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  Subjects -> BIOLOGY (Total: 2840 journals)
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    - ZOOLOGY (127 journals)

ZOOLOGY (127 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 Zoologica Cracoviensia     Free   (Followers: 2)
Acta zoológica mexicana     Open Access  
Advances in Zoology     Open Access  
Advances in Zoology and Botany     Open Access  
African Invertebrates     Open Access  
African Journal of Herpetology     Full-text available via subscription   (Followers: 1)
African Zoology     Hybrid Journal   (Followers: 7)
American Journal of Zoological Research     Open Access  
animal     Hybrid Journal   (Followers: 3)
Animal Behaviour     Hybrid Journal   (Followers: 146)
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: 9)
Animal Migration     Open Access   (Followers: 1)
Animal Studies Journal     Open Access   (Followers: 7)
Annales Zoologici     Full-text available via subscription  
Annales Zoologici Fennici     Open Access  
Annals of Animal Science     Open Access   (Followers: 1)
Annual Review of Animal Biosciences     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: 14)
Applied Entomology and Zoology     Partially Free   (Followers: 3)
Aquatic Mammals     Full-text available via subscription   (Followers: 4)
Aquatic Sciences     Hybrid Journal   (Followers: 11)
Arthropod Management Tests     Hybrid Journal  
Asian Journal of Animal and Veterinary Advances     Open Access   (Followers: 7)
Australian Journal of Zoology     Hybrid Journal   (Followers: 1)
Bioacoustics : The International Journal of Animal Sound and its Recording     Partially Free   (Followers: 3)
Bird Conservation International     Hybrid Journal   (Followers: 15)
Bird Study     Full-text available via subscription   (Followers: 13)
Brazilian Journal of Veterinary Research and Animal Science     Open Access   (Followers: 7)
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: 17)
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: 26)
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 Studies on Sparrows     Open Access  
International Zoo Yearbook     Hybrid Journal   (Followers: 2)
Invertebrate Reproduction & Development     Hybrid Journal   (Followers: 2)
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: 32)
Journal of Animal Physiology and Animal Nutrition     Hybrid Journal   (Followers: 5)
Journal of Apicultural Science     Open Access   (Followers: 1)
Journal of Applied Animal Research     Hybrid Journal   (Followers: 1)
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: 27)
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: 10)
Mammalia     Hybrid Journal   (Followers: 7)
Marine Ecology Progress Series MEPS     Hybrid Journal   (Followers: 10)
Mastozoología Neotropical     Open Access  
Memorias de la Conferencia Interna en Medicina y Aprovechamiento de Fauna Silvestre, Exótica y no Convencional     Open Access  
Natural History Sciences     Hybrid Journal  
Neotropical Primates     Open Access  
New Zealand Journal of Zoology     Hybrid Journal  
Papéis Avulsos de Zoologia     Open Access   (Followers: 1)
Parasite     Open Access   (Followers: 6)
Physiological and Biochemical Zoology     Full-text available via subscription   (Followers: 5)
Polish Journal of Entomology     Open Access   (Followers: 2)
Protist Genomics     Open Access   (Followers: 1)
Remote Sensing in Ecology and Conservation     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: 4)

        1 2     

Journal Cover   Journal of Animal Ecology
  [SJR: 3.074]   [H-I: 102]   [32 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  [1607 journals]
  • Inferring the effects of potential dispersal routes on the metacommunity
           structure of stream insects: as the crow flies, as the fish swims or as
           the fox runs?
    • Authors: Olli‐Matti Kärnä; Mira Grönroos, Harri Antikainen, Jan Hjort, Jari Ilmonen, Lauri Paasivirta, Jani Heino
      Abstract: 1. Metacommunity research relies largely on proxies for inferring the effect of dispersal on local community structure. Overland and watercourse distances have been typically used as such proxies. A good proxy for dispersal should, however, take into account more complex landscape features that can affect an organism's movement and dispersal. The cost distance approach does just that, allowing determining the path of least resistance across a landscape. 2. Here, we examined the distance decay of assemblage similarity within a subarctic stream insect metacommunity. We tested if overland, watercourse and cumulative cost distances performed differently as correlates of dissimilarity in assemblage composition between sites. We also investigated the effect of body size and dispersal mode on metacommunity organisation. 3. We found that dissimilarities in assemblage composition correlated more strongly with environmental than physical distances between sites. Overland and watercourse distances showed similar correlations to assemblage dissimilarity between sites, being sometimes significantly correlated with biological variation of entire insect communities. In metacommunities deconstructed by body size or dispersal mode, contrary to our expectation, passive dispersers showed a slightly stronger correlation than active dispersers to environmental differences between sites, although passive dispersers also showed a stronger correlation than active dispersers to physical distances between sites. The strength of correlation between environmental distance and biological dissimilarity also varied slightly among the body size classes. 4. After controlling for environmental differences between sites, cumulative cost distances were slightly better correlates of biological dissimilarities than overland or watercourse distances between sites. However, quantitative differences in correlation coefficients were small between different physical distances. 5. Although environmental differences typically override physical distances as determinants of the composition of stream insect assemblages, correlations between environmental distances and biological dissimilarities are typically rather weak. This undetermined variation may be attributable to dispersal processes, which may be captured using better proxies for the process. We suggest that further modifying the measurement of cost distances may be a fruitful avenue, especially if complemented by more direct natural history information on insect dispersal behaviour and distances travelled by them. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-18T04:04:20.700177-05:
      DOI: 10.1111/1365-2656.12397
       
  • The role of a dominant predator in shaping biodiversity over space and
           time in a marine ecosystem
    • Authors: Kari E. Ellingsen; Marti J. Anderson, Nancy L. Shackell, Torkild Tveraa, Nigel G. Yoccoz, Kenneth T. Frank
      Abstract: Exploitation of living marine resources has resulted in major changes to populations of targeted species and functional groups of large‐bodied species in the ocean. However, the effects of over‐fishing and collapse of large top predators on the broad‐scale biodiversity of oceanic ecosystems remains largely unexplored. Populations of the Atlantic cod (Gadus morhua) were overfished and several collapsed in the early 1990s across Atlantic Canada, providing a unique opportunity to study potential ecosystem‐level effects of the reduction of a dominant predator on fish biodiversity, and to identify how such effects might interact with other environmental factors, such as changes in climate, over time. We combined causal modelling with model selection and multi‐model inference to analyse 41 years of fishery‐independent survey data (1970‐2010) and quantify ecosystem‐level effects of over‐fishing and climate variation on the biodiversity of fishes across a broad area (172,000 km2) of the Scotian Shelf. We found that alpha and beta diversity increased with decreases in cod occurrence; fish communities were less homogeneous and more variable in systems where cod no longer dominated. These effects were most pronounced in the colder north‐eastern parts of the Scotian Shelf. Our results provide strong evidence that intensive harvesting (and collapse) of marine apex predators can have large impacts on biodiversity, with far‐reaching consequences for ecological stability across an entire ecosystem. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-18T04:03:18.416362-05:
      DOI: 10.1111/1365-2656.12396
       
  • Movement is the glue connecting home ranges and habitat selection
    • Authors: Bram Van Moorter; Christer M. Rolandsen, Mathieu Basille, Jean‐Michel Gaillard
      Abstract: 1.Animal space use has been studied by focusing either on geographic (e.g., home ranges, species’ distribution) or environmental (e.g., habitat use and selection) space. However, all patterns of space use emerge from individual movements, which are the primary means by which animals change their environment. 2.Individuals increase their use of a given area by adjusting two key movement components: the duration of their visit, and/or the frequency of re‐visits. Thus, in spatially heterogeneous environments animals exploit known, high‐quality resource areas by increasing their Residence Time (RT) in and/or decreasing their Time to Return (TtoR) to these areas. We expected that spatial variation in these two movement properties should lead to observed patterns of space use in both geographic and environmental spaces. We derived a set of 9 predictions linking spatial distribution of movement properties to emerging space use patterns. We predicted that, at a given scale, high variation in RT and TtoR among habitats leads to strong habitat selection, and that long RT and short TtoR result in a small home range size. 3.We tested these predictions using moose (Alces alces) GPS tracking data. We first modelled the relationship between landscape characteristics and movement properties. Then, we investigated how the spatial distribution of predicted movement properties (i.e., spatial autocorrelation, mean, and variance of RT and TtoR) influences home range size and hierarchical habitat selection. 4.In landscapes with high spatial autocorrelation of RT and TtoR, a high variation in both RT and TtoR occurred in home ranges. As expected, home range location was highly selective in such landscapes (i.e., 2nd‐order habitat selection); RT was higher and TtoR lower within the selected home range than outside, and moose home ranges were small. Within home ranges, a higher variation in both RT and TtoR was associated to higher selectivity among habitat types (i.e., 3rd‐order habitat selection). 5.Our findings show how patterns of geographic and environmental space use correspond to the two sides of a coin, linked by movement responses of individuals to environmental heterogeneity. By demonstrating the potential to assess the consequences of altering RT or TtoR (e.g., through human disturbance or climatic changes) on home range size and habitat selection, our work sets the basis for new theoretical and methodological advances in movement ecology. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-16T00:15:47.35042-05:0
      DOI: 10.1111/1365-2656.12394
       
  • Spatial distribution of fishes in a Northwest Atlantic ecosystem in
           relation to risk of predation by a marine mammal
    • Authors: Douglas P. Swain; Hugues P. Benoît, Mike O. Hammill
      Abstract: 1.Numerous studies have shown that, at spatial scales of meters to several kilometers, animals balance the trade‐off between foraging success and predation mortality by increasing their use of safer but less profitable habitats as predation risk increases. However, it is less clear whether prey respond similarly at the larger spatiotemporal scales of many ecosystems. 2.We determine whether this behaviour is evident in a large marine ecosystem, the southern Gulf of St. Lawrence (sGSL, 75,000 km2) over a 42‐year period. This ecosystem is characterized by a recent increase in the abundance of a large marine predator, the grey seal (Halichoerus grypus Fabricius), by more than an order of magnitude. 3.We compared changes in spatial distribution over the 1971‐2012 period between important prey of grey seals (Atlantic cod, Gadus morhua L.; white hake, Urophycis tenuis Mitchill; and thorny skate, Amblyraja radiata Donovan) and non‐prey fishes. Distribution was modelled using Generalized Additive Models incorporating spatially‐variable effects of predation risk, density dependence and water temperature. 4.Distributions of cod, hake and skate were strongly related to risk of predation by seals, with distribution shifting into lower risk areas as predation risk increased. Non‐prey species did not show similar changes in habitat use. Spatial variation in fish condition suggests that these low risk areas are also less profitable for cod and skate in terms of food availability. The effects of density‐dependence and water temperature were also important in models, but did not account for the changes in habitat use as risk of predation increased. 5.These results indicate that these fish are able to assess and respond to spatial variation in predation risk at very large spatial scales. They also suggest that non‐consumptive “risk” effects may be an important component of the declines in productivity of seal prey in this ecosystem, and of the indirect effects at lower trophic levels. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-14T08:52:49.322374-05:
      DOI: 10.1111/1365-2656.12391
       
  • Population density and climate shape early‐life survival and
           recruitment in a long‐lived pelagic seabird
    • Authors: R Fay; H Weimerskirch, K Delord, C Barbraud
      Abstract: 1. Our understanding of demographic processes is mainly based on analyses of traits from the adult component of populations. Early‐life demographic traits are poorly known mainly for methodological reasons. Yet, survival of juvenile and immature individuals is critical for the recruitment into the population and thus for the whole population dynamic, especially for long‐lived species. This bias currently restrains our ability to fully understand population dynamic of long‐lived species and life history theory. 2. The goal of this study was to estimate the early‐life demographic parameters of a long‐lived species with a long immature period (9‐10 years), to test for sex and age effects on these parameters, and to identify the environmental factors encountered during the period of immaturity that may influence survival and recruitment. 3. Using capture‐mark‐recapture multi‐event models allowing us to deal with uncertain and unobservable individual states, we analysed a long‐term data set of wandering albatrosses to estimate both age and sex specific early‐life survival and recruitment. We investigated environmental factors potentially driving these demographic traits using climatic and fisheries covariates and tested for density dependence. 4. Our study provides for the first time an estimate of annual survival during the first two years at sea for an albatross species (0.801±0.014). Both age and sex affected early‐life survival and recruitment processes of this long‐lived seabird species. Early‐life survival and recruitment were highly variable across years although the sensitivity of young birds to environmental variability decreased with age. Early‐life survival was negatively associated with sea surface temperature and recruitment rate was positively related to both Southern Annular Mode and sea surface temperature. We found strong evidence for density dependence mortality of juveniles. Population size explained 41% of the variation of this parameter over the study period. 5. These results indicate that early‐life survival and recruitment were strongly age and sex‐dependent in a dimorphic long‐lived species. In addition, early life demographic parameters were affected by natal environmental conditions and by environmental conditions faced during the period of immaturity. Finally, our results constitute one of the first demonstrations of density dependence on juvenile survival in seabirds, with major consequences for our understanding of population dynamics in seabirds. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-14T08:51:53.564576-05:
      DOI: 10.1111/1365-2656.12390
       
  • Double decomposition: decomposing the variance in subcomponents of male
           extra‐pair reproductive success
    • Authors: Sylvain Losdat; Peter Arcese, Jane M. Reid
      Abstract: 1.Extra‐pair reproductive success (EPRS) is a key component of male fitness in socially monogamous systems, and could cause selection on female extra‐pair reproduction if extra‐pair offspring (EPO) inherit high value for EPRS from their successful extra‐pair fathers. However, EPRS is itself a composite trait that can be fully decomposed into subcomponents of variation, each of which can be further decomposed into genetic and environmental variances. However, such decompositions have not been implemented in wild populations, impeding evolutionary inference. 2.We first show that EPRS can be decomposed into the product of three life‐history subcomponents: the number of broods available to a focal male to sire EPO, the male's probability of siring an EPO in an available brood, and the number of offspring in available broods. This decomposition of EPRS facilitates estimation from field data because all subcomponents can be quantified from paternity data without need to quantify extra‐pair matings. Our decomposition also highlights that the number of available broods, and hence population structure and demography, might contribute substantially to variance in male EPRS and fitness. 3.We then used 20 years of complete genetic paternity and pedigree data from wild song sparrows (Melospiza melodia) to partition variance in each of the three subcomponents of EPRS, and thereby estimate their additive genetic variance and heritability conditioned on effects of male coefficient of inbreeding, age and social status. 4.All three subcomponents of EPRS showed some degree of within‐male repeatability, reflecting combined permanent environmental and genetic effects. Number of available broods and offspring per brood showed low additive genetic variances. The estimated additive genetic variance in extra‐pair siring probability was larger, although the 95% credible interval still converged towards zero. Siring probability also showed inbreeding depression and increased with male age, while the numbers of available broods and offspring per brood did not. 5.Our results indicate that the probability that a male will sire an extra‐pair offspring in an available brood is the primary source of genetic variation in male EPRS, implying that the evolution of female extra‐pair reproduction could be facilitated by genetic covariance with this subcomponent of EPRS. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-14T08:41:15.056339-05:
      DOI: 10.1111/1365-2656.12389
       
  • Exploiting the richest patch has a fitness pay‐off for the migratory
           swift parrot
    • Authors: Dejan Stojanovic; Aleks Terauds, Martin J. Westgate, Matthew H. Webb, David A. Roshier, Robert Heinsohn
      Abstract: Unlike philopatric migrants, the ecology of nomadic migrants is less well understood. This life‐history strategy reflects responses to spatiotemporal variation in resource availability and the need to find resource rich patches to initiate breeding. The fitness consequences of movements between regions of patchily distributed resources can provide insight into ecology of all migrants and their responses to global change. We link broad‐scale data on spatiotemporal fluctuation in food availability to data on settlement patterns and fitness outcomes for a nomadic migrant, the endangered swift parrot Lathamus discolor. We test several predictions to determine whether facultative movements are adaptive for individual swift parrots in an environment where resources are patchily distributed over time and space. Variation in the availability of swift parrot food resources across our study period was dramatic. As a consequence, swift parrots moved to breed wherever food was most abundant and did not resettle nesting regions in successive years when food availability declined. By moving, swift parrots exploited a variable food resource and reproduced successfully. Exploiting the richest patches allowed swift parrots to maintain stable fitness outcomes between discrete breeding events at different locations. Unlike sedentary species that often produce few or lower quality offspring when food is scarce, nomadic migration buffered swift parrots against extreme environmental variation. We provide the first detailed evidence that facultative movements and nomadic migration are adaptive for individuals in unpredictable environments. Our data support the widely held assumption that nomadic migration allows animals to escape resource limitation. Exploiting the richest patch allowed swift parrots to maintain stable reproductive outcomes irrespective of the particular location where they bred. Unlike sedentary species that often produce few or lower quality offspring when food is scarce, nomadic migration buffered swift parrots against extreme environmental variation.
      PubDate: 2015-05-14T00:58:13.324726-05:
      DOI: 10.1111/1365-2656.12375
       
  • Age‐related effects of chronic hantavirus infection on female host
           fecundity
    • Authors: Eva R. Kallio; Heikki Helle, Esa Koskela, Tapio Mappes, Olli Vapalahti
      Abstract: 1.Pathogens often cause detrimental effects to their hosts and, consequently, may influence host population dynamics that may, in turn, feed back to pathogen transmission dynamics. Understanding fitness effects of pathogens upon animal host populations can help to predict the risks that zoonotic pathogens pose to humans. 2.Here we determine whether chronic infection by Puumala hantavirus (PUUV) affects important fitness related traits, namely the probability of breeding, reproductive effort and mother and offspring condition, in the bank vole (Myodes glareolus). Using nine years empirical data in a PUUV endemic area in Central Finland, we found differences between reproductive characteristics of PUUV‐infected and uninfected female bank voles. 3.Young infected females had a significantly higher, and old individuals lower, likelihood of reproducing than uninfected animals during the middle of the breeding season. The implication is that PUUV infection may have long‐term deleterious effects that are observed at old age, while in young individuals the infection may enhance breeding probability by directing resources towards current breeding. 4.Moreover, PUUV infection was related with the mother's body condition. Infected mothers were in poorer condition than uninfected mothers in the early breeding season, but were in better condition than uninfected mothers during the middle of the breeding season. Offspring body condition was positively associated with mother's body condition, which, in turn, was related to the PUUV infection status of the mother. 5.Our findings indicate that chronic infection may affect the reproduction of female hosts, but the effect is dependent on the host age. The effect of chronic hantavirus infection was small and density‐independent and hence unlikely to contribute to the cyclic population dynamics of the host. However, the effects on a female's reproductive output might affect the abundance of young susceptible individuals in the population and hence influence the transmission and persistence of the pathogen. Although experimental and long‐term capture‐mark‐recapture studies are required to further clarify the fitness effects of hantavirus infection and their consequences for pathogen dynamics, this study shows that the infection may have complex effects that are dependent on the age of the individual and the time of the breeding season. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-12T10:17:17.430852-05:
      DOI: 10.1111/1365-2656.12387
       
  • Predicting the continuum between corridors and barriers to animal
           movements using Step Selection Functions and Randomized Shortest Paths
    • Authors: Manuela Panzacchi; Bram Van Moorter, Olav Strand, Marco Saerens, Ilkka Kivimäki, Colleen Cassady St.Clair, Ivar Herfindal, Luigi Boitani
      Abstract: 1.The loss, fragmentation, and degradation of habitat everywhere on Earth prompt increasing attention to identifying landscape features that support animal movement (corridors) or impede it (barriers). Most algorithms used to predict corridors assume that animals move through preferred habitat either optimally (e.g. Least Cost Path), or as random‐walkers (e.g. Current Models), but neither extreme is realistic. 2.We propose that corridors and barriers are two sides of the same coin, and that animals experience landscapes as spatio‐temporally dynamic corridor‐barrier continua connecting (separating) functional areas where individuals fulfill specific ecological processes. Based on this conceptual framework, we propose a novel methodological approach that uses high‐resolution individual‐based movement data to predict corridor‐barrier continua with increased realism. 3.Our approach consists of two innovations. First, we use Step Selection Functions (SSF) to predict friction maps quantifying corridor‐barrier continua for tactical steps between consecutive locations. Second, we introduce to movement ecology the Randomized Shortest Path algorithm (RSP) which operates on friction maps to predict the corridor‐barrier continuum for strategic movements between functional areas. By modulating the parameter Ѳ, which controls the trade‐off between exploration and optimal exploitation of the environment, RSP bridges the gap between algorithms assuming optimal movements (when Ѳ approaches infinity, RSP is equivalent to LCP) or random‐walk (when Ѳ → 0, RSP → Current Models). 4.Using this approach, we identify migration corridors for GPS‐monitored wild reindeer (Rangifer t. tarandus) in Norway. We demonstrate that reindeer movement is best predicted by an intermediate value of Ѳ, indicative of a movement trade‐off between optimization and exploration. Model calibration allows identification of a corridor‐barrier continuum that closely fits empirical data, and demonstrates that RSP outperforms models that assume either optimality or random‐walk. 5.The proposed approach models the multi‐scale cognitive maps by which animals likely navigate real landscapes, and generalizes the most common algorithms for identifying corridors. Because sub‐optimal, but non‐random, movement strategies are likely widespread, our approach has the potential to predict more realistic corridor‐barrier continua for a wide range of species. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-07T03:56:33.585073-05:
      DOI: 10.1111/1365-2656.12386
       
  • Seasonal Demography of a Cyclic Lemming Population in the Canadian Arctic
    • Authors: Dominique Fauteux; Gilles Gauthier, Dominique Berteaux
      Abstract: 1.The causes of cyclical fluctuations in animal populations remain a controversial topic in ecology. Food limitation and predation are two leading hypotheses to explain small mammal population dynamics in northern environments. We documented the seasonal timing of the decline phases and demographic parameters (survival and reproduction) associated with population changes in lemmings, allowing us to evaluate some predictions from these two hypotheses. 2.We studied the demography of brown lemmings (Lemmus trimucronatus), a species showing 3‐4 year population cycles in the Canadian Arctic, by combining capture‐mark‐recapture analysis of summer live‐trapping with monitoring of winter nests over a 10‐year period. We also examined the effects of some weather variables on survival. 3.We found that population declines after a peak occurred between the summer and winter period and not during the winter. During the summer, population growth was driven by change in survival, but not in fecundity or proportion of juveniles, whereas in winter population growth was driven by changes in late summer and winter reproduction. 4.We did not find evidence for direct density‐dependence on summer demographic parameters, though our analysis was constrained by the paucity of data during the low phase. Body mass, however, was highest in peak years. 5.Weather effects were detected only in early summer when lemming survival was positively related to snow depth at the onset of melt but negatively related to rainfall. 6.Our results show that high mortality causes population declines of lemmings during summer and fall, which suggests that predation is sufficient to cause population crashes, whereas high winter fecundity is the primary factor leading to population irruptions. The positive association between snow depth and early summer survival may be due to the protective cover offered by snow against predators. It is still unclear why reproduction remains low during the low phase. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-05T02:16:32.001481-05:
      DOI: 10.1111/1365-2656.12385
       
  • Greater flexibility in metabolic rate confers a growth advantage under
           changing food availability
    • Authors: Sonya K. Auer; Karine Salin, Agata M. Rudolf, Graeme J. Anderson, Neil B. Metcalfe
      Abstract: 1.Phenotypic flexibility in physiological, morphological, and behavioural traits can allow organisms to cope with environmental challenges. Given recent climate change and the degree of habitat modification currently experienced by many organisms, it is therefore critical to quantify the degree of phenotypic variation present within populations, individual capacities to change, and what their consequences are for fitness. 2.Flexibility in standard metabolic rate (SMR) may be particularly important since SMR reflects the minimal energetic cost of living and is one of the primary traits underlying organismal performance. SMR can increase or decrease in response to food availability, but the consequences of these changes for growth rates and other fitness components are not well known. 3.We examined individual variation in metabolic flexibility in response to changing food levels and its consequences for somatic growth in juvenile brown trout (Salmo trutta). 4.SMR increased when individuals were switched to a high food ration and decreased when they were switched to a low food regime. These shifts in SMR, in turn, were linked with individual differences in somatic growth; those individuals that increased their SMR more in response to elevated food levels grew fastest, while growth at the low food level was fastest in those individuals that depressed their SMR most. 5.Flexibility in energy metabolism is therefore a key mechanism to maximize growth rates under the challenges imposed by variability in food availability and is likely to be an important determinant of species’ resilience in the face of global change. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-05T02:08:03.743865-05:
      DOI: 10.1111/1365-2656.12384
       
  • Digestive capacity predicts diet diversity in Neotropical frugivorous bats
    • Authors: Romeo A. Saldaña‐Vázquez; Eduardo Ruiz‐Sanchez, Leonel Herrera‐Alsina, Jorge E. Schondube
      Abstract: 1.Predicting the diet diversity of animals is important to basic and applied ecology. Knowledge of diet diversity in animals helps us understand niche partitioning, functional diversity and ecosystem services such as pollination, pest control and seed dispersal. 2.There is a negative relationship between the length of the digestive tract and diet diversity in animals; however the role of digestive physiology in determining diet diversity has been ignored. This is especially important in vertebrates with powered flight because, unlike non‐flying vertebrates, they have limitations that may constrain gut size. 3.Here we evaluate the relationship between digestive capacity and diet diversity in Carollinae and Stenodermatinae frugivorous bats. These bats disperse the seeds of plants that are key to Neotropical forest regeneration. 4.Our results show that digestive capacity is a good predictor of diet diversity in Carollinae and Stenodermatinae frugivorous bats (R2 = 0.77). 5.Surprisingly, the most phylogenetically closely related species were not similar in their digestive capacity or diet diversity. The lack of a phylogenetic signal for the traits evaluated implies differences in digestive physiology and diet in closely related species. 6.Our results highlight the predictive usefulness of digestive physiology for understanding the feeding ecology of animals. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-28T07:14:26.855774-05:
      DOI: 10.1111/1365-2656.12383
       
  • What is the animal doing' Tools for exploring behavioral structure in
           animal movements
    • Authors: Eliezer Gurarie; Chloe Bracis, Maria Delgado, Trevor D. Meckley, Ilpo Kojola, C. Michael Wagner
      Abstract: 1.Movement data provide a window ‐ often our only window ‐ into the cognitive, social and biological processes that underlie the behavioral ecology of animals in the wild. Robust methods for identifying and interpreting distinct modes of movement behavior are of great importance, but complicated by the fact that movement data are complex, multivariate, and dependent. Many different approaches to exploratory analysis of movement have been developed to answer similar questions and practitioners are often at a loss for how to choose an appropriate tool for a specific question. 2.We apply and compare four methodological approaches: first passage time (FPT), Bayesian partitioning of Markov models (BPMM), behavioral change point analysis (BCPA), and a fitted multi‐state random walk (MRW) to three simulated tracks and two animal trajectories ‐ a sea lamprey (Petromyzon marinus) tracked for 12 hours and a wolf (Canis lupus) tracked for one year. 3.The simulations ‐ in which, respectively, velocity, tortuosity, and spatial bias change ‐ highlight the sensitivity of all methods to model misspecification. Methods that do not account for autocorrelation in the movement variables lead to spurious change points while methods that do not account for spatial bias completely miss changes in orientation. We make suggestions towards unifying directions for methodological advances. 4.When applied to the animal data, the methods broadly agree on the structure of the movement behaviors. Important discrepancies, however, reect differences in the assumptions and nature of the outputs. Important trade‐offs are between the strength of the a priori assumptions (low in BCPA, high in MRW), complexity of output (high in the BCPA, low in the BPMM and MRW), and explanatory potential (highest in the MRW). 5.The animal track analysis suggests some general principles for the exploratory analysis of movement data, including ways to exploit the strengths of the various methods. We argue for close and detailed exploratory analysis of movement before fitting complex movement models. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-23T09:48:38.045866-05:
      DOI: 10.1111/1365-2656.12379
       
  • Social information from immigrants: multiple immigrant based sources of
           information for dispersal decisions in a ciliate
    • Authors: Staffan Jacob; Alexis S. Chaine, Nicolas Schtickzelle, Michèle Huet, Jean Clobert
      Abstract: Dispersal is increasingly recognized as being an informed process, based on information organisms obtain about the landscape. While local conditions are often found to drive dispersal decisions, local context is not always a reliable predictor of conditions in neighbouring patches, making the use of local information potentially useless or even maladaptive. In this case, using social information gathered by immigrants might allow adjusting dispersal decisions without paying the costs of prospecting. However, this hypothesis has been largely neglected despite its major importance for ecological and evolutionary processes. We investigated three fundamental questions about immigrant informed dispersal: do immigrants convey information that influences dispersal, do organisms use multiple cues from immigrants, and is immigrant informed dispersal genotype‐dependent' Using Tetrahymena thermophila ciliates in microcosms, we manipulated the number of immigrants arriving, the density of congeners and resource quality in neighbouring patches, matrix characteristics and the level of cooperation of individuals in the neighbouring populations. We provide the first experimental evidence that immigrants convey a number of different cues about neighbouring patches and matrix (patch quality, matrix characteristics, and cooperation in neighbouring populations) in this relatively simple organism. Furthermore, we demonstrate genotype‐dependent immigrant‐informed dispersal decisions about patch quality and matrix characteristics. Multiple cues from immigrants and genotype‐dependent use of cues have major implications for theoretical metapopulation dynamics and the potential for local adaptation. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-22T20:46:08.042846-05:
      DOI: 10.1111/1365-2656.12380
       
  • Disentangling direct and growth‐mediated influences on early
           survival: a mechanistic approach
    • Authors: Floriane Plard; Nigel G. Yoccoz, Christophe Bonenfant, François Klein, Claude Warnant, Jean‐Michel Gaillard
      Abstract: 1.Early survival is a key life‐history trait that often accounts for a large part of the variation in individual fitness and shapes population dynamics. The factors influencing early survival are multiple in large herbivores, including malnutrition, predation, cohort variation or maternal effects. However, the mechanistic pathways connecting these drivers to variation in early survival are much less studied. Indeed, whether these factors influence early survival directly or indirectly through early growth remains to be disentangled. 2.In this study, we used a path analysis to separate the direct and indirect (i.e. mediated by early growth) pathways through which sex, birth date, cohort and family effects influence early survival. We used a large dataset of marked roe deer newborns collected from 1985 to 2010 in the intensively monitored population of Trois Fontaines (France). 3.We found that most drivers have indirect influences on early survival through early growth. Indeed, cohort effects influenced early survival through the indirect effect of precipitation around birth on early growth during the birth period. Precipitation also had direct effects on early survival. Family effects indirectly influenced early survival. Twins from the same litter grew at about the same rate, so they had the same fate. Moreover, some factors, such as birth date, had both direct and indirect effects on roe deer early survival, with fawns born early in the season benefiting from high early survival both because they have more time to grow before the harsh season and because they grow faster during their first days of life than late‐born fawns. 4.These findings suggest that most drivers of early survival previously identified in large mammalian herbivores may affect early survival primarily through their influence on early growth. Disentangling the direct and indirect pathways by which different factors influence early survival is of crucial importance to understand the mechanisms shaping this key component of individual fitness. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-17T01:20:54.66407-05:0
      DOI: 10.1111/1365-2656.12378
       
  • Migration timing and its determinants for nocturnal migratory birds during
           autumn migration
    • Authors: Frank A. La Sorte; Wesley H. Hochachka, Andrew Farnsworth, Daniel Sheldon, Daniel Fink, Jeffrey Geevarghese, Kevin Winner, Benjamin M. Van Doren, Steve Kelling
      Abstract: 1.Migration is a common strategy used by birds that breed in seasonal environments, and multiple environmental and biological factors determine the timing of migration. How these factors operate in combination during autumn migration, which is considered to be under weaker time constraints relative to spring migration, is not clear. 2.Here, we examine the patterns and determinants of migration timing for nocturnal migrants during autumn migration in the northeastern USA using nocturnal reflectivity data from 12 weather surveillance radar stations and modeled diurnal probability of occurrence for 142 species of nocturnal migrants. We first model the capacity of seasonal atmospheric conditions (wind and precipitation) and ecological productivity (vegetation greenness) to predict autumn migration intensity. We then test predictions, formulated under optimal migration theory, on how migration timing should be related to assemblage‐level estimates of body size and total migration distance within the context of dietary guild (insectivore and omnivore) and level of dietary plasticity during autumn migration. 3.Our results indicate seasonal declines in ecological productivity delineate the beginning and end of peak migration, whose intensity is best predicted by the velocity of winds at migration altitudes. Insectivorous migrants departed earlier in the season and, consistent with our predictions, large‐bodied and long‐distance insectivorous migrants departed the earliest. Contrary to our predictions, large‐bodied and some long‐distance omnivorous migrants departed later in the season, patterns that were replicated in part by insectivorous migrants that displayed dietary plasticity during autumn migration. 4.Our findings indicate migration timing in the region is dictated by optimality strategies, modified based on the breadth and flexibility of migrant's foraging diets, with declining ecological productivity defining possible resource thresholds during which migration occurs when winds at migration altitudes are mild. These observations provide the basis to assess how avian migration strategies may be affected by adjustments in seasonal patterns of atmospheric circulation and ecological productivity that may occur under global climate change. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-08T01:49:08.480832-05:
      DOI: 10.1111/1365-2656.12376
       
  • Antagonistic effect of helpers on breeding male and female survival in a
           cooperatively breeding bird
    • Authors: Matthieu Paquet; Claire Doutrelant, Ben J. Hatchwell, Claire N. Spottiswoode, Rita Covas
      Abstract: 1.Cooperatively breeding species are typically long‐lived and hence, according to theory, are expected to maximise their lifetime reproductive success through maximising survival. Under these circumstances, the presence of helpers could be used to lighten the effort of current reproduction for parents to achieve higher survival. 2.In addition, individuals of different sexes and ages may follow different strategies, but whether male and female breeders and individuals of different ages benefit differently from the presence of helpers has often been overlooked. Moreover only one study that investigated the relationship between parental survival and the presence of helpers used Capture‐Mark‐Recaptures analyses (CMR). These methods are important since they allow us to account for the non‐detection of individuals that are alive in the population but not detected, and thus the effects on survival and recapture probability to be disentangled. 3.Here we used multi‐event CMR methods to investigate whether the number of helpers was associated with an increase in survival probability for male and female breeders of different ages in the sociable weaver Philetairus socius. In this species, both sexes reduce their feeding rate in presence of helpers. We therefore predicted that the presence of helpers should increase the breeders’ survival in both sexes, especially early in life when individuals potentially have more future breeding opportunities. In addition, sociable weaver females reduce their investment in eggs in the presence of helpers, so we predicted a stronger effect of helpers on female than male survival. 4.As expected we found that females had a higher survival probability when breeding with more helpers. Unexpectedly, however, male survival probability decreased with increasing number of helpers. This antagonistic effect diminished as the breeders grew older. 5.These results illustrate the complexity of fitness costs and benefits underlying cooperative behaviours and how these may vary with the individuals’ sex and age. They also highlight the need for further studies on the sex‐specific effects of helpers on survival. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-08T01:48:53.143626-05:
      DOI: 10.1111/1365-2656.12377
       
  • The interaction between the spatial distribution of resource patches and
           population density: consequences for intra‐specific growth and
           morphology
    • Authors: Bailey Jacobson; James W. A. Grant, Pedro R. Peres‐Neto
      Abstract: 1.How individuals within a population distribute themselves across resource patches of varying quality has been an important focus of ecological theory. The Ideal Free Distribution predicts equal fitness among individuals in a 1:1 ratio with resources, whereas resource defence theory predicts different degrees of monopolization (fitness variance) as a function of temporal and spatial resource clumping and population density. 2.One overlooked landscape characteristic is the spatial distribution of resource patches, altering the equitability of resource accessibility and thereby the effective number of competitors. While much work has investigated the influence of morphology on competitive ability for different resource types, less is known regarding the phenotypic characteristics conferring relative ability for a single resource type, particularly when exploitative competition predominates. 3.Here we used young‐of‐the‐year rainbow trout (Oncorhynchus mykiss) to test whether and how the spatial distribution of resource patches and population density interact to influence the level and variance of individual growth, as well as if functional morphology relates to competitive ability. Feeding trials were conducted within stream channels under three spatial distributions of 9 resource patches (distributed, semi‐ and clumped) at two density levels (9 and 27 individuals). 4.Average trial growth was greater in high‐density treatments with no effect of resource distribution. Within‐trial growth variance had opposite patterns across resource distributions. Here, variance decreased at low‐, but increased at high‐population densities as patches became increasingly clumped as the result of changes in the levels of interference versus exploitative competition. Within‐trial growth was related to both pre‐ and post‐trial morphology where competitive individuals were those with traits associated with swimming capacity and efficiency: larger heads/bodies/caudal fins and less angled pectoral fins. 5.The different degrees of within‐population growth variance at the same density level found here, as a function of spatial resource distribution, provides an explanation for the inconsistencies in within‐site growth variance and population regulation often noted with regards to density‐dependence in natural landscapes. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-06T08:34:11.414394-05:
      DOI: 10.1111/1365-2656.12365
       
  • Wolves adapt territory size, not pack size to local habitat quality
    • Authors: Andrew M. Kittle; Morgan Anderson, Tal Avgar, James A. Baker, Glen S. Brown, Jevon Hagens, Ed Iwachewski, Scott Moffatt, Anna Mosser, Brent R. Patterson, Douglas E.B. Reid, Arthur R. Rodgers, Jen Shuter, Garrett M. Street, Ian D. Thompson, Lucas M. Vander Vennen, John M. Fryxell
      Abstract: 1.Although local variation in territorial predator density is often correlated with habitat quality, the causal mechanism underlying this frequently observed association is poorly understood and could stem from facultative adjustment in either group size or territory size. 2.To test between these alternative hypotheses we used a novel statistical framework to construct a winter population‐level utilization distribution for wolves (Canis lupus) in northern Ontario, which we then linked to a suite of environmental variables to determine factors influencing wolf space use. Next we compared habitat quality metrics emerging from this analysis as well as an independent measure of prey abundance, with pack size and territory size to investigate which hypothesis was most supported by the data. 3.We show that wolf space use patterns were concentrated near deciduous, mixed deciduous/coniferous and disturbed forest stands favoured by moose (Alces alces), the predominant prey species in the diet of wolves in northern Ontario, and in proximity to linear corridors, including shorelines and road networks remaining from commercial forestry activities. 4.We then demonstrate that landscape metrics of wolf habitat quality – projected wolf use, probability of moose occupancy and proportion of preferred land cover classes ‐ were inversely related to territory size but unrelated to pack size. 5.These results suggest that wolves in boreal ecosystems alter territory size, but not pack size, in response to local variation in habitat quality. This could be an adaptive strategy to balance tradeoffs between territorial defense costs and energetic gains due to resource acquisition. That pack size was not responsive to habitat quality suggests that variation in group size is influenced by other factors such as intra‐specific competition between wolf packs. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-06T08:33:50.619013-05:
      DOI: 10.1111/1365-2656.12366
       
  • Drivers of climate change impacts on bird communities
    • Authors: James W. Pearce‐Higgins; Sarah M. Eglington, Blaise Martay, Dan E. Chamberlain
      Abstract: 1.Climate change is reported to have caused widespread changes to species’ populations and ecological communities. Warming has been associated with population declines in long‐distance migrants and habitat specialists, and increases in southerly distributed species. However, the specific climatic drivers behind these changes remain undescribed. 2.We analysed annual fluctuations in the abundance of 59 breeding bird species in England over 45 years to test the effect of monthly temperature and precipitation means upon population trends. 3.Strong positive correlations between population growth and both winter and breeding season temperature were identified for resident and short‐distance migrants. Lagged correlations between population growth and summer temperature and precipitation identified for the first time a widespread negative impact of hot, dry summer weather. Resident populations appeared to increase following wet autumns. Populations of long‐distance migrants were negatively affected by May temperature, consistent with a potential negative effect of phenological mismatch upon breeding success. There was evidence for some non‐linear relationships between monthly weather variables and population growth. 4.Habitat specialists and cold‐associated species showed consistently more negative effects of higher temperatures than habitat generalists and southerly‐distributed species associated with warm temperatures, suggesting that previously reported changes in community composition represent the accumulated effects of spring and summer warming. 5.Long‐term population trends were more significantly correlated with species’ sensitivity to temperature than precipitation, suggesting that warming had had a greater impact on population trends than changes in precipitation. Months where there had been the greatest warming were the most influential drivers of long‐term change. There was also evidence that species with the greatest sensitivity to extremes of precipitation have tended to decline. 6. Our results provide novel insights about the impact of climate change on bird communities. Significant lagged effects highlight the potential for altered species’ interactions to drive observed climate change impacts, although some community changes may have been driven by more immediate responses to warming. In England, resident and short‐distance migrant populations have increased in response to climate change, but potentially at the expense of long‐distance migrants, habitat‐specialists and cold‐associated species. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-06T08:30:16.588002-05:
      DOI: 10.1111/1365-2656.12364
       
  • Flowering time of butterfly nectar food plants is more sensitive to
           temperature than the timing of butterfly adult flight
    • Authors: Heather M. Kharouba; Mark Vellend
      Abstract: Variation among species in their phenological responses to temperature change suggests that shifts in the relative timing of key life cycle events between interacting species are likely to occur under climate warming. However, it remains difficult to predict the prevalence and magnitude of these shifts given that there have been few comparisons of phenological sensitivities to temperature across interacting species. Here, we used a broad‐scale approach utilizing collection records to compare the temperature sensitivity of the timing of adult flight in butterflies vs. flowering of their potential nectar food plants (days/°C) across space and time in British Columbia, Canada. On average, the phenology of both butterflies and plants advanced in response to warmer temperatures. However, the two taxa were differentially sensitive to temperature across space vs. across time, indicating the additional importance of non‐temperature cues and/or local adaptation for many species. Across butterfly‐plant associations, flowering time was significantly more sensitive to temperature than the timing of butterfly flight and these sensitivities were not correlated. Our results indicate that warming‐driven shifts in the relative timing of life cycle events between butterflies and plants are likely to be prevalent, but that predicting the magnitude and direction of such changes in particular cases is going to require detailed, fine‐scale data. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-31T04:19:03.570022-05:
      DOI: 10.1111/1365-2656.12373
       
  • Shape up or ship out: migratory behaviour predicts morphology across
           spatial scale in a freshwater fish
    • Authors: Ben B. Chapman; Kaj Hulthén, Christer Brönmark, P. Anders Nilsson, Christian Skov, Lars‐Anders Hansson, Jakob Brodersen
      Abstract: 1.Migration is a widespread phenomenon, with powerful ecological and evolutionary consequences. Morphological adaptations to reduce the energetic costs associated with migratory transport are commonly documented for migratory species. However few studies have investigated whether variation in body morphology can be explained by variation in migratory strategy within a species. 2.We address this question in roach Rutilus rutilus, a partially migratory freshwater fish that migrates from lakes into streams during winter. We both compare body shape between populations that differ in migratory opportunity (open versus closed lakes), and between individuals from a single population that vary in migratory propensity (migrants and residents from a partially migratory population). Following hydrodynamic theory, we posit that migrants should have a more shallow body depth, to reduce the costs associated with migrating into streams with higher flow conditions than the lakes the residents occupy all year round. 3.We find evidence both across and within‐populations to support our prediction, with individuals from open lakes and migrants from the partially migratory population having a more slender, shallow‐bodied morphology than fish from closed lakes and all‐year residents. 4.Our data suggest that a shallow body morphology is beneficial to migratory individuals and our study is one of the first to link migratory strategy and intraspecific variation in body shape. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-30T10:04:53.146635-05:
      DOI: 10.1111/1365-2656.12374
       
  • Patterns of trophic niche divergence between invasive and native fishes in
           wild communities are predictable from mesocosm studies
    • Authors: Thi Nhat Quyen Tran; Michelle C. Jackson, Danny Sheath, Hugo Verreycken, J. Robert Britton
      Abstract: 1.Ecological theory attempts to predict how impacts for native species arise from biological invasions. A fundamental question centres on the feeding interactions of invasive and native species: whether invasion will result in increased inter‐specific competition, which would result in negative consequences for the competing species, or trophic niche divergence, which would facilitate the invader's integration into the community and their co‐existence with native species. 2.Here, the feeding interactions of a highly invasive fish, topmouth gudgeon Pseudorasbora parva, with three native and functionally similar fishes were studied to determine whether patterns of either niche overlap or divergence detected in mesocosm experiments were apparent between the species at larger spatial scales. Using stable isotope analysis, their feeding relationships were assessed initially in the mesocosms (1000 L), and then in small ponds (< 400 square metres) and large ponds (> 600 square metres). 3.In the mesocosms, a consistent pattern of trophic niche divergence was evident between the sympatric fishes, with niches shifting further apart in isotopic space than suggested in allopatry, revealing that sharing of food resources was limited. Sympatric Pseudorasbora parva also had a smaller niche than their allopatric populations. 4.In eight small ponds where P. parva had coexisted for several years with at least one of the fish species used in the mesocosms, strong patterns of niche differentiation were also apparent, with P. parva always at a lower trophic position than the other fishes, as also occurred in the mesocosms. Where these fishes were sympatric within more complex fish communities in the large ponds, similar patterns were also apparent, with strong evidence of trophic niche differentiation. 5.Aspects of the ecological impacts of P. parva invasion for native communities in larger ponds were consistent with those in the mesocosm experiments. Their invasion resulted in divergence in trophic niches, partly due to their reduced niche widths when in sympatry with other species, facilitating their coexistence in invaded ecosystems. Our study highlights the utility of controlled mesocosm studies for predicting the trophic relationships that can develop from introductions of non‐native species into more complex ecosystems and at larger spatial scales. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-30T08:39:01.624524-05:
      DOI: 10.1111/1365-2656.12360
       
  • Optimal population prediction of sandhill crane recruitment based on
           climate‐mediated habitat limitations
    • Authors: Brian D. Gerber; William L. Kendall, Mevin B. Hooten, James A. Dubovsky, Roderic C. Drewien
      Abstract: 1.Prediction is fundamental to scientific inquiry and application; however, ecologists tend to favor explanatory modeling. We discuss a predictive modeling framework to evaluate ecological hypotheses and to explore novel/unobserved environmental scenarios to assist conservation and management decision makers. We apply this framework to develop an optimal predictive model for juvenile (
      PubDate: 2015-03-24T07:54:44.165516-05:
      DOI: 10.1111/1365-2656.12370
       
  • Informed herbivore movement and interplant communication determine the
           effects of induced resistance in an individual‐based model
    • Authors: Ilan N. Rubin; Stephen P. Ellner, Andre Kessler, Kimberly A. Morrell
      Abstract: 1.Plant induced resistance to herbivory affects the spatial distribution of herbivores, as well as their performance. In recent years, theories regarding the benefit to plants of induced resistance have shifted from ideas of optimal resource allocation towards a more eclectic set of theories that consider spatial and temporal plant variability and the spatial distribution of herbivores among plants. However, consensus is lacking on whether induced resistance causes increased herbivore aggregation or increased evenness, as both trends have been experimentally documented. 2.We created a spatial individual‐based model that can describe many plant‐herbivore systems with induced resistance, in order to analyze how different aspects of induced resistance might affect herbivore distribution, and the total damage to a plant population, during a growing season. 3.We analyze the specific effects on herbivore aggregation of informed herbivore movement (preferential movement to less‐damaged plants) and of information transfer between plants about herbivore attacks, in order to identify mechanisms driving both aggregation and evenness. We also investigate how the resulting herbivore distributions affect the total damage to plants and aggregation of damage. 4.Even, random and aggregated herbivore distributions can all occur in our model with induced resistance. Highest levels of aggregation occurred in the models with informed herbivore movement, and the most even distributions occurred when the average number of herbivores per plant was low. With constitutive resistance only random distributions occur. Damage to plants was spatially correlated, unless plants recover very quickly from damage; herbivore spatial autocorrelation was always weak. 5.Our model and results provide a simple explanation for the apparent conflict between experimental results indicating that both increased aggregation and increased evenness of herbivores can result from induced resistance. We demonstrate that information transfer from plants to herbivores, and from plants to neighboring plants, can both be major factors in determining nonrandom herbivore distributions. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-23T07:00:30.317305-05:
      DOI: 10.1111/1365-2656.12369
       
  • Measuring β‐diversity with species abundance data
    • Authors: Louise J. Barwell; Nick J. B. Isaac, William E. Kunin
      Abstract: In 2003, 24 presence‐absence β‐diversity metrics were reviewed and a number of trade‐offs and redundancies identified. We present a parallel investigation into the performance of abundance‐based metrics of β‐diversity is lacking. β‐diversity is a multi‐faceted concept, central to spatial ecology. There are multiple metrics available to quantify it: the choice of metric is an important decision. We test 16 conceptual properties and two sampling properties of a β‐diversity metric: metrics should be 1) independent of α‐diversity and 2) cumulative along a gradient of species turnover. Similarity should be 3) probabilistic when assemblages are independently and identically distributed. Metrics should have 4) a minimum of zero and increase monotonically with the degree of 5) species turnover, 6) decoupling of species ranks and 7) evenness differences. However, complete species turnover should always generate greater values of β than extreme 8) ranks shifts or 9) evenness differences. Metrics should 10) have a fixed upper limit, 11) symmetry (βA,B=βB,A), 12) double‐zero asymmetry for double‐absences and double‐presences and 13) not decrease in a series of nested assemblages. Additionally, metrics should be independent of 14) species replication 15) the units of abundance and 16) differences in total abundance between sampling units. When samples are used to infer β‐diversity, metrics should be 1) independent of sample sizes and 2) independent of unequal sample sizes. We test 29 metrics for these properties and five “personality” properties. Thirteen metrics were outperformed or equalled across all conceptual and sampling properties. Differences in sensitivity to species’ abundance lead to a performance trade‐off between sample size bias and the ability to detect turnover among rare species. In general, abundance‐based metrics are substantially less biased in the face of undersampling, although the presence‐absence metric, βsim, performed well overall. Only βBaselga R turn, βBaselga B‐C turn and βsim measured purely species turnover and were independent of nestedness. Among the other metrics, sensitivity to nestedness varied >4‐fold. Our results indicate large amounts of redundancy among existing β‐diversity metrics, while the estimation of unseen shared and unshared species is lacking and should be addressed in the design of new abundance‐based metrics. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-21T09:21:27.315014-05:
      DOI: 10.1111/1365-2656.12362
       
  • Resources, key traits, and the size of fungal epidemics in Daphnia
           populations
    • Authors: David J. Civitello; Rachel M. Penczykowski, Aimee N. Smith, Marta S. Shocket, Meghan A. Duffy, Spencer R. Hall
      Abstract: Parasites can profoundly affect host populations and ecological communities. Thus, it remains critical to identify mechanisms that drive variation in epidemics. Resource availability can drive epidemics via traits of hosts and parasites that govern disease spread. Here, we map resource‐trait‐epidemic connections to explain variation in fungal outbreaks (Metschnikowia bicuspidata) in a zooplankton host (Daphnia dentifera) among lakes. We predicted epidemics would grow larger in lakes with more phytoplankton via three energetic mechanisms. First, resources should stimulate Daphnia reproduction, potentially elevating host density. Second, resources should boost body size of hosts, enhancing exposure to environmentally distributed propagules through size‐dependent feeding. Third, resources should fuel parasite reproduction within hosts. To test these predictions, we sampled 12 natural epidemics and tracked edible algae, fungal infection prevalence, body size, fecundity, and density of hosts, as well as within‐host parasite loads. Epidemics grew larger in lakes with more algal resources. Structural equation modeling revealed that resource availability stimulated all three traits (host fecundity, host size, and parasite load). However, only parasite load connected resources to epidemic size. Epidemics grew larger in more dense Daphnia populations, but host density was unrelated to host fecundity (thus breaking its link to resources). Thus, via energetic mechanisms, resource availability can stimulate key trait(s) governing epidemics in nature. A synthetic focus on resources and resource‐trait links could yield powerful insights into epidemics. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-21T09:21:22.199205-05:
      DOI: 10.1111/1365-2656.12363
       
  • Space‐use behavior of woodland caribou based on a cognitive movement
           model
    • Authors: Tal Avgar; James A. Baker, Glen S. Brown, Jevon S. Hagens, Andrew M. Kittle, Erin E. Mallon, Madeleine T. McGreer, Anna Mosser, Steven G. Newmaster, Brent R. Patterson, Douglas E. B. Reid, Art R. Rodgers, Jennifer Shuter, Garrett M. Street, Ian Thompson, Merritt J. Turetsky, Philip A. Wiebe, John M. Fryxell
      Abstract: Movement patterns offer a rich source of information on animal behavior and the ecological significance of landscape attributes. This is especially useful for species occupying remote landscapes where direct behavioral observations are limited. In this study we fit a mechanistic model of animal cognition and movement to GPS positional data of woodland caribou (Rangifer tarandus caribou; Gmelin 1788) collected over a wide range of ecological conditions. The model explicitly tracks individual animal informational state over space and time, with resulting parameter estimates that have direct cognitive and ecological meaning. Three biotic landscape attributes were hypothesized to motivate caribou movement: forage abundance (dietary digestible biomass), wolf (Canis lupus; Linnaeus, 1758) density, and moose (Alces alces; Linnaeus, 1758) habitat. Wolves are the main predator of caribou in this system and moose are their primary prey. Resulting parameter estimates clearly indicated that forage abundance is an important driver of caribou movement patterns, with predator and moose avoidance often having a strong effect, but not for all individuals. From the cognitive perspective, our results support the notion that caribou rely on limited sensory inputs from their surroundings, as well as on long‐term spatial memory, to make informed movement decisions. Our study demonstrates how sensory, memory and motion capacities may interact with ecological fitness covariates to influence movement decisions by free‐ranging animals. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-20T04:49:52.072333-05:
      DOI: 10.1111/1365-2656.12357
       
  • Parasitoid wasps indirectly suppress seed production by stimulating
           consumption rates of their seed‐feeding hosts
    • Authors: Xinqiang Xi; Nico Eisenhauer, Shucun Sun
      Abstract: 1.In parasitoid‐herbivore‐plant food chains, parasitoids may be simultaneously linked with both herbivore hosts and plants, as occurs when herbivores attacked by parasitoids continue to consume plants although they are destined to die. This peculiar property may cause parasitoids to confer a differential trophic cascading effect on plants than that known for typical predators. 2.We hypothesized that larval koinobiont parasitoids would confer an immediate negative effect on plant seed production by stimulating consumption of their seed predator hosts. We tested this hypothesis in an alpine parasitic food chain of plant seeds, pre‐dispersal seed predators (tephritid fly larvae), and koinobiont parasitoids using field observations, a field experiment, and a microcosm study. 3.We first compared observed seed production in a) non‐infected capitula, b) capitula infected only by seed predators (tephritid flies), and c) capitula infected by both seed predators and their parasitoids in five Asteraceae species. Consistent with our hypothesis, seed loss in the capitula with both seed predators and parasitoids was significantly greater than in the capitula infested only by seed predators. 4.This effect was replicated in a controlled field experiment focusing on the most common parasitoid‐seed predator‐plant interaction chain in our system, in which confounding factors (e.g., density and phenology) were excluded. Here we show that parasitoids indirectly decreased plant seed production by changing the behavior of seed predators. 5.In a microcosm study we show that larval parasitoids significantly extended the growth period and increased the terminal size of their host tephritid maggots. Thus, parasitoids suppressed plant seed production by stimulating the growth and consumption of the fly maggots. 6.In contrast to the typical predator‐induced trophic cascade, we highlight the significance of parasitoids indirectly decreasing plant fitness by stimulating consumption by seed predators. Future studies on trophic interactions should consider the net effect of both increased consumption by seed predators and their death after development of parasitoids. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-20T04:49:25.781001-05:
      DOI: 10.1111/1365-2656.12361
       
  • Global patterns and predictors of fish species richness in estuaries
    • Authors: Rita P. Vasconcelos; Sofia Henriques, Susana França, Stéphanie Pasquaud, Inês Cardoso, Marina Laborde, Henrique N. Cabral
      Abstract: 1.Knowledge on global patterns of biodiversity and regulating variables is indispensable to develop predictive models. 2.The present study used predictive modelling approaches to investigate hypotheses that explain the variation in fish species richness between estuaries over a worldwide spatial extent. Ultimately, such models will allow assessment of future changes in ecosystem structure and function as a result of environmental changes. 3.A comprehensive worldwide database was compiled on the fish assemblage composition and environmental characteristics of estuaries. Generalized Linear Models were used to quantify how variation in species richness among estuaries is related to historical events, energy dynamics, and ecosystem characteristics, whilst controlling for sampling effect. 4.At the global extent, species richness differed among marine biogeographic realms and continents, and increased with mean sea surface temperature, terrestrial net primary productivity, and the stability of connectivity with marine ecosystem (open versus temporarily open estuaries). At a smaller extent (within marine biogeographic realm or continent) other characteristics were also important in predicting variation in species richness, with species richness increasing with estuary area and continental shelf width. 5.The results suggest that species richness in an estuary is defined by predictors that are spatially hierarchical. Over the largest spatial extents species richness is influenced by the broader distributions and habitat use patterns of marine and freshwater species that can colonize estuaries, which are in turn governed by history contingency, energy dynamics and productivity variables. Species richness is also influenced by more regional and local parameters that can further affect the process of community colonization in an estuary including the connectivity of the estuarine with the adjacent marine habitat, and, over smaller spatial extents, the size of these habitats. In summary, patterns of species richness in estuaries across large spatial extents seem to reflect from global to local processes acting on community colonization. The importance of considering spatial extent, sampling effects and of combining history and contemporary environmental characteristics when exploring biodiversity is highlighted. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-18T22:35:30.023007-05:
      DOI: 10.1111/1365-2656.12372
       
  • Plant resistance reduces the strength of consumptive and
           non‐consumptive effects of predators on aphids
    • Authors: Mônica F. Kersch‐Becker; Jennifer S. Thaler
      Abstract: 1.The impact of predators on prey has traditionally been attributed to the act of consumption. Prey responses to the presence of the predator (non‐consumptive effects), however, can be as important as predation itself. While plant defenses are known to influence predator‐prey interactions, their relative effects on consumptive versus non‐consumptive effects are not well understood. 2.We evaluated the consequences of plant resistance and predators (Hippodamia convergens) on the mass, number of nymphs, population growth, density, and dispersal of aphids (Macrosiphum euphorbiae). We tested for the effects of plant resistance on non‐consumptive and consumptive effects of predators on aphid performance and dispersal using a combination of path analysis and experimental manipulation of predation risk. 3.We manipulated plant resistance using genetically modified lines of tomato (Solanum lycopersicum) that vary incrementally in the expression of the jasmonate pathway, which mediates induced resistance to insects and manipulated aphid exposure to lethal and risk predators. Predation risk predators had mandibles impaired to prevent killing. 4.Plant resistance reduced predation rate (consumptive effect) on high‐resistance plants. As a consequence, predators had no impact on the number of nymphs, aphid density or population growth on high‐resistance plants, whereas on low‐resistance plants predators reduced aphid density by 35% and population growth by 86%. Path analysis and direct manipulation of predation risk showed that predation risk rather than predation rate promoted aphid dispersal, and varied with host plant resistance. Aphid dispersal in response to predation risk was greater on low‐ compared to high‐resistance plants. The predation risk experiment also showed that the number of aphid nymphs increased in the presence of risk predators but did not translate into increased population growth. 5.In conclusion, the consumptive and non‐consumptive components of predators affect different aspects of prey demography, acting together to shape prey population dynamics. While predation risk accounts for most of the total effect of the predator on aphid dispersal and number of nymphs, the suppressive effect of predators on aphid population occurred largely through consumption. These effects are strongly influenced by plant resistance levels, suggesting that they are context dependent. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-18T04:49:08.771202-05:
      DOI: 10.1111/1365-2656.12371
       
  • Context‐dependent survival, fecundity, and predicted
           population‐level consequences of brucellosis in African buffalo
    • Authors: Erin E. Gorsich; Vanessa O. Ezenwa, Paul C. Cross, Roy G. Bengis, Anna E. Jolles
      Abstract: 1.Chronic infections may have negative impacts on wildlife populations, yet their effects are difficult to detect in the absence of long‐term population monitoring. Brucella abortus, the bacteria responsible for bovine brucellosis, causes chronic infections and abortions in wild and domestic ungulates, but its impact on population dynamics is not well understood. 2.We report infection patterns and fitness correlates of bovine brucellosis in African buffalo based on (1) seven years of cross‐sectional disease surveys and (2) a four‐year longitudinal study in Kruger National Park (KNP), South Africa. We then used a matrix population model to translate these observed patterns into predicted population‐level effects. 3.Annual brucellosis seroprevalence ranged from 8.7% (95% CI=1.8‐15.6) to 47.6% (95% CI=35.1‐60.1), increased with age until adulthood (>6), and varied by location within KNP. Animals were on average in worse condition after testing positive for brucellosis (F=‐5.074, p
      PubDate: 2015-03-18T02:08:44.874922-05:
      DOI: 10.1111/1365-2656.12356
       
  • Population size structure dependent fitness and ecosystem consequences in
           trinidadian guppies
    • Authors: Ronald D. Bassar; Thomas Heatherly, Michael C. Marshall, Steven A. Thomas, Alexander S. Flecker, David N. Reznick
      Abstract: 1.Decades of theory and recent empirical results have shown that evolutionary, population, community and ecosystem properties are the result of feedbacks between ecological and evolutionary processes. The vast majority of theory and empirical research on these eco‐evolutionary feedbacks has focused on interactions among population size and mean traits of populations. 2.However, numbers and mean traits represent only a fraction of the possible feedback dimensions. Populations of many organisms consist of different size classes that differ in their impact on the environment and each other. Moreover, rarely do we know the map of ecological pathways through which changes in numbers or size structure cause evolutionary change. The goal of this study was to test the role of size structure in eco‐evolutionary feedbacks of Trinidadian guppies and to begin to build an eco‐evolutionary map along this unexplored dimension. 3.We used a factorial experiment in mesocosms wherein we crossed high and low predation guppy phenotypes with population size structure. We tested the ability of changes in size structure to generate selection on the demographic rates of guppies using an integral projection model (IPM). To understand how fitness differences among high and low predation phenotypes may be generated, we measured the response of the biomass of lower trophic levels and nutrient cycling to the different phenotype and size structure treatments. 4.We found a significant interaction between guppy phenotype and the size structure treatments for absolute fitness. Size structure had a very large effect on invertebrate biomass in the mesocosms, but there was little or no effect of the phenotype. The effect of size structure on algal biomass depended on guppy phenotype, with no difference in algal biomass in populations with more, smaller guppies, but a large decrease in algal biomass in mesocosms with phenotypes adapted to low predation risk. 5.These results indicate an important role for size structure partially driving eco‐evolutionary feedbacks in guppies. The changes in the ecosystem suggest that the absence of a steep decline in guppy fitness of the low predation risk populations is likely due to higher consumption of algae when invertebrates are comparatively rare. Overall, these results demonstrate size structure as a possible dimension through which eco‐evolutionary feedbacks may occur in natural populations. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-18T01:48:33.017414-05:
      DOI: 10.1111/1365-2656.12353
       
  • Habitat fragmentation alters the properties of a host‐parasite
           network: rodents and their helminths in South‐East Asia
    • Authors: Frédéric Bordes; Serge Morand, Shai Pilosof, Julien Claude, Boris R. Krasnov, Jean‐François Cosson, Yannick Chaval, Alexis Ribas, Kittipong Chaisiri, Kim Blasdell, Vincent Herbreteau, Stéphane Dupuy, Annelise Tran
      Abstract: 1.While the effects of deforestation and habitat fragmentation on parasite prevalence or richness are well investigated, host‐parasite networks are still understudied despite their importance in understanding the mechanisms of these major disturbances. Because fragmentation may negatively impact species occupancy, abundance and co‐occurrence, we predict a link between spatiotemporal changes in habitat and the architecture of host‐parasite networks. 2.For this we used an extensive data set on 16 rodent species and 29 helminth species from 7 localities of South‐East Asia. We analysed the effects of rapid deforestation on connectance and modularity of helminth‐parasite networks. We estimated both the degree of fragmentation and the rate of deforestation through the development of land uses and their changes through the last 20 to 30 years in order to take into account the dynamics of habitat fragmentation in our statistical analyses. 3.We found that rapid fragmentation does not affect helminth species richness per se but impacts host‐parasite interactions as the rodent‐helminth network becomes less connected and more modular. 4.Our results suggest that parasite sharing among host species may become more difficult to maintain with the increase of habitat disturbance. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-16T17:28:59.990357-05:
      DOI: 10.1111/1365-2656.12368
       
  • Differences in host species relationships and biogeographical influences
           produce contrasting patterns of prevalence, community composition and
           genetic structure in two genera of avian malaria parasites in southern
           Melanesia
    • Authors: Sophie Olsson‐Pons; Nicholas J. Clark, Farah Ishtiaq, Sonya M. Clegg
      Abstract: 1.Host‐parasite interactions have the potential to influence broad scale ecological and evolutionary processes, levels of endemism, divergence patterns and distributions in host populations. Understanding the mechanisms involved requires identification of the factors that shape parasite distribution and prevalence. 2.A lack of comparative information on community‐level host‐parasite associations limits our understanding of the role of parasites in host population divergence processes. Avian malaria (haemosporodian) parasites in bird communities offer a tractable model system to examine the potential for pathogens to influence evolutionary processes in natural host populations. 3.Using cytochrome b variation, we characterized phylogenetic diversity and prevalence of two genera of avian haemosporidian parasites, Plasmodium and Haemoproteus, and analysed biogeographic patterns of lineages across islands and avian hosts, in southern Melanesian bird communities to identify factors that explain patterns of infection. 4.Plasmodium spp. displayed isolation by distance effects, a significant amount of genetic variation distributed among islands but insignificant amounts among host species and families, and strong local island effects with respect to prevalence. Haemoproteus spp. did not display isolation by distance patterns, showed significant structuring of genetic variation among avian host species and families, and significant host species prevalence patterns. 5.These differences suggest that Plasmodium spp. infection patterns were shaped by geography and the abiotic environment, whereas Haemoproteus spp. infection patterns were shaped predominantly by host associations. Heterogeneity in the complement and prevalence of parasite lineages infecting local bird communities likely exposes host species to a mosaic of spatially divergent disease selection pressures across their naturally fragmented distributions in southern Melanesia. Host associations for Haemoproteus spp. indicate a capacity for the formation of locally co‐adapted host‐parasite relationships, a feature that may limit intraspecific gene flow or range expansions of closely related host species. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-16T02:56:45.635066-05:
      DOI: 10.1111/1365-2656.12354
       
  • Spatial variation in age structure among colonies of a marine snake: the
           influence of ectothermy
    • Authors: Xavier Bonnet; François Brischoux, David Pinaud, Catherine Louise Michel, Jean Clobert, Richard Shine, Thomas Fauvel
      Abstract: Several tetrapod lineages that have evolved to exploit marine environments (e.g., seals, seabirds, sea kraits) continue to rely upon land for reproduction; and thus, form dense colonies on suitable islands. In birds and mammals (endotherms) the offspring cannot survive without their parents. Terrestrial colonies contain all age classes. In reptiles (ectotherms) this constraint is relaxed, because offspring are independent from birth. Hence, each age class has the potential to select sites with characteristics that favour them. Our studies of sea snakes (sea kraits) in the lagoon of New Caledonia reveal marked spatial heterogeneity in age structure among colonies. Sea krait colonies exhibit the endothermic “seal‐seabird” pattern (mixed age classes within populations) only where the lagoon is narrow. Where the lagoon is wide, most snake colonies are comprised primarily of a single age cohort. Nurseries are located near the coast, adult colonies offshore, and mixed colonies in between. We suggest that ectothermy allows individuals to utilize habitats that are best‐suited to their own ecological requirements, a flexibility not available to endothermic marine taxa with obligate parental care. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-16T02:44:54.004887-05:
      DOI: 10.1111/1365-2656.12358
       
  • Can habitat selection predict abundance'
    • Authors: Mark S. Boyce; Chris J. Johnson, Evelyn H. Merrill, Scott E. Nielsen, Erling J. Solberg, Bram Moorter
      Abstract: Habitats have substantial influence on the distribution and abundance of animals. Animals’ selective movement yields their habitat use. Animals generally are more abundant in habitats that are selected most strongly. Models of habitat selection can be used to distribute animals on the landscape or their distribution can be modeled based on data of habitat use, occupancy, intensity of use, or counts of animals. When the population is at carrying capacity or in an ideal free distribution, habitat selection and related metrics of habitat use can be used to estimate abundance. If the population is not at equilibrium, models have the flexibility to incorporate density into models of habitat selection; but abundance might be influenced by factors influencing fitness that are not directly related to habitat thereby compromising the use of habitat‐based models for predicting population size. Scale and domain of the sampling frame, both in time and space, are crucial considerations limiting application of these models. Ultimately, identifying reliable models for predicting abundance from habitat data requires an understanding of the mechanisms underlying population regulation and limitation. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-16T02:44:25.832642-05:
      DOI: 10.1111/1365-2656.12359
       
  • Ant–mediated ecosystem functions on a warmer planet: effects on soil
           movement, decomposition and nutrient cycling
    • Authors: Israel Del Toro; Relena R. Ribbons, Aaron M. Ellison
      Abstract: 1.Direct and indirect consequences of global warming on ecosystem functions and processes mediated by invertebrates remain understudied but are likely to have major impacts on ecosystems in the future. Among animals, invertebrates are taxonomically diverse, responsive to temperature changes, and play major ecological roles which also respond to temperature changes. 2.We used a mesocosm experiment to evaluate impacts of two warming treatments (+3.5 and + 5 °C, set points) and the presence and absence of the ant Formica subsericea (a major mediator of processes in north‐temperate ecosystems) on decomposition rate, soil movement, soil respiration, and nitrogen availability. 3.Replicate 19‐Litre mesocosms were placed outdoors in lathe houses and continuously warmed for 30 days in 2011 and 85 days in 2012. Warming treatments mimicked expected temperature increases for future climates in eastern North America. 4.In both years, the amount of soil displaced and soil respiration increased in the warming and ant presence treatments (soil movement: 73 – 119%; soil respiration: 37 – 48% relative to the control treatments without ants). 5.Decomposition rate and nitrogen availability tended to decrease in the warmest treatments (decomposition rate: ‐26 – ‐30%; nitrate availability: ‐11 – ‐42%). 6.Path analyses indicated that ants had significant short term direct and indirect effects on the studied ecosystem processes. These results suggest that ants may be moving more soil and building deeper nests to escape increasing temperatures, but warming may also influence their direct and indirect effects on soil ecosystem processes. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-13T08:59:00.994513-05:
      DOI: 10.1111/1365-2656.12367
       
  • Detailed monitoring of a small but recovering population reveals sublethal
           effects of disease and unexpected interactions with supplemental feeding
    • Authors: Simon Tollington; Andrew Greenwood, Carl G. Jones, Paquita Hoeck, Aurélie Chowrimootoo, Donal Smith, Heather Richards, Vikash Tatayah, Jim J. Groombridge
      Abstract: Infectious diseases are widely recognized to have substantial impact on wildlife populations. These impacts are sometimes exacerbated in small endangered populations, and therefore, the success of conservation reintroductions to aid the recovery of such species can be seriously threatened by outbreaks of infectious disease. Intensive management strategies associated with conservation reintroductions can further compound these negative effects in such populations. Exploring the sublethal effects of disease outbreaks among natural populations is challenging and requires longitudinal, individual life‐history data on patterns of reproductive success and other indicators of individual fitness. Long‐term monitoring data concerning detailed reproductive information of the reintroduced Mauritius parakeet (Psittacula echo) population collected before, during and after a disease outbreak was investigated. Deleterious effects of an outbreak of beak and feather disease virus (BFDV) were revealed on hatch success, but these effects were remarkably short‐lived and disproportionately associated with breeding pairs which took supplemental food. Individual BFDV infection status was not predicted by any genetic, environmental or conservation management factors and was not associated with any of our measures of immune function, perhaps suggesting immunological impairment. Experimental immunostimulation using the PHA (phytohaemagglutinin assay) challenge technique did, however, provoke a significant cellular immune response. We illustrate the resilience of this bottlenecked and once critically endangered, island‐endemic species to an epidemic outbreak of BFDV and highlight the value of systematic monitoring in revealing inconspicuous but nonetheless substantial ecological interactions. Our study demonstrates that the emergence of such an infectious disease in a population ordinarily associated with increased susceptibility does not necessarily lead to deleterious impacts on population growth and that negative effects on reproductive fitness can be short‐lived. Using long‐term monitoring data of a once critically endangered parakeet species, the authors document the effect on reproductive parameters of an epidemic outbreak of infectious disease. The negative effect on the population characterised by reduced hatch success was remarkably short‐lived and associated only with individuals which consumed supplemental food.
      PubDate: 2015-03-09T03:15:42.189511-05:
      DOI: 10.1111/1365-2656.12348
       
  • In hot and cold water: differential life‐history traits are key to
           success in contrasting thermal deep‐sea environments
    • Authors: Leigh Marsh; Jonathan T. Copley, Paul A. Tyler, Sven Thatje
      Abstract: Few species of reptant decapod crustaceans thrive in the cold‐stenothermal waters of the Southern Ocean. However, abundant populations of a new species of anomuran crab, Kiwa tyleri, occur at hydrothermal vent fields on the East Scotia Ridge. As a result of local thermal conditions at the vents, these crabs are not restricted by the physiological limits that otherwise exclude reptant decapods south of the polar front. We reveal the adult life history of this species by piecing together variation in microdistribution, body size frequency, sex ratio, and ovarian and embryonic development, which indicates a pattern in the distribution of female Kiwaidae in relation to their reproductive development. High‐density ‘Kiwa’ assemblages observed in close proximity to sources of vent fluids are constrained by the thermal limit of elevated temperatures and the availability of resources for chemosynthetic nutrition. Although adult Kiwaidae depend on epibiotic chemosynthetic bacteria for nutrition, females move offsite after extrusion of their eggs to protect brooding embryos from the chemically harsh, thermally fluctuating vent environment. Consequently, brooding females in the periphery of the vent field are in turn restricted by low‐temperature physiological boundaries of the deep‐water Southern Ocean environment. Females have a high reproductive investment in few, large, yolky eggs, facilitating full lecithotrophy, with the release of larvae prolonged, and asynchronous. After embryos are released, larvae are reliant on locating isolated active areas of hydrothermal flow in order to settle and survive as chemosynthetic adults. Where the cold water restricts the ability of all adult stages to migrate over long distances, these low temperatures may facilitate the larvae in the location of vent sites by extending the larval development period through hypometabolism. These differential life‐history adaptations to contrasting thermal environments lead to a disjunct life history among males and females of K. tyleri, which is key to their success in the Southern Ocean vent environment. We highlight the complexity in understanding the importance of life‐history biology, in combination with environmental, ecological and physiological factors contributing to the overall global distribution of vent‐endemic species. This paper reveals key features of the life‐history biology of the visually dominant species at newly discovered Antarctic deep‐sea hydrothermal vents, demonstrating contrasting influences of hydrothermal and polar deep‐sea conditions on distribution, population structure, sex‐ratio, reproductive development and global biogeography of vent endemic species.
      PubDate: 2015-03-02T19:47:51.418857-05:
      DOI: 10.1111/1365-2656.12337
       
  • Host age modulates parasite infectivity, virulence and reproduction
    • Authors: Rony Izhar; Frida Ben‐Ami
      Abstract: 1.Host age is one of the most striking differences among hosts within most populations, but there is very little data on how age‐dependent effects impact ecological and evolutionary dynamics of both the host and the parasite. 2.Here we examined the influence of host age (juveniles, young and old adults) at parasite exposure on host susceptibility, fecundity and survival as well as parasite transmission, using two clones of the water flea Daphnia magna and two clones of its bacterial parasite Pasteuria ramosa. 3.Younger D. magna were more susceptible to infection than older ones, regardless of host or parasite clone. Also, younger‐infected D. magna became castrated faster than older hosts, but host and parasite clone effects contributed to this trait as well. Furthermore, the early‐infected D. magna produced considerably more parasite transmission stages than late‐infected ones, while host age at exposure did not affect virulence as it is defined in models (host mortality). 4.When virulence is defined more broadly as the negative effects of infection on host fitness, by integrating the parasitic effects on host fecundity and mortality, then host age at exposure seems to slide along a negative relationship between host and parasite fitness. Thus, the virulence‐transmission trade‐off differs strongly among age classes, which in turn affects predictions of optimal virulence. 5.Age‐dependent effects on host susceptibility, virulence and parasite transmission could pose an important challenge for experimental and theoretical studies of infectious disease dynamics and disease ecology. Our results present a call for a more explicit stage‐structured theory for disease, which will incorporate age‐dependent epidemiological parameters. This article is protected by copyright. All rights reserved.
      PubDate: 2015-02-09T00:56:28.845454-05:
      DOI: 10.1111/1365-2656.12352
       
  • Indirect effects of predators control herbivore richness and abundance in
           a benthic eelgrass (Zostera marina) mesograzer community
    • Authors: Sarah L. Amundrud; Diane S. Srivastava, Mary I. O'Connor
      Abstract: 1.Herbivore communities can be sensitive to changes in predator pressure (top‐down effects) and resource availability (bottom‐up effects) in a wide range of systems. However, it remains unclear whether such top‐down and bottom‐up effects reflect direct impacts of predators and/or resources on herbivores, or are indirect, reflecting altered interactions amongst herbivore species. 2.We quantified direct and indirect effects of bottom‐up and top‐down processes on an eelgrass (Zostera marina) herbivore assemblage. In a field experiment, we factorially manipulated water column nutrients (with Osmocote™ slow‐release fertilizer) and predation pressure (with predator‐exclusion cages) and measured the effects on herbivore abundance, richness, and beta diversity. We examined likely mechanisms of community responses by statistically exploring the response of individual herbivore species to trophic manipulations. 3.Predators increased herbivore richness and total abundance, in both cases through indirect shifts in community composition. Increases in richness occurred through predator suppression of common gammarid amphipod species (Monocorophium acherusicum and Photis brevipes), permitting the inclusion of rarer gammarid species (Aoroides columbiae and Pontogeneia rostrata). Increased total herbivore abundance reflected increased abundance of a caprellid amphipod species (Caprella sp.), concurrent with declines in the abundance of other common species. Furthermore, predators decreased beta diversity by decreasing variability in Caprella sp. abundance among habitat patches. 4.Osmocote™ fertilization increased nutrient concentrations locally, but nutrients dissipated to background levels within 3 m of the fertilizer. Nutrient addition weakly affected the herbivore assemblage, not affecting richness and increasing total abundance by increasing one herbivore species (Caprella sp.). Nutrient addition did not affect beta diversity. 5.We demonstrated that assemblage‐level effects of trophic manipulations on community structure are the result of distinct and often indirect responses of herbivore species. These results underscore the importance of understanding herbivore‐herbivore interactions in a system commonly subjected to both eutrophication and overfishing. This article is protected by copyright. All rights reserved.
      PubDate: 2015-02-09T00:51:52.168881-05:
      DOI: 10.1111/1365-2656.12350
       
  • Discriminative host sanction together with relatedness promote the
           cooperation in fig/fig wasp mutualism
    • Authors: Rui‐Wu Wang; Bao‐Fa Sun, Yan Yang
      Abstract: 1.Sanctioning or punishing are regarded as one of most important dynamics in the evolution of cooperation. However, it has not been empirically examined yet whether or not such enforcement selection by sanctioning or punishing and classical theories like kin or reciprocity selection are separate mechanisms contributing to the evolution of cooperation. In addition, it remains largely unclear what factors determine the intensity or effectiveness of sanction. 2.Here we show that in the obligate, inter‐specific cooperation between figs and fig wasps, the hosted figs can discriminatively sanction cheating individuals by decreasing the offspring development ratio. Concurrently, the figs can reward the cooperative pollinators with a higher offspring development ratio. This sanction intensity and effectiveness largely depend on how closely the host and symbiont are related either in terms of reciprocity exchange or genetic similarity as measured by the reciprocal of the foundress number. 3.Our results imply that in asymmetric systems, symbionts might be forced to evolve to be cooperative or even altruistic through discriminative sanction against the non‐cooperative symbiont and reward to the cooperative symbiont by the host (i.e., through a game of “carrot and stick”). This article is protected by copyright. All rights reserved.
      PubDate: 2015-02-09T00:51:36.547257-05:
      DOI: 10.1111/1365-2656.12351
       
  • To each its own: differential response of specialist and generalist
           herbivores to plant defence in willows
    • Authors: Martin Volf; Jan Hrcek, Riitta Julkunen‐Tiitto, Vojtech Novotny
      Abstract: 1.Plant‐insect food webs tend to be dominated by interactions resulting from diffuse coevolution between plants and multiple lineages of herbivores rather than by reciprocal coevolution and co‐cladogenesis. Plants therefore require defence strategies effective against a broad range of herbivore species. In one extreme, plants could develop a single universal defence effective against all herbivorous insects, or tailor‐made strategies for each herbivore species. The evolution and ecology of plant defence has to be studied with entire insect assemblages, rather than small subsets of pairwise interactions. 2.The present study examines whether specialists and generalists in three coexisting insect lineages, forming the leaf‐chewing guild, respond uniformly to plant phylogeny, secondary metabolites, nutrient content and mechanical anti‐herbivore defences of their hosts, thus permitting universal plant defence strategies against specialised and generalist folivorous insects from various taxa. 3.The extensive data on folivorous assemblages comprising three insect orders and 193 species are linked with plant phylogeny, secondary chemistry (salicylates, flavonoids and tannins), leaf morphological traits (SLA and trichome coverage), nutrient (C:N) content and growth‐form of eight willow (Salix) and one aspen (Populus) species growing in sympatry. 4.Generalists responded to overall host‐plant chemistry and trichomes, whilst specialists responded to host‐plant phylogeny and secondary metabolites that are unique to willows and that are capable of being utilised as an anti‐predator protection. We did not find any significant impact of other plant traits, i.e. specific leaf area, C:N ratio, flavonoids, tannins and growth‐form, on the composition of leaf‐chewing communities. 5.Our results show that the response to plant traits is differential among specialists and generalists. This finding constrains the ability of plants to develop defensive traits universally effective against herbivores and may lead to diversification of plant defensive mechanisms into several complementary syndromes, required for effective protection against generalists and specialists from multiple insect taxa comprising most leaf‐chewing assemblages. These results point to the necessity of broad studies of plant‐herbivore interactions, across multiple insect taxa and guilds. This article is protected by copyright. All rights reserved.
      PubDate: 2015-02-03T11:01:31.05106-05:0
      DOI: 10.1111/1365-2656.12349
       
  • Habitat traits and species interactions differentially affect abundance
           and body size in pond‐breeding amphibians
    • Authors: Brittany H. Ousterhout; Thomas L. Anderson, Dana L. Drake, William E. Peterman, Raymond D. Semlitsch
      Abstract: 1.In recent studies habitat traits have emerged as stronger predictors of species occupancy, abundance, richness and diversity than competition. However, in many cases it remains unclear whether habitat also mediates processes more subtle than competitive exclusion, such as growth, or if intra‐ and interspecific interactions among individuals of different species may be a better predictor of size. 2.To test whether habitat traits are a stronger predictor of abundance and body size than intra‐ and interspecific interactions, we measured the density and body size of three species of larval salamanders in 192 ponds across a landscape. 3.We found that the density of larvae was best predicted by models that included habitat features, while models incorporating interactions among individuals of different species best explained the body size of larvae. Additionally, we found a positive relationship between focal species density and congener density, while focal species body size was negatively related to congener density. 4.We posit that salamander larvae may not experience competitive exclusion, and thus reduced densities, but instead compensate for increased competition behaviorally (e.g. reduced foraging), resulting in decreased growth. The discrepancy between larval density and body size, a strong predictor of fitness in this system, also highlights a potential shortcoming in using density or abundance as a metric of habitat quality or population health. This article is protected by copyright. All rights reserved.
      PubDate: 2015-02-03T04:08:01.872334-05:
      DOI: 10.1111/1365-2656.12344
       
  • Determinants of Individual Foraging Specialisation in Large Marine
           Vertebrates, the Antarctic and Subantarctic Fur Seals
    • Authors: L. Kernaléguen; J. P. Y. Arnould, C. Guinet, Y. Cherel
      Abstract: 1.The degree of individual specialisation in resource use differs widely among wild populations where individuals range from fully generalised to highly specialised. This inter‐individual variation has profound implications in many ecological and evolutionary processes. A recent review proposed four main ecological causes of individual specialisation: inter‐ and intra‐specific competition, ecological opportunity and predation. 2.Using the isotopic signature of sub‐sampled whiskers, we investigated to what degree three of these factors (inter‐ and intra‐specific competition and ecological opportunity) affect the population niche width and the level of individual foraging specialisation in two fur seal species, the Antarctic and subantarctic fur seals (Arctocephalus gazella and A. tropicalis), over several years. 3.Population niche width was greater when the two seal species bred in allopatry (low inter‐specific competition) than in sympatry or when seals bred in high density stabilized colonies (high intra‐specific competition). In agreement with the Niche Variation Hypothesis (NVH), higher population niche width was associated with higher inter‐individual niche variation. However, in contrast with the NVH, all Antarctic females increased their niche width during the inter‐breeding period when they had potentially access to a wider diversity of foraging grounds and associated prey (high ecological opportunities), suggesting they all dispersed to a similar productive area. 4.The degree of individual specialisation varied among populations and within the annual cycle. Highest levels of inter‐individual variation were found in a context of lower inter‐ or higher intra‐specific competition. Contrasted results were found concerning the effect of ecological opportunity. Depending on seal species, females exhibited either a greater or lower degree of individual specialisation during the inter‐breeding period, reflecting species‐specific biological constraints during that period. 5.These results suggest a significant impact of ecological interactions on the population niche width and degree of individual specialisation. Such variation at the individual level may be an important factor in the species plasticity with significant consequences on how it may respond to environmental variability. This article is protected by copyright. All rights reserved.
      PubDate: 2015-02-02T09:45:42.500485-05:
      DOI: 10.1111/1365-2656.12347
       
  • Demographic mechanisms of inbreeding adjustment through extra‐pair
           reproduction
    • Authors: Jane M. Reid; A. Bradley Duthie, Matthew E. Wolak, Peter Arcese
      Abstract: 1.One hypothesis explaining extra‐pair reproduction is that socially monogamous females mate with extra‐pair males to adjust the coefficient of inbreeding (f) of extra‐pair offspring (EPO) relative to that of within‐pair offspring (WPO) they would produce with their socially‐paired male. Such adjustment of offspring f requires non‐random extra‐pair reproduction with respect to relatedness, which is in turn often assumed to require some mechanism of explicit pre‐copulatory or post‐copulatory kin discrimination. 2.We propose three demographic processes that could potentially cause mean f to differ between individual females’ EPO and WPO given random extra‐pair reproduction with available males without necessarily requiring explicit kin discrimination. Specifically, such a difference could arise if social pairings formed non‐randomly with respect to relatedness or persisted non‐randomly with respect to relatedness, or if the distribution of relatedness between females and their sets of potential mates changed during the period through which social pairings persisted. 3.We used comprehensive pedigree and pairing data from free‐living song sparrows (Melospiza melodia) to quantify these three processes and hence investigate how individual females could adjust mean offspring f through instantaneously random extra‐pair reproduction. 4.Female song sparrows tended to form social pairings with unrelated or distantly related males slightly less frequently than expected given random pairing within the defined set of available males. Furthermore, social pairings between more closely related mates tended to be more likely to persist across years than social pairings between less closely related mates. However, these effects were small and the mean relatedness between females and their sets of potential extra‐pair males did not change substantially across the years through which social pairings persisted. 5.Our framework and analyses illustrate how demographic and social structuring within populations might allow females to adjust mean f of offspring through random extra‐pair reproduction without necessarily requiring explicit kin discrimination, implying that adjustment of offspring f might be an inevitable consequence of extra‐pair reproduction. New theoretical and empirical studies are required to explore the general magnitude of such effects and the degree to which they could facilitate or constrain long‐term evolution of extra‐pair reproduction. This article is protected by copyright. All rights reserved.
      PubDate: 2015-02-02T08:41:37.597953-05:
      DOI: 10.1111/1365-2656.12340
       
  • No apparent benefits of allonursing for recipient offspring and mothers in
           the cooperatively breeding meerkat
    • Authors: K. J MacLeod; K. E McGhee, T. H Clutton‐Brock
      Abstract: Cooperative behaviours by definition are those that provide some benefit to another individual. Allonursing, the nursing of non‐descendent young, is often considered a cooperative behavior and is assumed to provide benefits to recipient offspring in terms of growth and survival, and to their mothers, by enabling them to share the lactation load. However, these proposed benefits are not well understood, in part because maternal and litter traits and other ecological and social variables are not independent of one another, making patterns hard to discern using standard univariate analyses. Here, we investigate the potential benefits of allonursing in the cooperatively breeding Kalahari meerkat, where socially subordinate females allonurse the young of a dominant pair without having young of their own. We use structural equation modelling to allow us to account for the interdependence of maternal traits, litter traits and environmental factors. We find no evidence that allonursing provides benefits to pups or mothers. Pups that received allonursing were not heavier at emergence and did not have a higher survival rate than pups that did not receive allonursing. Mothers whose litters were allonursed were not in better physical condition, did not reconceive faster, and did not reduce their own nursing investment compared to mothers who nursed their litters alone. These patterns were not significantly influenced by whether mothers were in relatively good, or poor, condition. We suggest that allonursing may persist in this species because the costs to allonurses may be low. Alternatively allonursing may confer other, more cryptic, benefits to pups or allonurses, such as immunological or social benefits. This article is protected by copyright. All rights reserved.
      PubDate: 2015-01-31T02:03:51.549794-05:
      DOI: 10.1111/1365-2656.12343
       
  • The path to host extinction can lead to loss of generalist parasites
    • Authors: Maxwell J. Farrell; Patrick R. Stephens, Lea Berrang‐Ford, John L. Gittleman, T. Jonathan Davies
      Abstract: Host extinction can alter disease transmission dynamics, influence parasite extinction, and ultimately change the nature of host‐parasite systems. While theory predicts that single‐host parasites are among the parasite species most susceptible to extinction following declines in their hosts, documented parasite extinctions are rare. Using a comparative approach, we investigate how the richness of single‐host and multi‐host parasites is influenced by extinction risk among ungulate and carnivore hosts. Host‐parasite associations for free‐living carnivores (order Carnivora) and terrestrial ungulates (orders Perrisodactlya + Cetartiodactlya minus cetaceans) were merged with host trait data and IUCN Red List status to explore the distribution of single‐host and multi‐host parasites among threatened and non‐threatened hosts. We find that threatened ungulates harbour a higher proportion of single‐host parasites compared to non‐threatened ungulates, which is explained by decreases in the richness of multi‐host parasites. However, among carnivores threat status is not a significant predictor of the proportion of single‐host parasites, or the richness of single‐host or multi‐host parasites. The loss of multi‐host parasites from threatened ungulates may be explained by decreased cross‐species contact as hosts decline and habitats become fragmented. Among carnivores threat status may not be important in predicting patterns of parasite specificity because host decline results in equal losses of both single‐host parasites and multi‐host parasites through reduction in average population density and frequency of cross‐species contact. Our results contrast with current models of parasite coextinction and highlight the need for updated theories that are applicable across host groups and account for both inter and intraspecific contact. This article is protected by copyright. All rights reserved.
      PubDate: 2015-01-31T01:52:35.213789-05:
      DOI: 10.1111/1365-2656.12342
       
  • Ecological opportunity leads to the emergence of an alternative
           behavioural phenotype in a tropical bird
    • Authors: Janeene M Touchton; Martin Wikelski
      Abstract: Loss of a dominant competitor can open ecological opportunities. Ecological opportunities are considered prerequisites for adaptive radiations. Nonetheless, initiation of diversification in response to ecological opportunity is seldom observed, so we know little about the stages by which behavioural variation either increases or coalesces into distinct phenotypes. Here, a natural experiment showed that in a tropical island's guild of army‐ant following birds, a new behavioural phenotype emerged in subordinate spotted antbirds (Hylophylax naevioides) after the socially dominant ocellated antbird (Phaenostictus mcleannani) died out. Individuals with this behavioural phenotype are less territorial; instead, they roam in search of ant swarms where they feed in locations from which dominant competitors formerly excluded them. Roaming individuals fledge more young than territorial individuals. We conclude that ecological opportunity arising from species loss may enhance the success of alternative behavioural phenotypes and can favour further intraspecific diversification in life‐history traits in surviving species. This article is protected by copyright. All rights reserved.
      PubDate: 2015-01-31T01:46:49.789493-05:
      DOI: 10.1111/1365-2656.12341
       
  • New insights: animal‐borne cameras and accelerometers reveal the
           secret lives of cryptic species
    • Authors: Graeme C. Hays
      First page: 587
      Abstract: Animal‐borne cameras, accelerometers and depth loggers have revealed the secret life on the world's largest bony fish the ocean sunfish (Mola mola). Photograph credit: Mike Johnson Nakamura, I., Goto, Y. & Sato, K. (2015) Ocean sunfish rewarm at the surface after deep excursions to forage for siphonophores. Journal of Animal Ecology, 84, 590–603. Logging cameras and accelerometers have opened our eyes to the secret lives of many enigmatic species. Here some of the new opportunities provided by this technology are reviewed. Recent discoveries are highlighted including the observation of selective feeding on energy‐rich parts of prey. As such, biologging cameras provide new opportunities for consideration of selective feeding within the same sort of theoretical framework (marginal value theory/optimal foraging) that exploitation of prey patches has been examined. A recent study with the world's largest bony fish, the ocean sunfish (Mola mola), is highlighted where animal‐borne cameras allowed the ground‐truthing of data sets collected with depth recorders and accelerometers. This synergistic use of a range of biologging approaches will help drive an holistic understanding of the free‐living behaviour of a range of species. Small logging cameras attached to animals can reveal amazing insights into their behaviour including patterns of movements and diet. The new opportunities provided by this technology are highlighted in a recent study in which cameras were attached to the world's largest fish, the ocean sunfish. Footage revealed the mysteries of sunfish feeding on jellyfish in the ocean depths.
      PubDate: 2015-04-21T06:00:16.675231-05:
      DOI: 10.1111/1365-2656.12355
       
  • Ocean sunfish rewarm at the surface after deep excursions to forage for
           siphonophores
    • Authors: Itsumi Nakamura; Yusuke Goto, Katsufumi Sato
      First page: 590
      Abstract: 1.Ocean sunfish (Mola mola) were believed to be inactive jellyfish feeders because they are often observed lying motionless at the sea surface. Recent tracking studies revealed that they are actually deep divers, but there has been no evidence of foraging in deep water. Furthermore, the surfacing behaviour of ocean sunfish was thought to be related to behavioural thermoregulation, but there was no record of sunfish body temperature. 2.Evidence of ocean sunfish feeding in deep water was obtained using a combination of an animal‐borne accelerometer and camera with a light source. Siphonophores were the most abundant prey items captured by ocean sunfish and were typically located at a depth of 50–200 m where the water temperature was
      PubDate: 2015-02-02T08:57:05.574721-05:
      DOI: 10.1111/1365-2656.12346
       
  • A sting in the spit: widespread cross‐infection of multiple RNA
           viruses across wild and managed bees
    • Authors: Dino P. McMahon; Matthias A. Fürst, Jesicca Caspar, Panagiotis Theodorou, Mark J. F. Brown, Robert J. Paxton
      First page: 615
      Abstract: 1.Declining populations of bee pollinators are a cause of concern, with major repercussions for biodiversity loss and food security. RNA viruses associated with honeybees represent a potential threat to other insect pollinators, but the extent of this threat is poorly understood. 2.This study aims to attain a detailed understanding of the current and on going risk of emerging infectious disease (EID) transmission between managed and wild pollinator species across a wide range of RNA viruses. 3.Within a structured large‐scale national survey across 26 independent sites, we quantify the prevalence and pathogen loads of multiple RNA viruses in co‐occurring managed honeybee (Apis mellifera) and wild bumblebee (Bombus spp.) populations. We then construct models that compare virus prevalence between wild and managed pollinators. 4.Multiple RNA viruses associated with honeybees are widespread in sympatric wild bumblebee populations. Virus prevalence in honeybees is a significant predictor of virus prevalence in bumblebees, but we remain cautious in speculating over the principle direction of pathogen transmission. We demonstrate species‐specific differences in prevalence, indicating significant variation in disease susceptibility or resilience. Pathogen loads within individual bumblebees may be high and in the case of at least one RNA virus, prevalence is higher in wild bumblebees than in managed honeybee populations. 5.Our findings indicate widespread transmission of RNA viruses between managed and wild bee pollinators, pointing to an interconnected network of potential disease pressures within and between pollinator species. In the context of the biodiversity crisis, our study emphasizes the importance of targeting a wide range of pathogens and defining host associations when considering potential drivers of population decline. This article is protected by copyright. All rights reserved.
      PubDate: 2015-02-02T08:47:56.394707-05:
      DOI: 10.1111/1365-2656.12345
       
  • Host life‐history and host‐parasite syntopy predict behavioral
           resistance and tolerance of parasites
    • Authors: Brittany F. Sears; Paul W. Snyder, Jason R. Rohr
      First page: 625
      Abstract: There is growing interest in the role that life‐history traits of hosts, such as their “pace‐of‐life”, play in the evolution of resistance and tolerance to parasites. Theory suggests that, relative to host species that have high syntopy (local spatial and temporal overlap) with parasites, host species with low syntopy should have lower selection pressures for more constitutive (always present) and costly defenses, such as tolerance, and greater reliance on more inducible and cheaper defenses, such as behavior. Consequently, we postulated that the degree of host‐parasite syntopy, which is negatively correlated with host pace‐of‐life (an axis reflecting the developmental rate of tadpoles and the inverse of their size at metamorphosis) in our tadpole‐parasitic cercarial (trematode) system, would be a negative and positive predictor of behavioral resistance and tolerance, respectively. To test these hypotheses, we exposed seven tadpole species to a range of parasite (cercarial) doses crossed with anesthesia treatments that controlled for anti‐parasite behavior. We quantified host behavior, successful and unsuccessful infections, and each species’ reaction norm for behavioral resistance and tolerance, defined as the slope between cercarial exposure (or attempted infections) and anti‐cercarial behaviors and mass change, respectively. Hence, tolerance is capturing any cost of parasite exposure. As hypothesized, tadpole pace‐of‐life was a significant positive predictor of behavioral resistance and negative predictor of tolerance, a result that is consistent with a trade‐off between behavioral resistance and tolerance across species that warrants further investigation. Moreover, these results were robust to considerations of phylogeny, all possible re‐orderings of the three fastest‐ or slowest‐paced species, and various measurements of tolerance. These results suggest that host pace‐of‐life and host‐parasite syntopy are powerful drivers of both the strength and type of host defense strategies against parasites. Future research should evaluate how often and how strongly host pace‐of‐life and host‐parasite syntopy are correlated and which is the better predictor of the strength and type of host investments in anti‐parasite defenses. This article is protected by copyright. All rights reserved.
      PubDate: 2015-02-04T00:58:01.019305-05:
      DOI: 10.1111/1365-2656.12333
       
  • Infectious disease transmission and behavioral allometry in wild mammals
    • Authors: Barbara A. Han; Andrew W. Park, A. Jolles, Sonia Altizer
      First page: 637
      Abstract: 1.Animal social and movement behaviors can impact the transmission dynamics of infectious diseases, especially for pathogens transmitted through close contact between hosts or through contact with infectious stages in the environment. 2.Estimating pathogen transmission rates and R0 from natural systems can be challenging. Because host behavioral traits that underlie the transmission process vary predictably with body size, one of the best‐studied traits among animals, body size might therefore also predict variation in parasite transmission dynamics. 3.Here, we examine how two host behaviors, social group living and the intensity of habitat use, scale allometrically using comparative data from wild primate, carnivore and ungulate species. We use these empirical relationships to parameterize classical compartment models for infectious micro‐ and macroparasitic diseases, and examine how the risk of pathogen invasion changes as a function of host behavior and body size. We then test model predictions using comparative data on parasite prevalence and richness from wild mammals. 4.We report a general pattern suggesting that smaller‐bodied mammal species utilizing home ranges more intensively experience greater risk for invasion by environmentally‐transmitted macroparasites. Conversely, larger‐bodied hosts exhibiting a high degree of social group living could be more readily invaded by directly‐transmitted microparasites. These trends were supported through comparison of micro‐ and macroparasite species richness across a large number of carnivore, primate and ungulate species, but empirical data on carnivore macroparasite prevalence showed mixed results. 5.Collectively, our study demonstrates that combining host behavioral traits with dynamical models of infectious disease scaled against host body size can generate testable predictions for variation in parasite risk across species; a similar approach might be useful in future work focused on predicting parasite distributions in local host communities. This article is protected by copyright. All rights reserved.
      PubDate: 2015-01-28T10:16:26.082183-05:
      DOI: 10.1111/1365-2656.12336
       
  • Trophic cascades from wolves to grizzly bears or changing abundance of
           bears and alternate foods'
    • Authors: Shannon M. Barber‐Meyer
      First page: 647
      Abstract: This is a Forum article commenting on: Ripple, W. J., Beschta, R. L., Fortin, J. K., & Robbins, C. T. (2014) Trophic cascades from wolves to grizzly bears in Yellowstone. Journal of Animal Ecology, 83, 223–233. Comparisons Ripple et al. (2014) used to demonstrate increased fruit availability and consumption by grizzly bears post‐wolf reintroduction are flawed and tenuous at best. Importantly, a more parsimonious (than trophic cascades) hypothesis, not sufficiently considered by Ripple et al., exists and is better supported by available data I review.
      PubDate: 2015-03-03T00:17:36.255746-05:
      DOI: 10.1111/1365-2656.12338
       
  • Wolves trigger a trophic cascade to berries as alternative food for
           grizzly bears
    • Authors: William J. Ripple; Robert L. Beschta, Jennifer K. Fortin, Charles T. Robbins
      First page: 652
      Abstract: This is a Forum article in response to: Barber‐Meyer, S. (2015) Trophic cascades from wolves to grizzly bears or changing abundance of bears and alternate foods' Journal of Animal Ecology, 83, doi: 10.1111/1365‐2656.12338. We used multiple data sets and study areas as well as several lines of evidence to investigate potential trophic linkages in Yellowstone National Park. Our results suggest that a trophic cascade from wolves to elk to berry production to berry consumption by grizzly bears may now be underway in the Park.
      PubDate: 2015-03-03T00:17:16.031295-05:
      DOI: 10.1111/1365-2656.12339
       
  • Non‐additive effects of intra‐ and interspecific competition
           between two larval salamanders
    • Authors: Thomas L. Anderson; Howard H. Whiteman
      First page: 765
      Abstract: 1.Assessment of the relative strengths of intra‐ and interspecific competition has increased in recent years, and is critical to understanding the importance of competition. Yet, whether intra‐ and interspecific competition can have non‐additive effects has rarely been tested. The resulting fitness consequences of such non‐additive interactions are important to provide the context necessary to advance our understanding of competition theory. 2.We compared the strength of additive and non‐additive intra‐ and interspecific competition by manipulating densities of a pair of larval salamanders (Ambystoma talpoideum and A. maculatum) in experimental mesocosms within a response surface design. 3.Intraspecific density had the strongest effect on the strength of competition for both species, and few observed comparisons indicated interspecific competition was an important factor in predicting body size, growth or larval period length of either species. 4.Non‐additive effects of intra‐ and interspecific competition influenced some response variables, including size and mass at metamorphosis in A. maculatum, but at a reduced strength compared to intraspecific effects alone. 5.Intraspecific competition was thus the dominant biotic interaction, but non‐additive effects also impact the outcome of competition in these species, validating the importance of testing for and incorporating non‐additive density effects into competition models. This article is protected by copyright. All rights reserved.
      PubDate: 2015-01-28T03:01:48.138107-05:
      DOI: 10.1111/1365-2656.12335
       
  • The effects of experimental warming on the timing of a plant‐insect
           herbivore interaction
    • Authors: Heather M. Kharouba; Mark Vellend, Rana M. Sarfraz, Judith H. Myers
      First page: 785
      Abstract: 1.The phenology of many species is shifting in response to climatic changes and these shifts are occurring at varying rates across species. This can potentially affect species’ interactions and individual fitness. However, few studies have experimentally tested the influence of warming on the timing of species interactions. This is an important gap in the literature given the potential for different direct and indirect effects of temperature via phenological change. 2.Our aim was to test the effects of warming on the western tent caterpillar (Malacosoma californicum pluviale). In addition to the direct effects of warming, we considered the two primary indirect effects mediated by warming‐driven changes in its host plant, red alder (Alnus rubra): changes in resource availability due to phenological mismatch (i.e. changes in the relative timing of the interaction), and changes in resource quality associated with leaf maturation. 3.We experimentally warmed egg masses and larvae of the western tent caterpillar placed on branches of red alder in the field. 4.Warming advanced the timing of larval but not leaf emergence. This led to varying degrees of phenological mismatch, with larvae emerging as much as 25 days before to 10 days after the emergence of leaves. Even the earliest‐emerging larvae, however, had high survival in the absence of leaves for up to three weeks, and they were surprisingly resistant to starvation. In addition, although warming created phenological mismatch that initially slowed the development of larvae that emerged before leaf emergence, it accelerated larval development once leaves were available. Therefore, warming had no net effect on our measures of insect performance. 5.Our results demonstrate that the indirect effects of warming, in creating phenological mismatch, are as important to consider as the direct effects on insect performance. Although future climatic warming might influence plants and insects in different ways, some insects may be well adapted to variation in the timing of their interactions. This article is protected by copyright. All rights reserved.
      PubDate: 2015-01-09T07:08:14.219539-05:
      DOI: 10.1111/1365-2656.12328
       
  • Larval melanism in a geometrid moth: promoted neither by a thermal nor
           seasonal adaptation but desiccating environments
    • Authors: Panu Välimäki; Sami M. Kivelä, Jani Raitanen, Veli‐Matti Pakanen, Emma Vatka, Maarit I. Mäenpää, Netta Keret, Toomas Tammaru
      First page: 817
      Abstract: 1.Spatio‐temporal variation in the degree of melanism is often considered in the context of thermal adaptation, melanism being advantageous under suboptimal thermal conditions. Yet, other mutually non‐exclusive explanations exist. Analysis of geographical patterns combined with laboratory experiments on the mechanisms of morph induction helps to unveil the adaptive value of particular cases of polyphenism. 2.In the context of the thermal melanism hypothesis and seasonal adaptations, we explored an array of environmental factors that may affect the expression and performance of non‐melanic vs. melanic larval morphs in different latitudinal populations of the facultatively bivoltine moth Chiasmia clathrata (Lepidoptera: Geometridae). 3.Geographic variation in larval coloration was independent of average temperatures experienced by the populations in the wild. The melanic morph was, however, more abundant in dry than in mesic habitats. In the laboratory, the melanic morph was induced especially under a high level of incident radiation but also at relatively high temperatures, but independently of photoperiod. Melanic larvae had higher growth rates and shorter development times than the non‐melanic ones when both temperature and the level of incident radiation were high. 4.Our results that melanism is induced and advantageous in warm desiccating conditions contradict the thermal melanism hypothesis for this species. Neither has melanism evolved to compensate time constraints due to forth‐coming autumn. Instead, larvae solve seasonal variation in the time available for growth by an elevated growth rate and a shortened larval period in the face of autumnal photoperiods. The phenotypic response to the level of incident radiation and a lack of adaptive adjustment of larval growth trajectories in univoltine populations underpin the role of deterministic environmental variation in the evolution of irreversible adaptive plasticity and seasonal polyphenism. This article is protected by copyright. All rights reserved.
      PubDate: 2015-02-04T00:25:25.785393-05:
      DOI: 10.1111/1365-2656.12330
       
  • Climate niche differentiation between two passerines despite ongoing gene
           flow
    • Authors: Pei‐Jen L. Shaner; Tzu‐Hsuan Tsao, Rong‐Chien Lin, Wei Liang, Chia‐Fen Yeh, Xiao‐Jun Yang, Fu‐Min Lei, Fang Zhou, Can‐Chao Yang, Le Manh Hung, Yu‐Cheng Hsu, Shou‐Hsien Li
      First page: 829
      Abstract: Niche evolution underpins the generation and maintenance of biological diversity, but niche conservatism, in which niches remain little changed over time in closely related taxa and the role of ecology in niche evolution are continually debated. To test whether climate niches are conserved in two closely related passerines in East Asia – the vinous‐throated (Paradoxornis webbianus) and ashy‐throated (P. alphonsianus) parrotbills – we established their potential allopatric and sympatric regions using ecological niche models and compared differences in their climate niches using niche overlap indices in background tests and multivariate statistical analyses. We also used polymorphism data on 44 nuclear genes to infer their divergence demography. We found that these two parrotbills occupy different climate niches, in both their allopatric and potential sympatric regions. Because the potential sympatric region is the area predicted to be suitable for both parrotbills based on the ecological niche models, it can serve as a natural common garden. Therefore, their observed niche differences in this potential sympatry were not simply rendered by phenotypic plasticity, and probably had a genetic basis. Our genetic analyses revealed that the two parrotbills are not evolutionarily independent for the most recent part of their divergence history. The two parrotbills diverged c. 856,000 years ago, and have had substantial gene flow since a presumed secondary contact c. 290,000 years ago. This study provides an empirical case demonstrating that climate niches may not be homogenized in nascent species in spite of substantial, ongoing gene flow, which in turn suggests a role for ecology in promoting and maintaining diversification among incipient species. This article is protected by copyright. All rights reserved.
      PubDate: 2015-01-13T01:28:43.896886-05:
      DOI: 10.1111/1365-2656.12331
       
  • Social integration confers thermal benefits in a gregarious primate
    • Authors: Richard McFarland; Andrea Fuller, Robyn S. Hetem, Duncan Mitchell, Shane K. Maloney, S. Peter Henzi, Louise Barrett
      First page: 871
      Abstract: Sociality has been shown to have adaptive value for gregarious species, with more socially integrated animals within groups experiencing higher reproductive success and longevity. The value of social integration is often suggested to derive from an improved ability to deal with social stress within a group; other potential stressors have received less attention. We investigated the relationship between environmental temperature, an important non‐social stressor, and social integration in wild female vervet monkeys (Chlorocebus pygerythrus), using implanted data‐loggers to obtain direct measures of core body temperature. Heterothermy (as measured by 24h amplitude of body temperature) increased, and 24h minima of body temperature decreased, as the 24h minimum ambient temperature decreased. As winter progressed, monkeys became increasingly heterothermic and displayed lower 24h minima of body temperature. Monkeys with a greater number of social partners displayed a smaller 24h amplitude (that is, were more homeothermic) and higher 24h minima of body temperature (that is, became less hypothermic), than did animals with fewer social partners. Our findings demonstrate that social integration has a direct influence on thermoregulatory ability: individual animals that form and maintain more social relationships within their group experience improved thermal competence compared to those with fewer social relationships. Given the likely energetic consequences of thermal benefits, our findings offer a viable physiological explanation that can help account for variations in fitness in relation to individual differences in social integration. This article is protected by copyright. All rights reserved.
      PubDate: 2015-01-30T04:59:50.677735-05:
      DOI: 10.1111/1365-2656.12329
       
  • Life‐stage specific physiology defines invasion extent of a riverine
           fish
    • Authors: David J. Lawrence; David A. Beauchamp, Julian D. Olden
      First page: 879
      Abstract: Many ecologists have called for mechanism‐based investigations to identify the underlying controls on species distributions. Understanding these controls can be especially useful to construct robust predictions of how a species range may change in response to climate change or the extent to which a non‐native species may spread in novel environments. Here we link spatially‐intensive observations with mechanistic models to illustrate how physiology determines the upstream extent of the aquatic ectotherm smallmouth bass (Micropterus dolomieu) in two headwater rivers. Our results demonstrate that as temperatures become increasingly cold across a downstream to upstream gradient, food consumption in age 0 bass becomes increasingly constrained, and as a result, these fish become growth limited. Sufficient first summer growth of age 0 bass is essential for overwinter survival because young bass must persist from energy reserves accumulated during the summer, and those reserves are determined by body size. Our field data reveals the upstream extent of adult bass reproduction corresponds to a point in the downstream/upstream gradient where cold temperatures impair growth opportunities in young bass. This pattern was repeated in both study streams, and explained why bass positioned nests twice as far upstream in the warm compared to the cold stream in the same basin. Placement of spawning nests by adult bass is likely subject to strong evolutionary selection in temperate systems: if bass spawn too far upstream their young are unlikely to grow large enough to survive the winter. Consumption and growth in older bass (age 3‐4) was far less sensitive to temperature. Based on these data we suggest that temperature‐sensitive age 0 bass constrain the upstream distribution limits of bass within temperate streams. In this study we investigated how temperature‐dependent physiology changed through the life history of a species, and in doing so, identified a climate‐sensitive life history stage that likely sets the distributional limits of all other life history stages. We anticipate the framework developed here could be employed to identify how similar stage‐specific environmental sensitivity determines distribution in many other ectothermic species. This article is protected by copyright. All rights reserved.
      PubDate: 2015-02-06T07:01:27.360108-05:
      DOI: 10.1111/1365-2656.12332
       
  • Weather‐driven dynamics in a dual‐migrant system: Moths and
           bats
    • Authors: Jennifer J. Krauel; John K. Westbrook, Gary F. McCracken
      Abstract: Animal migrations generate large spatial and temporal fluctuations in biomass that provide a resource base for many predator‐prey interactions. These interactions are often driven by continent‐scale weather patterns and are difficult to study. Few studies have included migratory animals on more than a single trophic level or for periods spanning multiple entire seasons. We tracked migrations of three species of agricultural pest noctuid moths over the 2010‐2012 autumn seasons as the moths traveled past a large colony of migratory Brazilian free‐tailed bats (Tadarida brasiliensis) in Texas. Increases in moth abundance, mass of bats, and duration of bat activity outside of the cave were correlated with passage of cold fronts over the study area and related increases in northerly wind. Moth responses to weather patterns varied among species and seasons, but overall moth abundances were low in late summer and spiked after one or more cold front passages in September and October. Changes in bat mass and behavior appear to be consequences of bat migration, as cave use transitioned from summer maternity roost to autumn migratory stopover sites. Weather‐driven migration is at considerable risk from climate change, and bat and moth responses to that change may have marked impacts on agricultural systems and bat ecosystem services. This article is protected by copyright. All rights reserved.
      PubDate: 2014-12-10T01:16:28.287898-05:
      DOI: 10.1111/1365-2656.12327
       
  • Adult acclimation to combined temperature and pH stressors significantly
           enhances reproductive outcomes compared to short‐term exposures
    • Authors: Coleen C. Suckling; Melody S. Clark, Joelle Richard, Simon A. Morley, Michael A. S. Thorne, Elizabeth M. Harper, Lloyd S. Peck
      Abstract: This study examined the effects of long‐term culture under altered conditions on the Antarctic sea urchin, Sterechinus neumayeri. Sterechinus neumayeri was cultured under the combined environmental stressors of lowered pH (−0·3 and −0·5 pH units) and increased temperature (+2 °C) for 2 years. This time‐scale covered two full reproductive cycles in this species and analyses included studies on both adult metabolism and larval development. Adults took at least 6–8 months to acclimate to the altered conditions, but beyond this, there was no detectable effect of temperature or pH. Animals were spawned after 6 and 17 months exposure to altered conditions, with markedly different outcomes. At 6 months, the percentage hatching and larval survival rates were greatest in the animals kept at 0 °C under current pH conditions, whilst those under lowered pH and +2 °C performed significantly less well. After 17 months, performance was not significantly different across treatments, including controls. However, under the altered conditions urchins produced larger eggs compared with control animals. These data show that under long‐term culture adult S. neumayeri appear to acclimate their metabolic and reproductive physiology to the combined stressors of altered pH and increased temperature, with relatively little measureable effect. They also emphasize the importance of long‐term studies in evaluating effects of altered pH, particularly in slow developing marine species with long gonad maturation times, as the effects of altered conditions cannot be accurately evaluated unless gonads have fully matured under the new conditions. This paper shows that acclimation to altered pH takes up to 8 months in Antarctic sea urchins and also that gonads matured for their full development time (2 years) in altered pH significantly enhances reproductive outcomes compared to short term exposures.
      PubDate: 2014-12-09T19:41:22.97748-05:0
      DOI: 10.1111/1365-2656.12316
       
  • Land‐use history alters contemporary insect herbivore community
           composition and decouples plant–herbivore relationships
    • Authors: Philip G. Hahn; John L. Orrock
      Abstract: Past land use can create altered soil conditions and plant communities that persist for decades, although the effects of these altered conditions on consumers are rarely investigated. Using a large‐scale field study at 36 sites in longleaf pine (Pinus palustris) woodlands, we examined whether historic agricultural land use leads to differences in the abundance and community composition of insect herbivores (grasshoppers, families Acrididae and Tettigoniidae). We measured the cover of six plant functional groups and several environmental variables to determine whether historic agricultural land use affects the relationships between plant cover or environmental conditions and grasshopper assemblages. Land‐use history had taxa‐specific effects and interacted with herbaceous plant cover to alter grasshopper abundances, leading to significant changes in community composition. Abundance of most grasshopper taxa increased with herbaceous cover in woodlands with no history of agriculture, but there was no relationship in post‐agricultural woodlands. We also found that grasshopper abundance was negatively correlated with leaf litter cover. Soil hardness was greater in post‐agricultural sites (i.e. more compacted) and was associated with grasshopper community composition. Both herbaceous cover and leaf litter cover are influenced by fire frequency, suggesting a potential indirect role of fire on grasshopper assemblages. Our results demonstrate that historic land use may create persistent differences in the composition of grasshopper assemblages, while contemporary disturbances (e.g. prescribed fire) may be important for determining the abundance of grasshoppers, largely through the effect of fire on plants and leaf litter. Therefore, our results suggest that changes in the contemporary management regimes (e.g. increasing prescribed fire) may not be sufficient to shift the structure of grasshopper communities in post‐agricultural sites towards communities in non‐agricultural habitats. Rather, repairing degraded soil conditions and restoring plant communities are likely necessary for restoring grasshopper assemblages in post‐agricultural woodlands. This paper highlights how agricultural land‐use legacies can decouple otherwise well‐established relationships between plant productivity and herbivore abundance. These results suggest that management efforts should consider the role of historic land use on herbivore assemblages, in addition to plant communities
      PubDate: 2014-11-23T19:59:00.820726-05:
      DOI: 10.1111/1365-2656.12311
       
  • Climatic conditions cause complex patterns of covariation between
           demographic traits in a long‐lived raptor
    • Authors: Ivar Herfindal; Martijn Pol, Jan Tøttrup Nielsen, Bernt‐Erik Sæther, Anders Pape Møller
      Abstract: 1.Environmental variation can induce life history changes that can last over a large part of the lifetime of an organism. If multiple demographic traits are affected, expected changes in climate may influence environmental covariances among traits in a complex manner. Thus, examining the consequences of environmental fluctuations requires that individual information at multiple life stages are available, which is particularly challenging in long‐lived species. 2.Here we analyse how variation in climatic conditions occurring in the year of hatching of female goshawks Accipiter gentilis (L.) affects age‐specific variation in demographic traits and lifetime reproductive success (LRS). LRS decreased with increasing temperature in April in the year of hatching, due to lower breeding frequency and shorter reproductive lifespan. In contrast, the probability for a female to successfully breed was higher in years with a warm April, but lower LRS of the offspring in these years generated a negative covariance among fecundity rates among generations. 3.The mechanism by which climatic conditions generated cohort effects was likely through influencing the quality of the breeding segment of the population in a given year, as the proportion of pigeons in the diet during the breeding period was positively related to annual and lifetime reproductive success, and the diet of adult females that hatched in warm years contained fewer pigeons. 4.Climatic conditions experienced during different stages of individual life histories caused complex patterns of environmental covariance among demographic traits even across generations. Such environmental covariances may either buffer or amplify impacts of climate change on population growth, emphasizing the importance of considering demographic changes during the complete life history of individuals when predicting the effect of climatic change on population dynamics of long‐lived species. This article is protected by copyright. All rights reserved.
      PubDate: 2014-11-17T06:12:55.607944-05:
      DOI: 10.1111/1365-2656.12318
       
  • Age‐dependent trait variation: the relative contribution of
           within‐individual change, selective appearance and disappearance in
           a long‐lived seabird.
    • Authors: He Zhang; Oscar Vedder, Peter H. Becker, Sandra Bouwhuis
      Abstract: 1.Within populations, the expression of phenotypic traits typically varies with age. Such age‐dependent trait variation can be caused by within‐individual change (improvement, senescence, terminal effects) and/or selective (dis)appearance of certain phenotypes among older age classes. 2.In this study we applied two methods (decomposition and mixed‐modelling) to attribute age‐dependent variation in seven phenological and reproductive traits to within‐individual change and selective (dis)appearance, in a long‐lived seabird, the common tern (Sterna hirundo). 3.At the population level, all traits, except the probability to breed, improved with age (i.e., phenology advanced and reproductive output increased). Both methods identified within‐individual change as the main responsible process, and within individuals, performance improved until age 6‐13, before levelling off. In contrast, within individuals, breeding probability decreased to age 10, then levelled off. 4.Effects of selective appearance and disappearance were small, but showed that longer‐lived individuals had a higher breeding probability and bred earlier, and that younger recruits performed better throughout life than older recruits in terms of both phenology and reproductive performance. In the year prior to death, individuals advanced reproduction, suggesting terminal investment. 5.The decomposition method attributed more age‐dependent trait variation to selective disappearance than the mixed‐modelling method: 14‐36% versus 0‐8%, respectively, which we identify to be due to covariance between rates of within‐individual change and selective (dis)appearance leading to biased results from the decomposition method. 6.We conclude that the decomposition method is ideal for visualising processes underlying population change in performance from one age class to the next, but that a mixed‐modelling method is required to investigate the significance and relative contribution of age‐effects. 7.Considerable variation in the contribution of the different age‐processes between the seven phenotypic traits studied, as well as notable differences between species in patterns of age‐dependent trait expression, calls for better predictions regarding optimal allocation strategies with age. This article is protected by copyright. All rights reserved.
      PubDate: 2014-11-14T09:03:19.033941-05:
      DOI: 10.1111/1365-2656.12321
       
  • Different foraging preferences of hummingbirds on artificial and natural
           
    • Authors: María Alejandra Maglianesi; Katrin Böhning–Gaese, Matthias Schleuning
      Abstract: 1.In plant–pollinator networks, the floral morphology of food plants is an important determinant of the interaction niche of pollinators. Studies on foraging preferences of pollinators combining experimental and observational approaches may help to understand the mechanisms behind patterns of interactions and niche partitioning within pollinator communities. 2.In this study, we tested whether morphological floral traits were associated with foraging preferences of hummingbirds for artificial and natural flower types in Costa Rica. We performed field experiments with artificial feeders, differing in length and curvature of flower types, to quantify the hummingbirds’ interaction niche under unlimited nectar resources. To quantify the interaction niche under real–world conditions of limited nectar resources, we measured foraging preferences of hummingbirds for a total of 34 plant species. 3.Artificial feeders were visited by Eupherusa nigriventris and Phaethornis guy in the pre–montane forest, and Lampornis calolaemus in the lower montane forest. Under experimental conditions, all three hummingbird species overlapped their interaction niches and showed a preference for the short artificial flower type over the long–straight and the long–curved flower types. Under natural conditions, the two co–occurring hummingbird species preferred to feed on plant species with floral traits corresponding to their bill morphology. The short–billed hummingbird E. nigriventris preferred to feed on short and straight flowers, whereas the long– and curved–billed P. guy preferred long and curved natural flowers. The medium–size billed species L. calolaemus preferred to feed on flowers of medium length and did not show preferences for plant species with specific corolla curvature. 4.Our results show that floral morphological traits constrain access by short–billed hummingbird species to nectar resources. Morphological constraints, therefore, represent one important mechanism structuring trophic networks. In addition, other factors, such as competition and differences in resource quantity or quality, define the interaction niches of consumer species in real–world communities, enforcing patterns of niche segregation between co–occurring consumer species. This suggests that experimental studies are needed to disentangle effects of morphological constraints from those of competition for resources in plant–pollinator interactions and other types of trophic interactions. This article is protected by copyright. All rights reserved.
      PubDate: 2014-11-14T09:00:57.318896-05:
      DOI: 10.1111/1365-2656.12319
       
  • “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
       
  • Effects of temperature on consumer‐resource interactions
    • Authors: Priyanga Amarasekare
      First page: 665
      Abstract: 1.Understanding how temperature variation influences the negative (e.g.,self‐limitation) and positive (e.g., saturating functional responses) feedback processes that characterize consumer‐resource interactions is an important research priority. Previous work on this topic has yielded conflicting out comes with some studies predicting that warming should increase consumer‐resource oscillations and others predicting that warming should decrease consumer‐resource oscillations. 2.Here I develop a consumer‐resource model that both synthesizes previous findings in a common framework and yields novel insights about temperature effects on consumer‐resource dynamics. I report three key findings. First, when the resource species’ birth rate exhibits a unimodal temperature response, as demonstrated by a large number of empirical studies, the temperature range over which the consumer‐resource interaction can persist is determined by the lower and upper temperature limits to the resource species’ reproduction. This contrasts with the prediction s of previous studies, which assume that the birth rate exhibits a monotonic temperature response, that consumer extinction is determined by temperature effects on consumer species’ traits, rather than the resource species’ traits. 3.Second, the comparative analysis I have conducted shows that whether warming leads to an increase or decrease in consumer‐resource oscillations depends on the manner in which temperature affects intra‐specific competition. When the strength of self‐limitation increases monotonically with temperature, warming causes a decrease in consumer‐resource oscillations. However, if self‐limitation is strongest at temperatures physiologically optimal for reproduction, a scenario previously unanalyzed by theory but amply substantiated by empirical data, warming can cause an increase in consumer‐resource oscillations. 4.Third, the model yields testable comparative predictions about consumer‐resource dynamics under alternative hypotheses for how temperature affects competitive and resource acquisition traits. Importantly, it does so through empirically quantifiable metrics for predicting temperature effects on consumer viability and consumer‐resource oscillations, which obviates the need for parameterizing complex dynamical models. Tests of these metrics with empirical data on a host‐parasitoid interaction yield realistic estimates of temperature limits for consumer persistence and the propensity for consumer‐resource oscillations, highlighting their utility in predicting temperature effects, particularly warming, on consumer‐resource interactions in both natural and agricultural settings. This article is protected by copyright. All rights reserved.
      PubDate: 2014-11-20T09:16:07.363393-05:
      DOI: 10.1111/1365-2656.12320
       
  • Trophic Whales’ as Biotic Buffers: Weak Interactions Stabilize
           Ecosystems against Nutrient Enrichment
    • Authors: Florian Schwarzmüller; Nico Eisenhauer, Ulrich Brose
      First page: 680
      Abstract: 1.Human activities may compromise biodiversity if external stressors such as nutrient enrichment endanger overall network stability by inducing unstable dynamics. However, some ecosystems maintain relatively high diversity levels despite experiencing continuing disturbances. 2.This indicates that some intrinsic properties prevent unstable dynamics and resulting extinctions. Identifying these “ecosystem buffers” is crucial for our understanding of the stability of ecosystems and an important tool for environmental and conservation biologists. In this vein, weak interactions have been suggested as stabilizing elements of complex systems, but their relevance has rarely been tested experimentally. 3.Here, using network and allometric theory we present a novel concept for a‐priori identification of species that buffer against externally induced instability of increased population oscillations via weak interactions. We tested our model in a microcosm experiment using a soil food‐web motif. 4.Our results show that large‐bodied species feeding at the food web's base, so called ‘trophic whales’, can buffer ecosystems against unstable dynamics induced by nutrient enrichment. Similar to the functionality of chemical or mechanical buffers, they serve as ‘biotic buffers’ that take up stressor effects and thus protect fragile systems from instability. 5.We discuss trophic whales as common functional building blocks across ecosystems. Considering increasing stressor effects under anthropogenic global change, conservation of these network‐intrinsic biotic buffers may help maintain the stability and diversity of natural ecosystems. This article is protected by copyright. All rights reserved.
      PubDate: 2014-11-25T06:44:47.36788-05:0
      DOI: 10.1111/1365-2656.12324
       
  • Age and sex‐selective predation as moderators of the overall impact
           of predation
    • Authors: S.R. Hoy; S.J. Petty, A. Millon, D.P. Whitfield, M. Marquiss, M. Davison, X. Lambin
      First page: 692
      Abstract: Currently, there is no general agreement about the extent to which predators’ impact prey population dynamics, as it is often poorly predicted by predation rates and species abundances. This could in part be caused by variation in the type of selective predation occurring. Notably, if predation is selective on categories of individuals that contribute little to future generations, it may moderate the impact of predation on prey population dynamics. However, despite its prevalence, selective predation has seldom been studied in this context. Using recoveries of ringed tawny owls (Strix aluco) predated by ‘superpredators’, northern goshawks (Accipiter gentilis) as they colonised the area, we investigated the extent to which predation was sex and age‐selective. Predation of juvenile owls was disproportionately high. Amongst adults, predation was strongly biased towards females and predation risk appeared to increase with age. This implies age‐selective predation may shape the decline in survival with age, observed in tawny owls. To determine whether selective predation can modulate the overall impact of predation, age‐based population matrix models were used to simulate the overall impact of five different patterns of age‐selective predation, including the pattern actually observed in the study site. The impact on owl population size varied by up to 50%, depending on the pattern of selective predation. The simulation of the observed pattern of predation had a relatively small impact on population size, close to the least harmful scenario, predation on juveniles only. The actual changes in owl population size and structure, observed during goshawk colonisation were also analysed. Owl population size and immigration were unrelated to goshawk abundance. However, goshawk abundance appeared to interact with owl food availability to have a delayed effect on recruitment into the population. This study provides strong evidence to suggest that predation of other predators is both age and sex‐selective and that selective predation of individuals with a low reproductive value may mitigate the overall impact of predators on prey population dynamics. Consequently, our results highlight how accounting for the type of selective predation occurring is likely to improve future predictions of the overall impact of predation. This article is protected by copyright. All rights reserved.
      PubDate: 2014-10-21T08:32:31.258082-05:
      DOI: 10.1111/1365-2656.12310
       
  • Density‐dependent movement and the consequences of the Allee effect
           in the model organism Tetrahymena
    • Authors: Emanuel A. Fronhofer; Tabea Kropf, Florian Altermatt
      First page: 712
      Abstract: 1.Movement and dispersal are critical processes for almost all organisms in natural populations. Understanding their causes and consequences is therefore of high interest. While both theoretical and empirical work suggests that dispersal, more exactly emigration, is plastic and may be a function of local population density, the functional relationship between the underlying movement strategies and population density has received less attention. 2.We here present evidence for the shape of this reaction norm and are able to differentiate between three possible cues: the relative number of individuals, the presence of metabolites (chemical cues) and resource availability. 3.We performed microcosm experiments with the ciliate model organism Tet‐rahymena in order to understand the plasticity of movement strategies with respect to local density while controlling for possible confounding effects mediated by the availability of different cues. In addition, we investigated how an Allee effect can influence movement and dispersal plasticity. 4.Our findings suggest that movement strategies in Tetrahymena are plastic and density‐dependent. The observed movement reaction norm was ushaped. This may be due to an Allee effect which led to negative densitydependence at low population densities and generally positive density‐dependence at high population densities due to local competition. This possibly adaptive density‐dependent movement strategy was likely mediated by chemical cues. 5.Our experimental work in highly controlled conditions indicates that both environmental cues as well as inherent population dynamics must be considered to understand movement and dispersal. This article is protected by copyright. All rights reserved.
      PubDate: 2014-11-06T01:51:59.807768-05:
      DOI: 10.1111/1365-2656.12315
       
  • Density‐ and trait‐mediated effects of a parasite and a
           predator in a tri‐trophic food web
    • Authors: Aabir Banerji; Alison B. Duncan, Joanne S. Griffin, Stuart Humphries, Owen L. Petchey, Oliver Kaltz
      First page: 723
      Abstract: 1.Despite growing interest in ecological consequences of parasitism in food webs, relatively little is known about effects of parasites on long‐term population dynamics of non‐host species or about whether such effects are density‐ or trait‐ mediated. 2.We studied a tri‐trophic food chain comprised of: (i) a bacterial basal resource (Serratia fonticola), (ii) an intermediate consumer (Paramecium caudatum), (iii) a top predator (Didinium nasutum), and (iv) a parasite of the intermediate consumer (Holospora undulata). A fully‐factorial experimental manipulation of predator and parasite presence/absence was combined with analyses of population dynamics, modelling, and analyses of host (Paramecium) morphology and behavior. 3.Predation and parasitism each reduced the abundance of the intermediate consumer (Paramecium), and parasitism indirectly reduced the abundance of the basal resource (Serratia). However, in combination, predation and parasitism had non‐additive effects on the abundance of the intermediate consumer, as well as on that of the basal resource. In both cases, the negative effect of parasitism seemed to be effaced by predation. 4.Infection of the intermediate consumer reduced predator abundance. Modelling and additional experimentation revealed that this was most likely due to parasite reduction of intermediate host abundance (a density‐mediated effect), as opposed to changes in predator functional or numerical response. 5.Parasitism altered morphological and behavioural traits, by reducing host cell length and increasing the swimming speed of cells with moderate parasite loads. Additional tests showed no significant difference in Didinium feeding rate on infected and uninfected hosts, suggesting that the combination of these modifications does not affect host vulnerability to predation. However, estimated rates of encounter with Serratia based on these modifications were higher for infected Paramecium than for uninfected Paramecium. 6.A mixture of density‐mediated and trait‐mediated indirect effects of parasitism on non‐host species creates rich and complex possibilities for effects of parasites in food webs that should be included in assessments of possible impacts of parasite eradication or introduction. This article is protected by copyright. All rights reserved.
      PubDate: 2014-11-07T10:00:45.979214-05:
      DOI: 10.1111/1365-2656.12317
       
  • Concomitant predation on parasites is highly variable but constrains the
           ways in which parasites contribute to food‐web structure
    • Authors: Alyssa R. Cirtwill; Daniel B. Stouffer
      First page: 734
      Abstract: 1.Previous analyses of empirical food webs (the networks of who eats whom in a community) have revealed that parasites exert a strong influence over observed food‐web structure and alter many network properties such as connectance and degree distributions. It remains unclear, however, whether these community‐level effects are fully explained by differences in the ways that parasites and free‐living species interact within a food‐web. 2.To rigorously quantify the interrelationship between food‐web structure, the types of species in a web and the distinct types of feeding links between them, we introduce a new methodology to quantify the structural roles of both species and feeding links. Roles are quantified based on the frequencies with which a species (or link) appears in different food‐web motifs‐the building blocks of networks. 3.We hypothesised that different types of species (e.g., top predators, basal resources, parasites) and different types of links between species (e.g., classic predation, parasitism, concomitant predation on parasites along with their hosts) will show characteristic differences in their food‐web roles. 4.We found that parasites do indeed have unique structural roles in food webs. Moreover, we demonstrate that different types of feeding links (e.g., parasitism, predation, or concomitant predation) are distributed differently in a food‐web context. More than any other interaction type, concomitant predation appears to constrain the roles of parasites. In contrast, concomitant predation links themselves have more variable roles than any other type of interaction. 5.Together, our results provide a novel perspective on how both species and feeding link composition shapes the structure of an ecological community, and vice‐versa. This article is protected by copyright. All rights reserved.
      PubDate: 2014-11-21T08:52:00.955938-05:
      DOI: 10.1111/1365-2656.12323
       
  • Rat eradication and the resistance and resilience of passerine bird
           assemblages in the Falkland Islands
    • Authors: Michael A. Tabak; Sally Poncet, Ken Passfield, Jacob R. Goheen, Carlos Martinez del Rio
      First page: 755
      Abstract: Norway rats (Rattus norvegicus) were introduced to the Falkland Islands and are detrimental to native passerines. Rat eradication programs are being used to help protect the avifauna. The present study assesses the effectiveness of eradication programs while using this conservation practice as a natural experiment to explore the ecological resistance, resilience, and homeostasis of bird communities. We conducted bird surveys on 230 islands: 85 in the presence of rats, 108 that were historically free of rats, and 37 from which rats had been eradicated. Bird detection data were used to build occupancy models for each species and estimate species‐area relationships. Count data were used to estimate relative abundance and community structure. Islands with invasive rats had reduced species richness of passerines and a different community structure than islands on which rats were historically absent. Although the species richness of native passerines was remarkably similar on eradicated and historically rat‐free islands, community structure on eradicated islands was more similar to that of rat‐infested islands than to historically rat‐free islands. The results suggest that in the Falkland Islands, species richness of passerines is not resistant to invasive rats, but seems to be resilient following their removal. In contrast, community structure seems to be neither resistant nor resilient. From a conservation perspective, rat eradication programs in the Falkland Islands appear to be effective at restoring native species richness, but they are not necessarily beneficial for species of conservation concern. For species that do not recolonize, translocations following eradications may be necessary. This article is protected by copyright. All rights reserved.
      PubDate: 2014-10-30T02:16:02.78452-05:0
      DOI: 10.1111/1365-2656.12312
       
  • Cruising the rain forest floor: butterfly wing shape evolution and gliding
           in ground effect
    • Authors: A. Cespedes; C. M. Penz, P. J. DeVries
      First page: 808
      Abstract: Flight is a key innovation in the evolutionary success of insects and essential to dispersal, territoriality, courtship and oviposition. Wing shape influences flight performance and selection likely acts to maximize performance for conducting essential behaviours that in turn results in evolution of wing shape. As wing shape also contributes to fitness, optimal shapes for particular flight behaviours can be assessed with aerodynamic predictions and placed in an ecomorphological context. Butterflies in the tribe Haeterini (Nymphalidae) are conspicuous members of understory faunas in lowland Neotropical forests. Field observations indicate that the five genera in this clade differ in flight height and behaviour: four use gliding flight at the forest floor level, and one utilizes flapping flight above the forest floor. Nonetheless, the association of ground level gliding flight behaviour and wing shape has never been investigated in this or any other butterfly group. We used landmark‐based geometric morphometrics to test whether wing shapes in Haeterini and their close relatives reflected observed flight behaviours. Four genera of Haeterini and some distantly related Satyrinae showed significant correspondence between wing shape and theoretical expectations in performance tradeoffs that we attribute to selection for gliding in ground effect. Forewing shape differed between sexes for all taxa, and male wing shapes were aerodynamically more efficient for gliding flight than corresponding females. This suggests selection acts differentially on male and female wing shapes, reinforcing the idea that sex‐specific flight behaviours contribute to the evolution of sexual dimorphism. Our study indicates that wing shapes in Haeterini butterflies evolved in response to habitat‐specific flight behaviors, namely gliding in ground effect along the forest floor, resulting in ecomorphological partitions of taxa in morphospace. The convergent flight behaviour and wing morphology between tribes of Satyrinae suggests that the flight environment may offset phylogenetic constraints. Overall, this study provides a basis for exploring similar patterns of wing shape evolution in other taxa that glide in ground effect. This article is protected by copyright. All rights reserved.
      PubDate: 2014-12-05T07:49:06.976472-05:
      DOI: 10.1111/1365-2656.12325
       
  • Top‐down and bottom‐up forces interact at thermal range
           extremes on American lobster
    • Authors: Stephanie A. Boudreau; Sean C. Anderson, Boris Worm
      First page: 840
      Abstract: 1.Exploited marine populations are thought to be regulated by the effects of fishing, species interactions, and climate. Yet it is unclear how these forces interact and vary across a species’ range. 2.We conducted a meta‐analysis of American lobster (Homarus americanus) abundance data throughout the entirety of the species’ range, testing competing hypotheses about bottom‐up (climate, temperature) versus top‐down (predation, fishing) regulation along a strong thermal gradient. 3.Our results suggest an interaction between predation and thermal range ‐ predation effects dominated at the cold and warm extremes, but not at the center of the species’ range. Similarly, there was consistent support for a positive climate effect on lobster recruitment at warm range extremes. In contrast, fishing effort followed, rather than led changes in lobster abundance over time. 4.Our analysis suggests that the relative effects of top‐down and bottom‐up forcing in regulating marine populations may intensify at thermal range boundaries, and weaken at the core of a species’ range. This article is protected by copyright. All rights reserved.
      PubDate: 2014-11-21T08:52:24.021735-05:
      DOI: 10.1111/1365-2656.12322
       
  • Untangling human and environmental effects on geographic gradients of
           mammal species richness: a global and regional evaluation
    • Authors: Erik Joaquín Torres‐Romero; Miguel Á. Olalla‐Tárraga
      First page: 851
      Abstract: Different hypotheses (geographic, ecological, evolutionary or a combination of them) have been suggested to account for the spatial variation in species richness. However, the relative importance of environment and human impacts in explaining these patterns, either globally or at the biogeographic region level, remains largely unexplored. Here we jointly evaluate how current environmental conditions and human impacts shape global and regional gradients of species richness in terrestrial mammals. We processed IUCN global distributional data for 3939 mammal species and a set of seven environmental and two human impact variables at a spatial resolution of 96.5x 96.5 km. We used simple, multiple and partial regression techniques to evaluate environmental and human effects on species richness. Actual evapotranspiration is the main driver of mammal species richness globally. Together with our results at the biogeographic realm level, this lends strong support for the Hawkins et al. (2003) conjecture (i.e. global diversity gradients are best explained by the interaction of water and energy, with a latitudinal shift in the relative importance of ambient energy vs. water as we move from the poles to the equator). While human effects on species richness are not easily detected at a global scale due to the large proportion of shared variance with the environment, these effects significantly emerge at the regional level. In the Nearctic, Palearctic and Oriental regions, the independent contribution of human impacts is almost as important as current environmental conditions in explaining richness patterns. The intersection of human impacts with climate drives the geographic variation in mammal species richness in the Palearctic, Nearctic and Oriental regions. Using a human accessibility variable we show, for the first time, that the zones most accessible to humans are often those where we find lower mammal species richness. This article is protected by copyright. All rights reserved.
      PubDate: 2014-10-30T02:21:27.905553-05:
      DOI: 10.1111/1365-2656.12313
       
  • Predicting rates of isotopic turnover across the animal kingdom: a
           synthesis of existing data
    • Authors: Stephen M. Thomas; Thomas W. Crowther
      First page: 861
      Abstract: The stable isotopes of carbon (13C /12C) and nitrogen (15N /14N) represent powerful tools in food‐web ecology, providing a wide range of dietary information in animal consumers. However, identifying the temporal window over which a consumer's isotopic signature reflects its diet requires an understanding of elemental incorporation, a process that varies from days to years across species and tissue types. Though theory predicts body size and temperature are likely to control incorporation rates, this has not been tested empirically across a morphologically and phylogenetically diverse range of taxa. Readily available estimates of this relationship would, however, aid in the design of stable isotope food‐web investigations and improve the interpretation of isotopic data collected from natural systems. Using literature‐derived turnover estimates from animal species ranging in size from 1 mg to 2000 kg, we develop a predictive tool for stable isotope ecologists, allowing for estimation of incorporation rates in the structural tissues of entirely novel taxa. In keeping with metabolic scaling theory, we show that isotopic turnover rates of carbon and nitrogen in whole organisms and muscle tissue scale allometrically with body mass raised approximately to the power ‐0.19, an effect modulated by body temperature. This relationship did not, however, apply to incorporation rates in splanchnic tissues, which were instead dependent on the thermoregulation tactic employed by an organism, being considerably faster in endotherms than ectotherms. We believe the predictive turnover equations we provide can improve the design of experiments and interpretation of results obtained in future stable isotopic food‐web studies. This article is protected by copyright. All rights reserved.
      PubDate: 2014-12-05T08:01:40.178363-05:
      DOI: 10.1111/1365-2656.12326
       
 
 
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