastic functional response model in which foragers alternate between three behavioural states: searching, handling and moving. 4.Using behavioural observations on a molluscivore migrant shorebird (red knot, Calidris canutus canutus), at its main wintering area (Banc d'Arguin, Mauritania), we estimated transition rates between foraging states as a function of conspecific densities and densities of the two main bivalve prey. 5.Intake rate decreased with conspecific density. This interference effect was not due to decreased searching efficiency, but resulted from time lost to avoidance movements. 6.Red knots showed a strong functional response to one prey (Dosinia isocardia), but a weak response to the other prey (Loripes lucinalis). This corroborates predictions from a recently developed optimal diet model that accounts for the mildly toxic effects due to consuming Loripes. 7.Using model‐averaging across the most plausible multi‐state models, the fully parameterized functional response model was then used to predict intake rate for an independent dataset on habitat choice by red knot. 8.Comparison of the sites selected by red knots with random sampling sites showed that the birds fed at sites with higher than average Loripes and Dosinia densities, i.e. sites for which we predicted higher than average intake rates. 9.We discuss the limitations of Holling's classical functional response model that ignores movement and the limitations of contemporary movement ecological theory ignoring consumer‐resource interactions. With the rapid advancement of technologies to track movements of individual foragers at fine spatial scales, the time seems ripe to integrate descriptive tracking studies with stochastic movement‐based functional response models. This article is protected by copyright. All rights reserved.
      PubDate: 2014-10-05T06:01:53.341006-05:
      DOI: 10.1111/1365-2656.12301
       
  • Assembly Patterns Of Mixed‐Species Avian Flocks In The Andes
    • Authors: Gabriel J.Z. Colorado; Amanda D. Rodewald
      Pages: n/a - n/a
      Abstract: The relative contribution of deterministic and stochastic processes in the assembly of biotic communities is a central issue of controversy in community ecology. However, several studies have shown patterns of species segregation that are consistent with the hypothesis that deterministic factors such as competition and niche‐partitioning structure species assemblages in animal communities. Community assembly provides a theoretical framework for understanding these processes, but it has been seldom applied to social aggregations within communities. In this research we assessed patterns of non‐randomness in Andean mixed‐species flocks using three assembly models: (a) co‐occurrence patterns (b) guild proportionality; and (c) constant body‐size ratios using data from 221 species of resident and Neotropical migrant birds participating in 311 mixed‐species flocks at 13 regions distributed in Venezuela, Colombia, Ecuador, and Peru. Significant assembly patterns for mixed‐species flocks based on co‐occurrence models and guild proportionality models suggest that competitive interactions play an important role in structuring this social system in the Andes. Distribution of species among foraging guilds (i.e. insectivore, frugivore, omnivore, nectivore) was generally similar among flocks, though with some regional variation. In contrast, we found little evidence that structuring of mixed‐species flocks in the Andes was mediated by body size. Rather, we found greater than expected variance of body‐size ratios within flocks, indicating that birds did not segregate morphologically. Overall, our findings suggest that deterministic factors associated to competitive interactions are important contributors to mixed‐species flock assemblages across the Andes. This article is protected by copyright. All rights reserved.
      PubDate: 2014-10-05T06:01:38.704785-05:
      DOI: 10.1111/1365-2656.12300
       
  • Season‐specific and guild‐specific effects of anthropogenic
           landscape modification on metacommunity structure of tropical bats
    • Authors: Laura M. Cisneros; Matthew E. Fagan, Michael R. Willig
      Pages: n/a - n/a
      Abstract: 1.Fragmentation per se due to human land conversion is a landscape‐scale phenomenon. Accordingly, assessment of distributional patterns across a suite of potentially connected communities (i.e. metacommunity structure) is an appropriate approach for understanding the effects of landscape modification, and complements the plethora of fragmentation studies that have focused on local community structure. To date, metacommunity structure within human‐modified landscapes has been assessed with regard to nestedness along species richness gradients. This is problematic because there is little support that species richness gradients are associated with the factors moulding species distributions. More importantly, many alternative patterns are possible, and different patterns may manifest during different seasons and for different guilds because of variation in resource availability and resource requirements of taxa. 2.We determined the best‐fit metacommunity structure of a phyllostomid bat assemblage, frugivore ensemble, and gleaning animalivore ensemble within a human‐modified landscape in the Caribbean lowlands of Costa Rica during the dry and wet seasons to elucidate important structuring mechanisms. Furthermore, we identified the landscape characteristics associated with the latent gradient underlying metacommunity structure. 3.We discriminated among multiple metacommunity structures by assessing coherence, range turnover, and boundary clumping of an ordinated site‐by‐species matrix. We identified the landscape characteristics associated with the latent gradient underlying metacommunity structure via hierarchical partitioning. 4.Metacommunity structure was never nested nor structured along a richness gradient. 5.The phyllostomid assemblage and frugivore ensemble exhibited Gleasonian structure (range turnover along a common gradient) during the dry season and Clementsian structure (range turnover and shared boundaries along a common gradient) during the wet season. Distance between forest patches and forest edge density structured the phyllostomid metacommunity during the dry and wet seasons, respectively. Proportion of pasture and forest patch density structured the frugivore metacommunity during the dry season. 6.Gleaning animalivores exhibited chequerboard structure (mutually exclusive species‐pairs) during the dry season and random structure during the wet season. 7.Metacommunity structure was likely mediated by differential resource use or interspecific relationships. Furthermore, the interaction between landscape characteristics and seasonal variation in resources resulted in season‐specific and guild‐specific distributional patterns. This article is protected by copyright. All rights reserved.
      PubDate: 2014-10-05T06:01:23.570449-05:
      DOI: 10.1111/1365-2656.12299
       
  • Drivers of parasite sharing among Neotropical freshwater fishes
    • Authors: Mariana P. Braga; Emanuel Razzolini, Walter A. Boeger
      Pages: n/a - n/a
      Abstract: 1.Because host‐parasite interactions are so ubiquitous, it is of primary interest for ecologists to understand the factors that generate, maintain, and constrain these associations. Phylogenetic comparative studies have found abundant evidence for host‐switching to relatively unrelated hosts, sometimes related to diversification events, in a variety of host‐parasite systems. For Monogenoidea (Platyhelminthes) parasites, it has been suggested that the co‐speciation model alone cannot explain host occurrences, hence host‐switching and/or non‐vicariant modes of speciation should be associated with the origins and diversification of several monogenoid taxa. 2.The factors that shape broad patterns of parasite sharing were investigated using path analysis as a way to generate hypotheses about the origins of host‐parasite interactions between monogenoid gill parasites and Neotropical freshwater fishes. 3.Parasite sharing was assessed from an interaction matrix, and explanatory variables included phylogenetic relationships, environmental preferences, biological traits, and geographic distribution for each host species. 4.Although geographic distribution of hosts and host ecology are important factors to understand host‐parasite interactions, especially within host lineages that share a relatively recent evolutionary history, phylogeny had the strongest overall direct effect on parasite sharing. 5.Phylogenetic contiguity of host communities may allow a “stepping‐stone” mode of host‐switching, which increases parasite sharing. Our results reinforce the importance of including evolutionary history in the study of ecological associations, including EID risk assessment. This article is protected by copyright. All rights reserved.
      PubDate: 2014-10-05T06:01:06.064332-05:
      DOI: 10.1111/1365-2656.12298
       
  • Density‐dependent habitat selection of spawning Chinook salmon:
           broad scale evidence and implications
    • Authors: Matthew R. Falcy
      Pages: n/a - n/a
      Abstract: 1.An extensive body of theory suggests that density‐dependent habitat selection drives many fundamental ecological processes. The ideal free distribution and the ideal despotic distribution make contrasting predictions about the effect of total population size on relative abundances among habitats. Empirical assessment of these habitat selection models is uncommon because data must be collected over large temporal and spatial scales. 2.I ask whether fluctuation in Chinook salmon (Oncorhynchus tshawytscha) spawner population size through time leads to different relative densities over space. 3.Twenty six years of monitoring data on spawning Chinook salmon across the entire coast of Oregon, USA, were used to evaluate models that make contrasting statements about the interactions of a latent population abundance parameter with physical habitat characteristics. 4.There is strong information‐theoretic support for models that include terms that allow the spatial variation in density to change as population size changes through time. Analysis of the best model reveals nonlinear isodars, which suggests a “despotic” or “preemptive” distribution of individuals across habitats, indicating that dominant or early arriving individuals exclude others from breeding sites. 5.This finding has implications for genetic dynamics, population dynamics, and conservation metrics of these highly valued fish. The novel application of modeling techniques used here to assess mechanisms of habitat selection from observational data can be used in the emerging field of eco‐evolutionary dynamics. This article is protected by copyright. All rights reserved.
      PubDate: 2014-10-05T06:00:54.088917-05:
      DOI: 10.1111/1365-2656.12297
       
  • Phylogenetic diversity and coevolutionary signals among trophic levels
           change across a habitat edge
    • Authors: Guadalupe Peralta; Carol M. Frost, Raphael K. Didham, Arvind Varsani, Jason M. Tylianakis
      Abstract: 1. Incorporating the evolutionary history of species into community ecology enhances understanding of community composition, ecosystem functioning and responses to environmental changes. 2. Phylogenetic history might partly explain the impact of fragmentation and land‐use change on assemblages of interacting organisms, and even determine potential cascading effects across trophic levels. However, it remains unclear whether phylogenetic diversity of basal resources is reflected at higher trophic levels in the food web. In particular, phylogenetic determinants of community structure have never been incorporated into habitat edge studies, even though edges are recognised as key factors affecting communities in fragmented landscapes. 3. Here we test whether phylogenetic diversity at different trophic levels (plants, herbivores, parasitoids) and signals of coevolution (i.e. phylogenetic congruence) among interacting trophic levels change across an edge gradient between native and plantation forests. To ascertain whether there is a signal of coevolution across trophic levels, we test whether related consumer species generally feed on related resource species. 4. We found differences across trophic levels in how their phylogenetic diversity responded to the habitat edge gradient. Plant and native parasitoid phylogenetic diversity changed markedly across habitats, while phylogenetic variability of herbivores (which were predominantly native) did not change across habitats, though phylogenetic evenness declined in plantation interiors. Related herbivore species did not appear to feed disproportionately on related plant species (i.e. there was no signal of coevolution) even when considering only native species, potentially due to the high trophic generality of herbivores. However, related native parasitoid species tended to feed on related herbivore species, suggesting the presence of a coevolutionary signal at higher trophic levels. Moreover, this signal was stronger in plantation forests, indicating that this habitat may impose stresses on parasitoids that constrain them to attack only host species for which they are best adapted. 5. Overall, changes in land use across native to plantation forest edges differentially affected phylogenetic diversity across trophic levels, and may also exert a strong selective pressure for particular coevolved herbivore‐parasitoid interactions. This article is protected by copyright. All rights reserved.
      PubDate: 2014-10-03T06:07:08.936076-05:
      DOI: 10.1111/1365-2656.12296
       
  • Latitudinal and photic effects on diel foraging and predation risk in
           freshwater pelagic ecosystems
    • Authors: Adam G. Hansen; David A. Beauchamp
      Abstract: 1. Clark & Levy (1988) described an antipredation window for smaller planktivorous fish during crepuscular periods when light permits feeding on zooplankton, but limits visual detection by piscivores. Yet, how the window is influenced by the interaction between light regime, turbidity and cloud cover over a broad latitudinal gradient remains unexplored. 2. We evaluated how latitudinal and seasonal shifts in diel light regimes alter the foraging‐risk environment for visually‐feeding planktivores and piscivores across a natural range of turbidities and cloud covers. Pairing a model of aquatic visual feeding with a model of sun and moon illuminance, we estimated foraging rates of an idealized planktivore and piscivore over depth and time across factorial combinations of latitude (0‐70º), turbidity (0.1‐5 NTU) and cloud cover (clear to overcast skies) during the summer solstice and autumnal equinox. We evaluated the foraging‐risk environment based on changes in the magnitude, duration and peak timing of the antipredation window. 3. The model scenarios generated up to 10‐fold shifts in magnitude, 24‐fold shifts in duration, and 5.5 h shifts in timing of the peak antipredation window. The size of the window increased with latitude. This pattern was strongest during the solstice. In clear water at low turbidity (0.1‐0.5 NTU), peaks in the magnitude and duration of the window formed at 57‐60º latitude, before falling to near zero as surface waters became saturated with light under a midnight sun and clear skies at latitudes near 70º. Overcast dampened the midnight sun enough to allow larger windows to form in clear water at high latitudes. Conversely, at turbidities ≥ 2 NTU, greater reductions in the visual range of piscivores than planktivores created a window for long periods at high latitudes. Latitudinal dependencies were essentially lost during the equinox, indicating a progressive compression of the window from early summer into autumn. 4. Model results show that diel‐seasonal foraging and predation risk in freshwater pelagic ecosystems changes considerably with latitude, turbidity and cloud cover. These changes alter the structure of pelagic predator‐prey interactions, and in turn, the broader role of pelagic consumers in habitat coupling in lakes. This article is protected by copyright. All rights reserved.
      PubDate: 2014-09-29T10:57:11.417498-05:
      DOI: 10.1111/1365-2656.12295
       
  • Persistent sex‐by‐environment effects on offspring fitness and
           sex‐ratio adjustment in a wild bird population
    • Authors: E. Keith Bowers; Charles F. Thompson, Scott K. Sakaluk
      Abstract: A major component of sex‐allocation theory, the Trivers‐Willard Model (TWM), posits that sons and daughters are differentially affected by variation in the rearing environment. In many species, the amount of parental care received is expected to have differing effects on the fitness of males and females. When this occurs, the TWM predicts that selection should favour adjustment of the offspring sex ratio in relation to the expected fitness return from offspring. However, evidence for sex‐by‐environment effects is mixed and little is known about the adaptive significance of producing either sex. Here, we test whether offspring sex ratios vary according to predictions of the TWM in the house wren (Troglodytes aedon, Vieillot). We also test the assumption of a sex‐by‐environment effect on offspring using two experiments, one in which we manipulated age‐differences among nestlings within broods, and another in which we held nestling age constant but manipulated brood size. As predicted, females with high investment ability over‐produced sons relative to those with lower ability. Males were also over‐produced early within breeding seasons. In our experiments, the body mass of sons was more strongly affected by the sibling‐competitive environment and resource availability than that of daughters: males grew heavier than females when reared in good conditions but were lighter than females when in poor conditions. Parents rearing broods with 1:1 sex ratios were more productive than parents rearing broods biased more strongly towards sons or daughters, suggesting that selection favours the production of mixed‐sex broods. However, differences in the condition of offspring as neonates persisted to adulthood, and their reproductive success as adults varied with the body mass of sons, but not daughters, prior to independence from parental care. Thus, selection should favour slight but predictable variations in the sex ratio in relation to the quality of offspring that parents are able to produce. Offspring sex interacts with the neonatal environment to influence offspring fitness, thus favouring sex‐ratio adjustment by parents. However, increased sensitivity of males to environmental conditions, such as sibling rivalry and resource availability, reduces the fitness returns from highly male‐biased broods. This article is protected by copyright. All rights reserved.
      PubDate: 2014-09-29T10:56:56.394628-05:
      DOI: 10.1111/1365-2656.12294
       
  • Spatial patterns of extra‐pair paternity: beyond paternity gains and
           losses
    • Authors: Lotte Schlicht; Mihai Valcu, Bart Kempenaers
      Abstract: Most studies on extra‐pair paternity (EPP) focus either on a specific male's extra‐pair gains or his extra‐pair losses. For an individual bird however, mate choice or mate availability may underlie strong spatial restrictions. Disregarding this spatial aspect may underestimate or mask effects of parameters influencing observed EPP patterns. Here, we propose a spatially explicit model for investigating the probability of having extra‐pair offspring (EPO) within local networks of breeding pairs. The dataset includes all realized and unrealized potential extra‐pair matings. This method is biologically meaningful because it allows (a) considering both members of an extra‐pair mating as well as their social mates, and (b) direct modelling of the spatial context in which extra‐pair behaviour occurs. The method has the advantage that it can provide inference about the relative contribution of spatial and non‐spatial parameters, and about the relative importance of male and female neighbourhoods. We apply this method to parentage data from 1025 broods collected over 12 breeding seasons in two independent study populations of blue tits (Cyanistes caeruleus). We investigate a set of predictions based on the EPP literature, namely that EPP depends on male age and body size, breeding density, and breeding synchrony. In all analyses, we control for breeding distance, a parameter that is expected to influence EPP even under random mating. The results show that older and larger males were more likely to sire EPO, but both effects decreased with increasing breeding distance. Local breeding density but not synchrony predicted whether a particular male‐female combination had EPO, at least in one of the study areas. Apart from breeding distance, male age had the strongest effect on EPP, followed by a measure of breeding density. The method thus allows a comprehensive assessment of the relative importance of different types of spatial and non‐spatial parameters to explain variation in the occurrence of EPP, while controlling for the fact that individuals that breed further apart are less likely to have EPO. The proposed approach is not limited to investigate EPP, but can be applied to other behavioural interactions between two individuals, such as dominance, competition, and (social) mating. This article is protected by copyright. All rights reserved.
      PubDate: 2014-09-29T10:56:41.956803-05:
      DOI: 10.1111/1365-2656.12293
       
  • Predicting invasive species impacts: a community module functional
           response approach reveals context dependencies
    • Authors: Rachel A. Paterson; Jaimie T. A. Dick, Daniel W. Pritchard, Marilyn Ennis, Melanie J. Hatcher, Alison M. Dunn
      Abstract: Predatory functional responses play integral roles in predator‐prey dynamics, and their assessment promises greater understanding and prediction of the predatory impacts of invasive species. Other inter‐specific interactions, however, such as parasitism and higher‐order predation, have the potential to modify predator‐prey interactions and thus the predictive capability of the comparative functional response approach. We used a four‐species community module (higher‐order predator; focal native or invasive predators; parasites of focal predators; native prey) to compare the predatory functional responses of native Gammarus duebeni celticus and invasive Gammarus pulex amphipods towards three invertebrate prey species (Asellus aquaticus, Simulium spp., Baetis rhodani), thus quantifying the context dependencies of parasitism and a higher‐order fish predator on these functional responses. Our functional response experiments demonstrated that the invasive amphipod had a higher predatory impact (lower handling time) on two of three prey species, which reflects patterns of impact observed in the field. The community module also revealed that parasitism had context dependent influences, for one prey species, with the potential to further reduce the predatory impact of the invasive amphipod or increase the predatory impact of the native amphipod in the presence of a higher‐order fish predator. Partial consumption of prey was similar for both predators and occurred increasingly in the order A. aquaticus, Simulium spp., and B. rhodani. This was associated with increasing prey densities, but showed no context dependencies with parasitism or higher‐order fish predator. This study supports the applicability of comparative functional responses as a tool to predict and assess invasive species impacts incorporating multiple context dependencies. This article is protected by copyright. All rights reserved.
      PubDate: 2014-09-29T10:56:26.519042-05:
      DOI: 10.1111/1365-2656.12292
       
  • Diapause induction and relaxed selection on alternative developmental
           pathways in a butterfly
    • Authors: Inger M. Aalberg Haugen; Karl Gotthard
      Abstract: 1.Seasonal phenotypic plasticity entails differential trait expression depending on the time of season. The facultative induction of winter diapause in temperate insects is a developmental switch mechanism often leading to differential expression in life‐history traits. However, when there is a latitudinal shift from a bivoltine to univoltine life‐cycle, selection for pathway‐specific expression is disrupted, which may allow drift towards less optimal trait values within the non‐selected pathway. 2.We use field‐ and experimental data from five Swedish populations of Pararge aegeria to investigate latitudinal variation in voltinism, local adaptation in the diapause switch, and footprints of selection on pathway‐specific regulation of life‐history traits and sexual dimorphism in larval development. 3.Field data clearly illustrated how natural populations gradually shift from bivoltinism to univoltinism as latitude increases. This was supported experimentally as the decrease in direct development at higher latitudes was accompanied by increasing critical daylengths, suggesting local adaptation in the diapause switch. 4.The differential expression among developmental pathways in development time and growth rate was significantly less pronounced in univoltine populations. Univoltine populations showed no significant signs of protandry during larval development, suggesting that erosion of the direct development pathway under relaxed selection has led to the loss of its sex‐specific modifications. This article is protected by copyright. All rights reserved.
      PubDate: 2014-09-29T10:56:09.603057-05:
      DOI: 10.1111/1365-2656.12291
       
  • Hidden semi‐Markov models reveal multiphasic movement of the
           endangered Florida panther
    • Authors: Madelon kerk; David P. Onorato, Marc A. Criffield, Benjamin M. Bolker, Ben C. Augustine, Scott A. Mckinley, Madan K. Oli
      Abstract: Animals must move to find food and mates, and to avoid predators; movement thus influences survival and reproduction, and ultimately determines fitness. Precise description of movement and understanding of spatial and temporal patterns as well as relationships with intrinsic and extrinsic factors is important both for theoretical and applied reasons. We applied hidden semi‐Markov models (HSMM) to hourly geographic positioning system (GPS) location data to understand movement patterns of the endangered Florida panther (Puma concolor coryi) and to discern factors influencing these patterns. Three distinct movement modes were identified: (1) Resting mode, characterized by short step lengths and turning angles around 180o; (2) Moderately active (or intermediate) mode characterized by intermediate step lengths and variable turning angles, and (3) Traveling mode, characterized by long step lengths and turning angles around 0o. Males and females, and females with and without kittens, exhibited distinctly different movement patterns. Using the Viterbi algorithm, we show that differences in movement patterns of male and female Florida panthers were a consequence of sex‐specific differences in diurnal patterns of state occupancy and sex‐specific differences in state‐specific movement parameters, whereas the differences between females with and without dependent kittens were caused solely by variation in state occupancy. Our study demonstrates the use of HSMM methodology to precisely describe movement and to dissect differences in movement patterns according to sex, and reproductive status. This article is protected by copyright. All rights reserved.
      PubDate: 2014-09-24T00:10:41.421186-05:
      DOI: 10.1111/1365-2656.12290
       
  • Trans‐generational parasite protection associated with paternal diet
    • Authors: Eleanore D. Sternberg; Jacobus C. Roode, Mark D. Hunter
      Abstract: Multiple generations of hosts are often exposed to the same pathogens, favoring the evolution of trans‐generational defenses. Because females have more opportunities to transfer protective molecules to offspring, many studies have focused on maternally derived protection. However, males of many species can transfer compounds along with sperm, including chemicals that could provide protection. Here, we assess maternally and paternally derived protection in a monarch butterfly‐protozoan parasite system where parasite resistance is heavily influenced by secondary plant chemicals, known as cardenolides, present in the larval diet of milkweed plants. We reared monarch butterflies on medicinal and non‐medicinal milkweed species, then measured resistance of their offspring to infection. We also measured cardenolide content in adult monarchs reared on the two species, and in the eggs that they produced. We found that offspring were more resistant to infection when their fathers were reared on medicinal milkweed, while maternal diet had less of an effect. We also found that eggs contained the highest levels of cardenolides when both parents were reared on the medicinal species. Moreover, females reared on non‐medicinal milkweed produced eggs with significantly higher levels of cardenolides if they mated with males reared on the medicinal milkweed species. However, we found an equivocal relationship between the cardenolides present in eggs and parasite resistance in the offspring. Our results demonstrate that males reared on medicinal plants can transfer protection to their offspring, but the exact mechanism remains unresolved. This suggests that paternal protection from parasitism might be important, particularly when there are environmental sources of parasite resistance and when males transfer spermatophores during mating. This article is protected by copyright. All rights reserved.
      PubDate: 2014-09-24T00:10:29.587383-05:
      DOI: 10.1111/1365-2656.12289
       
  • Phantom alternatives influence food preferences in the eastern honey bee
           Apis cerana
    • Authors: Ken Tan; Shihao Dong, Xiwen Liu, Weiweng Chen, Yuchong Wang, Benjamin P. Oldroyd, Tanya Latty
      Abstract: 1.Most models of animal choice behaviour assume that desirable but unavailable options, such as a high quality, but inhabited nest sites, do not influence an individual's preferences for the remaining options. However, experiments suggest that in mammals the mere presence of such ‘phantom’ alternatives can alter, and even reverse, an individual's preferences for other items in a choice set. 2.Phantom alternatives may be widespread in nature, as they occur whenever a resource is visible, but unavailable at the time of choice. They are particularly relevant for nectar‐foraging animals, where previously rewarding flowers may sometimes be empty. Here we investigate the effect of phantom alternatives on feeder preferences in the eastern honey bee, Apis cerana. 3.First, we tested the effects of unattractive and attractive phantom alternatives by presenting individual bees with either a binary choice set containing two feeders that differed strongly in two qualities, but were equally preferred overall (‘option 1’ and ‘option 2’), or a ternary choice set containing option 1, option 2 and one of two phantom types (unattractive and attractive). Second, we determined whether phantoms increase (similarity effect) or decrease (dissimilarity effect) preference for phantom‐similar choices. 4.In binary trials, bees had no significant preference for option 1 or option 2. However, after encountering an attractive phantom alternative, individual bees preferred option 2. The unattractive phantom did not influence bee preferences. Phantoms consistently changed individual bee preferences in favour of the phantom‐similar choice. This means that the presence of an attractive food source, even if it is unavailable, can influence preference relationships between remaining items in the choice set. 5.Our findings highlight the importance of considering the potential for phantom effects when studying the foraging behaviour of animals. Our results are particularly relevant for nectarivores, where empty, but previously rewarding flowers are a common occurrence. Since an increase in pollinator visits can result in higher seed set, our results open up the possibility that by shifting pollinator preferences, empty flowers could have otherwise‐unpredicted influences on community composition, plant‐pollinator interactions and pollinator behaviour. This article is protected by copyright. All rights reserved.
      PubDate: 2014-09-22T11:39:17.153979-05:
      DOI: 10.1111/1365-2656.12288
       
  • Elements of regional beetle faunas: faunal variation and compositional
           breakpoints along climate, land cover and geographical gradients
    • Authors: Jani Heino; Janne Alahuhta
      Abstract: 1. Regional faunas are structured by historical, spatial and environmental factors. We studied large‐scale variation in four ecologically different beetle groups (Coleoptera: Dytiscidae, Carabidae, Hydrophiloidea, Cerambycidae) along climate, land cover and geographical gradients, examined faunal breakpoints in relation to environmental variables, and investigated the best fit pattern of assemblage variation (i.e. randomness, checkerboards, nestedness, evenly‐spaced, Gleasonian, Clementsian). We applied statistical methods typically used in the analysis of local ecological communities to provide novel insights into faunal compositional patterns at large spatial grain and geographical extent. 2. We found that spatially‐structured variation in climate and land cover accounted for most variation in each beetle group in partial redundancy analyses, whereas the individual effect of each explanatory variable group was generally much less important in accounting for variation in provincial species composition. 3. We also found that climate variables were most strongly associated with faunal breakpoints, with temperature‐related variables alone accounting for about 20% of variation at the first node of multivariate regression tree for each beetle group. The existence of faunal breakpoints was also shown by the “elements of faunal structure” analyses, which suggested Clementsian gradients across the provinces, i.e., that there were two or more clear groups of species responding similarly to the underlying ecological gradients. 4. The four beetle groups showed highly similar biogeographical patterns across our study area. The fact that temperature was related to faunal breakpoints in the species composition of each beetle group suggests that climate sets a strong filter to the distributions of species at this combination of spatial grain and spatial extent. This finding held true despite the ecological differences among the four beetle groups, ranging from fully aquatic to fully terrestrial, and from herbivorous to predaceous species. 5. The existence of Clementsian gradients may be a common phenomenon at large scales, and it is likely to be caused by crossing multiple species pools determined by climatic and historical factors on the distributions of species. This article is protected by copyright. All rights reserved.
      PubDate: 2014-09-22T11:39:02.032429-05:
      DOI: 10.1111/1365-2656.12287
       
  • Ant‐Caterpillar Antagonism at the Community Level: Interhabitat
           Variation of Tritrophic Interactions in a Neotropical Savanna
    • Authors: Sebastián F. Sendoya; Paulo S. Oliveira
      Abstract: Ant foraging on foliage can substantially affect how phytophagous insects use host plants and represents a high predation risk for caterpillars, which are important folivores. Ant‐plant‐herbivore interactions are especially pervasive in cerrado savanna due to continuous ant visitation to liquid food sources on foliage (extrafloral nectaries, insect honeydew). While searching for liquid rewards on plants, aggressive ants frequently attack or kill insect herbivores, decreasing their numbers. Because ants vary in diet and aggressiveness, their effect on herbivores also varies. Additionally, the differential occurrence of ant attractants (plant and insect exudates) on foliage produces variable levels of ant foraging within local floras and among localities. Here, we investigate how variation of ant communities and of traits among host plant species (presence or absence of ant attractants) can change the effect of carnivores (predatory ants) on herbivore communities (caterpillars) in a cerrado savanna landscape. We sampled caterpillars and foliage‐foraging ants in four cerrado localities (70‐460 km apart). We found that: (i) caterpillar infestation was negatively related with ant visitation to plants; (ii) this relationship depended on local ant abundance and species composition, and on local preference by ants for plants with liquid attractants, and (iii) was not related to local plant richness or plant size; (iv) the relationship between presence of ant attractants and caterpillar abundance varied among sites from negative to neutral; and (v) caterpillars feeding on plants with ant attractants are more resistant to ant predation than those feeding on plants lacking attractants. Liquid food on foliage mediates host plant quality for lepidopterans by promoting generalized ant‐caterpillar antagonism. Our study in cerrado shows that the negative effects of generalist predatory ants on herbivores are detectable at a community level, affecting patterns of abundance and host plant use by lepidopterans. The magnitude of ant‐induced effects on caterpillar occurrence across the cerrado landscape may depend on how ants use plants locally and how they respond to liquid food on plants at different habitats. This study enhances the relevance of plant‐ant and ant‐herbivore interactions in cerrado, and highlights the importance of a tritrophic perspective in this ant‐rich environment. This article is protected by copyright. All rights reserved.
      PubDate: 2014-09-22T11:38:51.493839-05:
      DOI: 10.1111/1365-2656.12286
       
  • Changes in host‐parasitoid food web structure with elevation
    • Authors: Sarah C. Maunsell; Roger L. Kitching, Chris J. Burwell, Rebecca J. Morris
      Abstract: Gradients in elevation are increasingly used to investigate how species respond to changes in local climatic conditions. While many studies have shown elevational patterns in species richness and turnover, little is known about how food web structure is affected by elevation. Contrasting responses of predator and prey species to elevation may lead to changes in food web structure. We investigated how the quantitative structure of a herbivore‐parasitoid food web changes with elevation in Australian subtropical rainforest. On four occasions, spread over one year, we hand‐collected leaf miners at twelve sites, along three elevational gradients (between 493 m and 1159 m a.s.l). A total of 5030 insects, including 603 parasitoids were reared, and summary food webs were created for each site. We also carried out a replicated manipulative experiment by translocating an abundant leaf‐mining weevil, Platynotocis sp., which largely escaped parasitism at high elevations (≥900m a.s.l.), to lower, warmer elevations, to test if it would experience higher parasitism pressure. We found strong evidence that the environmental change that occurs with increasing elevation affects food web structure. Quantitative measures of generality, vulnerability and interaction evenness decreased significantly with increasing elevation (and decreasing temperature), whilst elevation did not have a significant effect on connectance. Mined plant composition also had a significant effect on generality and vulnerability, but not on interaction evenness. Several relatively abundant species of leaf miner appeared to escape parasitism at higher elevations, but contrary to our prediction, Platynotocis sp. did not experience greater levels of parasitism when translocated to lower elevations. Our study indicates that leaf‐mining herbivores and their parasitoids respond differently to environmental conditions imposed by elevation, thus producing structural changes in their food webs. Increasing temperatures and changes in vegetation communities that are likely to result from climate change may have a restructuring effect on host‐parasitoid food webs. Our translocation experiment, however, indicated that leaf miners currently escaping parasitism at high elevations may not automatically experience higher parasitism under warmer conditions and future changes in food web structure may depend on the ability of parasitoids to adapt to novel hosts. This article is protected by copyright. All rights reserved.
      PubDate: 2014-09-22T02:56:07.595024-05:
      DOI: 10.1111/1365-2656.12285
       
  • Effects of land‐use intensity on arthropod species abundance
           distributions in grasslands
    • Authors: Nadja K. Simons; Martin M. Gossner, Thomas M. Lewinsohn, Markus Lange, Manfred Türke, Wolfgang W. Weisser
      Abstract: 1.As a rule, communities consist of few abundant and many rare species, which is reflected in the characteristic shape of species abundance distributions (SADs). The processes that shape these SADs have been a longstanding problem for ecological research. Although many studies found strong negative effects of increasing land‐use intensity on diversity, few reports consider land‐use effects on SADs. 2.Arthropods (insects and spiders) were sampled on 142 grassland plots in three regions in Germany, which were managed with different modes (mowing, fertilisation and/or grazing) and intensities of land use. We analysed the effect of land use on three parameters characterizing the shape of SADs: abundance decay rate (the steepness of the rank abundance curve, represented by the niche‐preemption model parameter), dominance (Berger‐Parker dominance) and rarity (Fisher's alpha). Furthermore, we tested the core‐satellite hypothesis by comparing the species’ rank within the SAD to their distribution over the land‐use gradient. 3.When data on Araneae, Cicadina, Coleoptera, Heteroptera and Orthoptera were combined, abundance decay rate increased with combined land‐use intensity (including all modes). Among the single land‐use modes, increasing fertilisation and grazing intensity increased the decay rate of all taxa while increasing mowing frequency significantly affected the decay rate only in interaction with fertilisation. Results of single taxa differed in their details, but all significant interaction effects included fertilisation intensity. Dominance generally increased with increasing fertilisation and rarity decreased with increasing grazing or mowing intensity, despite small differences among taxa and regions. The majority of species found on less than 10% of the plots per region were generally rare (
      PubDate: 2014-09-02T11:57:08.463227-05:
      DOI: 10.1111/1365-2656.12278
       
  • Ecological Implications of Reduced Forage Quality on Growth and Survival
           of Sympatric Geese
    • Authors: Samantha E. Richman; James O. Leafloor, William H. Karasov, Scott R. McWilliams
      Abstract: 1.Allometric constraints associated with digesting leaves require relatively small avian herbivores to consume high‐quality forage. How such constraints are overcome during ontogeny when energy and nutrient requirements are relatively high has not been adequately explored. 2.We compared growth trajectories of Canada and lesser snow goose goslings raised on grass‐based diets that differed in protein (10, 14, or 18%) and fiber (30 or 45%) with those of free‐living goslings on Akimiski Island, Canada. This common‐garden experiment allowed us to test the hypotheses that (1) smaller‐bodied geese are more negatively affected by reduced forage quality than larger‐bodied geese, and (2) goslings from subarctic brood‐rearing areas have a limited capacity to slow growth in response to reduced forage quality. 3.Canada goose goslings fed low protein (10%) diets were on average 44% lighter in body mass, had slower growth rates, and were delayed >20 days in reaching 90% of asymptotic size compared to Canada goose goslings fed 18% protein. In contrast, snow goose goslings were unable to survive on the low protein diets, and those fed high or medium protein diets grew at a similar rate and achieved similar asymptotic size. Canada and snow goose goslings fed low protein diets had reduced growth rates of the tarsus and delayed emergence of the 9th primary. 4.Free‐ranging Canada goslings on Akimiski Island were similar in mass and structural size to captive‐reared goslings fed low protein diets. In contrast, snow goslings were similar in mass and structural size to the captive‐reared goslings fed the high and medium protein diets. This suggests that degraded habitats with mostly low protein forage may be able to support Canada goslings better than snow goslings which require higher quality forage to survive. 5.Size‐related differences in gosling growth and survival in response to diminished diet quality may influence population size when available food reaches a lower threshold in protein content. However, goslings can avoid such density‐dependent population regulation if they are able to move their broods and find adequate quality and quantity of forage. This article is protected by copyright. All rights reserved.
      PubDate: 2014-08-27T00:20:32.285098-05:
      DOI: 10.1111/1365-2656.12270
       
  • “You shall not pass!”: quantifying barrier permeability and
           proximity avoidance by animals
    • Authors: Hawthorne L. Beyer; Eliezer Gurarie, Luca Börger, Manuela Panzacchi, Mathieu Basille, Ivar Herfindal, Bram Van Moorter, Subhash R. Lele, Jason Matthiopoulos
      Abstract: 1. Impediments to animal movement are ubiquitous and vary widely in both scale and permeability. It is essential to understand how impediments alter ecological dynamics via their influence on animal behavioural strategies governing space use and, for anthropogenic features such as roads and fences, how to mitigate these effects to effectively manage species and landscapes. 2. Here, we focused primarily on barriers to movement, which we define as features that cannot be circumnavigated but may be crossed. Responses to barriers will be influenced by the movement capabilities of the animal, its proximity to the barriers, and habitat preference. We developed a mechanistic modelling framework for simultaneously quantifying the permeability and proximity effects of barriers on habitat preference and movement. 3. We used simulations based on our model to demonstrate how parameters on movement, habitat preference and barrier permeability can be estimated statistically. We then applied the model to a case study of road effects on wild mountain reindeer summer movements. 4. This framework provided unbiased and precise parameter estimates across a range of strengths of preferences and barrier permeabilities. The quality of permeability estimates, however, was correlated with the number of times the barrier is crossed and the number of locations in proximity to barriers. In the case study we found reindeer avoided areas near roads and that roads are semi‐permeable barriers to movement. There was strong avoidance of roads extending up to approximately 1 km for four of five animals, and having to cross roads reduced the probability of movement by 68.6% (range 3.5‐99.5%). 5. Human infrastructure has embedded within it the idea of networks: nodes connected by linear features such as roads, rail tracks, pipelines, fences and cables, many of which divide the landscape and limit animal movement. The unintended but potentially profound consequences of infrastructure on animals remain poorly understood. The rigorous framework for simultaneously quantifying movement, habitat preference and barrier permeability developed here begins to address this knowledge gap. This article is protected by copyright. All rights reserved.
      PubDate: 2014-08-25T02:18:19.581003-05:
      DOI: 10.1111/1365-2656.12275
       
  • Seed perishability determines the caching behaviour of a
           food‐hoarding bird
    • Authors: Eike Lena Neuschulz; Thomas Mueller, Kurt Bollmann, Felix Gugerli, Katrin Böhning‐Gaese
      Abstract: 1. Many animals hoard seeds for later consumption and establish seed caches that are often located at sites with specific environmental characteristics. One explanation for the selection of non‐random caching locations is the avoidance of pilferage by other animals. Another possible hypothesis is that animals choose locations that hamper the perishability of stored food, allowing the consumption of unspoiled food items over long time periods. 2. We examined seed perishability and pilferage‐avoidance as potential drivers for caching behaviour of Spotted nutcrackers (Nucifraga caryocatactes) in the Swiss Alps where the birds are specialized on caching seeds of Swiss stone pine (Pinus cembra). 3. We used seedling establishment as an inverse measure of seed perishability, as established seedlings cannot longer be consumed by nutcrackers. We recorded the environmental conditions (i.e., canopy openness and soil moisture) of seed caching, seedling establishment and pilferage sites. 4. Our results show that sites of seed caching and seedling establishment had opposed micro‐environmental conditions. Canopy openness and soil moisture were negatively related to seed caching but positively related to seedling establishment, i.e., nutcrackers cached seeds preferentially at sites where seed perishability was low. We found no effects of environmental factors on cache pilferage, i.e. neither canopy openness nor soil moisture had significant effects on pilferage rates. We thus could not relate caching behaviour to pilferage‐avoidance. 5. Our study highlights the importance of seed perishability as a mechanism for seed caching behaviour, which should be considered in future studies. Our findings could have important implications for the regeneration of plants whose seeds are dispersed by seed‐caching animals, as the potential of seedlings to establish may strongly decrease if animals cache seeds at sites that favour seed perishability rather than seedling establishment. This article is protected by copyright. All rights reserved.
      PubDate: 2014-08-22T10:26:45.554514-05:
      DOI: 10.1111/1365-2656.12283
       
  • Movement propensity and ability correlate with ecological specialisation
           in European land snails: comparative analysis of a dispersal syndrome
    • Authors: Maxime Dahirel; Eric Olivier, Annie Guiller, Marie‐Claire Martin, Luc Madec, Armelle Ansart
      Abstract: Intra‐ and inter‐specific differences in movement behaviour play an important role in the ecology and evolution of animals, particularly in fragmented landscapes. As a consequence of rarer and generally more fragmented habitat, and because dispersal tends to disrupt benefits brought by local adaptation, theory predicts that mobility and dispersal should be counter‐selected in specialists. Using experimental data and phylogenetic comparative tools, we analysed movement propensity and capacity, as well as dispersal‐related phenotypic traits, in controlled conditions in 20 species of European land snails from the Helicoidea superfamily. Costs of movement in terrestrial gastropods are among the highest in animals, which make them a potentially powerful model to test these predictions. Habitat specialists were indeed less likely to cross a boundary between a familiar and an unfamiliar substrate than generalists. They also had smaller feet, after accounting for size. Furthermore, exploring specialists were slower than generalists, and had more tortuous trajectories, leading them to stay closer to the familiar patch. Movement traits were generally evolutionary labile, but some were constrained by body size, a phylogenetically conserved trait. High specialisation and low dispersal ability are two traits often considered to increase species vulnerability to fragmentation, climate changes and extinction. This study confirms they should not be considered separately, due to their integration in a dispersal syndrome. Therefore, specialist species face double penalty under habitat loss and other environmental changes, making them more vulnerable to extinction and contributing to the biotic homogenization of communities. This article is protected by copyright. All rights reserved.
      PubDate: 2014-08-20T11:13:06.809776-05:
      DOI: 10.1111/1365-2656.12276
       
  • How detectable is predation in stage‐structured populations'
           Insights from a simulation‐testing analysis
    • Authors: Kiva L. Oken; Timothy E. Essington
      Abstract: The potential of predation to structure marine food webs is widely acknowledged. However, available tools to detect the regulation of prey population dynamics by predation are limited, partly because available population data often aggregate a population's age structure into a single biomass or abundance metric. Additionally, many food webs are relatively complex, with prey species subject to different assemblages of predators throughout their ontogeny. The goal of this study was to evaluate the extent to which stage‐structured predation could be reliably detected from time series of total biomass of predators and prey. We simulated age‐structured populations of four mid‐trophic level fish species with distinct life history traits, exposed them to variable predation at different life stages, and fit production models to resulting population biomass to determine how reliably the effects of predators could be detected. Predation targeting early life history and juvenile life stages generally led to larger fluctuations in annual production, and was therefore more detectable. However, ecologically‐realistic levels of observation error and environmental stochasticity masked most predator signals. The addition of predation at a second life stage sharply decreased the ability to detect the effect of each predator. We conclude an absence of detectable species interactions from biomass time series may be partly due to the interactive effects of environmental variability and complex food web linkages and life histories. We also note that predation signals are most robust for predator‐prey systems where predators primarily act on mortality of sub‐mature life history stages. Simulation testing can be applied widely to evaluate the statistical power of analyses to detect predation effects. This article is protected by copyright. All rights reserved.
      PubDate: 2014-08-16T02:14:01.724805-05:
      DOI: 10.1111/1365-2656.12274
       
  • Long‐term phenological trends, species accumulation rates, aphid
           traits and climate: five decades of change in migrating aphids.
    • Authors: JR Bell; L Alderson, D Izera, T Kruger, S Parker, J Pickup, CR Shortall, Taylor, P Verrier, R Harrington
      Abstract: 1. Aphids represent a significant challenge to food production. The Rothamsted Insect Survey (RIS) runs a network of 12.2m suction‐traps throughout the year to collect migrating aphids. In 2014 the RIS celebrated its 50th anniversary. This paper marks that achievement with an extensive spatio‐temporal analysis and the provision of the first British annotated checklist of aphids since 1964. 2. Our main aim was to elucidate mechanisms that advance aphid phenology under climate change and explain these using life history traits. We then highlight emerging pests using accumulation patterns. 3. Linear and non‐linear mixed‐effect models estimated the average rate of change per annum and effects of climate on annual counts, first and last flights and length of flight season since 1965. Two climate drivers were used: the accumulated day degrees above 16°C (ADD16) indicated the potential for migration during the aphid season; the North Atlantic Oscillation (NAO) signalled the severity of the winter before migration took place. 4. All 55 species studied had earlier first flight trends at rate of β=‐0.611 ±se 0.015 days year‐1. Of these species, 49% had earlier last flights but the average species effect appeared relatively stationary (β=‐0.010 ±se 0.022 days year‐1). Most species (85%) showed increasing duration of their flight season (β=0.336 ±se 0.026 days year‐1), even though only 54% increased their annual count (β=0.002 ±se
      PubDate: 2014-08-13T23:56:59.943688-05:
      DOI: 10.1111/1365-2656.12282
       
  • Empirical tests of harvest‐induced body‐size evolution along a
           geographic gradient in Australian macropods
    • Authors: Thomas A. A. Prowse; Rachel A. Correll, Christopher N. Johnson, Gavin J. Prideaux, Barry W. Brook
      Abstract: 1.Life‐history theory predicts the progressive dwarfing of animal populations that are subjected to chronic mortality stress but the evolutionary impact of harvesting terrestrial herbivores has seldom been tested. In Australia, marsupials of the genus Macropus (kangaroos and wallabies) are subjected to size‐selective commercial harvesting. Mathematical modelling suggests that harvest quotas (ca. 10–20% of population estimates annually) could be driving body‐size evolution in these species. 2.We tested this hypothesis for three harvested macropod species with continental‐scale distributions. To do so, we measured more than 2 000 macropod skulls sourced from wildlife collections spanning the last 130 years. We analysed these data using spatial Bayesian models that controlled for the age and sex of specimens as well as environmental drivers and island effects. 3.We found no evidence for the hypothesized decline in body size for any species; rather, models that fit trend terms supported minor body size increases over time. This apparently counterintuitive result is consistent with reduced mortality due to a depauperate predator guild and increased primary productivity of grassland vegetation following European settlement in Australia. 4.Spatial patterns in macropod body size supported the heat dissipation limit and productivity hypotheses proposed to explain geographic body‐size variation (i.e., skull size increased with decreasing summer maximum temperature and increasing rainfall, respectively). 5.There is no empirical evidence that size‐selective harvesting has driven the evolution of smaller body size in Australian macropods. Bayesian models are appropriate for investigating the long‐term impact of human harvesting because they can impute missing data, fit non‐linear growth models and account for non‐random spatial sampling inherent in wildlife collections. This article is protected by copyright. All rights reserved.
      PubDate: 2014-08-13T11:14:05.52666-05:0
      DOI: 10.1111/1365-2656.12273
       
  • Forecasting spring from afar' Timing of migration and predictability
           of phenology along different migration routes of an avian herbivore
    • Authors: A. Kölzsch; S. Bauer, R. Boer, L. Griffin, D. Cabot, K.‐M. Exo, H.P. Jeugd, B.A. Nolet
      Abstract: 1.Herbivorous birds are hypothesized to migrate in spring along a seasonal gradient of plant profitability towards their breeding grounds (green wave hypothesis). For Arctic‐breeding species in particular, following highly profitable food is important, so that they can replenish resources along the way and arrive in optimal body condition to start breeding early. 2.We compared the timing of migratory movements of Arctic‐breeding geese on different flyways to examine whether flyways differed in the predictability of spring conditions at stopovers, and whether this was reflected in the degree to which birds were following the green wave. 3.Barnacle geese (Branta leucopsis) were tracked with solar Argos/GPS PTTs from their wintering grounds to breeding sites in Greenland (N = 7), Svalbard (N = 21) and the Barents Sea (N = 12). The numerous stopover sites of all birds were combined into a set of 16 general stopover regions. 4.The predictability of climatic conditions along the flyways was calculated as the correlation and slope between onsets of spring at consecutive stopovers. These values differed between sites, mainly because of the presence or absence of ecological barriers. Goose arrival at stopovers was more closely tied to the local onset of spring when predictability was higher and when geese attempted breeding that year. 5.All birds arrived at early stopovers after the onset of spring and arrived at the breeding grounds before the onset of spring, thus overtaking the green wave. This is in accordance with patterns expected for capital breeders: first they must come into condition; at intermediate stopovers arrival with the food quality peak is important to stay in condition and at the breeding grounds early arrival is favoured so that hatching of young can coincide with the peak of food quality. 6.Our results suggest that a chain of correlations between climatic conditions at subsequent stopovers enables geese to closely track the green wave. However, the birds’ precision of migratory timing seems uninfluenced by ecological barriers, indicating partly fixed migration schedules. These might become non‐optimal due to climate warming and preclude accurate timing of long‐distance migrants in the future. This article is protected by copyright. All rights reserved.
      PubDate: 2014-08-13T00:27:16.469225-05:
      DOI: 10.1111/1365-2656.12281
       
  • Habitat‐based polymorphism is common in stream fishes
    • Authors: Caroline Senay; Daniel Boisclair, Pedro R. Peres‐Neto
      Abstract: 1. Morphological differences (size and shape) across habitats are common in lake fish where differences relate to two dominant contrasting habitats: the pelagic and littoral habitat. Repeated occurrence of littoral and pelagic morphs across multiple populations of several lake fish species has been considered as important evidence that polymorphism is adaptive in these systems. It has been suggested that these habitat‐based polymorphic differences are due to the temporal stability of the differences between littoral and pelagic habitats. 2. Although streams are spatially heterogeneous, they are also more temporally dynamic than lakes and it is still an open question whether streams provide the environmental conditions that promote habitat‐based polymorphism. We tested whether fish from riffle, run and pool habitats, respectively, differed consistently in their morphology. 3. Our test compared patterns of morphological variation (size and shape) in 10 fish species from the three stream habitat types in 36 separate streams distributed across three watersheds. 4. For most species, body size and shape (after controlling for body size) differed across riffle, run and pool habitats. Unlike many lake species, the nature of these differences was not consistent across species, possibly because these species use these habitat types in different ways. 5. Our results suggest that habitat‐based polymorphism is an important feature also in stream‐fishes despite the fact that streams are temporally variable in contrast to lake systems. Future research is required to assess whether the patterns of habitat‐polymorphism encountered in streams have a genetic basis or they are simply the result of within generation phenotypic plasticity. This article is protected by copyright. All rights reserved.
      PubDate: 2014-08-12T03:47:23.790546-05:
      DOI: 10.1111/1365-2656.12269
       
  • Predator‐dependent functional response in wolves: From food
           limitation to surplus killing
    • Authors: B. Zimmermann; H. Sand, P. Wabakken, O. Liberg, H. Andreassen
      Abstract: The functional response of a predator describes the change in per capita kill rate to changes in prey density. This response can be influenced by predator densities, giving a predator‐dependent functional response. In social carnivores which defend a territory, kill rates also depend on the individual energetic requirements of group members and their contribution to the kill rate. This study aims to provide empirical data for the functional response of wolves Canis lupus to the highly managed moose Alces alces population in Scandinavia. We explored prey and predator dependence, and how the functional response relates to the energetic requirements of wolf packs. Winter kill rates of GPS‐collared wolves and densities of cervids were estimated for a total of 22 study periods in 15 wolf territories. The adult wolves were identified as the individuals responsible for providing kills to the wolf pack, while pups could be described as inept hunters. The predator‐dependent, asymptotic functional response models (i.e. Hassell‐Varley type II and Crowley‐Martin) performed best among a set of 23 competing linear, asymptotic and sigmoid models. Small wolf packs acquired > 3 times as much moose biomass as required to sustain their field metabolic rate (FMR), even at relatively low moose abundances. Large packs (6 ‐ 9 wolves) acquired less biomass than required in territories with low moose abundance. We suggest the surplus‐killing by small packs is a result of an optimal foraging strategy to consume only the most nutritious parts of easy accessible prey while avoiding the risk of being detected by humans. Food limitation may have a stabilizing effect on pack size in wolves, as supported by the observed negative relationship between body weight of pups and pack size. This article is protected by copyright. All rights reserved.
      PubDate: 2014-08-11T05:57:33.92158-05:0
      DOI: 10.1111/1365-2656.12280
       
  • Predators, energetics and fitness drive neonatal reproductive failure in
           red squirrels
    • Authors: E.K. Studd; S. Boutin, A.G. McAdam, C.J. Krebs, M.M. Humphries
      Abstract: Neonatal reproductive failure should occur when energetic costs of parental investment outweigh fitness benefits. However, little is known about the drivers of neonatal reproductive failure in free ranging species experiencing continuous natural variation in predator abundance and in the energetic and fitness costs and benefits associated with parental investment. Long‐term comprehensive studies are required to better understand how biotic, abiotic, and life history conditions interact to drive occurrences of reproductive failure in the wild. Using 24 years (1987‐2011) of reproductive data from a northern boreal population of North American red squirrels in southwestern Yukon, we examined the effects of predator abundance, energetics (resource availability, ambient temperature and litter size), and fitness benefits (probability of overwinter juvenile survival and maternal age) on occurrences of neonatal reproductive failure (494/2670 reproductive attempts; 18.5%). Neonatal reproductive failure was driven by a combination of predator abundance, and the energetic and fitness costs and benefits of parental investment. The abundance of mustelids and maternal age were positively related to the occurrence of neonatal reproductive failure. High energy costs associated with a combination of low resource availability and cold ambient temperatures or large litters, corresponded to increased occurrences of neonatal reproductive failure. However, the strength of these relationships was influenced by variation in juvenile overwinter survival (i.e. fitness benefits). We provide evidence that predation pressure is an important driver of neonatal reproductive failure. In addition, we found a trade‐off occurs between resource‐dependent energetic and fitness costs and benefits of raising the current litter to independence. This article is protected by copyright. All rights reserved.
      PubDate: 2014-08-08T05:18:08.943898-05:
      DOI: 10.1111/1365-2656.12279
       
  • How topography induces reproductive asynchrony and alters gypsy moth
           invasion dynamics
    • Authors: Jonathan A. Walter; Marcia S. Meixler, Thomas Mueller, William F. Fagan, Patrick C. Tobin, Kyle J. Haynes
      Abstract: 1. Reproductive asynchrony, a temporal mismatch in reproductive maturation between an individual and potential mates, may contribute to mate‐finding failure and Allee effects that influence the establishment and spread of invasive species. Variation in elevation is likely to promote variability in maturation times for species with temperature‐dependent development, but it is not known how strongly this influences reproductive asynchrony or the population growth of invasive species. 2. We examined whether spatial variation in reproductive asynchrony, due to differences in elevation and local heterogeneity in elevation (hilliness), can explain spatial heterogeneity in the population growth rate of the gypsy moth, Lymantria dispar (L.), along its invasion front in Virginia and West Virginia, USA. 3. We used a spatially explicit model of the effects of reproductive asynchrony on mating success to develop predictions of the influences of elevation and elevational heterogeneity on local population growth rates. Population growth rates declined with increased elevation and more modestly with increased elevational heterogeneity. As in earlier work, we found a positive relationship between the population growth rate and the number of introduced egg masses, indicating a demographic Allee effect. At high elevations and high heterogeneity in elevation, the population growth rate was lowest and the density at which the population tended to replace itself (i.e., the Allee threshold) was highest. 4. An analysis of 22 years of field data also showed decreases in population growth rates with elevation and heterogeneity in elevation that were largely consistent with the model predictions. 5. These results highlight how topographic characteristics can affect reproductive asynchrony and influence mate‐finding Allee effects in an invading non‐native insect population. Given the dependence of developmental rates on temperature in poikilotherms, topographic effects on reproductive success could potentially be important to the population dynamics of many organisms. This article is protected by copyright. All rights reserved.
      PubDate: 2014-08-04T10:34:17.887648-05:
      DOI: 10.1111/1365-2656.12272
       
  • Individual and species specific traits explain niche size and functional
           role in spiders as generalist predators
    • Authors: Dirk Sanders; Esther Vogel, Eva Knop
      Abstract: 1. The function of a predator within a community is greatly based on its trophic niche, i.e. the number and the strength of feeding links. In generalist predators, which feed on a wide range of prey, the size and position of the trophic niche is likely determined by traits such as hunting mode, the stratum they occur in, their body size and age. 2. We used stable isotope analyses (13C and 15N) to measure the trophic niche size of nine spider species within a forest hedge community and tested for species traits and individual traits that influence stable isotope enrichment, niche size, and resource use. 3. The spiders Enoplognatha, Philodromus, Floronia, and Heliophanus had large isotopic niches, which correspond to a more generalistic feeding behaviour. In contrast, Araneus, Metellina, and Agelena, as top predators in the system, had rather narrow niches. We found a negative correlation between trophic position and niche size. Differences in trophic position in spiders were explained by body size, hunting modes and stratum, while niche size was influenced by hunting mode. In Philodromus the size of the trophic niche increased significantly with age. 4. Fitting spiders to functional groups according to their mean body size, hunting mode and their habitat domain resulted in largely separated niches, which indicates that these traits are meaningful for separating functional entities in spiders. Functional groups based on habitat domain (stratum) caught the essential functional differences between the species with species higher up in the vegetation feeding on flying insects and herb and ground species also preying on forest floor decomposers. 5. Interestingly, we found a gradient from large species using a higher habitat domain and having a smaller niche to smaller species foraging closer to the ground and having a larger niche. This shows that even within generalist predators, such as spiders, there is a gradient of specialism that can be predicted by functional traits. This article is protected by copyright. All rights reserved.
      PubDate: 2014-07-31T05:06:53.493512-05:
      DOI: 10.1111/1365-2656.12271
       
  • Territoriality and home‐range dynamics in meerkats, Suricata
           suricatta: a mechanistic modelling approach
    • Authors: Andrew W. Bateman; Mark A. Lewis, Gabriella Gall, Marta B. Manser, Tim H. Clutton‐Brock
      Abstract: Multiple approaches exist to model patterns of space use across species, among them resource selection analysis, statistical home range modelling, and mechanistic movement modelling. Mechanistic home‐range models combine the benefits of these approaches, describing emergent territorial patterns based on fine‐scale individual‐ or group‐movement rules and incorporating interactions with neighbours and the environment. These models have not, to date, been extended to dynamic contexts. Using mechanistic home‐range models, we explore meerkat (Suricata suricatta) territorial patterns, considering scent marking, direct group interactions, and habitat selection. We also extend the models to accommodate dynamic aspects of meerkat territoriality (territory development and territory shift). We fit models, representing multiple working hypotheses, to data from a long‐term meerkat study in South Africa, and we compare models using Akaike's and Bayesian information criteria. Our results identify important features of meerkat territorial patterns. Notably, larger groups do not seem to control larger territories, and groups apparently prefer dune edges along a dry riverbed. Our model extensions capture instances in which 1) a newly formed group interacts more strongly with its parent groups over time and 2) a group moves its territory core out of aversive habitat. This extends our mechanistic modelling framework in previously unexplored directions. This article is protected by copyright. All rights reserved.
      PubDate: 2014-07-29T04:25:16.244007-05:
      DOI: 10.1111/1365-2656.12267
       
  • How Ebola impacts social dynamics in gorillas: a multistate modelling
           approach
    • Authors: Céline Genton; Amandine Pierre, Romane Cristescu, Florence Lévréro, Sylvain Gatti, Jean‐Sébastien Pierre, Nelly Ménard, Pascaline Le Gouar
      Abstract: Emerging infectious diseases can induce rapid changes in population dynamics and threaten population persistence. In socially structured populations, the transfers of individuals between social units, for example, from breeding groups to non‐breeding groups, shape population dynamics. We suggest that diseases may affect these crucial transfers. We aimed to determine how disturbance by an emerging disease affects demographic rates of gorillas, especially transfer rates within populations and immigration rates into populations. We compared social dynamics and key demographic parameters in a gorilla population affected by Ebola using a long‐term observation data set including pre‐, during and post‐outbreak periods. We also studied a population of undetermined epidemiological status in order to assess whether this population was affected by the disease. We developed a multistate model that can handle transition between social units while optimizing the number of states. During the Ebola outbreak, social dynamics displayed increased transfers from a breeding to a non‐breeding status for both males and females. Six years after the outbreak, demographic and most of social dynamics parameters had returned to their initial rates, suggesting a certain resilience in the response to disruption. The formation of breeding groups increased just after Ebola, indicating that environmental conditions were still attractive. However, population recovery was likely delayed because compensatory immigration was probably impeded by the potential impact of Ebola in the surrounding areas. The population of undetermined epidemiological status behaved similarly to the other population before Ebola. Our results highlight the need to integrate social dynamics in host‐population demographic models to better understand the role of social structure in the sensitivity and the response to disease disturbances. The authors provide a general framework for studying social dynamics in disturbed contexts and apply it to the case of a gorilla population affected by Ebola.
      PubDate: 2014-07-24T01:02:04.169657-05:
      DOI: 10.1111/1365-2656.12268
       
  • Experimental manipulation of female reproduction demonstrates its fitness
           costs in kangaroos
    • Authors: Uriel Gélin; Michelle E. Wilson, Graeme Coulson, Marco Festa‐Bianchet
      Abstract: When resources are scarce, female mammals should face a trade‐off between lactation and other life‐history traits such as growth, survival and subsequent reproduction. Kangaroos are ideal to test predictions about reproductive costs because they may simultaneously lactate and carry a young, and have indeterminate growth and a long breeding season. An earlier study in three of our five study populations prevented female eastern grey kangaroos (Macropus giganteus) from reproducing during one reproductive season by either inserting contraceptive implants or removing very small pouch young. We explored how individual and environmental variables affect the costs of reproduction over time, combining this experimental reduction of reproductive effort with multi‐year monitoring of 270 marked females. Experimental manipulation should control for individual heterogeneity, revealing the costs of reproduction and their likely sources. We also examined the fitness consequences of reproductive effort and offspring sex among unmanipulated individuals to test whether sex allocation strategies affected trade‐offs. Costs of reproduction included longer inter‐birth intervals and lower probability of producing a young that survived to 7 months in the subsequent reproductive event. Weaning success, however, did not differ significantly between manipulated and control females. By reducing reproductive effort, manipulation appeared to increase individual condition and subsequent reproductive success. Effects of offspring sex upon subsequent reproductive success varied according to year and study population. Mothers of sons were generally more likely to have a young that survived to 7 months, compared to mothers of daughters. The fitness costs of reproduction arise from constraints in both acquisition and allocation of resources. To meet these costs, females delay subsequent parturition and may manipulate offspring sex. Reproductive tactics thus vary according to the amount of resource available to each individual, promoting a wide range in reproductive performance within and among individuals and populations. By combining the first experimental manipulation of reproductive effort in wild marsupials with long‐term monitoring of multiple populations, the authors quantify the fitness consequences of reproduction.
      PubDate: 2014-07-22T10:31:33.609396-05:
      DOI: 10.1111/1365-2656.12266
       
  • Ecological causes of multilevel covariance between size and
           first‐year survival in a wild bird population
    • Authors: Sandra Bouwhuis; Oscar Vedder, Colin J. Garroway, Ben C. Sheldon
      Abstract: Estimates of selection in natural populations are frequent but our understanding of ecological causes of selection, and causes of variation in the direction, strength and form of selection is limited. Here, we apply a multilevel framework to partition effects of great tit fledging mass on first‐year survival to hierarchical levels and quantify their ecological dependence using a data set spanning 51 years. We show that estimates of the effect of fledging mass on first‐year survival decline threefold from year‐ to brood‐ to individual level, so that estimates of selection depend strongly on the level at which they are calculated. We identify variables related to summer and winter food availability as underlying higher‐level effects of fledging mass on first‐year survival and show experimentally that brood‐level effects originate early in development. Further, we show that predation and conspecific density modulate individual‐level effects of fledging mass on first‐year survival. These analyses demonstrate how correlations between traits, fitness and environment influence estimates of selection and show how partitioning trait effects between levels of selection and environmental factors is a promising approach to identify potential agents of selection. The paper demonstrates how correlations between traits, fitness and environment influence estimates of selection, and shows how partitioning trait‐effects between levels of selection and environmental factors is a promising approach to identify potential agents of selection.
      PubDate: 2014-07-17T10:52:20.016296-05:
      DOI: 10.1111/1365-2656.12264
       
  • Impacts of breeder loss on social structure, reproduction and population
           growth in a social canid
    • Authors: Bridget L. Borg; Scott M. Brainerd, Thomas J. Meier, Laura R. Prugh
      Abstract: The importance of individuals to the dynamics of populations may depend on reproductive status, especially for species with complex social structure. Loss of reproductive individuals in socially complex species could disproportionately affect population dynamics by destabilizing social structure and reducing population growth. Alternatively, compensatory mechanisms such as rapid replacement of breeders may result in little disruption. The impact of breeder loss on the population dynamics of social species remains poorly understood. We evaluated the effect of breeder loss on social stability, recruitment and population growth of grey wolves (Canis lupus) in Denali National Park and Preserve, Alaska using a 26‐year dataset of 387 radiocollared wolves. Harvest of breeding wolves is a highly contentious conservation and management issue worldwide, with unknown population‐level consequences. Breeder loss preceded 77% of cases (n = 53) of pack dissolution from 1986 to 2012. Packs were more likely to dissolve if a female or both breeders were lost and pack size was small. Harvest of breeders increased the probability of pack dissolution, likely because the timing of harvest coincided with the breeding season of wolves. Rates of denning and successful recruitment were uniformly high for packs that did not experience breeder loss; however, packs that lost breeders exhibited lower denning and recruitment rates. Breeder mortality and pack dissolution had no significant effects on immediate or longer term population dynamics. Our results indicate the importance of breeding individuals is context dependent. The impact of breeder loss on social group persistence, reproduction and population growth may be greatest when average group sizes are small and mortality occurs during the breeding season. This study highlights the importance of reproductive individuals in maintaining group cohesion in social species, but at the population level socially complex species may be resilient to disruption and harvest through strong compensatory mechanisms. This paper quantitatively evaluates how the death of reproductive individuals in socially complex canid species could affect social group cohesion and population growth.
      PubDate: 2014-07-07T12:34:55.325959-05:
      DOI: 10.1111/1365-2656.12256
       
  • Unravelling the annual cycle in a migratory animal: breeding‐season
           habitat loss drives population declines of monarch butterflies
    • Authors: D. T. Tyler Flockhart; Jean‐Baptiste Pichancourt, D. Ryan Norris, Tara G. Martin
      Abstract: Threats to migratory animals can occur at multiple periods of the annual cycle that are separated by thousands of kilometres and span international borders. Populations of the iconic monarch butterfly (Danaus plexippus) of eastern North America have declined over the last 21 years. Three hypotheses have been posed to explain the decline: habitat loss on the overwintering grounds in Mexico, habitat loss on the breeding grounds in the United States and Canada, and extreme weather events. Our objectives were to assess population viability, determine which life stage, season and geographical region are contributing the most to population dynamics and test the three hypotheses that explain the observed population decline. We developed a spatially structured, stochastic and density‐dependent periodic projection matrix model that integrates patterns of migratory connectivity and demographic vital rates across the annual cycle. We used perturbation analysis to determine the sensitivity of population abundance to changes in vital rate among life stages, seasons and geographical regions. Next, we compared the singular effects of each threat to the full model where all factors operate concurrently. Finally, we generated predictions to assess the risk of host plant loss as a result of genetically modified crops on current and future monarch butterfly population size and extinction probability. Our year‐round population model predicted population declines of 14% and a quasi‐extinction probability (5% within a century. Monarch abundance was more than four times more sensitive to perturbations of vital rates on the breeding grounds than on the wintering grounds. Simulations that considered only forest loss or climate change in Mexico predicted higher population sizes compared to milkweed declines on the breeding grounds. Our model predictions also suggest that mitigating the negative effects of genetically modified crops results in higher population size and lower extinction risk. Recent population declines stem from reduction in milkweed host plants in the United States that arise from increasing adoption of genetically modified crops and land‐use change, not from climate change or degradation of forest habitats in Mexico. Therefore, reducing the negative effects of host plant loss on the breeding grounds is the top conservation priority to slow or halt future population declines of monarch butterflies in North America. Threats to migratory animals occur at multiple periods of the annual cycle that are separated by thousands of kilometers and span international borders. Using a year‐round population model, we show that population declines of monarch butterflies result from loss of breeding habitats in the United States, not from loss of wintering habitats in Mexico.
      PubDate: 2014-06-25T05:32:12.807958-05:
      DOI: 10.1111/1365-2656.12253
       
  • Ecological divergence among colour morphs mediated by changes in spatial
           network structure associated with disturbance
    • Authors: Matthew S. Lattanzio; Donald B. Miles
      Abstract: Differences in individual behaviour affect social interactions and contribute to the spatial structuring of animal populations. However, disturbance should also affect spatial networks by altering habitat heterogeneity and resource availability. Variation in resource availability should perturb the frequency and nature of social and ecological interactions within a population by affecting the spatial distribution of individuals. In disturbed habitats where resources are limiting, spatial relationships should reflect behavioural differences among individuals, with higher‐quality resources controlled by dominant individuals. In contrast, all individuals may exploit preferred resources in resource‐rich habitats. Environmental variation and population reorganization may also result in variation in morphological, behavioural and ecological traits, which ultimately affect fitness. We addressed these considerations for male tree lizards (Urosaurus ornatus) at three sites that differ in levels of disturbance. The habitats at these localities differed in the availability of live trees, the preferred microhabitat of U. ornatus. In addition, male U. ornatus exhibits a polymorphism in dewlap colour linked with differences in aggression, which should influence their position in a network and access to resources. We applied a network framework to characterize the spatial organization of male morphs at each site and quantified male aggressive behaviour in the laboratory. We also compared body size, body condition, number of bite marks, parasite load and the microhabitat use and diet, of males among the sites. We detected no significant differences in spatial network structure between unburned and infrequently burned sites. However, at a frequently burned site, the network shifted towards geographically closer, heteromorphic male neighbour associations. Males at this site were also larger, more aggressive and had more bite marks but fewer parasites than males at the other sites. Moreover, we detected divergence in microhabitat use and diet among the morphs at the frequently burned site that reflected the shift in spatial network structure and differences in morph behaviour. That is, only more aggressive morphs usurped trees and consumed prey from higher trophic levels. We conclude that environmental variation may influence animal spatial network structure. Jointly, behavioural and environmental variation may promote despotic social dynamics and ecological divergence in resource‐limited habitats. Our study provides unique insight into how environmental variation resulting from disturbance may interact with variation in individual behaviour to influence the spatial structuring of animal populations. We highlight some of the key social and ecological ramifications of this interaction for populations in resource‐limited habitats.
      PubDate: 2014-06-24T02:31:58.588541-05:
      DOI: 10.1111/1365-2656.12252
       
  • Why is eusociality an almost exclusively terrestrial phenomenon'
    • Authors: Graeme D. Ruxton; Stuart Humphries, Lesley J. Morrell, David M. Wilkinson
      Abstract: Eusociality has evolved multiple times across diverse terrestrial taxa, and eusocial species fundamentally shape many terrestrial ecosystems. However, eusocial species are far less common and have much less ecological impact, in aquatic than terrestrial environments. Here, we offer a potential explanation for these observations. It appears that a precondition for the evolution of eusociality is the defence and repeated feeding of offspring in a nest or other protected cavity, and so eusocial species must be able to exploit a predator‐safe, long‐lasting (multigenerational) expandable nest. We argue that a range of factors mean that opportunities for such nests are much more widespread and the advantages more compelling in terrestrial than aquatic ecosystems. In this thought‐provoking forum paper, the authors discuss the strange observation that while social insects such as ants, termites, bees and wasps play large roles in terrestrial ecosystems, truly social taxa are far less common in aquatic environments.
      PubDate: 2014-06-24T02:16:37.06241-05:0
      DOI: 10.1111/1365-2656.12251
       
  • Life-history trade-offs mediate ‘personality’ variation in two
           colour morphs of the pea aphid, Acyrthosiphon pisum
    • Authors: W. Schuett; S.R.X. Dall, M.H. Kloesener, J. Baeumer, F. Beinlich, T. Eggers
      Pages: n/a - n/a
      Abstract: (1) Life-history trade-offs are considered a major driving force in the emergence of consistent behavioural differences (personality variation); but empirical tests are scarce. (2) We investigated links between a personality trait (escape response), life-history and state variables (growth rate, size and age at first reproduction, age-dependent reproductive rates, lifetime reproductive success, lifespan) in red and green colour morphs of clonal pea aphids, Acyrthosiphon pisum. Escape response (dropping/non-dropping off a plant upon a predatory attack) was measured repeatedly to classify individuals as consistent droppers, consistent non-droppers or inconsistents. (3) Red morphs experienced stronger trade-offs between early reproduction and lifespan than green morphs; and red consistent (non-)droppers had highest lifetime reproductive success. Red droppers followed a risk-averse life-history strategy (high late reproduction), red non-droppers a risk-prone strategy (high early reproduction), while reproductive rates were equivalent for all green behavioural types and red inconsistents. (4) This suggests that red morphs suffer the highest costs of dropping (they are most conspicuous to predators), which ‘equivalates’ fitness payoffs to both risk-takers (red non-droppers) and risk-averse red droppers. The strong trade-off also means that committing to a particular lifestyle (being consistent) maximises fitness. (5) Our study suggests that life-history trade-offs likely mediate personality variation but effects might depend on interactions with other organismal characteristics (here: colour morph). This article is protected by copyright. All rights reserved.
      PubDate: 2014-06-18T22:47:26.75794-05:0
      DOI: 10.1111/1365-2656.12263
       
  • Species undersampling in tropical bat surveys: effects on emerging
           biodiversity patterns
    • Authors: Christoph F. J. Meyer; Ludmilla M. S. Aguiar, Luis F. Aguirre, Julio Baumgarten, Frank M. Clarke, Jean-François Cosson, Sergio Estrada Villegas, Jakob Fahr, Deborah Faria, Neil Furey, Mickaël Henry, Richard K. B. Jenkins, Thomas H. Kunz, M. Cristina MacSwiney Gonzalez, Isabel Moya, Jean-Marc Pons, Paul A. Racey, Katja Rex, Erica M. Sampaio, Kathryn E. Stoner, Christian C. Voigt, Dietrich Staden, Christa D. Weise, Elisabeth K. V. Kalko
      Pages: n/a - n/a
      Abstract: 1. Undersampling is commonplace in biodiversity surveys of species-rich tropical assemblages in which rare taxa abound, with possible repercussions for our ability to implement surveys and monitoring programs in a cost-effective way. 2. We investigated the consequences of information loss due to species undersampling (missing subsets of species from the full species pool) in tropical bat surveys for the emerging patterns of species richness and compositional variation across sites. 3. For 27 bat assemblage datasets from across the tropics, we used correlations between original datasets and subsets with different numbers of species deleted either at random, or according to their rarity in the assemblage, to assess to what extent patterns in species richness and composition in data subsets are congruent with those in the initial dataset. We then examined to what degree high sample representativeness (r ≥ 0.8) was influenced by biogeographic region, sampling method, sampling effort, or structural assemblage characteristics. 4. For species richness, correlations between random subsets and original datasets were strong (r ≥ 0.8) with moderate (ca. 20%) species loss. Bias associated with information loss was greater for species composition; on average ca. 90% of species in random subsets had to be retained to adequately capture among-site variation. For non-random subsets, removing only the rarest species (on average ~10% of the full dataset) yielded strong correlations (r> 0.95) for both species richness and composition. Eliminating greater proportions of rare species resulted in weaker correlations and large variation in the magnitude of observed correlations among datasets. 5. Species subsets that comprised ca. 85% of the original set can be considered reliable surrogates, capable of adequately revealing patterns of species richness and temporal or spatial turnover in many tropical bat assemblages. Our analyses thus demonstrate the potential as well as limitations for reducing survey effort and streamlining sampling protocols, and consequently for increasing the cost-effectiveness in tropical bat surveys or monitoring programs. The dependence of the performance of species subsets on structural assemblage characteristics (total assemblage abundance, proportion of rare species), however, underscores the importance of adaptive monitoring schemes and of establishing surrogate performance on a site-by-site basis based on pilot surveys. This article is protected by copyright. All rights reserved.
      PubDate: 2014-06-18T22:47:25.025463-05:
      DOI: 10.1111/1365-2656.12261
       
  • Climate and the landscape of fear in an African savanna
    • Authors: Corinna Riginos
      Pages: n/a - n/a
      Abstract: 1.Herbivores frequently have to make tradeoffs between two basic needs: the need to acquire forage and the need to avoid predation. One manifestation of this tradeoff is the “landscape of fear” phenomenon – wherein herbivores avoid areas of high perceived predation risk even if forage is abundant or of high quality in those areas. Although this phenomenon is well-established among invertebrates, its applicability to terrestrial large herbivores remains debated, in part because experimental evidence is scarce. 2.This study was designed to (a) experimentally test the effects of tree density – a key landscape feature associated with predation risk for African ungulates – on herbivore habitat use, and (b) establish whether habitat use patterns could be explained by tradeoffs between foraging opportunities and predation risk-avoidance. 3.In a Kenyan savanna system, replicate plots dominated by the tree Acacia drepanolobium were cleared, thinned, or left intact. Ungulate responses were measured over four years, which included years of moderate rainfall as well as a severe drought. 4.Under average rainfall conditions, most herbivores (primarily plains zebra, Grant's gazelle, and hartebeest) favored sites with fewer trees and higher visibility – regardless of grass production – while elephants (too large to be vulnerable to predation) favored sites with many trees. During the drought, however, herbivores favored sites that had high grass biomass, but not high visibility. Thus, during the drought, herbivores sought areas where food was more abundant, despite probable higher risk of predation. 5.These results illustrate that the “landscape of fear”, and the associated interactions between top-down and bottom-up effects, is not static, but rather shifts markedly under different conditions. Climate thus has the potential to alter the strength and spatial dynamics of behaviorally-mediated cascades in large herbivore systems. This article is protected by copyright. All rights reserved.
      PubDate: 2014-06-18T10:48:00.244796-05:
      DOI: 10.1111/1365-2656.12262
       
  • Multi‐taxa trait and functional responses to physical disturbance
    • Authors: Scott M. Pedley; Paul M. Dolman
      Abstract: Examining assemblage trait responses to environmental stressors extends our understanding beyond patterns of taxonomic diversity and composition, with results potentially transferable among bioregions. But the degree to which trait responses may be generalized across taxonomic groups remains incompletely understood. We compared trait responses among carabids, spiders and plants to an experimentally manipulated gradient of physical disturbance, replicated in open habitats within a forested landscape. Recolonization of recently disturbed habitats is expected to favour species with traits that promote greater dispersal ability, independent of taxa. We specifically predicted that physical disturbance would increase the representation of carabids with smaller body size, wings or wing dimorphism, spiders able to disperse aerially, and plants with therophyte life‐history and wind‐dispersed seed. We sampled 197 arthropod species (14 738 individuals) and 164 species of plant. The strength of association between each trait and the disturbance intensity was quantified by correlating matrices of species by traits, species abundance by sites and sites by environment, with significance assessed by comparison with a null model. Responses of biological traits varied among taxa but could be consistently interpreted in terms of dispersal ability. Trait shifts for carabid and plant assemblages were as predicted and correspond to those observed in other disturbance regimes. Assemblages after disturbance comprised smaller and winged carabids, and smaller plants with wind‐dispersed seed, consistent with selection for species with better dispersal ability. In contrast, aerial dispersal did not appear important in spider recolonization, instead terrestrial dispersal ability was suggested by the increased abundance of larger‐bodied and cursorial species. However, larger spider body size was also associated with an active‐hunting strategy, also favoured in the post‐disturbance environment. Trait–function linkage differed among taxa and was sometimes diffuse, with covariance among biological traits and the mapping of individual traits to multiple ecological functions. In particular, body size responses reflected correlations with life history, susceptibility to perturbation and dispersal ability that were inconsistent between the two arthropod groups. Selection of traits for assessment should therefore be taxa specific. Generalizations of trait responses across taxa should only be conducted where functional or ecological significance of assembly‐level changes can be understood. This is the first study to contrast trait responses from two diverse terrestrial arthropod groups to those of vascular plants, along a single environmental gradient. The authors show that generalizations of trait response across taxa should be cautious as responses vary among taxa.
      PubDate: 2014-06-18T08:59:02.103907-05:
      DOI: 10.1111/1365-2656.12249
       
  • Growth trajectory influences temperature preference in fish through an
           effect on metabolic rate
    • Authors: Shaun S. Killen
      Abstract: Most animals experience temperature variations as they move through the environment. For ectotherms, in particular, temperature has a strong influence on habitat choice. While well studied at the species level, less is known about factors affecting the preferred temperature of individuals; especially lacking is information on how physiological traits are linked to thermal preference and whether such relationships are affected by factors such feeding history and growth trajectory. This study examined these issues in the common minnow Phoxinus phoxinus, to determine the extent to which feeding history, standard metabolic rate (SMR) and aerobic scope (AS), interact to affect temperature preference. Individuals were either: 1) food deprived (FD) for 21 days, then fed ad libitum for the next 74 days; or 2) fed ad libitum throughout the entire period. All animals were then allowed to select preferred temperatures using a shuttle‐box, and then measured for SMR and AS at 10 °C, estimated by rates of oxygen uptake. Activity within the shuttle‐box under a constant temperature regime was also measured. In both FD and control fish, SMR was negatively correlated with preferred temperature. The SMR of the FD fish was increased compared with the controls, probably due to the effects of compensatory growth, and so these growth‐compensated fish preferred temperatures that were on average 2·85 °C cooler than controls fed a maintenance ration throughout the study. Fish experiencing compensatory growth also displayed a large reduction in activity. In growth‐compensated fish and controls, activity measured at 10 °C was positively correlated with preferred temperature. Individual fish prefer temperatures that vary predictably with SMR and activity level, which are both plastic in response to feeding history and growth trajectories. Cooler temperatures probably allow individuals to reduce maintenance costs and divert more energy towards growth. A reduction in SMR at cooler temperatures, coupled with a decrease in spontaneous activity, could also allow individuals to increase surplus AS for coping with environmental stressors. In warming climates, however, aquatic ectotherms could experience frequent fluctuations in food supply with long‐lasting effects on metabolic rate due to compensatory growth, while simultaneously having limited access to preferred cooler habitats. This study demonstrates for the first time that dietary history and growth trajectory influence preferred temperatures of fish, with the underlying cause being the effect of compensatory growth on individual metabolic rate. As a consequence, even in regularly growing fish, increased resting metabolic demand causes a preference for cooler environments
      PubDate: 2014-06-17T10:30:55.078166-05:
      DOI: 10.1111/1365-2656.12244
       
  • The number of competitor species is unlinked to sexual dimorphism
    • Authors: Shai Meiri; Amy E. Kadison, Maria Novosolov, Panayiotis Pafilis, Johannes Foufopoulos, Yuval Itescu, Pasquale Raia, Daniel Pincheira‐Donoso
      Abstract: Sexual size dimorphism (SSD) can allow males and females of the same species to specialize on different sized food items and therefore minimize intraspecific competition. Interspecific competition, however, is thought to limit sexual dimorphism, as larger competitors in the community will prevent the larger sex from evolving larger size, and smaller species may prevent the smaller sex from becoming even smaller. We tested this prediction using data on the sexual size dimorphism of lizards, and mammalian carnivores, on islands world‐wide. Because insular communities are depauperate, and guilds are species‐poor, it is often assumed that enhanced sexual size dimorphism is common on islands. The intensity of interspecific competition, hindering enhanced dimorphism, is thought to increase with competitor richness. We tested whether intraspecific sexual size dimorphism of mammalian carnivores and lizards decreases with increasing island species richness. We further computed the average sexual dimorphism of species on islands and tested whether species‐rich islands are inhabited by relatively monomorphic species. Within families and guilds across carnivores and lizards, and with both intraspecific and interspecific approaches, we consistently failed to find support for the notion that species‐poor islands harbour more sexually dimorphic individuals or species. We conclude that either interspecific competition does not affect the sexual size dimorphism of insular lizards and carnivores (i.e. character displacement and species sorting are rare in these taxa), or that the number of species in an assemblage or guild is a poor proxy for the intensity of interspecific competition in insular assemblages. Sexual size dimorphism within three lizard species does not change with the number of putative competitors they face on different‐sized islands in the Aegean Sea. We found, counter to expected ecological theory, sexual dimorphism does not diminish as guilds acquire more species.
      PubDate: 2014-06-16T06:32:22.025131-05:
      DOI: 10.1111/1365-2656.12248
       
  • Prevalence and beta diversity in avian malaria communities: host species
           is a better predictor than geography
    • Authors: Elizabeth S. C. Scordato; Melissa R. Kardish
      Abstract: Patterns of diversity and turnover in macroorganism communities can often be predicted from differences in habitat, phylogenetic relationships among species and the geographical scale of comparisons. In this study, we asked whether these factors also predict diversity and turnover in parasite communities. We studied communities of avian malaria in two sympatric, ecologically similar, congeneric host species at three different sites. We asked whether parasite prevalence and community structure varied with host population, host phylogeography or geographical distance. We used PCR to screen birds for infections and then used Bayesian methods to determine phylogenetic relationships among malaria strains. Metrics of both community and phylogenetic beta diversity were used to examine patterns of malaria strain turnover between host populations, and partial Mantel tests were used determine the correlation between malaria beta diversity and geographical distance. Finally, we developed microsatellite markers to describe the genetic structure of host populations and assess the relationship between host phylogeography and parasite beta diversity. We found that different genera of malaria parasites infect the two hosts at different rates. Within hosts, parasite communities in one population were phylogenetically clustered, but there was otherwise no correlation between metrics of parasite beta diversity and geographical or genetic distance between host populations. Patterns of parasite turnover among host populations are consistent with malaria transmission occurring in the winter rather than on the breeding grounds. Our results indicate greater turnover in parasite communities between different hosts than between different study sites. Differences in host species, as well as transmission location and vector ecology, seem to be more important in structuring malaria communities than the distance–decay relationships frequently found in macroorganisms. Determining the factors affecting parasite community diversity and turnover has wide‐ranging implications for understanding the selective pressures shaping host ecology and ecosystem structure. This study shows that metrics of community and phylogenetic beta diversity can be useful tools for disentangling the ecological and evolutionary processes that underlie geographical variation in parasite communities. This paper uses measures of phylogenetic and community beta diversity to show that host species is a better predictor of malaria community turnover than site, providing no evidence for a distance–decay relationship in these parasite communities.
      PubDate: 2014-06-16T06:32:04.435173-05:
      DOI: 10.1111/1365-2656.12246
       
  • Relationship between growth and standard metabolic rate: measurement
           artefacts and implications for habitat use and life-history adaptation in
           salmonids
    • Authors: Jordan Rosenfeld; Travis Leeuwen, Jeffrey Richards, David Allen
      Pages: n/a - n/a
      Abstract: 1) Mass-specific standard metabolic rate (SMR, or maintenance metabolism) varies greatly among individuals. Metabolism is particularly sensitive to variation in food consumption and growth creating the potential for significant bias in measured SMR for animals that are growing (e.g. juveniles) or of uncertain nutritional status. 2) Consequently, interpreting individual variation in metabolism requires a sound understanding of the potentially confounding role of growth, and the relative importance of fixed (genetic) vs. environmental drivers of SMR variation. 3) We review the role of growth in measured SMR variation in juvenile salmonids, with the goals of i) understanding the contribution of growth (and food consumption) to SMR variation through ontogeny, ii) understanding the relative contributions of tissue maintenance and biosynthesis (overhead costs of growth) to apparent SMR variation, and iii) using intrinsic growth effects on SMR to model how alternate life-history strategies may influence growth and measured SMR in juvenile salmonids. 3) SMR measures on juveniles, even when post-absorptive, may be inflated by delayed growth-associated overhead costs unless juveniles are on a maintenance ration (i.e. not growing). Empirical measurements of apparent SMR in food restricted vs. satiated 2 to 5 g juvenile salmon demonstrate that estimates may be inflated by as much as 67% due to delayed overhead costs of growth, even when SMR measurements are made 35 hours post-feeding. 4) These results indicate that a substantial component of variation in apparent SMR among juvenile salmonids may be associated with i) environmentally-driven variation in ration (where elevated SMR measurements are an artefact of delayed growth overhead costs), ii) intrinsic (genetic) or plastic organ system tradeoffs related to increasing investment in metabolically expensive digestive tissue responsible for processing food, and iii) intrinsic (genetic) variation in maximum body size and growth among individuals or life-history types. We suggest that selection for differences in adult body size among resident and anadromous forms leading to differences in juvenile growth trajectories may contribute to both SMR variation and habitat segregation in freshwater, where juveniles with higher growth are constrained to foraging in high velocity habitats to meet their greater consumption needs. This article is protected by copyright. All rights reserved.
      PubDate: 2014-06-16T02:30:46.877771-05:
      DOI: 10.1111/1365-2656.12260
       
  • Fitness prospects: effects of age, sex and recruitment age on reproductive
           value in a long-lived seabird
    • Authors: He Zhang; Maren Rebke, Peter H. Becker, Sandra Bouwhuis
      Pages: n/a - n/a
      Abstract: (1) Reproductive value is an integrated measure of survival and reproduction fundamental to understanding life-history evolution and population dynamics, but little is known about intra-specific variation in reproductive value and factors explaining such variation, if any. (2) By applying generalized additive mixed models to longitudinal individual-based data of the common tern Sterna hirundo we estimated age-specific annual survival probability, breeding probability and reproductive performance, based on which we calculated age-specific reproductive values. We investigated effects of sex and recruitment age on each trait. (3) We found age effects on all traits, with survival and breeding probability declining with age, while reproductive performance first improved with age before levelling off. We only found a very small, marginally significant, sex-effect on survival probability, but evidence for decreasing age-specific breeding probability and reproductive performance with recruitment age. (4) As a result, males had slightly lower age-specific reproductive values than females, while birds of both sexes that recruited at the earliest ages of 2 and 3 years (i.e. 54% of the tern population) had somewhat higher fitness prospects than birds recruiting at later ages. While the recruitment age effects on breeding probability and reproductive performance were statistically significant, these effects were not large enough to translate to significant effects on reproductive value. (5) Age-specific reproductive values provided evidence for senescence, which came with fitness costs in a range of 17-21% for the sex-recruitment age groups. (6) Our study suggests that intra-specific variation in reproductive value may exist, but that, in the common tern, the differences are small. This article is protected by copyright. All rights reserved.
      PubDate: 2014-06-16T02:30:01.074599-05:
      DOI: 10.1111/1365-2656.12259
       
  • A continental scale trophic cascade from wolves through coyotes to foxes
    • Authors: Thomas M Newsome; William J Ripple
      Pages: n/a - n/a
      Abstract: Top-down processes, via the direct and indirect effects of interspecific competitive killing (no consumption of the kill) or intraguild predation (consumption of the kill), can potentially influence the spatial distribution of terrestrial predators, but few studies have demonstrated the phenomenon at a continental scale. For example, in North America, grey wolves (Canis lupus) are known to kill coyotes (Canis latrans), and coyotes, in turn, may kill foxes (Vulpes spp.), but the spatial effects of these competitive interactions at large scales are unknown. Here, we analyse fur return data across eight jurisdictions in North America to test whether the presence or absence of wolves has caused a continent-wide shift in coyote and red fox (Vulpes vulpes) density. Our results support the existence of a continental scale cascade whereby coyotes outnumber red foxes in areas where wolves have been extirpated by humans, whereas red foxes outnumber coyotes in areas where wolves are present. However, for a distance of up to 200 km on the edge of wolf distribution, there is a transition zone where the effects of top-down control are weakened, possibly due to the rapid dispersal and reinvasion capabilities of coyotes into areas where wolves are sporadically distributed or at low densities. Our results have implications for understanding how the restoration of wolf populations across North America could potentially affect co-occurring predators and prey. We conclude that large carnivores may need to occupy large continuous areas to facilitate among-carnivore cascades and that studies of small areas may not be indicative of the effects of top-down mesopredator control. This article is protected by copyright. All rights reserved.
      PubDate: 2014-06-14T10:05:25.254605-05:
      DOI: 10.1111/1365-2656.12258
       
  • Variation in abundance of nectarivorous birds: does a competitive despot
           interfere with flower tracking'
    • Authors: Joanne M. Bennett; Rohan H. Clarke, James R. Thomson, Ralph Mac Nally
      Abstract: Adaptive resource tracking in space and time may be disrupted by the modification of resources and competitors. Major global change drivers (e.g. land‐use change) have induced declines in many native species, while facilitating only a few. Given that many resources are predicted to become increasingly scarce under the joint effects of climate and land‐use change, disturbance‐tolerant species that are able to defend high‐value resources may further limit the persistence of disturbance‐sensitive species. We sought to determine which nectarivorous birds track variation in flowering and if relationships between nectarivores and flowering are affected by on‐transect vegetation structure or the occurrence of a native, hyper‐aggressive species, the noisy miner Manorina melanocephala, which has become more prevalent. We measured eucalypt flowering and abundances of nectarivorous birds over the course of a year; we measured vegetation structure on the same forest transects. Nectarivores tracked spatial and some temporal variation in flowering, but this relationship was disrupted by noisy miners. Where present in sufficient numbers, the noisy miner excluded small‐bodied nectarivores (
      PubDate: 2014-06-09T12:49:50.183662-05:
      DOI: 10.1111/1365-2656.12245
       
  • Ecological generalism and behavioral innovation in birds: technical
           intelligence or the simple incorporation of new foods'
    • Authors: S Ducatez; J Clavel, L Lefebvre
      Abstract: 1.Generalist species are more successful than specialists in anthropogenically‐modified environments or in environments in which they have been introduced, but the nature of the link between generalism and establishment success is unclear. 2.A higher feeding innovation rate has previously been reported in habitat generalist birds from North America. By allowing them to exploit new resources, this higher feeding innovation rate might explain the generalists’ advantage. This result might be due to generalists being more likely to find new resources because they are exposed to more diverse environmental conditions. Alternatively, they might differ from specialists in other traits, in particular cognitive skills that might allow them to innovate more complex food searching and handling techniques. 3.To test these hypotheses, we separated avian feeding innovations into a “technical” (novel searching and handling behavior) and a “food type” (incorporation of a new food in a species’ diet) category. Technical innovations, but not food type innovations, have previously been shown to correlate with avian brain size, suggesting they reflect cognitive ability. We used a worldwide database of 2339 feeding innovations recorded in the literature, covering a total of 765 avian species and assessed the correlations between brain size and feeding innovation rates on one side and habitat and diet generalism on the other. 4.Habitat generalism was positively related with food type innovation rate, but not technical innovation rate or brain size. This suggests that habitat generalist species are more likely to incorporate new food types in their diet because of higher chances to find new food resources in their environment, or of a higher opportunism, but not enhanced cognitive skills. In contrast, diet generalist species had higher food type and technical innovation rates, as well as larger brains, suggesting that cognitive skills might help species expand their diet breadth, or that an increase in diet breadth might favor the evolution of enhanced cognitive abilities. 5.Our results provide new insights into the nature of the generalists’ advantage in the face of environmental changes, and suggest that dietary and habitat generalism are different, but convergent, routes to feeding flexibility and adaptation to changed environments. This article is protected by copyright. All rights reserved.
      PubDate: 2014-06-06T10:17:27.327537-05:
      DOI: 10.1111/1365-2656.12255
       
  • Allometric scaling of indirect effects: Body size ratios predict
           non‐consumptive effects in multi‐predator systems
    • Authors: Lauren Krenek; Volker H.W. Rudolf
      Abstract: 1Non‐consumptive effects (NCES) frequently lead to non‐independent effects of multiple predators. While such emergent predator effects are ubiquitous in natural communities, the strength of these effects varies among studies and systems, making it difficult to predict a priory how changes in predator diversity influence prey suppression. Thus, identifying general scaling rules which can explain this variation of non‐independent effects is vital for modeling natural communities and how they respond to biodiversity loss. 2Body size is a key trait determining the nature and strength of ecological interactions. While great progress has been made using allometric relationships to predict the interaction strength of predator‐prey pairs, it is unknown whether similar relationships explain variation in the strength of NCEs, and how they are related to consumptive effects. 3Here we experimentally manipulate the relative size difference of multiple predators to determine whether NCEs follow general allometric scaling relationships in an aquatic multi‐predator system. 4Results demonstrate that the presence and strength of NCEs can vary dramatically across predator combinations. However, this variation scaled predictably with the size ratio of predators; increasing the size difference among predators increased NCEs. This pattern was driven by a size‐mediated shift in “food web motif” from competition to intraguild predation and a positive correlation of NCEs and intraguild predation rate. 5Results indicate that models which assume that consumers have independent effects are particularly likely to make erroneous predictions when predators differ substantially in size, but simple allometric relationships of NCEs could be used to correct this bias. This article is protected by copyright. All rights reserved.
      PubDate: 2014-06-06T10:17:26.11756-05:0
      DOI: 10.1111/1365-2656.12254
       
  • Overcompensation and phase effects in a cyclic common vole population:
           between first and second‐order cycles
    • Authors: Frédéric Barraquand; Adrien Pinot, Nigel G. Yoccoz, Vincent Bretagnolle
      Abstract: Population cycles in voles are often thought to be generated by one‐year delayed density‐dependence on the annual population growth rate. In common voles, however, it has been suggested by Turchin (2003) that some populations exhibit first‐order cycles, resulting from strong overcompensation (i.e. carrying capacity overshoots in peak years, with only an effect of the current year abundance on annual growth rates). We focus on a common vole (Microtus arvalis) population from western France, that exhibits 3‐year cycles. Several overcompensating nonlinear models for populations dynamics are fitted to the data, notably those of Hassell, and Maynard‐Smith and Slatkin. Overcompensating direct density‐dependence (DD) provides a satisfactory description of winter crashes, and one‐year delayed density‐dependence is not responsible for the crashes, thus these are not classical second‐order cycles. A phase‐driven modulation of direct density‐dependence maintains a low‐phase, explaining why the cycles last three years instead of two. Our analyses suggest that some of this phase‐dependence can be expressed as one‐year delayed DD, but phase‐dependence provides a better description. Hence modelling suggests that cycles in this population are first‐order cycles with a low phase after peaks, rather than fully second‐order cycles. However, based on the popular log‐linear second‐order autoregressive model, we would conclude only that negative delayed density‐dependence exists. The additive structure of this model cannot show when delayed DD occurs (here, during lows rather than peaks). Our analyses thus call into question the automated use of second‐order log‐linear models, and suggests that more attention should be given to non‐(log)linear models when studying cyclic populations. From a biological viewpoint, the fast crashes through overcompensation that we found suggest they might be caused by parasites or food rather than predators, though predators might have a role in maintaining the low phase and spatial synchrony. This article is protected by copyright. All rights reserved.
      PubDate: 2014-06-06T08:37:48.597212-05:
      DOI: 10.1111/1365-2656.12257
       
  • Parasites and genetic diversity in an invasive bumblebee
    • Authors: Catherine M. Jones; Mark J. F. Brown
      Abstract: Biological invasions are facilitated by the global transportation of species and climate change. Given that invasions may cause ecological and economic damage and pose a major threat to biodiversity, understanding the mechanisms behind invasion success is essential. Both the release of non‐native populations from natural enemies, such as parasites, and the genetic diversity of these populations may play key roles in their invasion success. We investigated the roles of parasite communities, through enemy release and parasite acquisition, and genetic diversity in the invasion success of the non‐native bumblebee, Bombus hypnorum, in the United Kingdom. The invasive B. hypnorum had higher parasite prevalence than most, or all native congeners for two high‐impact parasites, probably due to higher susceptibility and parasite acquisition. Consequently parasites had a higher impact on B. hypnorum queens’ survival and colony‐founding success than on native species. Bombus hypnorum also had lower functional genetic diversity at the sex‐determining locus than native species. Higher parasite prevalence and lower genetic diversity have not prevented the rapid invasion of the United Kingdom by B. hypnorum. These data may inform our understanding of similar invasions by commercial bumblebees around the world. This study suggests that concerns about parasite impacts on the small founding populations common to re‐introduction and translocation programs may be less important than currently believed. Using an ecologically and economically important genus of pollinators as a model system, the authors ask how enemy release, at the level of parasite communities and real parasite impact, and functional genetic diversity, contribute to the invasion success of a non‐native bumblebee in the United Kingdom.
      PubDate: 2014-06-03T12:26:49.163985-05:
      DOI: 10.1111/1365-2656.12235
       
  • Effects of spatial structure of population size on the population dynamics
           of barnacles across their elevational range
    • Authors: Keiichi Fukaya; Takehiro Okuda, Masahiro Nakaoka, Takashi Noda
      Abstract: Explanations for why population dynamics vary across the range of a species reflect two contrasting hypotheses: (i) temporal variability of populations is larger in the centre of the range compared to the margins because overcompensatory density dependence destabilizes population dynamics and (ii) population variability is larger near the margins, where populations are more susceptible to environmental fluctuations. In both of these hypotheses, positions within the range are assumed to affect population variability. In contrast, the fact that population variability is often related to mean population size implies that the spatial structure of the population size within the range of a species may also be a useful predictor of the spatial variation in temporal variability of population size over the range of the species. To explore how population temporal variability varies spatially and the underlying processes responsible for the spatial variation, we focused on the intertidal barnacle Chthamalus dalli and examined differences in its population dynamics along the tidal levels it inhabits. Changes in coverage of barnacle populations were monitored for 10·5 years at 25 plots spanning the elevational range of this species. Data were analysed by fitting a population dynamics model to estimate the effects of density‐dependent and density‐independent processes on population growth. We also examined the temporal mean–variance relationship of population size with parameters estimated from the population dynamics model. We found that the relative variability of populations tended to increase from the centre of the elevational range towards the margins because of an increase in the magnitude of stochastic fluctuations of growth rates. Thus, our results supported hypothesis (2). We also found that spatial variations in temporal population variability were well characterized by Taylor's power law, the relative population variability being inversely related to the mean population size. Results suggest that understanding the population dynamics of a species over its range may be facilitated by taking the spatial structure of population size into account as well as by considering changes in population processes as a function of position within the range of the species. This study explores the variability–range relationship of population size by analysing long‐term data of intertidal barnacles collected over their vertical range. Results show a tendency that populations are variable at range margins due to increased stochastic fluctuation in growth rate, as well as an association between population size and its variability.
      PubDate: 2014-06-02T06:56:41.913819-05:
      DOI: 10.1111/1365-2656.12234
       
  • Year‐round effects of climate on demographic parameters of an
           arctic‐nesting goose species
    • Authors: Louise Oudenhove; Gilles Gauthier, Jean‐Dominique Lebreton
      Abstract: Understanding how climate change will affect animal population dynamics remains a major challenge, especially in long‐distant migrants exposed to different climatic regimes throughout their annual cycle. We evaluated the effect of temperature throughout the annual cycle on demographic parameters (age‐specific survival and recruitment, breeding propensity and fecundity) of the greater snow goose (Chen caerulescens atlantica L.), an arctic‐nesting species. As this is a hunted species, we used the theory of exploited populations to estimate hunting mortality separately from natural mortality in order to evaluate climatic effects only on the latter form of mortality. Our analysis was based on a 22‐year marking study (n = 27 150 females) and included live recaptures at the breeding colony and dead recoveries from hunters. We tested the effect of climatic covariates by applying a procedure that accounts for unexplained environmental variation in the demographic parameter to a multistate capture–mark–recapture recruitment model. Breeding propensity, clutch size and hatching probability all increased with high temperatures on the breeding grounds. First‐year survival to natural causes of mortality increased when temperature was high at the end of the summer, whereas adult survival was not affected by temperature. On the contrary, accession to reproduction decreased with warmer climatic conditions during the non‐breeding season. Survival was strongly negatively related to hunting mortality in adults, as expected, but not in first‐year birds, which suggests the possibility of compensation between natural and hunting mortality in the latter group. We show that events occurring both at and away from the breeding ground can affect the demography of migratory birds, either directly or through carryover effects, and sometimes in opposite ways. This highlights the need to account for the whole life cycle of an animal when attempting to project the response of populations to future climatic changes. Understanding how climate changes affect animal populations remains a major challenge, especially in arctic‐nesting migratory birds exposed to different climatic regimes. With a 23‐year data set, this study highlights how temperatures encountered throughout the annual cycle affect the vital rates of the greater snow geese.
      PubDate: 2014-06-02T06:50:28.334468-05:
      DOI: 10.1111/1365-2656.12230
       
  • Mate finding, Allee effects and selection for sex‐biased dispersal
    • Authors: Allison K. Shaw; Hanna Kokko
      Abstract: Although dispersal requires context‐dependent decision‐making in three distinct stages (emigration, transit, immigration), these decisions are commonly ignored in simple models of dispersal. For sexually reproducing organisms, mate availability is an important factor in dispersal decisions. Difficulty finding mates can lead to an Allee effect where population growth decreases at low densities. Surprisingly, theoretical studies on mate finding and on sex‐biased dispersal produce opposing predictions: in the former, one sex is predicted to move less if the other sex evolves to search more, whereas in the latter, mate‐finding difficulties can select for less sex bias in dispersal when mate finding occurs after dispersal. Here, we develop a pair of models to examine the joint evolution of dispersal and settlement behaviour. Our first model resolves the apparent contradiction from the mate search and dispersal literatures. Our second model demonstrates that the relationship between mating system and sex‐biased dispersal is more complex than a simple contrast between resource defence monogamy and female defence polygyny. Our results highlight that a key factor is the timing of mating relative to dispersal (before, during, or after). We also show that although movement has the potential to alleviate a mate‐finding Allee effect, in some cases, it can actually exacerbate the effect. This article resolves contradicting predictions from the mate search and dispersal literatures about correlation between male and female dispersal and demonstrates that sex bias in dispersal depends on when mating occurs during the dispersal process.
      PubDate: 2014-06-02T06:34:49.960446-05:
      DOI: 10.1111/1365-2656.12232
       
  • Exotic birds increase generalization and compensate for native bird
           decline in plant–frugivore assemblages
    • Authors: Daniel García; Daniel Martínez, Daniel B. Stouffer, Jason M. Tylianakis
      Abstract: Exotic species are thought to alter the structure of natural communities and disrupt ecosystem functioning through invasion. Nevertheless, exotic species may also provide ecological insurance when they contribute to maintain ecosystem functions after the decline of native species following anthropogenic disturbance. Here, this hypothesis is tested with the assemblage of frugivorous birds and fleshy‐fruited plants of New Zealand, which has suffered strong historical declines in native birds while simultaneously gaining new frugivores introduced by European settlers. We studied the plant–frugivore assemblage from measures of fruit and bird abundances and fruit consumption in nine forest patches, and tested how this changed across a gradient of relative abundance of exotic birds. We then examined how each bird species' role in the assemblage (the proportion of fruits and the number of plant species consumed) varied with their relative abundance, body size and native/exotic status. The more abundant and, to a lesser extent, larger birds species consumed a higher proportion of fruits from more plant species. Exotic birds consumed fruits less selectively and more proportionate to the local availability than did native species. Interaction networks in which exotic birds had a stronger role as frugivores had higher generalization, higher nestedness and higher redundancy of plants. Exotic birds maintained frugivory when native birds became rarer, and diversified the local spectrum of frugivores for co‐occurring native plants. These effects seemed related to the fact that species abundances, rather than trait‐matching constraints, ultimately determined the patterns of interactions between birds and plants. By altering the structure of plant–frugivore assemblages, exotic birds likely enhance the stability of the community‐wide seed dispersal in the face of continued anthropogenic impact. This study shows that the stronger the integration of exotic birds in the frugivore assemblages of New Zealand, the higher the degree of generalization of plant–frugivore networks. By diversifying the frugivore guild for native plants, exotic birds may increase the resilience of seed dispersal against native bird extinction (Artwork by Daniel Martinez).
      PubDate: 2014-06-02T06:34:47.371296-05:
      DOI: 10.1111/1365-2656.12237
       
  • Does variation in the intensity and duration of predation drive
           evolutionary changes in senescence'
    • Authors: Matthew R. Walsh; Deirdre Whittington, Melissa J. Walsh
      Abstract: The evolutionary theory of senescence predicts that increased rates of extrinsic mortality select for faster declines in fertility and survival with age. One predicted mechanism is that increased mortality favours alleles that enhance fitness early in life at the expense of survival or reproduction later in life (antagonistic pleiotropy). We tested these predictions in natural populations of Daphnia ambigua from lakes that vary in the severity and duration of fish predation. Daphnia are found in lakes with (i) anadromous alewife (Alosa pseudoharengus) that migrate between marine and freshwater, (ii) permanent landlocked alewife and (iii) no alewife. Daphnia are rare year‐round in ‘landlocked lakes’ and are seasonally eliminated from the water column in ‘anadromous lakes’ due to the very strong predatory impact of anadromous alewife on populations of zooplankton. Previous work has also shown that intense seasonal bouts of predation by anadromous alewife has selected for increased allocation towards growth and reproduction in Daphnia found in lakes with anadromous alewife. Such variation in the risk of mortality and the expression of life‐history traits early in life provides the raw materials to test the evolutionary theory of ageing. We reared replicate populations of Daphnia from all three lake types and quantified lifetime rates of offspring production and intrinsic survival. We found no differences in age‐related declines in fertility or survival. Daphnia from anadromous lakes produced significantly more offspring throughout their lifetime despite no differences in life span or in the number of reproductive bouts compared with Daphnia from lakes with landlocked and no alewife. The lack of divergence in ageing contradicts the prediction that elevated mortality rates drive evolutionary shifts in ageing. We reconcile these results by considering the predictions of theoretical frameworks that incorporate feedbacks associated with increased mortality such as density‐ and condition‐dependent processes. Our results, which are better explained by a consideration of these processes, thus call for a greater consideration of models that more explicitly consider the ecology of focal organisms. This is a rare test of the evolutionary theory of senescence, evaluating the importance of predation on ageing and showing that increased mortality does not select for faster ageing. Such results challenge our current understanding of the importance of predation on senescence.
      PubDate: 2014-05-28T11:57:58.523147-05:
      DOI: 10.1111/1365-2656.12247
       
  • Special structures of hoopoe eggshells enhance the adhesion of
           symbiont‐carrying uropygial secretion that increase hatching success
           
    • Authors: Manuel Martín‐Vivaldi; Juan J. Soler, Juan M. Peralta‐Sánchez, Laura Arco, Antonio M. Martín‐Platero, Manuel Martínez‐Bueno, Magdalena Ruiz‐Rodríguez, Eva Valdivia
      Abstract: Animals live in a bacterial world, and detecting and exploring adaptations favouring mutualistic relationships with antibiotic‐producing bacteria as a strategy to fight pathogens are of prime importance for evolutionary ecologists. Uropygial secretion of European hoopoes (Upupa epops, Linnaeus) contains antimicrobials from mutualistic bacteria that may be used to prevent embryo infection. Here, we investigated the microscopic structure of hoopoe eggshells looking for special features favouring the adhesion of antimicrobial uropygial secretions. We impeded female access to the uropygial gland and compared microscopic characteristics of eggshells, bacterial loads of eggs and of uropygial secretion, and hatching success of experimental and control females. Then, we explored the link between microbiological characteristics of uropygial secretion and these of eggs of hoopoes, as well as possible fitness benefits. The microscopic study revealed special structures in hoopoes' eggshells (crypts). The experimental prevention of females' gland access demonstrated that crypts are filled with uropygial secretion and that symbiotic enterococci bacteria on the eggshells come, at least partially, from those in the female's uropygial gland. Moreover, the experiment resulted in a higher permeability of eggshells by several groups of bacteria and in elimination of the positive relationships detected for control nests between hatching success and density of symbiotic bacteria, either in the uropygial secretion of females or on the eggshell. The findings of specialized crypts on the eggshells of hoopoes, and of video‐recorded females smearing secretion containing symbiotic bacteria at a high density onto the eggshells strongly support a link between secretion and bacteria on eggs. Moreover, the detected associations between bacteria and hatching success suggest that crypts enhancing the adhesion of symbiont‐carrying uropygial secretion likely protect embryos against infections. This study provides strong evidence of a mutualistic association between hoopoes and antibiotic producing bacteria, whereby the bacteria protect embryos against infection. Video
      PubDate: 2014-05-28T11:56:15.95679-05:0
      DOI: 10.1111/1365-2656.12243
       
  • Temperature‐dependent variation in alternative migratory tactics and
           its implications for fitness and population dynamics in a salmonid fish
    • Authors: Kentaro Morita; Tsuyoshi Tamate, Mari Kuroki, Toru Nagasawa
      Abstract: Temperature‐driven life‐history modifications by adaptation occur in ectotherms, and therefore, life‐history modifications by adaptation need to be taken into consideration when predicting population responses to the climate change. Partial migration is a common form of life‐history diversity in which a population contains both migratory and resident behaviours. Salmonid fish exhibit a wide range of life‐history diversity and, in particular, partial migration. We evaluated the effect of temperature‐driven life‐history modifications on population dynamics in partially migratory masu salmon (Oncorhynchus masou) by field observations and theoretical models. Field observations revealed that spatial patterns of alternative migratory tactics were associated with temperature gradients. The occurrence of resident males increased, whereas the proportion of migrant males and the proportion of delayed migrants including both sexes decreased with increasing temperature and, thereby, with improved early growth conditions. The expected fitness for each migratory tactic was computed in a life‐history model with early growth conditions as a function. Individual fitness was maximized by adopting resident tactics under favourable early growth conditions, early migrant tactics under intermediate early growth conditions and delayed migrant tactics under unfavourable early growth conditions. The results suggest that individuals exhibited a status‐dependent conditional strategy, that is, the adoption of alternative migratory tactics is influenced by the status of individuals to make the best of a situation. A simulation model suggests that increased residency by males to increased temperature leads to a substantial decrease in the number of migrants. Moreover, the decrease in the number of delayed (older) migrants with increasing temperature magnified fluctuations in abundance. Our findings indicate the importance of temperature‐driven life‐history modifications for predicting dynamics of natural populations under climate warming. This study showed that the proportion of male masu salmon exhibiting migratory behavior decreased with increasing temperature. Additionally, the occurrence of delayed age at migration decreased with increasing temperature. These responses to increased temperature are explained by an adaptation to maximize fitness.
      PubDate: 2014-05-27T05:58:32.49975-05:0
      DOI: 10.1111/1365-2656.12240
       
  • Forest structure drives global diversity of primates
    • Authors: Sidney F. Gouveia; Fabricio Villalobos, Ricardo Dobrovolski, Raone Beltrão‐Mendes, Stephen F. Ferrari
      Abstract: Geographic gradients in the species richness of non‐human primates have traditionally been attributed to the variation in forest productivity (related to precipitation levels), although an all‐inclusive, global‐scale analysis has never been conducted. We perform a more comprehensive test on the role of precipitation and biomass production and propose an alternative hypothesis – the variation in vertical structure of forest habitats as measured by forest canopy height – in determining primate species richness on a global scale. Considering the potential causal relationships among precipitation, productivity and forest structure, we arranged these variables within a path framework to assess their direct and indirect associations with the pattern of primate species richness using structural equation modelling. The analysis also accounted for the influence of spatial autocorrelation in the relationships and assessed possible historical differences among biogeographical regions. The path coefficients indicate that forest canopy height (used as a proxy for vertical forest structure) is a better predictor of primate species richness than either precipitation or productivity on both global and continental scales. The only exception was Asia, where precipitation prevailed, albeit independently from productivity or forest structure. The influence of spatially structured processes varied markedly among biogeographical regions. Our results challenge the traditional rainfall‐based viewpoint in favour of forest distribution and structure as primary drivers of primate species richness, which aggregate potential effects from both climatic factors and habitat complexity. These findings may support predictions of the impact of forest removal on primate species richness. This study provides a novel account on the likely causes of the global pattern of primate species richness, namely the vertical forest structure, thus challenging previous hypothesis based on levels of rainfall or productivity.
      PubDate: 2014-05-27T05:50:25.731381-05:
      DOI: 10.1111/1365-2656.12241
       
  • Trait‐based diet selection: Prey behaviour and morphology predict
           vulnerability to predation in reef fish communities
    • Authors: Stephanie J. Green; Isabelle M. Côté
      Abstract: 1.Understanding how predators select their prey can provide important insights into community structure and dynamics. However, the suite of prey species available to a predator is often spatially and temporally variable. As a result, species‐specific selectivity data are of limited use for predicting novel predator‐prey interactions because they are assemblage‐specific. 2.We present a method for predicting diet selection that is applicable across prey assemblages, based on identifying general morphological and behavioural traits of prey that confer vulnerability to predation independent of species identity. We apply this trait‐based approach to examining prey selection by Indo‐Pacific lionfish (Pterois volitans), an invasive predator that preys upon species‐rich reef fish communities and is rapidly spreading across the Western Atlantic. 3.We first generate hypotheses about morphological and behavioural traits recurring across fish species that could facilitate or deter predation by lionfish. Constructing generalised linear mixed‐models that account for relatedness among prey taxa, we test whether these traits predict patterns of diet selection by lionfish within two independent data sets collected at different spatial scales: 1) in situ visual observations of prey consumption and availability for individual lionfish, and (2) comparisons of prey abundance in lionfish stomach contents to availability in invaded reefs at large. 4.Both analyses reveal that a number of traits predicted to affect vulnerability to predation, including body size, body shape, position in the water column and aggregation behaviour, are important determinants of diet selection by lionfish. Small, shallow‐bodied solitary fishes found resting on or just above reefs are the most vulnerable. Fishes that exhibit parasite cleaning behaviour experience a significantly lower risk of predation than non‐cleaning fishes, and fishes that are nocturnally active are at significantly greater risk. Together, vulnerable traits heighten the risk of predation by a factor of nearly 200. 5.Our study reveals that a trait‐based approach to studying diet selection yields insights into predator‐prey interactions that are robust across prey assemblages. Importantly, in situ observations of selection yield similar results to broad‐scale comparisons of prey use and availability, which are more typically gathered for predator species. A trait‐based approach could therefore be of use across predator species and ecosystems to predict the outcomes of changing predator‐prey interactions on community dynamics. This article is protected by copyright. All rights reserved.
      PubDate: 2014-05-24T10:36:29.250758-05:
      DOI: 10.1111/1365-2656.12250
       
  • Density‐dependent intraspecific aggression regulates survival in
           northern Yellowstone wolves (Canis lupus)
    • Authors: Sarah Cubaynes; Daniel R. MacNulty, Daniel R. Stahler, Kira A. Quimby, Douglas W. Smith, Tim Coulson
      Abstract: Understanding the population dynamics of top‐predators is essential to assess their impact on ecosystems and to guide their management. Key to this understanding is identifying the mechanisms regulating vital rates. Determining the influence of density on survival is necessary to understand the extent to which human‐caused mortality is compensatory or additive. In wolves (Canis lupus), empirical evidence for density‐dependent survival is lacking. Dispersal is considered the principal way in which wolves adjust their numbers to prey supply or compensate for human exploitation. However, studies to date have primarily focused on exploited wolf populations, in which density‐dependent mechanisms are likely weak due to artificially low wolf densities. Using 13 years of data on 280 collared wolves in Yellowstone National Park, we assessed the effect of wolf density, prey abundance and population structure, as well as winter severity, on age‐specific survival in two areas (prey‐rich vs. prey‐poor) of the national park. We further analysed cause‐specific mortality and explored the factors driving intraspecific aggression in the prey‐rich northern area of the park. Overall, survival rates decreased during the study. In northern Yellowstone, density dependence regulated adult survival through an increase in intraspecific aggression, independent of prey availability. In the interior of the park, adult survival was less variable and density‐independent, despite reduced prey availability. There was no effect of prey population structure in northern Yellowstone, or of winter severity in either area. Survival was similar among yearlings and adults, but lower for adults older than 6 years. Our results indicate that density‐dependent intraspecific aggression is a major driver of adult wolf survival in northern Yellowstone, suggesting intrinsic density‐dependent mechanisms have the potential to regulate wolf populations at high ungulate densities. When low prey availability or high removal rates maintain wolves at lower densities, limited inter‐pack interactions may prevent density‐dependent survival, consistent with our findings in the interior of the park. This article provides empirical support for the hypothesis that intrinsic density‐dependent mechanisms might regulate territorial carnivore populations at high ungulate densities.
      PubDate: 2014-05-21T12:36:25.477589-05:
      DOI: 10.1111/1365-2656.12238
       
  • Disentangling the effects of exposure and susceptibility on transmission
           of the zoonotic parasite Schistosoma mansoni
    • Authors: David J. Civitello; Jason R. Rohr
      Abstract: For all parasites, transmission is composed of two processes: host contact with parasites (‘exposure’) and risk of infection given such contact (‘susceptibility’). Classic models, such as mass action (density‐dependent) transmission, lump these processes together. However, separating these processes could enhance predictions for disease dynamics, especially for free‐living parasites. Here, we outline three transmission models that partition exposure and susceptibility. Using data from a study of Schistosoma mansoni (trematode) infections in Biomphalaria glabrata snails, we competed these three models against four alternative models, including the mass action model (which lumps exposure and susceptibility). The models that separately accounted for exposure and susceptibility best predicted prevalence across the density gradients of hosts and parasites, outperforming all other models based on Akaike information criterion. When embedded into a dynamic epidemiological model, the exposure‐explicit models all predicted lower equilibrium densities of infected snails and human‐infectious cercariae. Thus, population‐level epidemiological models that utilize the classic mass action transmission model might overestimate human risk of schistosomiasis. More generally, the presented approach for disentangling exposure and susceptibility can distinguish between behavioural and immunological resistance, identify mechanisms of ‘disease dilution’ and provide a more complete dissection of drivers of parasite transmission. Here, the authors develop mechanistic disease transmission models to separate exposure and susceptibility and enhance predictions of the spread of a human zoonotic disease in its wildlife hosts. This approach could improve predictions of human risk and be applied to many host–parasite disease systems.
      PubDate: 2014-05-20T11:46:57.229209-05:
      DOI: 10.1111/1365-2656.12222
       
  • Community‐level demographic consequences of urbanization: an
           ecological network approach
    • Authors: Amanda D. Rodewald; Rudolf P. Rohr, Miguel A. Fortuna, Jordi Bascompte
      Abstract: Ecological networks are known to influence ecosystem attributes, but we poorly understand how interspecific network structure affect population demography of multiple species, particularly for vertebrates. Establishing the link between network structure and demography is at the crux of being able to use networks to understand population dynamics and to inform conservation. We addressed the critical but unanswered question, does network structure explain demographic consequences of urbanization' We studied 141 ecological networks representing interactions between plants and nesting birds in forests across an urbanization gradient in Ohio, USA, from 2001 to 2011. Nest predators were identified by video‐recording nests and surveyed from 2004 to 2011. As landscapes urbanized, bird–plant networks were more nested, less compartmentalized and dominated by strong interactions between a few species (i.e. low evenness). Evenness of interaction strengths promoted avian nest survival, and evenness explained demography better than urbanization, level of invasion, numbers of predators or other qualitative network metrics. Highly uneven networks had approximately half the nesting success as the most even networks. Thus, nest survival reflected how urbanization altered species interactions, particularly with respect to how nest placement affected search efficiency of predators. The demographic effects of urbanization were not direct, but were filtered through bird–plant networks. This study illustrates how network structure can influence demography at the community level and further, that knowledge of species interactions and a network approach may be requisite to understanding demographic responses to environmental change. This paper is the first to establish a link between population demography of several species and network structure. The authors demonstrate that demographic variation among populations can be explained only by using networks, not with traditional ecological predictors, including numbers of predators, landscape composition and habitat structure.
      PubDate: 2014-05-19T11:43:35.922671-05:
      DOI: 10.1111/1365-2656.12224
       
  • Linking body mass and group dynamics in an obligate cooperative breeder
    • Authors: Arpat Ozgul; Andrew W. Bateman, Sinead English, Tim Coulson, Tim H. Clutton‐Brock
      Abstract: Social and environmental factors influence key life‐history processes and population dynamics by affecting fitness‐related phenotypic traits such as body mass. The role of body mass is particularly pronounced in cooperative breeders due to variation in social status and consequent variation in access to resources. Investigating the mechanisms underlying variation in body mass and its demographic consequences can help elucidate how social and environmental factors affect the dynamics of cooperatively breeding populations. In this study, we present an analysis of the effect of individual variation in body mass on the temporal dynamics of group size and structure of a cooperatively breeding mongoose, the Kalahari meerkat, Suricata suricatta. First, we investigate how body mass interacts with social (dominance status and number of helpers) and environmental (rainfall and season) factors to influence key life‐history processes (survival, growth, emigration and reproduction) in female meerkats. Next, using an individual‐based population model, we show that the models explicitly including individual variation in body mass predict group dynamics better than those ignoring this morphological trait. Body mass influences group dynamics mainly through its effects on helper emigration and dominant reproduction. Rainfall has a trait‐mediated, destabilizing effect on group dynamics, whereas the number of helpers has a direct and stabilizing effect. Counteracting effects of number of helpers on different demographic rates, despite generating temporal fluctuations, stabilizes group dynamics in the long term. Our study demonstrates that social and environmental factors interact to produce individual variation in body mass and accounting for this variation helps to explain group dynamics in this cooperatively breeding population. By applying an individual‐ and trait‐based population model to an exceptional life‐history data set, the authors reveal the mechanisms through which environmental and social factors affect the group dynamics of a cooperatively breeding mammal.
      PubDate: 2014-05-16T12:06:30.539772-05:
      DOI: 10.1111/1365-2656.12239
       
  • Trait‐mediated functional responses: predator behavioural type
           mediates prey consumption
    • Authors: Benjamin J. Toscano; Blaine D. Griffen
      Abstract: The predator functional response (i.e. per capita consumption rate as a function of prey density) is central to our understanding of predator–prey population dynamics. This response is behavioural, depending on the rate of attack and time it takes to handle prey. Consistent behavioural differences among conspecific individuals, termed behavioural types, are a widespread feature of predator and prey populations but the effects of behavioural types on the functional response remain unexplored. We tested the effects of crab (Panopeus herbstii) behavioural type, specifically individual activity level, on the crab functional response to mussel (Brachidontes exustus) prey. We further tested whether the effects of activity level on the response are mediated by the presence of toadfish (Opsanus tau) predation threat in the form of waterborne chemical cues known to reduce crab activity level. The effects of crab activity level on the functional response were dependent on crab body size. Individual activity level increased the magnitude (i.e. slope and asymptote) of the type II functional response of small crabs, potentially through an increase in time spent foraging, but had no effect on the functional response of large crabs. Predation threat did not interact with activity level to influence mussel consumption, but independently reduced the slope of the type II functional response. Overall, this study demonstrates size‐specific effects of a behavioural type on a predator–prey interaction, as well as a general pathway (modification of the functional response) by which the effects of individual behavioural types can scale up to influence predator–prey population dynamics. Consistent individual variation in behaviour (i.e. behavioural types) is ubiquitous in predator populations, but the effects of behavioural types on the functional response remain uninvestigated. This study demonstrates size‐dependent effects of individual crab activity level on the crab functional response to mussel prey density.
      PubDate: 2014-05-15T06:56:22.851958-05:
      DOI: 10.1111/1365-2656.12236
       
  • Dual fuels: intra‐annual variation in the relative importance of
           benthic and pelagic resources to maintenance, growth and reproduction in a
           generalist salmonid fish
    • Authors: Brian Hayden; Chris Harrod, Kimmo K. Kahilainen
      Abstract: Ecological systems are often characterized as stable entities. However, basal productivity in most ecosystems varies between seasons, particularly in subarctic and polar areas. How this variability affects higher trophic levels or entire food webs remains largely unknown, especially in these high‐latitude regions. We undertook a year‐long study of benthic (macroinvertebrate) and pelagic (zooplankton) resource availability, along with short (day/days: stomach content)‐, medium (month: liver δ13C and δ15N isotopes)‐ and long‐term (season: muscle δ13C and δ15N isotopes) assessments of resource use by a generalist fish, the European whitefish, in a deep, oligotrophic, subarctic lake in northern Europe. Due to the long ice‐covered winter period, we expected to find general benthic reliance throughout the year, but also a seasonal importance of zooplankton to the diet, somatic growth and gonadal development of whitefish. Benthic and pelagic resource availability varied between seasons: peak littoral benthic macroinvertebrate density occurred in mid‐winter, whereas maximum zooplankton density was observed in summer. Whitefish stomach content revealed a reliance on benthic prey items during winter and pelagic prey in summer. A seasonal shift from benthic to pelagic prey was evident in liver isotope ratios, but muscle isotope ratios indicated a year‐round reliance on benthic macroinvertebrates. Whitefish activity levels as well as somatic and gonadal growth all peaked during the summer, coinciding with the zooplankton peak and the warmest water temperature. Stable isotopes of muscle consistently depicted the most important resource, benthic macroinvertebrates, whereas short‐term indicators, that is, diet and stable isotopes of liver, revealed the seasonal significance of pelagic zooplankton for somatic growth and gonad development. Seasonal variability in resource availability strongly influences consumer growth and reproduction and may also be important in other ecosystems facing pronounced annual weather fluctuations. This study highlights the dual importance of benthic invertebrates, which fuel winter survival, and pelagic zooplankton, which fuels summer growth, to the annual development of generalist fish. These results represent an important contribution to the ongoing debate regarding the relative importance of benthic and pelagic productivity to lake food webs.
      PubDate: 2014-05-15T06:56:15.398646-05:
      DOI: 10.1111/1365-2656.12233
       
  • Ant functional responses along environmental gradients
    • Authors: Xavier Arnan; Xim Cerdá, Javier Retana
      Abstract: Understanding species distributions and diversity gradients is a central challenge in ecology and requires prior knowledge of the functional traits mediating species’ survival under particular environmental conditions. While the functional ecology of plants has been reasonably well explored, much less is known about that of animals. Ants are among the most diverse, abundant and ecologically significant organisms on earth, and they perform a great variety of ecological functions. In this study, we analyse how the functional species traits present in ant communities vary along broad gradients in climate, productivity and vegetation type in the south‐western Mediterranean. To this end, we compiled one of the largest animal databases to date: it contains information on 211 local ant communities (including eight climate variables, productivity, and vegetation type) and 124 ant species, for which 10 functional traits are described. We used traits that characterize different dimensions of the ant functional niche with respect to morphology, life history and behaviour at both individual and colony level. We calculated two complementary functional trait community indices (‘trait average’ and ‘trait dissimilarity’) for each trait, and we analysed how they varied along the three different gradients using generalized least squares models that accounted for spatial autocorrelation. Our results show that productivity, vegetation type and, to a lesser extent, each climate variable per se might play an important role in shaping the occurrence of functional species traits in ant communities. Among the climate variables, temperature and precipitation seasonality had a much higher influence on functional responses than their mean values, whose effects were almost lacking. Our results suggest that strong relationships might exist between the abiotic environment and the distribution of functional traits among south‐western Mediterranean ant communities. This finding indicates that functional traits may modulate the responses of ant species to the environment. Since these traits act as the link between species distributions and the environment, they could potentially be used to predict community changes under future global change scenarios. Relationships among traits, function and the environment are poorly understood in animals, where large databases are hardly available. This study is one of the first to analyse changes in a large number of animal functional traits along wide and different environmental gradients concurrently.
      PubDate: 2014-05-13T14:19:07.291155-05:
      DOI: 10.1111/1365-2656.12227
       
  • Body size, carry‐over effects and survival in a seasonal
           environment: consequences for population dynamics
    • Authors: Gustavo S. Betini; Cortland K. Griswold, Livia Prodan, D. Ryan Norris
      Abstract: In seasonal populations, vital rates are not only determined by the direct effects of density at the beginning of each season, but also by density at the beginning of past seasons. Such delayed density dependence can arise via non‐lethal effects on individuals that carry over to influence per capita rates. In this study, we examine (i) whether parental breeding density influences offspring size, (ii) how this could carry over to affect offspring survival during the subsequent non‐breeding period and (iii) the population consequences of this relationship. Using Drosophila melanogaster, the common fruit fly, submitted to distinct breeding and non‐breeding seasons, we first used a controlled laboratory experiment to show that high parental breeding density leads to small offspring size, which then affects offspring survival during the non‐breeding period but only at high non‐breeding densities. We then show that a model with the interaction between parental breeding density and offspring density at the beginning of the non‐breeding season best explained offspring survival over 36 replicated generations. Finally, we developed a biseasonal model to show that the positive relationship between parental density and offspring survival can dampen fluctuations in population size between breeding and non‐breeding seasons. These results highlight how variation in parental density can lead to differences in offspring quality which result in important non‐lethal effects that carry over to influence per capita rates the following season, and demonstrate how this phenomenon can have important implications for the long‐term dynamics of seasonal populations. Most populations live in seasonal environments, yet the implications of seasonality on population dynamics are not well understood. Here, we used a model system to show how variation in parental breeding density carries over to influence offspring survival during the non‐breeding season and how this can stabilize long‐term population dynamics.
      PubDate: 2014-05-13T14:18:41.385317-05:
      DOI: 10.1111/1365-2656.12225
       
  • Cheetahs and wild dogs show contrasting patterns of suppression by lions
    • Authors: Alexandra Swanson; Tim Caro, Harriet Davies‐Mostert, Michael G. L. Mills, David W. Macdonald, Markus Borner, Emmanuel Masenga, Craig Packer
      Abstract: Top predators can dramatically suppress populations of smaller predators, with cascading effects throughout communities, and this pressure is often unquestioningly accepted as a constraint on mesopredator populations. In this study, we reassess whether African lions suppress populations of cheetahs and African wild dogs and examine possible mechanisms for coexistence between these species. Using long‐term records from Serengeti National Park, we tested 30 years of population data for evidence of mesopredator suppression, and we examined six years of concurrent radio‐telemetry data for evidence of large‐scale spatial displacement. The Serengeti lion population nearly tripled between 1966 and 1998; during this time, wild dogs declined but cheetah numbers remained largely unchanged. Prior to their local extinction, wild dogs primarily occupied low lion density areas and apparently abandoned the long‐term study area as the lion population ‘saturated’ the region. In contrast, cheetahs mostly utilized areas of high lion density, and the stability of the cheetah population indicates that neither high levels of lion‐inflicted mortality nor behavioural avoidance inflict sufficient demographic consequences to translate into population‐level effects. Population data from fenced reserves in southern Africa revealed a similar contrast between wild dogs and cheetahs in their ability to coexist with lions. These findings demonstrate differential responses of subordinate species within the same guild and challenge a widespread perception that lions undermine cheetah conservation efforts. Paired with several recent studies that document fine‐scale lion‐avoidance by cheetahs, this study further highlights fine‐scale spatial avoidance as a possible mechanism for mitigating mesopredator suppression. African lions have contrasting effects on populations of cheetahs and wild dogs. Lions do not suppress cheetah populations despite inflicting considerable cub mortality, but their impacts on wild dogs are greater than previously supposed, explaining the disappearance of the iconic Serengeti dog population. Fine‐scale avoidance behavior may allow apex‐mesopredator coexistence.
      PubDate: 2014-05-13T14:08:00.801771-05:
      DOI: 10.1111/1365-2656.12231
       
  • Predator avoidance during reproduction: diel movements by spawning sockeye
           salmon between stream and lake habitats
    • Authors: Kale T. Bentley; Daniel E. Schindler, Timothy J. Cline, Jonathan B. Armstrong, Daniel Macias, Lindsy R. Ciepiela, Ray Hilborn
      Abstract: Daily movements of mobile organisms between habitats in response to changing trade‐offs between predation risk and foraging gains are well established; however, less in known about whether similar tactics are used during reproduction, a time period when many organisms are particularly vulnerable to predators. We investigated the reproductive behaviour of adult sockeye salmon (Oncorhynchus nerka) and the activity of their principal predator, brown bears (Ursus arctos), on streams in south‐western Alaska. Specifically, we continuously monitored movements of salmon between lake habitat, where salmon are invulnerable to bears, and three small streams, where salmon spawn and are highly vulnerable to bears. We conducted our study across 2 years that offered a distinct contrast in bear activity and predation rates. Diel movements by adult sockeye salmon between stream and lake habitat were observed in 51·3% ± 17·7% (mean ± SD) of individuals among years and sites. Fish that moved tended to hold in the lake for most of the day and then migrated into spawning streams during the night, coincident with when bear activity on streams tended to be lowest. Additionally, cyclic movements between lakes and spawning streams were concentrated earlier in the spawning season. Individuals that exhibited diel movements had longer average reproductive life spans than those who made only one directed movement into a stream. However, the relative effect was dependent on the timing of bear predation, which varied between years. When predation pressure primarily occurred early in the spawning run (i.e., during the height of the diel movements), movers lived 120–310% longer than non‐movers. If predation pressure was concentrated later in the spawning run (i.e. when most movements had ceased), movers only lived 10–60% longer. Our results suggest a dynamic trade‐off in reproductive strategies of sockeye salmon; adults must be in the stream to reproduce, but must also avoid predation long enough to spawn. Given the interannual variation in the timing and intensity of predation pressure, the advantages of a particular movement strategy will likely vary among years. Regardless, movements by salmon allowed individuals to exploit fine‐scale habitat heterogeneity during reproduction, which appears to be a strategy to reduce predation risk on the spawning grounds. Animals often face habitat‐mediated trade‐offs between reproductive success and predation risk. This study provides one of the first examples of individuals exploiting fine‐scale habitat heterogeneity during reproduction through daily cyclic movements, which appears to be a strategy used by salmon to reduce predation risk by their principal predator, brown bears.
      PubDate: 2014-05-08T11:48:33.2614-05:00
      DOI: 10.1111/1365-2656.12223
       
  • The evolutionary significance of latent reproductive rate in a
           long‐lived vertebrate
    • Authors: Emmanuelle Cam
      First page: 1003
      Abstract: Kittiwake (Rissa tridactyla) feeding a chick, 4 July 2014, Brittany, France. Chambert, T., Rotella, J.J. & Garrott, R.A. (2014) An evolutionary perspective on reproductive individual heterogeneity in a marine vertebrate. Journal of Animal Ecology, 83, 1158–1168. Chambert, Rotella & Garrott () used long‐term data to assess the evolutionary significance of individual latent reproductive rate in female Weddell seals. Latent reproductive rates capture the differences among individuals in terms of their propensity to breed; they are conceptual and mathematical constructs. Neither recruitment probability nor age of first breeding of daughters was related to the mother's latent reproductive rate, but there was evidence of a weak positive relationship between the latent reproductive rates of mothers and daughters, suggesting some degree of heritability in this trait. Females with a high latent reproductive rate were expected to produce 2·0 times as many recruited females and 2·1 times as many grandchildren as females with a low reproductive rate. There was substantial stochastic variation in the number of offspring and grandchildren produced, but the inter‐individual variability in female latent reproductive rate may have important fitness consequences. The authors use long‐term data to assess the evolutionary significance of individual latent reproductive rate in female Weddell seals. They find evidence of a weak positive relationship between the latent reproductive rates of mothers and daughters, suggesting some degree of heritability in this trait. This is one of the handful of recent studies addressing the heritability of a latent life‐history trait in wild vertebrates.
      PubDate: 2014-08-20T11:21:40.445894-05:
      DOI: 10.1111/1365-2656.12277
       
  • The smell of good food: volatile infochemicals as resource quality
           indicators
    • Authors: Jana Moelzner; Patrick Fink
      First page: 1007
      Abstract: Foraging success generally depends on various environmental and physiological factors. Particularly for organisms with limited motility such as gastropods, food searching is a very cost‐intensive process. As energy gain through foraging is dependent on both resource quality and quantity, consumers have to be able to differentiate between varying resource items. The effectiveness of food searching could be increased through the perception of diet‐derived chemical signals that convey information about a food resource's quality over a certain distance. This strategy would clearly help to optimize movement decisions. In this study, we investigated the foraging behaviour of a freshwater gastropod towards volatile signal substances released from benthic algae grown under high and low nutrient availability, representing high and low food quality, using behavioural assays in the laboratory. Our results demonstrate that volatile organic compounds (VOCs) serve as foraging kairomones for these aquatic, benthic herbivores. Further, we were able to show for the first time that snails are able to differentiate between high‐ and low‐quality food sources, only by the perception of food odours alone (volatile infochemicals). Gas chromatography coupled with mass spectrometry demonstrated quantitative as well as qualitative differences in the chemical composition of the VOCs bouquet, dependent on algal nutrient content. Our results suggest that the recognition of resource quality via the reception of signal substances is likely to be adaptive for consumers with low mobility to maximize ingestion of high‐quality resources. The authors demonstrate for the first time that an herbivorous consumer can evaluate a resource's dietary quality over a distance. The observed foraging behaviour clearly shows that gastropods are able to perceive and distinguish chemical cues released from a resource as food quality indicators. Credit: Dr. Lars Peters, www.blueseapictures.de.
      PubDate: 2014-05-13T14:57:58.54812-05:0
      DOI: 10.1111/1365-2656.12220
       
  • Immigrants are attracted by local pre‐breeders and recruits in a
           seabird colony
    • Authors: K. Lesley Szostek; Michael Schaub, Peter H. Becker
      First page: 1015
      Abstract: Immigration is a major demographic factor shaping population dynamics. However, due to methodological difficulties, the extent of immigration and factors affecting immigration are insufficiently studied. This is also true for seabird colonies. We estimated annual immigration based on a long‐term study of a colony of common terns Sterna hirundo marked with transponders, using a Bayesian integrated population model that links colony size and productivity with individual life histories. Strong annual fluctuations in the number of immigrants were found. To identify whether colony‐specific covariates influenced immigration, we related the number of immigrants to various proxy variables for breeding site quality, specifically colony size, productivity, number of local subadults and local recruits. Numbers of local recruits and local subadults showed strong positive correlations with number of immigrants. We found that variation in immigration rate had strongly contributed to variation in colony growth rate, more so than variation in local recruitment or adult survival. Collectively, results suggest that immigration strongly affects colony growth rate, that the driving force behind immigration is natal dispersal and that immigrants were attracted by local recruits. The authors estimate annual immigration rates in a common tern colony, using Bayesian modelling based on long‐term individual life‐history data. They find that immigration is the most important driver of colony growth, and its driving force is young first‐time breeders, attracted to the colony by the presence of potential mates. Video
      PubDate: 2014-03-14T17:29:13.863481-05:
      DOI: 10.1111/1365-2656.12206
       
  • Ecological opportunities and intraspecific competition alter trophic niche
           specialization in an opportunistic stream predator
    • Authors: Charlotte Evangelista; Anatole Boiche, Antoine Lecerf, Julien Cucherousset
      First page: 1025
      Abstract: Many generalist populations are composed of specialized individuals that use a narrow part of the population's niche. Ecological theories predict that individual specialization and population trophic niche are determined by biotic interactions and resource diversity emerging from environmental variations (i.e. ecological opportunities). However, due to the paucity of empirical and experimental demonstrations, the genuine importance of each of these drivers in determining trophic niche attributes is not fully appreciated. The present study aimed at determining the population level and individual responses of brown trout (Salmo trutta) to variations in ecological opportunities (terrestrial prey inputs) and autochthonous prey communities among 10 stream reaches along a riparian condition gradient using individual longitudinal monitoring and stable isotope analyses. Our results suggested that trophic niche diversity varied along the environmental gradient, while individual trophic specialization was indirectly driven by ecological opportunities through strengthened intraspecific competition. Individual diet was repeatable over the study period, and the growth rate of juvenile brown trout increased with their specialization for aquatic predatory invertebrates. Our findings highlight the dual influences of intraspecific competition and ecological opportunities on individual trophic specialization and population trophic niche. This study describes how human‐induced disturbances (i.e. forestry management), by modifying ecological opportunities, impact the trophic ecology of an aquatic predator. Based on longitudinal monitoring of individuals and stable isotope analyses, it provides a rare empirical evidence that trophic specialization can be indirectly driven by ecological opportunities through strengthened intraspecific competition.
      PubDate: 2014-03-14T17:29:09.344368-05:
      DOI: 10.1111/1365-2656.12208
       
  • Life‐history diversity and its importance to population stability
           and persistence of a migratory fish: steelhead in two large North American
           watersheds
    • Authors: Jonathan W. Moore; Justin D. Yeakel, Dean Peard, Jeff Lough, Mark Beere
      First page: 1035
      Abstract: Life‐history strategies can buffer individuals and populations from environmental variability. For instance, it is possible that asynchronous dynamics among different life histories can stabilize populations through portfolio effects. Here, we examine life‐history diversity and its importance to stability for an iconic migratory fish species. In particular, we examined steelhead (Oncorhynchus mykiss), an anadromous and iteroparous salmonid, in two large, relatively pristine, watersheds, the Skeena and Nass, in north‐western British Columbia, Canada. We synthesized life‐history information derived from scales collected from adult steelhead (N = 7227) in these watersheds across a decade. These migratory fishes expressed 36 different manifestations of the anadromous life‐history strategy, with 16 different combinations of freshwater and marine ages, 7·6% of fish performing multiple spawning migrations, and up to a maximum of four spawning migrations per lifetime. Furthermore, in the Nass watershed, various life histories were differently prevalent through time – three different life histories were the most prevalent in a given year, and no life history ever represented more than 45% of the population. These asynchronous dynamics among life histories decreased the variability of numerical abundance and biomass of the aggregated population so that it was > 20% more stable than the stability of the weighted average of specific life histories: evidence of a substantial portfolio effect. Year of ocean entry was a key driver of dynamics; the median correlation coefficient of abundance of life histories that entered the ocean the same year was 2·5 times higher than the median pairwise coefficient of life histories that entered the ocean at different times. Simulations illustrated how different elements of life‐history diversity contribute to stability and persistence of populations. This study provides evidence that life‐history diversity can dampen fluctuations in population abundances and biomass via portfolio effects. Conserving genetic integrity and habitat diversity in these and other large watersheds can enable a diversity of life histories that increases population and biomass stability in the face of environmental variability. The authors analyse life‐history trajectories of an iconic migratory fish in large and relatively pristine watersheds, discovering an astonishing 36 different life histories. Via portfolio effects, this diversity increases stability in this era of rising variability.
      PubDate: 2014-03-24T07:14:24.734183-05:
      DOI: 10.1111/1365-2656.12212
       
  • Dispersal‐mediated effect of microhabitat availability and density
           dependence determine population dynamics of a forest floor web spider
    • Authors: Mayura B. Takada; Tadashi Miyashita
      First page: 1047
      Abstract: Landscapes in nature can be viewed as a continuum of small total habitable area with high fragmentation to widely spreading habitats. The dispersal‐mediated rescue effect predominates in the former landscapes, while classical density‐dependent processes generally prevail in widely spread habitats. A similar principle should be applied to populations of organisms utilizing microhabitats in limited supply. To test this hypothesis, we examined the population dynamics of a web spider, Neriene brongersmai, in 16 populations with varying degrees of microhabitat availability, and we explored whether: (i) high microhabitat availability improves survival rate during density‐independent movement, while the resultant high density reduces survival rate in a density‐dependent manner; and (ii) temporal population stability increases with microhabitat availability at the population level. Furthermore, we conducted two types of field experiments to verify whether high microhabitat availability actually reduces mortality associated with web‐site movement. Field observations revealed that demographic change in N. brongersmai populations was affected by three factors at different stages, namely the microhabitat limitation from the early to late juvenile stages, the density dependence from the late juvenile to adult stages and the food limitation from the adult to the next early juvenile stages. In addition, there was a tendency for a positive association between population stability and microhabitat availability at the population level. A small‐scale experiment, where the frequency of spider web relocation was equalized artificially, revealed that high microhabitat availability elevated the survival rate during a movement event between web‐sites. The larger spatiotemporal scale experiment also revealed an improved spider survival rate following treatment with high microhabitat availability, even though spider density was kept at a relatively low level. The population dynamics of N. brongersmai can be determined primarily by density‐independent processes based on web‐site fragmentation and density‐dependent processes driven by interference competition. We conclude that depending on the amount of habitat resources, the relative importance of the two contrasting paradigms—equilibrium and non‐equilibrium—appears to vary, even within a particular system. The authors provide novel integrative evidence that fragmentation paradigm and density‐dependent paradigm in population dynamics could operate in a particular system, using populations of a web spider.
      PubDate: 2014-03-24T07:14:09.359951-05:
      DOI: 10.1111/1365-2656.12213
       
  • Survival in macaroni penguins and the relative importance of different
           drivers: individual traits, predation pressure and environmental
           variability
    • Authors: Catharine Horswill; Jason Matthiopoulos, Jonathan A. Green, Michael P. Meredith, Jaume Forcada, Helen Peat, Mark Preston, Phil N. Trathan, Norman Ratcliffe
      First page: 1057
      Abstract: Understanding the demographic response of free‐living animal populations to different drivers is the first step towards reliable prediction of population trends. Penguins have exhibited dramatic declines in population size, and many studies have linked this to bottom‐up processes altering the abundance of prey species. The effects of individual traits have been considered to a lesser extent, and top‐down regulation through predation has been largely overlooked due to the difficulties in empirically measuring this at sea where it usually occurs. For 10 years (2003–2012), macaroni penguins (Eudyptes chrysolophus) were marked with subcutaneous electronic transponder tags and re‐encountered using an automated gateway system fitted at the entrance to the colony. We used multistate mark–recapture modelling to identify the different drivers influencing survival rates and a sensitivity analysis to assess their relative importance across different life stages. Survival rates were low and variable during the fledging year (mean = 0·33), increasing to much higher levels from age 1 onwards (mean = 0·89). We show that survival of macaroni penguins is driven by a combination of individual quality, top‐down predation pressure and bottom‐up environmental forces. The relative importance of these covariates was age specific. During the fledging year, survival rates were most sensitive to top‐down predation pressure, followed by individual fledging mass, and finally bottom‐up environmental effects. In contrast, birds older than 1 year showed a similar response to bottom‐up environmental effects and top‐down predation pressure. We infer from our results that macaroni penguins will most likely be negatively impacted by an increase in the local population size of giant petrels. Furthermore, this population is, at least in the short term, likely to be positively influenced by local warming. More broadly, our results highlight the importance of considering multiple causal effects across different life stages when examining the survival rates of seabirds. Understanding the factors that explain changes in survival rates is central to population ecology. This is the first seabird demography study to use mark–recapture modelling approaches to simultaneously consider and demonstrate the influence of multiple regulatory effects and assess their relative importance across different life stages.
      PubDate: 2014-05-21T05:21:19.557534-05:
      DOI: 10.1111/1365-2656.12229
       
  • Greater migratory propensity in hosts lowers pathogen transmission and
           impacts
    • Authors: Richard J. Hall; Sonia Altizer, Rebecca A. Bartel
      First page: 1068
      Abstract: Animal migrations are spectacular and migratory species have been shown to transmit pathogens that pose risks to human health. Although migration is commonly assumed to enhance pathogen dispersal, empirical work indicates that migration can often have the opposite effect of lowering disease risk. Key to assessing disease threats to migratory species is the ability to predict how migratory behaviour influences pathogen invasion success and impacts on migratory hosts, thus motivating a mechanistic understanding of migratory host–pathogen interactions. Here, we develop a quantitative framework to examine pathogen transmission in animals that undergo two‐way directed migrations between wintering and breeding grounds annually. Using the case of a pathogen transmitted during the host's breeding season, we show that a more extreme migratory strategy (defined by the time spent away from the breeding site and the total distance migrated) lowers the probability of pathogen invasion. Moreover, if migration substantially lowers the survival probability of infected animals, then populations that spend comparatively less time at the breeding site or that migrate longer distances are less vulnerable to pathogen‐induced population declines. These findings provide theoretical support for two non‐exclusive mechanisms proposed to explain how seasonal migration can lower infection risk: (i) escape from habitats where parasite transmission stages have accumulated and (ii) selective removal of infected hosts during strenuous journeys. Our work further suggests that barriers to long‐distance movement could increase pathogen prevalence for vulnerable species, an effect already seen in some animal species undergoing anthropogenically induced migratory shifts. This is the first theoretical demonstration that long‐distance migration can lower pathogen transmission and impacts, with implications for predicting and managing pathogen threats in imperilled migratory species.
      PubDate: 2014-03-06T12:16:01.219662-05:
      DOI: 10.1111/1365-2656.12204
       
  • Frequent and seasonally variable sublethal anthrax infections are
           accompanied by short‐lived immunity in an endemic system
    • Authors: Carrie A. Cizauskas; Steven E. Bellan, Wendy C. Turner, Russell E. Vance, Wayne M. Getz
      First page: 1078
      Abstract: Few studies have examined host‐pathogen interactions in wildlife from an immunological perspective, particularly in the context of seasonal and longitudinal dynamics. In addition, though most ecological immunology studies employ serological antibody assays, endpoint titre determination is usually based on subjective criteria and needs to be made more objective. Despite the fact that anthrax is an ancient and emerging zoonotic infectious disease found world‐wide, its natural ecology is not well understood. In particular, little is known about the adaptive immune responses of wild herbivore hosts against Bacillus anthracis. Working in the natural anthrax system of Etosha National Park, Namibia, we collected 154 serum samples from plains zebra (Equus quagga), 21 from springbok (Antidorcas marsupialis) and 45 from African elephants (Loxodonta africana) over 2–3 years, resampling individuals when possible for seasonal and longitudinal comparisons. We used enzyme‐linked immunosorbent assays to measure anti‐anthrax antibody titres and developed three increasingly conservative models to determine endpoint titres with more rigourous, objective mensuration. Between 52 and 87% of zebra, 0–15% of springbok and 3–52% of elephants had measurable anti‐anthrax antibody titres, depending on the model used. While the ability of elephants and springbok to mount anti‐anthrax adaptive immune responses is still equivocal, our results indicate that zebra in ENP often survive sublethal anthrax infections, encounter most B. anthracis in the wet season and can partially booster their immunity to B. anthracis. Thus, rather than being solely a lethal disease, anthrax often occurs as a sublethal infection in some susceptible hosts. Though we found that adaptive immunity to anthrax wanes rapidly, subsequent and frequent sublethal B. anthracis infections cause maturation of anti‐anthrax immunity. By triggering host immune responses, these common sublethal infections may act as immunomodulators and affect population dynamics through indirect immunological and co‐infection effects. In addition, with our three endpoint titre models, we introduce more mensuration rigour into serological antibody assays, even under the often‐restrictive conditions that come with adapting laboratory immunology methods to wild systems. With these methods, we identified significantly more zebras responding immunologically to anthrax than have previous studies using less comprehensive titre analyses. Here, the authors examine anthrax hosts in a natural system and find that herbivores are capable of surviving anthrax, with zebras contracting sublethal anthrax at a very high rate. The study also helps to establish more rigourous protocols for running and interpreting ELISAs, a very commonly used assay in immunological ecology.
      PubDate: 2014-03-14T17:29:16.02263-05:0
      DOI: 10.1111/1365-2656.12207
       
  • Predictors of malaria infection in a wild bird population:
           landscape‐level analyses reveal climatic and anthropogenic factors
    • Authors: Catalina Gonzalez‐Quevedo; Richard G. Davies, David S. Richardson
      First page: 1091
      Abstract: How the environment influences the transmission and prevalence of disease in a population of hosts is a key aspect of disease ecology. The role that environmental factors play in host–pathogen systems has been well studied at large scales, that is, differences in pathogen pressures among separate populations of hosts or across land masses. However, despite considerable understanding of how environmental conditions vary at fine spatial scales, the effect of these parameters on host–pathogen dynamics at such scales has been largely overlooked. Here, we used a combination of molecular screening and GIS‐based analysis to investigate how environmental factors determine the distribution of malaria across the landscape in a population of Berthelot's pipit (Anthus berthelotii, Bolle 1862) on the island of Tenerife (Canary Islands, Spain) using spatially explicit models that account for spatial autocorrelation. Minimum temperature of the coldest month was found to be the most important predictor of malaria infection at the landscape scale across this population. Additionally, anthropogenic factors such as distance to artificial water reservoirs and distance to poultry farms were important predictors of malaria. A model including these factors, and the interaction between distance to artificial water reservoirs and minimum temperature, best explained the distribution of malaria infection in this system. These results suggest that levels of malaria infection in this endemic species may be artificially elevated by the impact of humans. Studies such as the one described here improve our understanding of how environmental factors, and their heterogeneity, affect the distribution of pathogens within wild populations. The results demonstrate the importance of measuring fine‐scale variation – and not just regional effects – to understand how environmental variation can influence wildlife diseases. Such understanding is important for predicting the future spread and impact of disease and may help inform disease management programmes as well as the conservation of specific host species. This paper explores the role of fine‐scale environmental variation on the distribution of a wildlife disease. Interestingly, the authors find a key role for a climatic variable previously described as an important predictor of malaria, but also find an effect of anthropogenic variables.
      PubDate: 2014-03-24T07:14:27.165057-05:
      DOI: 10.1111/1365-2656.12214
       
  • Heterogeneous hosts: how variation in host size, behaviour and immunity
           affects parasite aggregation
    • Authors: Pieter T. J. Johnson; Jason T. Hoverman
      First page: 1103
      Abstract: Infection heterogeneity is one of the most fundamental patterns in disease ecology, yet surprisingly few studies have experimentally explored its underlying drivers. Here, we used large‐scale field assessments to evaluate the degree of parasite aggregation within amphibian host populations followed by a novel experimental approach to assess the potential influence of host size, behaviour and immunity in reproducing such heterogeneity. Among 227 wetlands, 2468 hosts and seven parasite species, infections were consistently aggregated among host individuals within populations of the Pacific chorus frog (Pseudacris regilla). For each parasite species, the relationship between the log‐mean and log‐variance of infection load was strongly linear (R2: 0·91–0·98) with a slope between 1·37 and 1·67, indicative of aggregation relative to the expected Poisson slope of unity. In laboratory trials with P. regilla and the most virulent trematode (Ribeiroia ondatrae), experimental reductions in either host immunity (through corticosterone exposure) or antiparasite behaviours (through anaesthesia exposure) increased parasite infection loads in isolated hosts by 62–102% relative to unmanipulated individuals. In a second experiment designed to test how variation in host immunity, behaviour and body size affected variation in infection load within small groups (dyads), a reduction in immune function or behaviour of one host significantly amplified infection heterogeneity within the group, effectively doubling the variance‐to‐mean ratio. However, immunity affected aggregation only in the absence of behavioural manipulation, and changing the size distribution of hosts did not appreciably affect aggregation. Using Taylor's Power Law to integrate field and laboratory data, we found that only treatments involving behavioural reductions achieved aggregation levels comparable to natural host populations. Thus, despite their short duration, our treatments generated heterogeneity in infection loads similar to natural observations. These results emphasize how, alongside extrinsic variation in parasite exposure risk, individual host attributes generally and behaviour in particular have the potential to influence infection success and parasite aggregation. Continued integration of infection heterogeneity research across space, among host species, and over time has important implications for understanding and managing human and wildlife diseases. Despite the ubiquity of parasite aggregation, experimental studies investigating the proposed drivers of such variation or their interactions remain rare. By combining field surveys with controlled experiments, the authors show that only manipulations of host behaviour – and not size or immunity – reproduce infection heterogeneity comparable to field patterns.
      PubDate: 2014-03-17T13:45:27.534758-05:
      DOI: 10.1111/1365-2656.12215
       
  • Ectoparasitism and stress hormones: strategy of host exploitation, common
           host–parasite history and energetics matter
    • Authors: Justin R. St. Juliana; Irina S. Khokhlova, Nadja Wielebnowski, Burt P. Kotler, Boris R. Krasnov
      First page: 1113
      Abstract: Parasites are thought to have numerous negative effects on their hosts. These negative effects may be associated with stress in a host. We evaluated the effects of four species of flea ectoparasites (Parapulex chephrenis, Synosternus cleopatrae, Xenopsylla conformis and Xenopsylla ramesis) on non‐specific responses of eight species of rodents (Meriones crassus, Gerbillus dasyurus, Gerbillus andersoni, Gerbillus pyramidum, Gerbillus nanus, Acomys cahirinus, Acomys russatus and Mesocricetus auratus) and measured faecal glucocorticoid metabolites concentrations (FGMC) produced by the hosts. We found no effect of body mass of an individual rodent on FGMCs. Parasitism by fleas with a ‘stay on the host body’ exploitation strategy was associated with higher host FGMCs than parasitism by fleas that spent most of their life ‘off‐host’. FGMCs among rodents infested by the same flea species were correlated positively with the phylogenetic distance of a given rodent from the principal host of this flea; changes in FGMCs were lower in the host species more closely related to the flea's principal host. Changes in FMGCs of a host while parasitized were correlated with a host's change in body mass, where hosts that lost more body mass had higher FGMCs. Our results suggest that ectoparasitism can be stressful to their hosts. However, the occurrence of parasite‐induced stress seems to depend on the identity of both host and parasite species and the evolutionary history of a host–parasite association. To our knowledge, this is the first multispecies study to evaluate the effect of ectoparasites on glucocorticoid hormones in small mammals. This study is novel in investigating the impacts of ectoparasites on stress hormones in small mammals. The authors find that strategy of host exploitation, common host–parasite history and energetics all influence the stress hormones of a host.
      PubDate: 2014-05-20T11:47:04.879437-05:
      DOI: 10.1111/1365-2656.12217
       
  • Multiple dimensions of bat biodiversity along an extensive tropical
           elevational gradient
    • Authors: Laura M. Cisneros; Kevin R. Burgio, Lindsay M. Dreiss, Brian T. Klingbeil, Bruce D. Patterson, Steven J. Presley, Michael R. Willig
      First page: 1124
      Abstract: Research concerning spatial dynamics of biodiversity generally has been limited to considerations of the taxonomic dimension, which is insensitive to interspecific variation in ecological or evolutionary characteristics that play important roles in species assembly and provide linkages to ecosystem services. Consequently, the assumption that the taxonomic dimension is a good surrogate for other dimensions remains unconfirmed. We assessed variation in taxonomic (species richness) as well as phylogenetic and functional (Rao's quadratic entropy, a measurement of dispersion) dimensions of bat biodiversity along an elevational gradient in the Manu Biosphere Reserve of Peru. Phylogenetic dispersion was based on relatedness of species derived from a mammalian supertree. Functional dispersion was estimated separately for each of six functional components that reflect particular niche axes (e.g. diet, foraging strategy, body size) and for all functional components combined. Species richness declined nonlinearly with elevation, whereas phylogenetic dispersion and functional dispersion based on all functional components were not significantly associated with elevation (orthogonal polynomial regression). Moreover, considerable heterogeneity in the form of elevational relationships existed among functional components. After accounting for variation in species richness, dispersion of phylogenetic, diet and foraging strategy attributes were significantly greater than expected at high elevations, whereas dispersion of body size was significantly less than expected at high elevations. Species richness was a poor surrogate for phylogenetic or functional dispersion. Functional dispersion based on multiple components obscured patterns detected by particular components and hindered identification of mechanistic explanations for elevational variation in biodiversity. Variation in phylogenetic dispersion effectively captured the composite variation represented by all functional components, suggesting a phylogenetic signal in functional attributes. Mechanisms that give rise to variation in richness do not fully account for variation in phylogenetic or functional characteristics of assemblages. Greater than expected phylogenetic, diet and foraging strategy dispersion at high elevations were associated with the loss of phylogenetically or functionally redundant species, suggesting that increasing interspecific competition with decreasing productivity resulted in competitive exclusion. In contrast, low dispersion of size attributes at high elevations suggests the importance of abiotic filtering that favours small‐sized species that can more easily enter torpor. This study demonstrates that species richness is not always an effective surrogate of phylogenetic or functional dimensions of biodiversity. Deviations of phylogenetic or functional dispersion from that expected based on species richness suggest that competitive exclusion and abiotic filtering operate simultaneously on different aspects of bat assemblages at high elevations. Photo credit: L.M. Cisneros.
      PubDate: 2014-02-12T05:46:11.832901-05:
      DOI: 10.1111/1365-2656.12201
       
  • Let's go beyond taxonomy in diet description: testing a trait‐based
           approach to prey–predator relationships
    • Authors: Jérôme Spitz; Vincent Ridoux, Anik Brind'Amour
      First page: 1137
      Abstract: Understanding ‘Why a prey is a prey for a given predator'’ can be facilitated through trait‐based approaches that identify linkages between prey and predator morphological and ecological characteristics and highlight key functions involved in prey selection. Enhanced understanding of the functional relationships between predators and their prey is now essential to go beyond the traditional taxonomic framework of dietary studies and to improve our knowledge of ecosystem functioning for wildlife conservation and management. We test the relevance of a three‐matrix approach in foraging ecology among a marine mammal community in the northeast Atlantic to identify the key functional traits shaping prey selection processes regardless of the taxonomy of both the predators and prey. Our study reveals that prey found in the diet of marine mammals possess functional traits which are directly and significantly linked to predator characteristics, allowing the establishment of a functional typology of marine mammal–prey relationships. We found prey selection of marine mammals was primarily shaped by physiological and morphological traits of both predators and prey, confirming that energetic costs of foraging strategies and muscular performance are major drivers of prey selection in marine mammals. We demonstrate that trait‐based approaches can provide a new definition of the resource needs of predators. This framework can be used to anticipate bottom‐up effects on marine predator population dynamics and to identify predators which are sensitive to the loss of key prey functional traits when prey availability is reduced. Here the authors demonstrate the utility of a trait‐based method that is that original for dietary data and opens a new avenue to investigate predator‐prey relationships and aspects of prey selection of wild fauna
      PubDate: 2014-05-20T11:46:53.447392-05:
      DOI: 10.1111/1365-2656.12218
       
  • A trophic cascade induced by predatory ants in a fig–fig wasp
           mutualism
    • Authors: Bo Wang; Xiang‐Zong Geng, Li‐Bin Ma, James M. Cook, Rui‐Wu Wang
      First page: 1149
      Abstract: A trophic cascade occurs when predators directly decrease the densities, or change the behaviour, of herbivores and thus indirectly increase plant productivity. The predator–herbivore–plant context is well known, but some predators attack species beneficial to plants (e.g. pollinators) and/or enemies of herbivores (e.g. parasites), and their role in the dynamics of mutualisms remains largely unexplored. We surveyed the predatory ant species and studied predation by the dominant ant species, the weaver ant Oecophylla smaragdina, associated with the fig tree Ficus racemosa in southwest China. We then tested the effects of weaver ants on the oviposition behaviour of pollinating and non‐pollinating fig wasps in an ant‐exclusion experiment. The effects of weaver ants on fig wasp community structure and fig seed production were then compared between trees with and without O. smaragdina. Oecophylla smaragdina captured more non‐pollinating wasps (Platyneura mayri) than pollinators as the insects arrived to lay eggs. When ants were excluded, more non‐pollinators laid eggs into figs and fewer pollinators entered figs. Furthermore, trees with O. smaragdina produced more pollinator offspring and fewer non‐pollinator offspring, shifting the community structure significantly. In addition, F. racemosa produced significantly more seeds on trees inhabited by weaver ants. Oecophylla smaragdina predation reverses the dominance of the two commonest wasp species at the egg‐laying stage and favours the pollinators. This behavioural pattern is mirrored by wasp offspring production, with pollinators' offspring dominating figs produced by trees inhabited by weaver ants, and offspring of the non‐pollinator P. mayri most abundant in figs on trees inhabited by other ants. Overall, our results suggest that predation by weaver ants limits the success of the non‐pollinating P. mayri and therefore indirectly benefits the mutualism by increasing the reproductive success of both the pollinators and the plant. Predation is thus a key functional factor that can shape the community structure of a pollinator‐plant mutualistic system. This paper reports a trophic cascade induced by weaver ants on a fig–fig wasp mutualism. We show that predation by weaver ants limits the success of the non‐pollinating wasp and therefore indirectly benefits the mutualism by increasing the reproductive success of both the pollinator and the plant. Predation is therefore a key functional factor that shapes the community structure of a multi‐species mutualistic system and determines its functioning.
      PubDate: 2014-05-20T11:46:55.649751-05:
      DOI: 10.1111/1365-2656.12219
       
  • An evolutionary perspective on reproductive individual heterogeneity in a
           marine vertebrate
    • Authors: Thierry Chambert; Jay J. Rotella, Robert A. Garrott
      First page: 1158
      Abstract: Although the quantification of individual heterogeneity in wild populations' vital rates has recently attracted growing interest among ecologists, the investigation of its evolutionary consequences remains limited, mainly because of the difficulties in assessing fitness and heritability from field studies on free‐ranging animals. In the presence of individual variability, evaluation of fitness consequences can notably be complicated by the existence of trade‐offs among different vital rates. In this study, to further assess the evolutionary significance of previously quantified levels of individual heterogeneity in female Weddell seal (Leptonychotes weddellii Lesson) reproductive rates (Chambert et al. ), we investigated how several life‐history characteristics of female offspring were related to their mother's reproductive rate, as well as to other maternal traits (age and experience) and environmental conditions at birth. The probability and age of first reproduction (recruitment) of female offspring was not related to their mother's reproductive rate, suggesting the absence of a maternal trade‐off between the number and quality of offspring a female produces. Evidence of a positive, but relatively weak, relationship between the reproductive rates of a mother and her female offspring was found, suggesting some degree of heritability in this trait. Using a simulation approach based on these statistical findings, we showed that substantial differences in the number of grandchildren, produced through female progeny, can be expected among females with different reproductive rates. Despite the presence of substantial stochastic variability, due to environmental fluctuations and other unidentified mechanisms, and in the light of the fact that the metrics obtained do not provide a full measure of real fitness, our results do suggest that the individual reproductive variability found in female Weddell seals could potentially have important fitness consequences. This study is the first to address the evolutionary consequences of individual reproductive heterogeneity in a long‐lived vertebrate. Using Weddell seals as a model, the authors show that females producing more offspring do not trade off with the quality of their offspring and find evidence for heritability in female reproductive rates.
      PubDate: 2014-03-17T14:00:51.468947-05:
      DOI: 10.1111/1365-2656.12211
       
  • Evidence of localized resource depletion following a natural colonization
           event by a large marine predator
    • Authors: Carey E. Kuhn; Jason D. Baker, Rodney G. Towell, Rolf R. Ream
      First page: 1169
      Abstract: For central place foragers, forming colonies can lead to extensive competition for prey around breeding areas and a zone of local prey depletion. As populations grow, this area of reduced prey can expand impacting foraging success and forcing animals to alter foraging behaviour. Here, we examine a population of marine predators, the northern fur seal (Callorhinus ursinus), which colonized a recently formed volcanic island, and assess changes in foraging behaviour associated with increasing population density. Specifically, we measured pup production and adult foraging behaviour over a 15‐year period, during which the population increased 4‐fold. Using measures of at‐sea movements and dive behaviour, we found clear evidence that as the population expanded, animals were required to allot increasing effort to obtain resources. These changes in behaviour included longer duration foraging trips, farther distances travelled, a larger foraging range surrounding the island and deeper maximum dives. Our results suggest that as the northern fur seal population increased, local prey resources were depleted as a result of increased intraspecific competition. In addition, the recent slowing of population growth indicates that this population may be approaching carrying capacity just 31 years after a natural colonization event. Our study offers insight into the dynamics of population growth and impacts of increasing population density on a large marine predator. Such data could be vital for understanding future population fluctuations that occur in response to the dynamic environment, as natural and anthropogenic factors continue to modify marine habitats. By taking advantage of a rare colonization event, this study examined the impact of population growth on the foraging behaviour of a large marine predator. As the population increase 4‐fold, northern fur seals were required to allot increasing effort to obtain prey as a result of localized resource depletion.
      PubDate: 2014-03-04T07:19:25.331998-05:
      DOI: 10.1111/1365-2656.12202
       
  • Habitat degradation is threatening reef replenishment by making fish
           fearless
    • Authors: Oona M. Lönnstedt; Mark I. McCormick, Douglas P. Chivers, Maud C. O. Ferrari
      First page: 1178
      Abstract: Habitat degradation is one of the ‘Big Five’ drivers of biodiversity loss. However, the mechanisms responsible for this progressive loss of biodiversity are poorly understood. In marine ecosystems, corals play the role of ecosystem engineers, providing essential habitat for hundreds of thousands of species and hence their health is crucial to the stability of the whole ecosystem. Climate change is causing coral bleaching and degradation, and while this has been known for a while, little do we know about the cascading consequences of these events on the complex interrelationships between predators and their prey. The goal of our study was to investigate, under completely natural conditions, the effect of coral degradation on predator–prey interactions. Settlement stage ambon damselfish (Pomacentrus amboinensis), a common tropical fish, were released on patches of healthy or dead corals, and their behaviours in situ were measured, along with their response to injured conspecific cues, a common risk indicator. This study also explored the effect of habitat degradation on natural levels of mortality at a critical life‐history transition. We found that juveniles in dead corals displayed risk‐prone behaviours, sitting further away and higher up on the reef patch, and failed to respond to predation cues, compared to those on live coral patches. In addition, in situ survival experiments over 48 h indicated that juveniles on dead coral habitats had a 75% increase in predation‐related mortality, compared to fish released on live, healthy coral habitats. Our results provide the first of many potential mechanisms through which habitat degradation can impact the relationship between prey and predators in the coral reef ecosystem. As the proportion of dead coral increases, the recruitment and replenishment of coral reef fishes will be threatened, and so will the level of diversity in these biodiversity hot spots. In one of the world's most biologically diverse ecosystems, coral reefs, climate change is causing coral degradation. The authors find that recruitment and replenishment of reef fish will be affected by coral death via predation‐mediated changes, as fish in dead habitats fail to respond to predators with severe consequences for survival.
      PubDate: 2014-03-17T13:54:11.954452-05:
      DOI: 10.1111/1365-2656.12209
       
  • Individual and sex‐specific differences in intrinsic growth rate
           covary with consistent individual differences in behaviour
    • Authors: Peter A. Biro; Bart Adriaenssens, Portia Sampson
      First page: 1186
      Abstract: The evolutionary causes of consistent individual differences in behaviour are currently a source of debate. A recent hypothesis suggests that consistent individual differences in life‐history productivity (growth and/or fecundity) may covary with behavioural traits that contribute to growth‐mortality trade‐offs, such as risk‐proneness (boldness) and foraging activity (voraciousness). It remains unclear, however, to what extent individual behavioural and life‐history profiles are set early in life, or are a more flexible result of specific environmental or developmental contexts that allow bold and active individuals to acquire more resources. Longitudinal studies of individually housed animals under controlled conditions can shed light on this question. Since growth and behaviour can both vary within individuals (they are labile), studying between‐individual correlations in behaviour and growth rate requires repeated scoring for both variables over an extended period of time. However, such a study has not yet been done. Here, we repeatedly measured individual mass seven times each, boldness 40 times each and voracity eight times each during the first 4 months of life on 90 individually housed crayfish (Cherax destructor). Animals were fed ad libitum, generating a context where individuals can express their intrinsic growth rate (i.e. growth capacity), but in which bold and voracious behaviour is not necessary for high resource acquisition (crayfish can and do hoard food back to their burrow). We show that individuals that were consistently bold over time during the day were also bolder at night, were more voracious and maintained higher growth rates over time than shy individuals. Independent of individual differences, we also observed that males were faster‐growing, bolder and more voracious than females. Our findings imply that associations between bold behaviour and fast growth can occur in unlimited food contexts where there is no necessary link between bold behaviour and resource acquisition – offering support for the ‘personality–productivity’ hypothesis. We suggest future research should study links between consistent individual differences in behaviour and life history under a wider range of contexts, in order to shed light on the role of biotic and abiotic conditions in the strength, direction and stability of their covariance. Why individuals within a given population consistently differ in behaviour is an important question, given the lability of behaviour. Here, the authors show that individual differences in intrinsic growth rate are a strong predictor of behavioural differences that persist over several months.
      PubDate: 2014-03-17T14:00:38.074914-05:
      DOI: 10.1111/1365-2656.12210
       
  • The effect of fire on habitat selection of mammalian herbivores: the role
           of body size and vegetation characteristics
    • Authors: Stephanie L. Eby; T. Michael Anderson, Emilian P. Mayemba, Mark E. Ritchie
      First page: 1196
      Abstract: Given the role of fire in shaping ecosystems, especially grasslands and savannas, it is important to understand its broader impact on these systems. Post‐fire stimulation of plant nutrients is thought to benefit grazing mammals and explain their preference for burned areas. However, fire also reduces vegetation height and increases visibility, thereby potentially reducing predation risk. Consequently, fire may be more beneficial to smaller herbivores, with higher nutritional needs and greater risks of predation. We tested the impacts of burning on different sized herbivores' habitat preference in Serengeti National Park, as mediated by burning's effects on vegetation height, live : dead biomass ratio and leaf nutrients. Burning caused a less than 4 month increase in leaf nitrogen (N), and leaf non‐N nutrients [copper (Cu), potassium (K), and magnesium (Mg)] and a decrease in vegetation height and live : dead biomass. During this period, total herbivore counts were higher on burned areas. Generally, smaller herbivores preferred burned areas more strongly than larger herbivores. Unfortunately, it was not possible to determine the vegetation characteristics that explained burned area preference for each of the herbivore species observed. However, total herbivore abundance and impala (Aepyceros melampus) preference for burned areas was due to the increases in non‐N nutrients caused by burning. These findings suggest that burned area attractiveness to herbivores is mainly driven by changes to forage quality and not potential decreases in predation risk caused by reductions in vegetation height. This paper is one of the first to intensively study reasons for herbivore preference of burned areas. Additionally, it explores how long impacts of burning affect herbivore distributions, which is important given the large roles that herbivores and fire play in savanna and grassland ecosystems.
      PubDate: 2014-05-19T11:42:18.990266-05:
      DOI: 10.1111/1365-2656.12221
       
  • Linking phenological shifts to species interactions through
           size‐mediated priority effects
    • Authors: Nick L. Rasmussen; Benjamin G. Van Allen, Volker H. W. Rudolf
      First page: 1206
      Abstract: Interannual variation in seasonal weather patterns causes shifts in the relative timing of phenological events of species within communities, but we currently lack a mechanistic understanding of how these phenological shifts affect species interactions. Identifying these mechanisms is critical to predicting how interannual variation affects populations and communities. Species' phenologies, particularly the timing of offspring arrival, play an important role in the annual cycles of community assembly. We hypothesize that shifts in relative arrival of offspring can alter interspecific interactions through a mechanism called size‐mediated priority effects (SMPE), in which individuals that arrive earlier can grow to achieve a body size advantage over those that arrive later. In this study, we used an experimental approach to isolate and quantify the importance of SMPE for species interactions. Specifically, we simulated shifts in relative arrival of the nymphs of two dragonfly species to determine the consequences for their interactions as intraguild predators. We found that shifts in relative arrival altered not only predation strength but also the nature of predator–prey interactions. When arrival differences were great, SMPE allowed the early arriver to prey intensely upon the late arriver, causing exclusion of the late arriver from nearly all habitats. As arrival differences decreased, the early arriver's size advantage also decreased. When arrival differences were smallest, there was mutual predation, and the two species coexisted in similar abundances across habitats. Importantly, we also found a nonlinear scaling relationship between shifts in relative arrival and predation strength. Specifically, small shifts in relative arrival caused large changes in predation strength while subsequent changes had relatively minor effects. These results demonstrate that SMPE can alter not only the outcome of interactions but also the demographic rates of species and the structure of communities. Elucidating the mechanisms that link phenological shifts to species interactions is crucial for understanding the dynamics of seasonal communities as well as for predicting the effects of climate change on these communities. Shifts in phenological timing can occur due to interannual variation in seasonal weather patterns as well as anthropogenic climate change, but the consequences for species interactions remain poorly understood. Using an experimental approach, this study demonstrates that phenological shifts can alter not only interaction strength but also demographic rates of species and community structure through a mechanism called size‐mediated priority effects, in which individuals that arrive earlier can achieve a body size advantage over those that arrive later.
      PubDate: 2014-03-10T13:13:48.246099-05:
      DOI: 10.1111/1365-2656.12203
       
  • A critical examination of indices of dynamic interaction for wildlife
           telemetry studies
    • Authors: Jed A. Long; Trisalyn A. Nelson, Stephen L. Webb, Kenneth L. Gee
      First page: 1216
      Abstract: Wildlife scientists continue to be interested in studying ways to quantify how the movements of animals are interdependent – dynamic interaction. While a number of applied studies of dynamic interaction exist, little is known about the comparative effectiveness and applicability of available methods used for quantifying interactions between animals. We highlight the formulation, implementation and interpretation of a suite of eight currently available indices of dynamic interaction. Point‐ and path‐based approaches are contrasted to demonstrate differences between methods and underlying assumptions on telemetry data. Correlated and biased correlated random walks were simulated at a range of sampling resolutions to generate scenarios with dynamic interaction present and absent. We evaluate the effectiveness of each index at identifying different types of interactive behaviour at each sampling resolution. Each index is then applied to an empirical telemetry data set of three white‐tailed deer (Odocoileus virginianus) dyads. Results from the simulated data show that three indices of dynamic interaction reliant on statistical testing procedures are susceptible to Type I error, which increases at fine sampling resolutions. In the white‐tailed deer examples, a recently developed index for quantifying local‐level cohesive movement behaviour (the di index) provides revealing information on the presence of infrequent and varying interactions in space and time. Point‐based approaches implemented with finely sampled telemetry data overestimate the presence of interactions (Type I errors). Indices producing only a single global statistic (7 of the 8 indices) are unable to quantify infrequent and varying interactions through time. The quantification of infrequent and variable interactive behaviour has important implications for the spread of disease and the prevalence of social behaviour in wildlife. Guidelines are presented to inform researchers wishing to study dynamic interaction patterns in their own telemetry data sets. Finally, we make our code openly available, in the statistical software R, for computing each index of dynamic interaction presented herein. The authors compare currently available techniques for detecting interactive behaviour – termed dynamic interaction‐when multiple animals are tracked simultaneously (e.g. GPS collars). A recently developed metric for looking at local‐level changes in interactive behaviour is highlighted.
      PubDate: 2014-02-22T02:20:17.375508-05:
      DOI: 10.1111/1365-2656.12198
       
  • Using dynamic Brownian bridge movement modelling to measure temporal
           patterns of habitat selection
    • Authors: Michael E. Byrne; J. Clint McCoy, Joseph W. Hinton, Michael J. Chamberlain, Bret A. Collier
      First page: 1234
      Abstract: Accurately describing animal space use is vital to understanding how wildlife use habitat. Improvements in GPS technology continue to facilitate collection of telemetry data at high spatial and temporal resolutions. Application of the recently introduced dynamic Brownian bridge movement model (dBBMM) to such data is promising as the method explicitly incorporates the behavioural heterogeneity of a movement path into the estimated utilization distribution (UD). Utilization distributions defining space use are normally estimated for time‐scales ranging from weeks to months, obscuring much of the fine‐scale information available from high‐volume GPS data sets. By accounting for movement heterogeneity, the dBBMM provides a rigorous, behaviourally based estimate of space use between each set of relocations. Focusing on UDs generated between individual sets of locations allows us to quantify fine‐scale circadian variation in habitat use. We used the dBBMM to estimate UDs bounding individual time steps for three terrestrial species with different life histories to illustrate how the method can be used to identify fine‐scale variations in habitat use. We also demonstrate how dBBMMs can be used to characterize circadian patterns of habitat selection and link fine‐scale patterns of habitat use to behaviour. We observed circadian patterns of habitat use that varied seasonally for a white‐tailed deer (Odocoileus virginianus) and coyote (Canis latrans). We found seasonal patterns in selection by the white‐tailed deer and were able to link use of conifer forests and agricultural fields to behavioural state of the coyote. Additionally, we were able to quantify the date in which a Rio Grande wild turkey (Meleagris gallopavo intermedia) initiated laying as well as when during the day, she was most likely to visit the nest site to deposit eggs. The ability to quantify circadian patterns of habitat use may have important implications for research and management of wildlife. Additionally, the ability to link such patterns to behaviour may aid in the development of mechanistic models of habitat selection. The authors use the dynamic Brownian bridge motion model to estimate space use of an animal between individual GPS telemetry locations based on movement behaviour and show how that information can be used to investigate fine‐scale temporal variation in habitat use.
      PubDate: 2014-03-06T12:16:26.497342-05:
      DOI: 10.1111/1365-2656.12205
       
  • Corrigendum
    • First page: 1244
      PubDate: 2014-08-20T11:21:44.918366-05:
      DOI: 10.1111/1365-2656.12265
       
  • The Consequences of Co‐Infections for Parasite Transmission in the
           Mosquito Aedes aegypti
    • Abstract: 1)Co‐infections may modify parasite transmission opportunities directly as a consequence of interactions in the within host environment, but also indirectly through changes in host life‐history. Furthermore, host and parasite traits are sensitive to the abiotic environment with variable consequences for parasite transmission in co‐infections. (2)We investigate how co‐infection of the mosquito Aedes aegypti with two microsporidian parasites (Vavraia culicis and Edhazardia aedis) at two levels of larval food availability affects parasite transmission directly, and indirectly through effects on host traits (3)In a laboratory infection experiment we compared how co‐infection, at low and high larval food availability, affected the probability of infection, within‐host growth and the transmission potential of each parasite, compared to single infections. Horizontal transmission was deemed possible for both parasites when infected hosts died harbouring horizontally‐transmitting spores. Vertical transmission was judged possible for E. aedis when infected females emerged as adults. We also compared the total input number of spores used to seed infections with output number, in single and co‐infections for each parasite. (4)The effects of co‐infection on parasite fitness were complex, especially for V. culicis. In low larval food conditions, co‐infection increased the chances of mosquitoes dying as larvae or pupae, thus increasing opportunities for V. culicis’ horizontal transmission. However, co‐infection reduced larval longevity and hence time available for V. culicis spore production. Overall there was a negative net effect of co‐infection on V. culicis whereby the number of spores produced was less than the number used to seed infection. Co‐infections also negatively affected horizontal transmission of the more virulent parasite, E. aedis, through reduced longevity of pre‐adult hosts. However, its potential transmission suffered less relative to V. culicis. (5)Our results show that co‐infection can negatively affect parasite transmission opportunities, both directly as well as indirectly via effects on host life‐history. We also find that transmission is contingent on the combined effect of the abiotic environment. This article is protected by copyright. All rights reserved.
       
  • Do intraspecific or interspecific interactions determine responses to
           predators feeding on a shared size‐structured prey community'
    • Abstract: 1.Coexistence of predators that share the same prey is common. This is still the case in size structured predator communities where predators consume prey species of different sizes (interspecific prey responses) or consume different size classes of the same species of prey (intraspecific prey responses). 2.A mechanism has recently been proposed to explain coexistence between predators that differ in size but share the same prey species, emergent facilitation, which is dependent on strong intraspecific responses from one or more prey species. Under emergent facilitation predators can depend on each other for invasion, persistence or success in a size structured prey community. 3.Experimental evidence for intraspecific size‐structured responses in prey populations remain rare and further questions remain about direct interactions between predators that could prevent or limit any positive effects between predators (e.g. intraguild predation). 4.Here we provide a community wide experiment on emergent facilitation including natural predators. We investigate both the direct interaction between two predators that differ in body size (fish vs. invertebrate predator) and the indirect interaction between them via their shared prey community (zooplankton). 5.Our evidence supports the most likely expectation of interactions between differently sized predators, that intraguild predation rates are high and interspecific interactions in the shared prey community dominate the response to predation (i.e. predator‐mediated competition). The question of whether emergent facilitation occurs frequently in nature requires more empirical and theoretical attention, specifically to address the likelihood that its pre‐conditions may co‐occur with high rates of intraguild predation. This article is protected by copyright. All rights reserved.
       
  • Linking niche theory to ecological impacts of successful invaders:
           insights from resource fluctuation‐specialist herbivore interactions
           
    • Abstract: 1.Theories of species coexistence and invasion ecology are fundamentally connected and provide a common theoretical framework for studying the mechanisms underlying successful invasions and their ecological impacts. Temporal fluctuations in resource availability and differences in life‐history traits between invasive and resident species are considered as likely drivers of the dynamics of invaded communities. Current critical issues in invasion ecology thus relate to the extent to which such mechanisms influence coexistence between invasive and resident species, and to the ability of resident species to persist in an invasive‐dominated ecosystem. 2.We tested how a fluctuating resource and species traits differences may explain and help predict long‐term impacts of biological invasions in forest specialist insect communities. We used a simple invasion system comprising closely related invasive and resident seed‐specialized wasps (Hymenoptera: Torymidae) competing for a well‐known fluctuating resource, and displaying divergent diapause, reproductive and phenological traits. 3.Based on extensive long‐term field observations (1977‐2010), we developed a combination of mechanistic and statistical models aiming to (i) obtain a realistic description of the population dynamics of these interacting species over time, and (ii) clarify the respective contributions of fluctuation‐dependent and fluctuation‐independent mechanisms to long‐term impact of invasion on the population dynamics of the resident wasp species. 4.We showed that a fluctuation‐dependent mechanism was unable to promote coexistence of the resident and invasive species. Earlier phenology of the invasive species was the main driver of invasion success, enabling the invader to exploit an empty niche. Phenology also had the greatest power to explain the long‐term negative impact of the invasive on the resident species, through resource preemption. 5.This study provides strong support for the critical role of species differences in interspecific competition outcomes within animal communities. Our mechanisticstatistical approach allows disentangling the critical drivers of the dynamics of coexistence and exclusion within novel species assemblages, following both intentional and non‐intentional species introductions. This article is protected by copyright. All rights reserved.
       
 
 
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