Journal Cover Ecology
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   ISSN (Print) 0012-9658 - ISSN (Online) 1939-9170
   Published by John Wiley and Sons Homepage  [1589 journals]
  • Contrasting effects of specialist and generalist herbivores on resistance
           evolution in invasive plants
    • Authors: Zhijie Zhang; Xiaoyun Pan, Dana Blumenthal, Mark Kleunen, Mu Liu, Bo Li
      Abstract: Invasive alien plants are likely to be released from specialist herbivores and at the same time encounter biotic resistance from resident generalist herbivores in their new ranges. The Shifting Defense Hypothesis predicts that this will result in evolution of decreased defense against specialist herbivores and increased defense against generalist herbivores. To test this, we performed a comprehensive meta-analysis of 61 common garden studies that provide data on resistance and/or tolerance for both introduced and native populations of 32 invasive plant species. We demonstrate that introduced populations, relative to native populations, decreased their resistance against specialists, and increased their resistance against generalists. These differences were significant when resistance was measured in terms of damage caused by the herbivore, but not in terms of performance of the herbivore. Furthermore, we found the first evidence that the magnitude of resistance differences between introduced and native populations depended significantly on herbivore origin (i.e. whether the test herbivore was collected from the native or non-native range of the invasive plant). Finally, tolerance to generalists was found to be higher in introduced populations, while neither tolerance to specialists nor that to simulated herbivory differed between introduced and native plant populations. We conclude that enemy release from specialist herbivores and biotic resistance from generalist herbivores have contrasting effects on resistance evolution in invasive plants. Our results thus provide strong support for the Shifting Defense Hypothesis.This article is protected by copyright. All rights reserved.
      PubDate: 2018-01-20T01:50:27.690838-05:
      DOI: 10.1002/ecy.2155
  • Temporal heterogeneity increases with spatial heterogeneity in ecological
    • Authors: Scott L. Collins; Meghan L. Avolio, Corinna Gries, Lauren M. Hallett, Sally E. Koerner, Kimberly J. La Pierre, Andrew L. Rypel, Eric R. Sokol, Samuel B. Fey, Dan F. B. Flynn, Sydney K. Jones, Laura M. Ladwig, Julie Ripplinger, Matt B. Jones
      Abstract: Heterogeneity is increasingly recognized as a foundational characteristic of ecological systems. Under global change, understanding temporal community heterogeneity is necessary for predicting the stability of ecosystem functions and services. Indeed, spatial heterogeneity is commonly used in alternative stable state theory as a predictor of temporal heterogeneity and therefore an early indicator of regime shifts. To evaluate whether spatial heterogeneity in species composition is predictive of temporal heterogeneity in ecological communities, we analyzed 68 community datasets spanning freshwater and terrestrial systems where measures of species abundance were replicated over space and time. Of the 68 data sets 55 (81%) had a weak to strongly positive relationship between spatial and temporal heterogeneity, while in the remaining communities the relationship was weak to strongly negative (19%). Based on a mixed model analysis, we found a significant but weak overall positive relationship between spatial and temporal heterogeneity across all data sets combined, and within aquatic and terrestrial data sets separately. In addition, lifespan and successional stage were negatively and positively related to temporal heterogeneity, respectively. We conclude that spatial heterogeneity may be a predictor of temporal heterogeneity in ecological communities, and that this relationship may be a general property of many terrestrial and aquatic communities.This article is protected by copyright. All rights reserved.
      PubDate: 2018-01-20T01:45:21.455038-05:
      DOI: 10.1002/ecy.2154
  • Experimental evidence that density dependence strongly influences plant
           invasions through fragmented landscapes
    • Authors: Jennifer L. Williams; Jonathan M. Levine
      Abstract: Populations of range expanding species encounter patches of both favorable and unfavorable habitat as they spread across landscapes. Theory shows that increasing patchiness slows the spread of populations modeled with continuously varying population density when dispersal is not influence by the environment or individual behavior. However, as is found in uniformly favorable landscapes, spread remains driven by fecundity and dispersal from low density individuals at the invasion front. In contrast, when modeled populations are composed of discrete individuals, patchiness causes populations to build up to high density before dispersing past unsuitable habitat, introducing an important influence of density dependence on spread velocity. To test the hypothesized interaction between habitat patchiness and density dependence, we simultaneously manipulated these factors in a greenhouse system of annual plants spreading through replicated experimental landscapes. We found that increasing the size of gaps and amplifying the strength of density dependence both slowed spread velocity, but contrary to predictions, the effect of amplified density dependence was similar across all landscape types. Our results demonstrate that the discrete nature of individuals in spreading populations has a strong influence on how both landscape patchiness and density dependence influence spread through demographic and dispersal stochasticity. Both finiteness and landscape structure should be critical components to theoretical predictions of future spread for range expanding native species or invasive species colonizing new habitat.This article is protected by copyright. All rights reserved.
      PubDate: 2018-01-20T01:20:47.920436-05:
      DOI: 10.1002/ecy.2156
  • Temperature-dependency of intraguild predation between native and invasive
    • Authors: Tanya L. Rogers; Tarik C. Gouhier, David L. Kimbro
      Abstract: Environmental factors such as temperature can affect the geographical distribution of species directly by exceeding physiological tolerances, or indirectly by altering physiological rates that dictate the sign and strength of species interactions. Although the direct effects of environmental conditions are relatively well studied, the effects of environmentally-mediated species interactions have garnered less attention. In this study, we examined the temperature-dependency of size-structured intraguild predation (IGP) between native blue crabs (Callinectes sapidus, the IG predator) and invasive green crabs (Carcinus maenas, the IG prey) to evaluate how the effect of temperature on competitive and predatory rates may influence the latitudinal distribution of these species. In outdoor mesocosm experiments, we quantified interactions between blue crabs, green crabs, and shared prey (mussels) at 3 temperatures reflective of those across their range, using 2 size classes of blue crab. At low temperatures, green crabs had a competitive advantage and IGP by blue crabs on green crabs was low. At high temperatures, size-matched blue and green crabs were competitively similar, large blue crabs had a competitive advantage, and IGP on green crabs was high. We then used parameter values generated from these experiments (temperature- and size-dependent attack rates and handling times) in a size-structured IGP model in which we varied IGP attack rate, maturation rate of the blue crab from the non-predatory to predatory size class, and resource carrying capacity at each of the 3 temperatures. In the model, green crabs were likely to competitively exclude blue crabs at low temperature, whereas blue crabs were likely to competitively and consumptively exclude green crabs at higher temperatures, particularly when resource productivities and rates of IGP were high. While many factors may play a role in delimiting species ranges, our results suggest that temperature-dependent interactions can influence local coexistence and are worth considering when developing mechanistic species distribution models and evaluating responses to environmental change.This article is protected by copyright. All rights reserved.
      PubDate: 2018-01-20T01:20:46.145845-05:
      DOI: 10.1002/ecy.2157
  • Competitive ability, stress tolerance and plant interactions along stress
    • Authors: Man Qi; Tao Sun, SuFeng Xue, Wei Yang, DongDong Shao, Javier Martínez-López
      Abstract: Exceptions to the generality of the stress-gradient hypothesis (SGH) may be reconciled by considering species-specific traits and stress tolerance strategies. Studies have tested stress tolerance and competitive ability in mediating interaction outcomes, but few have incorporated this to predict how species interactions shift between competition and facilitation along stress gradients. We used field surveys, salt tolerance and competition experiments to develop a predictive model interspecific interaction shifts across salinity stress gradients. Field survey and greenhouse tolerance tests revealed trade-offs between stress tolerance and competitive ability. Modelling showed that along salinity gradients, 1) plant interactions shifted from competition to facilitation at high salinities within the physiological limits of salt-intolerant plants, 2) facilitation collapsed when salinity stress exceeded the physiological tolerance of salt-intolerant plants, and 3) neighbor removal experiments overestimate interspecific facilitation by including intraspecific effects. A community-level field experiment, suggested that 1) species interactions are competitive in benign and, facilitative in harsh condition, but fuzzy under medium environmental stress due to niche differences of species and weak stress amelioration, and 2) the SGH works on strong but not weak stress gradients, so SGH confusion arises when it is applied across questionable stress gradients. Our study clarifies how species interactions vary along stress gradients. Moving forward, focusing on SGH applications rather than exceptions on weak or nonexistent gradients would be most productive.This article is protected by copyright. All rights reserved.
      PubDate: 2018-01-18T08:15:50.765486-05:
      DOI: 10.1002/ecy.2147
  • Microbial Mitigation-Exacerbation Continuum: A novel framework for
           microbiome effects on hosts in the face of stress
    • Authors: Aaron S. David; Khum B. Thapa-Magar, Michelle E. Afkhami
      Abstract: A key challenge to understanding microbiomes and their role in ecological processes is contextualizing their effects on host organisms, particularly when faced with environmental stress. One influential theory, the Stress Gradient Hypothesis, might predict that the frequency of positive interactions increases with stressful conditions such that microbial taxa would mitigate harmful effects on host performance. Yet, equally plausible is that microbial taxa could exacerbate these effects. Here, we introduce the “Mitigation-Exacerbation Continuum” as a novel framework to conceptualize microbial mediation of stress. We (1) use this continuum to quantify microbial mediation of stress for six plant species, and (2) test the association between these continuum values and natural species abundance. We factorially manipulated a common stress (allelopathy) and the presence of soil microbes to quantify microbial effects in benign and stressed environments for two critical early life-history metrics, seed germination and seedling biomass. Although we found evidence of both mitigation and exacerbation among the six species, exacerbation was more common. Across species, the degree of microbial-mediated effects on germination explained>80% of the variation of natural field abundances. Our results suggest a critical role of soil microbes in mediating plant stress responses, and a potential microbial mechanism underlying species abundance.This article is protected by copyright. All rights reserved.
      PubDate: 2018-01-18T08:15:19.842809-05:
      DOI: 10.1002/ecy.2153
  • Toward more robust plant-soil feedback research
    • Authors: Matthew J. Rinella; Kurt O. Reinhart
      Abstract: Understanding if and how plant-soil biota feedbacks (PSFs) shape plant communities has become a major research priority. In this paper, we draw on a recent, high-profile PSF study to illustrate that certain widely used experimental methods cannot reliably determine if PSFs occur. One problem involves gathering soil samples adjacent to multiple conditioning plants, mixing the samples and then growing phytometers in the mixtures to test for PSFs. This mixed soil approach does not establish that the conditioning plant being present caused the soil biota to be present, the first step of a PSF. Also, soil mixing approximates replacing raw data with averages prior to analysis, a move certain to generate falsely precise statistical estimates. False precision also results from sample sizes being artificially inflated when phytometers are misinterpreted as experimental units. Plant biomass ratios become another source of false precision when individual plant values contribute to multiple ratio observations. Any one of these common missteps can cause still living null hypotheses to be pronounced dead, and risks of this increase with numbers of missteps. If soil organisms truly structure plant communities, then null hypotheses indicating otherwise will not survive proper testing. We discuss conceptual, experimental and analytical refinements to facilitate accurate testing.This article is protected by copyright. All rights reserved.
      PubDate: 2018-01-18T08:00:40.541621-05:
      DOI: 10.1002/ecy.2146
  • Anthropogenic nitrogen deposition ameliorates the decline in tree growth
           caused by a drier climate
    • Authors: Inés Ibáñez; Donald R. Zak, Andrew J. Burton, Kurt S. Pregitzer
      Abstract: Most forest ecosystems are simultaneously affected by concurrent global change drivers. However, when assessing these effects, studies have mainly focused on the responses to single factors and have rarely evaluated the joined effects of the multiple aspects of environmental change. Here, we analyzed the combined effects of anthropogenic nitrogen (N) deposition and climatic conditions on the radial growth of Acer saccharum, a dominant tree species in eastern North American forests. We capitalized on a long-term N deposition study, replicated along a latitudinal gradient, that has been taking place for more than 20 yr. We analyzed tree radial growth as a function of anthropogenic N deposition (ambient and experimental addition) and of summer temperature and soil water conditions. Our results reveal that experimental N deposition enhances radial growth of this species, an effect that was accentuated as temperature increased and soil water became more limiting. The spatial and temporal extent of our data also allowed us to assert that the positive effects of growing under the experimental N deposition are likely due to changes in the physiological performance of this species, and not due to the positive correlation between soil N and soil water holding capacity, as has been previously speculated in other studies. Our simulations of tree growth under forecasted climate scenarios specific for this region also revealed that although anthropogenic N deposition may enhance tree growth under a large array of environmental conditions, it will not mitigate the expected effects of growing under the considerably drier conditions characteristic of our most extreme climatic scenario.
      PubDate: 2018-01-17T10:00:03.974038-05:
      DOI: 10.1002/ecy.2095
  • Variation and drivers of airflow patterns associated with olfactory
           concealment and habitat selection
    • Authors: Dillon T. Fogarty; R. Dwayne Elmore, Samuel D. Fuhlendorf, Scott R. Loss
      Abstract: Many terrestrial predators rely on olfaction to detect prey; therefore, prey should select habitat to reduce detectability of their odor cues. One way prey can potentially conceal their odor is by selecting locations with high turbulence and/or updrafts, conditions that disperse odor plumes and make odor sources difficult to locate. However, it is unclear how these conditions vary among vegetation cover types and which vegetative features drive them. We assessed variation and drivers of variables hypothesized to influence olfactory concealment (turbulence intensity and airflow slope) and experimentally evaluated whether these variables indeed influence predator detection of simulated prey. Specifically, we compared vegetation patch-scale values of turbulence intensity and airflow slope among grassland, shrubland, and forest and assessed relationships among these airflow variables and local-scale vegetative features within each vegetation type. Additionally, we experimentally investigated the importance of turbulence intensity, airflow slope, and visual concealment for predicting predator detection of scented quail eggs. In all vegetation types, we documented high variability in airflow conditions. At the patch scale, turbulence intensity was greater in shrubland and grassland than in forest, and updrafts were most common in shrubland whereas downdrafts were most common in grassland. Grassland was the only vegetation type with strong relationships among turbulence intensity and local vegetation features; both visual concealment and vegetation height were positively related to turbulence intensity. Additionally, persistence of scented quail eggs in grassland was best predicted by turbulence intensity; egg persistence increased with turbulence intensity. Our characterization of differences in olfactory variables among vegetation types provides an important step towards building a clearer understanding of olfactory landscapes. Further, our observation of both patch- and local-scale variation in olfactory variables suggests that prey can potentially select for olfactory concealment at multiple scales. We hypothesize that olfactory concealment provided by high levels of turbulence intensity is an important component of cover in grassland, and that in grassland/shrubland landscapes, prey selection of shrubland patches reduces odor detectability. Our finding of a positive relationship between turbulence intensity and visual concealment also suggests that olfactory concealment may be a previously underappreciated confounding factor in studies of habitat selection.
      PubDate: 2018-01-17T10:00:03.10928-05:0
      DOI: 10.1002/ecy.2102
  • Non-volant mammals from the Upper ParanĂ¡ River Basin: a data set from a
           critical region for conservation in Brazil
    • Authors: Fernando Gonçalves; Wellington Hannibal, Mauricio N. Godoi, Fernando I. Martins, Roniel F. Oliveira, Valquiria V. Figueiredo, Janaina Casella, Érica F. G. G. Sá
      Abstract: The data set represents the first attempt at a large-scale inventory of non-volant mammals, with potential applications to performing macroecological studies, developing conservation strategies, and undertaking population and community ecology research, but also to evaluate the ecological consequences of fragmentation and defaunation. Our objectives for compiling these data were to summarize information about inventories of non-volant mammals in the critically important area of the Upper Paraná River Basin by focusing on species richness and index of frequency of occurrence and to identify gaps in knowledge regarding non-volant mammal communities in order to guide future sampling efforts. The data set comprises studies on communities of non-volant mammals from 52 locations covering more than 1,000 km2 and comprises portion of four Brazilian states in the Upper Paraná River Basin. We listed 81 species of non-volant mammals distributed among 58 genera, 22 families, and 9 orders. Rodentia (28 species) was the richest order, followed by Carnivora (17 spp.) and Didelphimorphia (15 spp.). The richest family was Cricetidae (20 spp.), followed by Didelphidae (15 spp.), and Dasypodidae and Felidae (six spp.). Considering national conservation status, one species are considered endangered and 16 vulnerable. Considering global conservation status, 7 species are considered vulnerable, 10 are considered near threatened, and 6 are data deficient. According to the index of frequency of occurrence, Myrmecophaga tridactyla was the most frequent species, occurring at 88.64% of all sites, while 25 species were considered very restricted, occurring in just 2.56% of all sites. In general, the non-volant mammal fauna was composed of mainly very restricted (VR, 25 species) and localized species (L, 25 species), which account for 61.7% of the known species, while 38.3% are restricted (R, 8 species), common (C, 16 species), and widespread (W, 7 species). Seven marsupials and five small rodents had their distributions extended in the central-south of Brazil. All of these species are considered data deficient or threatened, which highlights the importance of these records. No copyright restrictions are associated with the use of this data set. Please cite this data paper when the data are used in publications. We also request that researchers and teachers inform us of how they are using the data.
      PubDate: 2018-01-17T10:00:01.361279-05:
      DOI: 10.1002/ecy.2107
  • Recent Publications of Interest
    • PubDate: 2018-01-16T11:00:20.113411-05:
      DOI: 10.1002/ecy.2117
  • The century experiment: the first twenty years of UC Davis' Mediterranean
           agroecological experiment
    • Authors: Kristina M. Wolf; Emma E. Torbert, Dennis Bryant, Martin Burger, R. Ford Denison, Israel Herrera, Jan Hopmans, Will Horwath, Stephen Kaffka, Angela Y. Y. Kong, R. F. Norris, Johan Six, Thomas P. Tomich, Kate M. Scow
      Abstract: The Century Experiment at the Russell Ranch Sustainable Agriculture Facility at the University of California, Davis provides long-term agroecological data from row crop systems in California's Central Valley starting in 1993. The Century Experiment was initially designed to study the effects of a gradient of water and nitrogen availability on soil properties and crop performance in ten different cropping systems to measure tradeoffs and synergies between agricultural productivity and sustainability. Currently systems include 11 different cropping systems–consisting of four different crops and a cover crop mixture–and one native grass system. This paper describes the long-term core data from the Century Experiment from 1993–2014, including crop yields and biomass, crop elemental contents, aerial-photo-based Normalized Difference Vegetation Index data, soil properties, weather, chemical constituents in irrigation water, winter weed populations, and operational data including fertilizer and pesticide application amounts and dates, planting dates, planting quantity and crop variety, and harvest dates. This data set represents the only known long-term set of data characterizing food production and sustainability in irrigated and rainfed Mediterranean annual cropping systems. There are no copyright restrictions associated with the use of this dataset.
      PubDate: 2018-01-16T10:51:34.670238-05:
      DOI: 10.1002/ecy.2105
  • Drivers and demographic consequences of seasonal mass changes in an alpine
    • Authors: Mathieu Douhard; Simon Guillemette, Marco Festa-Bianchet, Fanie Pelletier
      Abstract: We know little about the determinants and demographic consequences of the marked seasonal mass changes exhibited by many northern and alpine mammals. We analysed 43 years of data on individual winter mass loss (the difference between mass in early June and mass in mid-September the previous year) and summer mass gain (the difference between mass in mid-September and in early June of the same year) in adult bighorn sheep (Ovis canadensis). We calculated relative seasonal mass change as a proportion of individual body mass at the start of each season. We first examined the effects of weather and population density on relative changes in body mass. We then assessed the consequences of relative seasonal mass changes on reproduction. Mean April-May temperature was the main driver of relative seasonal mass changes: warm springs reduced both relative winter mass loss and summer mass gain of both sexes, likely partially due to a trade-off between growth rate of plants and duration of access to high-quality forage. Because these effects cancelled each other, spring temperature did not influence mass in mid-September. Mothers that lost relatively more mass during the winter had lambs that gained less mass during summer, likely because these females allocated fewer resources to lactation. Winter survival of lambs increased with their summer mass gain. In males, relative mass loss during winter, which includes the rut, did not influence the probability of siring at least one lamb, possibly indicating that greater mating effort did not necessarily translate into greater reproductive success. Our findings improve our understanding of how weather influences recruitment and underline the importance of cryptic mechanisms behind the effects of climate change on demographic traits.This article is protected by copyright. All rights reserved.
      PubDate: 2018-01-16T06:58:25.837584-05:
      DOI: 10.1002/ecy.2141
  • Species co-occurrence networks: can they reveal trophic and non-trophic
           interactions in ecological communities'
    • Authors: Mara A. Freilich; Evie Wieters, Bernardo R. Broitman, Pablo A. Marquet, Sergio A. Navarrete
      Abstract: Co-occurrence methods are increasingly utilized in ecology to infer networks of species interactions where detailed knowledge based on empirical studies is difficult to obtain. Their use is particularly common, but not restricted to, microbial networks constructed from metagenomic analyses. In this study, we test the efficacy of this procedure by comparing an inferred network constructed using spatially intensive co-occurrence data from the rocky intertidal zone in central Chile to a well-resolved, empirically-based, species interaction network from the same region. We evaluated the overlap in the information provided by each network and whether there is a bias for co-occurrence data to better detect known trophic or non-trophic, positive or negative interactions. We found a poor correspondence between the co-occurrence network and the known species interactions with overall sensitivity (probability of true link detection) equal to 0.469, and specificity (true non-interaction) equal to 0.527. The ability to detect interactions varied with interaction type. Positive non-trophic interactions such as commensalism and facilitation were detected at the highest rates. These results demonstrate that co-occurrence networks do not represent well classical ecological networks in which interactions are defined by direct observations or experimental manipulations. Co-occurrence networks provide information about the joint spatial effects of environmental conditions, recruitment, and, to some extent, biotic interactions, and among the latter, they tend to better detect niche-expanding interactions such as positive non-trophic interactions including habitat engineering. Detection of links (sensitivity or specificity) was not higher for well-known intertidal keystone species than for the rest of consumers in the community. Thus, as observed in previous empirical and theoretical studies, patterns of interactions in co-occurrence networks must be interpreted with caution, especially when extending interaction-based ecological theory to interpret network variability and stability. Co-occurrence networks may be particularly valuable for analysis of community dynamics that blends interactions and environment, rather than pairwise interactions alone.This article is protected by copyright. All rights reserved.
      PubDate: 2018-01-16T06:40:27.021375-05:
      DOI: 10.1002/ecy.2142
  • Litter removal in a tropical rain forest reduces fine root biomass and
           production but litter addition has few effects
    • Authors: C. Rodtassana; E.V.J. Tanner
      Abstract: Many old-growth lowland tropical rain forests are potentially nutrient limited, and it has long been thought that many such forests maintain growth by recycling nutrients from decomposing litter. We investigated this by continuously removing (for ten years) freshly fallen litter from five (45 m x 45 m) plots, adding it to five other plots, there were five controls. From monthly measures over one year we show that litter removal caused lower: fine root (≤2 mm diameter) standing mass, fine root standing length, fine root length production and fine root length survivorship. Litter addition did not significantly change fine root mass or length or production. Nutrient concentrations in fine roots in litter removal plots were lower than those in controls for nitrogen (N), calcium (Ca) and magnesium (Mg), concentrations in fine roots in litter addition plots were higher for N and Ca. Chronic litter removal has resulted in reduced forest growth due to lack of nutrients, probably nitrogen. Conversely, long-term litter addition has had fewer effects.This article is protected by copyright. All rights reserved.
      PubDate: 2018-01-16T06:40:24.718191-05:
      DOI: 10.1002/ecy.2143
  • Mapping environmental ethics in the age of climate change
    • Authors: Thomas Bretz
      PubDate: 2018-01-12T10:45:43.836934-05:
      DOI: 10.1002/ecy.2114
  • Books and Monographs Received through November 2017
    • PubDate: 2018-01-12T10:45:42.722968-05:
      DOI: 10.1002/ecy.2113
  • Biogeophysical history, fragility and future of a global biodiversity and
           cultural hotspot: the Himalaya
    • Authors: Dave M. Augeri
      PubDate: 2018-01-12T10:45:41.774377-05:
      DOI: 10.1002/ecy.2112
  • Economy of scale: third partner strengthens a keystone ant-plant mutualism
    • Authors: Kirsten M. Prior; Todd M. Palmer
      Abstract: While foundation species can stabilize ecosystems at landscape scales, their ability to persist is often underlain by keystone interactions occurring at smaller scales. Acacia drepanolobium is a foundation tree, comprising>95% of woody cover in East African black-cotton savanna ecosystems. Its dominance is underlain by a keystone mutualistic interaction with several symbiotic ant species in which it provides housing (swollen thorns) and carbohydrate-rich nectar from extra-floral nectaries (EFN). In return, it gains protection from catastrophic damage from mega-herbivores. Crematogaster mimosae is the ecologically dominant symbiotic ant in this system, also providing the highest protection services. In addition to tending EFN, C. mimosae tend scale insects for carbohydrate-rich honeydew. We investigated the role of scale insects in this specialized ant-plant interaction. Specifically, does this putatively redundant third partner strengthen the ant-plant mutualism by making the ant a better protector of the tree' Or does it weaken the mutualism by being costly to the tree while providing no additional benefit to the ant-plant mutualism' We coupled observational surveys with two scale-manipulation experiments and found evidence that this third partner strengthens the ant-plant mutualism. Trees with scale insects experimentally removed experienced a 2.5X increase in elephant damage compared to trees with scale insects present over 10 months. Reduced protection was driven by scale removal causing a decrease in ant colony size and per capita baseline activity and defensive behavior. We also found that ants increased scale-tending and the density of scale insects on trees when EFN were experimentally reduced. Thus, in this system, scale insects and EFN are likely complementary, rather than redundant, resources with scale insects benefitting ants when EFN production is low (such as during annual dry periods in this semi-arid ecosystem). This study reveals that a third-partner strengthens an ant-plant mutualism that serves to stabilize a whole ecosystem.
      PubDate: 2018-01-12T10:45:40.605176-05:
      DOI: 10.1002/ecy.2104
  • High refuge availability on coral reefs increases the vulnerability of
           reef-associated predators to overexploitation
    • Authors: Alice Rogers; Julia L. Blanchard, Steven P. Newman, Charlie S. Dryden, Peter J. Mumby
      Abstract: Refuge availability and fishing alter predator-prey interactions on coral reefs, but our understanding of how they interact to drive food web dynamics, community structure and vulnerability of different trophic groups is unclear. Here, we apply a size-based ecosystem model of coral reefs, parameterized with empirical measures of structural complexity, to predict fish biomass, productivity and community structure in reef ecosystems under a broad range of refuge availability and fishing regimes. In unfished ecosystems, the expected positive correlation between reef structural complexity and biomass emerges, but a non-linear effect of predation refuges is observed for the productivity of predatory fish. Reefs with intermediate complexity have the highest predator productivity, but when refuge availability is high and prey are less available, predator growth rates decrease, with significant implications for fisheries. Specifically, as fishing intensity increases, predators in habitats with high refuge availability exhibit vulnerability to over-exploitation, resulting in communities dominated by herbivores. Our study reveals mechanisms for threshold dynamics in predators living in complex habitats and elucidates how predators can be food-limited when most of their prey are able to hide. We also highlight the importance of nutrient recycling via the detrital pathway, to support high predator biomasses on coral reefs.
      PubDate: 2018-01-12T10:45:33.997572-05:
      DOI: 10.1002/ecy.2103
  • Applied ecology in the 21st century
    • Authors: Nathalie Pettorelli
      PubDate: 2018-01-12T10:45:22.923318-05:
      DOI: 10.1002/ecy.2116
  • Wildfire in the American West
    • Authors: Andrew J. Larson
      PubDate: 2018-01-12T10:45:19.918849-05:
      DOI: 10.1002/ecy.2115
  • Positive diversity-functioning relationships in model communities of
           methanotrophic bacteria
    • Authors: Elvira Schnyder; Paul L.E. Bodelier, Martin Hartmann, Ruth Henneberger, Pascal A. Niklaus
      Abstract: Biodiversity enhances ecosystem functions such as biomass production and nutrient cycling. Although the majority of the terrestrial biodiversity is hidden in soils, very little is known about the importance of the diversity of microbial communities for soil functioning. Here, we tested effects of biodiversity on the functioning of methanotrophs, a specialized group of soil bacteria that plays a key role in mediating greenhouse gas emissions from soils. Using pure strains of methanotrophic bacteria, we assembled artificial communities of different diversity levels, with which we inoculated sterile soil microcosms. To assess the functioning of these communities, we measured methane oxidation by gas chromatography throughout the experiment and determined changes in community composition and community size at several time points by quantitative PCR and sequencing. We demonstrate that microbial diversity had a positive overyielding-effect on methane oxidation, in particular at the beginning of the experiment. This higher assimilation of CH4 at high diversity translated into increased growth and significantly larger communities towards the end of the study. The overyielding of mixtures with respect to CH4 consumption and community size was positively correlated. The temporal CH4 consumption profiles of strain monocultures differed, raising the possibility that temporal complementarity of component strains drove the observed community-level strain richness effects; however, the community niche metric we derived from the temporal activity profiles did not explain the observed strain richness effect. The strain richness effect also was unrelated to both the phylogenetic and functional trait diversity of mixed communities. Overall, our results suggest that positive biodiversity–ecosystem function relationships show similar patterns across different scales and may be widespread in nature. Additionally, biodiversity is probably also important in natural methanotrophic communities for the ecosystem function methane oxidation. Therefore, maintaining soil conditions that support a high diversity of methanotrophs may help to reduce the emission of the greenhouse gas methane.This article is protected by copyright. All rights reserved.
      PubDate: 2018-01-11T08:35:23.929497-05:
      DOI: 10.1002/ecy.2138
  • Ecological drivers of soil microbial diversity and soil biological
           networks in the Southern Hemisphere
    • Authors: Manuel Delgado-Baquerizo; Frank Reith, Paul G. Dennis, Kelly Hamonts, Jeff R. Powell, Andrew Young, Brajesh K. Singh, Andrew Bissett
      Abstract: The ecological drivers of soil biodiversity in the Southern Hemisphere remain underexplored. Here, in a continental survey comprising 647 sites, across 58 degrees of latitude between tropical Australia and Antarctica, we evaluated the major ecological patterns in soil biodiversity and relative abundance of ecological clusters within a co-occurrence network of soil bacteria, archaea and eukaryotes. Six major ecological clusters (modules) of co-occurring soil taxa were identified. These clusters exhibited strong shifts in their relative abundances with increasing distance from the equator. Temperature was the major environmental driver of the relative abundance of ecological clusters when Australia and Antarctica are analyzed together. Temperature, aridity, soil properties and vegetation types were the major drivers of the relative abundance of different ecological clusters within Australia. Our data supports significant reductions in the diversity of bacteria, archaea and eukaryotes in Antarctica vs. Australia linked to strong reductions in temperature. However, we only detected small latitudinal variations in soil biodiversity within Australia. Different environmental drivers regulate the diversity of soil archaea (temperature and soil carbon), bacteria (aridity, vegetation attributes and pH) and eukaryotes (vegetation type and soil carbon) across Australia. Together, our findings provide new insights into the mechanisms driving soil biodiversity in the Southern Hemisphere.This article is protected by copyright. All rights reserved.
      PubDate: 2018-01-09T11:10:52.176232-05:
      DOI: 10.1002/ecy.2137
  • Climate sensitivity functions and net primary production: A framework for
           incorporating climate mean and variability
    • Authors: Jennifer A. Rudgers; Y.Anny Chung, Gregory E. Maurer, Douglas I. Moore, Esteban H. Muldavin, Marcy E. Litvak, Scott L. Collins
      Abstract: Understanding controls on net primary production (NPP) has been a long-standing goal in ecology. Climate is a well-known control on NPP, although the temporal differences among years within a site are often weaker than the spatial pattern of differences across sites. Climate sensitivity functions describe the relationship between an ecological response (e.g., NPP) and both the mean and variance of its climate driver (e.g., aridity index), providing a novel framework for understanding how climate trends in both mean and variance vary with NPP over time. Nonlinearities in these functions predict whether an increase in climate variance will have a positive effect (convex nonlinearity) or negative effect (concave nonlinearity) on NPP. The influence of climate variance may be particularly intense at ecosystem transition zones, if species reach physiological thresholds that create nonlinearities at these ecotones. Long-term data collected at the confluence of three dryland ecosystems in central New Mexico revealed that each ecosystem exhibited a unique climate sensitivity function that was consistent with long-term vegetation change occurring at their ecotones. Our analysis suggests that rising temperatures in drylands could alter the nonlinearities that determine the relative costs and benefits of variance in precipitation for primary production.This article is protected by copyright. All rights reserved.
      PubDate: 2018-01-09T11:10:48.722278-05:
      DOI: 10.1002/ecy.2136
  • An ignored role of sartenejas to mitigate water shortage hazards for
           tropical forest vertebrates
    • Authors: Carlos M. Delgado-Martínez; Fredy Alvarado, Eduardo Mendoza, Sandra Flores-Hernández, Audomaro Navarrete, Eutimio Navarrete, Francisco Botello
      PubDate: 2018-01-09T10:51:29.446038-05:
      DOI: 10.1002/ecy.2078
  • Mixing alters the lytic activity of viruses in the dark ocean
    • Authors: Christian Winter; Nicole Köstner, Carl-Philip Kruspe, Damaris Urban, Simone Muck, Thomas Reinthaler, Gerhard J. Herndl
      Abstract: In aquatic habitats, viral lysis of prokaryotic cells lowers the overall efficiency of the microbial loop, by which dissolved organic carbon is transfered to higher trophic levels. Mixing of water masses in the dark ocean occurs on a global scale and may have far reaching consequences for the different prokaryotic and virus communities found in these waters by altering the environmental conditions these communities experience. We hypothesize that mixing of deep ocean water masses enhances the lytic activity of viruses infecting prokaryotes. To address this hypothesis, major deep-sea water masses of the Atlantic Ocean such as North Atlantic Deep Water, Mediterranean Sea Overflow Water, Antarctic Intermediate Water, and Antarctic Bottom Water were sampled at five locations. Prokaryotic cells from these samples were collected by filtration and subsequently incubated in virus-reduced water from either the same (control) or a different water mass (transplantation treatment). Additionally, mixtures of prokaryotes obtained from two different water masses were incubated in a mixture of virus-reduced water from the same water masses (control) or in virus-reduced water from the source water masses separately (mixing treatments). Pronounced differences in productivity-related parameters (prokaryotic leucine incorporation, prokaryotic and viral abundance) between water masses caused strong changes in viral lysis of prokaryotes. Often, mixing of water masses increased viral lysis of prokaryotes, indicating that lysogenic viruses were induced into the lytic cycle. Mixing-induced changes in viral lysis had a strong effect on the community composition of prokaryotes and viruses. Our data show that mixing of deep-sea water masses alters levels of viral lysis of prokaryotes and in many cases weakens the efficiency of the microbial loop by enhancing the recycling of organic carbon in the deep ocean.This article is protected by copyright. All rights reserved.
      PubDate: 2018-01-08T03:44:13.479504-05:
      DOI: 10.1002/ecy.2135
  • Resource competition model predicts zonation and increasing nutrient use
           efficiency along a wetland salinity gradient
    • Authors: D. R. Schoolmaster; C. L. Stagg
      Abstract: A trade-off between competitive ability and stress tolerance has been hypothesized and empirically supported to explain the zonation of species across stress gradients for a number of systems. Since stress often reduces plant productivity, one might expect a pattern of decreasing productivity across the zones of the stress gradient. However, this pattern is often not observed in coastal wetlands that show patterns of zonation along a salinity gradient. To address the potentially complex relationship between stress, zonation and productivity in coastal wetlands, we developed a model of plant biomass as a function of resource competition and salinity stress. Analysis of the model confirms the conventional wisdom that a trade-off between competitive ability and stress tolerance is a necessary condition for zonation. It also suggests that a negative relationship between salinity and production can be overcome if 1) the supply of the limiting resource increases with greater salinity stress or 2) nutrient use efficiency increases with increasing salinity. We fit the equilibrium solution of the dynamic model to data from Louisiana coastal wetlands to test its ability to explain patterns of production across the landscape gradient and derive predictions that could be tested with independent data. We found support for a number of the model predictions, including patterns of decreasing competitive ability and increasing nutrient use efficiency across a gradient from freshwater to saline wetlands. In addition to providing a quantitative framework to support the mechanistic hypotheses of zonation, these results suggest that this simple model is a useful platform to further build upon, simulate and test mechanistic hypotheses of more complex patterns and phenomena in coastal wetlands.This article is protected by copyright. All rights reserved.
      PubDate: 2018-01-08T03:42:46.696792-05:
      DOI: 10.1002/ecy.2131
  • Predation risk and patch size jointly determine perceived patch quality in
           ovipositing treefrogs, Hyla chrysoscelis
    • Authors: William J. Resetarits; Jason R. Bohenek, Tyler Breech, Matthew R. Pintar
      Abstract: Two of the most important factors determining community structure and diversity within and among habitat patches are patch size and patch quality. Despite the importance of patch size in existing paradigms in island biogeography, metapopulation biology, landscape ecology, and metacommunity ecology, and growing conservation concerns with habitat fragmentation, there has been little investigation into how patch size interacts with patch quality. We crossed three levels of patch size (1.13 m2, 2.54 m2 and 5.73 m2) with two levels of patch quality [fish presence/absence - green sunfish (Lepomis cyanellus) and golden shiners (Notemigonus chrysoleucus) in 6 replicate experimental landscapes (3 x 2 x 6 = 36 patches). Both fish predators have been previously shown to elicit avoidance in ovipositing treefrogs. We examined how patch size and patch quality, as well as the interaction between size and quality, affected female oviposition preference and male calling site choice in a natural population of treefrogs (Hyla chrysoscelis). Females almost exclusively oviposited in the largest fishless patches, indicating that females use both risk, in the form of fish predators, and size itself, as components of patch quality. Females routinely use much smaller natural and experimental patches, suggesting that the responses to patch size are highly context dependent. Responses to fish were unaffected by patch size. Male responses largely mimicked those of females, but did not drive female oviposition. We suggest that patch size itself functions as another aspect of patch quality for Hyla chrysoscelis, and serves as another niche dimension across which species may behaviorally sort in natural systems. Because of strong, shared avoidance of fish (as well as other predators), among many colonizing taxa, patch size may be a critical factor in species sorting and processes of community assembly in freshwater habitats, allowing species to behaviorally segregate along gradients of patch size in fishless ponds. Conversely, lack of variation in patch size may concentrate colonization activity, leading to intensification of species interactions and/or increased use of lesser quality patches.This article is protected by copyright. All rights reserved.
      PubDate: 2018-01-07T22:50:22.703525-05:
      DOI: 10.1002/ecy.2130
  • Fasting or fear: Disentangling the roles of predation risk and food
           deprivation in the nitrogen metabolism of consumers
    • Authors: Christopher M. Dalton; Karen E. Tracy, Nelson G. Hairston, Alexander S. Flecker
      Abstract: Predators can alter nutrient cycles simply by inducing stress in prey. This stress accelerates prey's protein catabolism, nitrogen waste production, and nitrogen cycling. Yet predators also reduce the feeding rates of their prey, inducing food deprivation that is expected to slow protein catabolism and nitrogen cycling. The physiology of prey under predation risk thus balances the influences of predation risk and food deprivation, and this balance is central to understanding the role of predators in nutrient cycles. We explored the separate and combined effects of predation risk and food deprivation on prey physiology and nutrient cycling by exposing guppies (Poecilia reticulata) to predation risk and food deprivation in a 2 x 2 design. We simulated predation risk using chemical cues from a natural predator of guppies, and we created food deprivation by rationing food availability. We measured guppy response as food consumption, growth, tissue energy density, tissue carbon:nitrogen, and nitrogen (N) excretion and assimilation. We found that N-linked physiological processes (N consumption, assimilation, excretion) were strongly affected by predation risk, independent of food consumption. Guppies excreted substantially less under predation risk than they did under food deprivation or control conditions. These results suggest that predation risk, per se, triggers physiological changes in guppies that increase N retention and decrease N excretion. We suggest that slower N metabolism under predation risk is an adaptive response that minimizes protein loss in the face of predictable, predator-induced food restriction. Notably, N metabolism shares common hormonal control with food seeking behavior, and we speculate that increased N retention is a direct and immediate result of reduced food-seeking under predation risk. Contrary to predation-stress-based hypotheses for how predators affect nutrient cycling by prey, our result indicates that even short-term exposure to predators may decelerate, rather than accelerate, the speed of N cycling by suppressing N turnover by prey.This article is protected by copyright. All rights reserved.
      PubDate: 2018-01-07T22:50:20.650982-05:
      DOI: 10.1002/ecy.2132
  • Observed trends of soil fauna in the Antarctic Dry Valleys: early signs of
           shifts predicted under climate change
    • Authors: W. S. Andriuzzi; B. J. Adams, J. E. Barrett, R. A. Virginia, D. H. Wall
      Abstract: Long-term observations of ecological communities are necessary for generating and testing predictions of ecosystem responses to climate change. We investigated temporal trends and spatial patterns of soil fauna along similar environmental gradients in three sites of the McMurdo Dry Valleys, Antarctica, spanning two distinct climatic phases: a decadal cooling trend from the early 1990s through the austral summer of February 2001, followed by a shift to the current trend of warming summers and more frequent discrete warming events. After February 2001, we observed a decline in the dominant species (the nematode Scottnema lindsayae) and increased abundance and expanded distribution of less common taxa (rotifers, tardigrades, and other nematode species). Such diverging responses have resulted in slightly greater evenness and spatial homogeneity of taxa. However, total abundance of soil fauna appears to be declining, as positive trends of the less common species so far have not compensated for the declining numbers of the dominant species. Interannual variation in the proportion of juveniles in the dominant species was consistent across sites, whereas trends in abundance varied more. Structural equation modeling supports the hypothesis that the observed biological trends arose from dissimilar responses by dominant and less common species to pulses of water availability resulting from enhanced ice melt. No direct effects of mean summer temperature were found, but there is evidence of indirect effects via its weak but significant positive relationship with soil moisture. Our findings show that combining an understanding of species responses to environmental change with long-term observations in the field can provide a context for validating and refining predictions of ecological trends in the abundance and diversity of soil fauna.
      PubDate: 2018-01-05T08:50:40.163487-05:
      DOI: 10.1002/ecy.2090
  • Issue Information
    • Pages: 1 - 4
      PubDate: 2018-01-04T08:55:04.410489-05:
      DOI: 10.1002/ecy.2111
  • Small genome separates native and invasive populations in an ecologically
           important cosmopolitan grass
    • Authors: Petr Pyšek; Hana Skálová, Jan Čuda, Wen-Yong Guo, Jan Suda, Jan Doležal, Ondřej Kauzál, Carla Lambertini, Magdalena Lučanová, Terezie Mandáková, Lenka Moravcová, Klára Pyšková, Hans Brix, Laura A. Meyerson
      Pages: 79 - 90
      Abstract: The literature suggests that small genomes promote invasion in plants, but little is known about the interaction of genome size with other traits or about the role of genome size during different phases of the invasion process. By intercontinental comparison of native and invasive populations of the common reed Phragmites australis, we revealed a distinct relationship between genome size and invasiveness at the intraspecific level. Monoploid genome size was the only significant variable that clearly separated the North American native plants from those of European origin. The mean Cx value (the amount of DNA in one chromosome set) for source European native populations was 0.490 ± 0.007 (mean ± SD), for North American invasive 0.506 ± 0.020, and for North American native 0.543 ± 0.021. Relative to native populations, the European populations that successfully invaded North America had a smaller genome that was associated with plant traits favoring invasiveness (long rhizomes, early emerging abundant shoots, resistance to aphid attack, and low C:N ratio). The knowledge that invasive populations within species can be identified based on genome size can be applied to screen potentially invasive populations of Phragmites in other parts of the world where they could grow in mixed stands with native plants, as well as to other plant species with intraspecific variation in invasion potential. Moreover, as small genomes are better equipped to respond to extreme environmental conditions such as drought, the mechanism reported here may represent an emerging driver for future invasions and range expansions.
      PubDate: 2018-01-04T08:55:00.039229-05:
      DOI: 10.1002/ecy.2068
  • Will a small randomly-assembled community be feasible and stable'
    • Authors: Chuliang Song; Serguei Saavedra
      Abstract: How likely is that few species can randomly assemble into a feasible and stable community' Some studies have answered that as long as the community is feasible, it will nearly always be stable. In contrast, other studies have answered that the likelihood is almost null. Here, we show that the origin of this debate has been the underestimation of the association of the parameter space of intrinsic growth rates with the feasibility and stability properties of small randomly-assembled communities. In particular, we demonstrate that not all parameterizations and sampling distributions of intrinsic growth rates lead to the same probabilities of stability and feasibility, which could mistakenly lead to under or overestimate the stability properties of feasible communities. Additionally, we find that stability imposes a filtering of species abundances towards more even distributions in small feasible randomly-assembled communities. This indicates that the stability of feasible communities is inherently linked to the starting distribution of species abundances, a characteristic that many times has been ignored, but should be incorporated in manageable lab and field experiments. Overall, the return to this debate is a central reminder that a more systematic exploration of the feasible parameter space is necessary to derive general conclusions about the stability properties of ecological communities.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-28T23:00:26.716189-05:
      DOI: 10.1002/ecy.2125
  • The dimensionality of individual niche variation
    • Authors: Travis Ingram; Raul Costa-Pereira, Márcio S. Araújo
      Abstract: The inherently multidimensional nature of the niche has not yet been integrated into the investigation of individual niche specialization within populations. We propose a framework for modeling the between- and within-individual components of the population niche as a set of variance-covariance matrices, which can be visualized with ellipses or ellipsoids. These niche components can be inferred using multiple response mixed models, and can incorporate diverse types of data, including diet composition, stable isotopes, spatial location, and other continuous measures of niche dimensions. We outline how considering both individual and population niches in multiple dimensions may enhance our understanding of key concepts in ecology and evolution. Considering multiple dimensions as well as the within-individual component of variation can lead to more meaningful measures of niche overlap between species. The impact of a population on its food web or ecosystem can depend on the degree of individual variation (via Jensen's inequality), and we suggest how the dimensionality of individual specialization could amplify this effect. Finally, we draw from concepts in quantitative genetics and the study of animal personalities to propose new hypotheses about the ecological and evolutionary basis of niche shifts in multiple dimensions. We illustrate key ideas using empirical data from sea otters, wetland frogs, and threespine stickleback, and discuss outstanding questions about the consequences of multidimensional niche variation. Setting variation among individuals in an explicitly multivariate framework has the potential to transform our understanding of a range of ecological and evolutionary processes.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-28T01:45:49.840969-05:
      DOI: 10.1002/ecy.2129
  • Bottom-up processes mediated by social systems drive demographic traits of
           coral-reef fishes
    • Authors: Brett M. Taylor; Simon J. Brandl, Maia Kapur, William D. Robbins, Garrett Johnson, Charlie Huveneers, Phil Renaud, J. Howard Choat
      Abstract: Ectotherms exhibit considerable plasticity in their life-history traits. This plasticity can reflect variability in environmental and social factors, but the causes of observed patterns are often obscured with increasing spatial scales. We surveyed dichromatic parrotfishes across the northern Great Barrier Reef to examine variation in body size distributions and concomitant size at sex change (L∆50) against hypotheses of directional influence from biotic and abiotic factors known to affect demography. By integrating top-down, horizontal, and bottom-up processes, we demonstrate a strong association between exposure regimes (which are known to influence nutritional ecology and mating systems) and both body size distribution and L∆50 (median length at female-to-male sex change), with an accompanying lack of strong empirical support for other biotic drivers previously hypothesized to affect body size distributions. Across sites, body size was predictably linked to variation in temperature and productivity, but the strongest predictor was whether subpopulations occurred at sheltered mid and inner shelf reefs or at wave-exposed outer shelf reef systems. Upon accounting for the underlying influence of body size distribution, this habitat-exposure gradient was highly associated with further L∆50 variation across species, demonstrating that differences in mating systems across exposure gradients affect the timing of sex change beyond variation concomitant with differing overall body sizes. We posit that exposure-driven differences in habitat disturbance regimes have marked effects on the nutritional ecology of parrotfishes, leading to size-related variation in mating systems, which underpin the observed patterns. Our results call for better integration of life-history, social factors, and ecosystem processes to foster an improved understanding of complex ecosystems such as coral reefs.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-28T01:41:01.036784-05:
      DOI: 10.1002/ecy.2127
  • Predator-prey interactions cause apparent competition between marine
           zooplankton groups
    • Authors: Leif Christian Stige; Kristina Ø. Kvile, Bjarte Bogstad, Øystein Langangen
      Abstract: Predator-mediated apparent competition is an indirect negative interaction between two prey species mediated by a shared predator. Quantifying such indirect ecosystem effects is methodologically challenging but important for understanding ecosystem functioning. Still, there are few examples of apparent competition from pelagic marine environments. Using state-space statistical modelling, we here provide evidence for apparent competition between two dominant zooplankton groups in a large marine ecosystem, i.e., krill and copepods in the Barents Sea. This effect is mediated by a positive association between krill biomass and survival of the main planktivorous fish in the Barents Sea, capelin Mallotus villosus, and a negative association between capelin and copepod biomasses. The biomass of Atlantic krill species is expected to increase in the Barents Sea due to ongoing climate change, thereby potentially negatively affecting copepods through apparent competition. By demonstrating and quantifying apparent competition in a large marine ecosystem, our study paves the way for more realistic projections of indirect ecosystem effects of climate change and harvesting.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-27T13:50:29.743208-05:
      DOI: 10.1002/ecy.2126
  • Associations among arbuscular mycorrhizal fungi and seedlings are
           predicted to change with tree successional status
    • Authors: Bachelot Benedicte; María Uriarte, Robert Muscarella, Jimena Forero-Montaña, Jill Thompson, Krista McGuire, Jess Zimmerman, Nathan G. Swenson, James S. Clark
      Abstract: Arbuscular mycorrhizal (AM) fungi in the soil may influence tropical tree dynamics and forest succession. The mechanisms are poorly understood, because the functional characteristics and abundances of tree species and AM fungi are likely to be codependent. We used generalized joint attribute modeling to evaluate if AM fungi are associated with three forest community metrics for a sub-tropical montane forest in Puerto Rico. The metrics chosen to reflect changes during forest succession are: the abundance of seedlings of different successional status, the amount of foliar damage on seedlings of different successional status, and community-weighted mean functional trait values (adult specific leaf area (SLA), adult wood density, and seed mass). We used high-throughput DNA sequencing to identify fungal operational taxonomic units (OTUs) in the soil. Model predictions showed that seedlings of mid- and late-successional species had less leaf damage when the 12 most common AM fungi were abundant compared to when these fungi were absent. We also found that seedlings of mid-successional species were predicted to be more abundant when the 12 most common AM fungi were abundant compared to when these fungi were absent. In contrast, early-successional tree seedlings were predicted to be less abundant when the 12 most common AM fungi were abundant compared to when these fungi were absent. Finally, we showed that, among the 12 most common AM fungi, different AM fungi were correlated with functional trait characteristics of early- or late-successional species. Together, these results suggest that early-successional species might not rely as much as mid- and late-successional species on AM fungi, and AM fungi might accelerate forest succession.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-27T13:45:29.155994-05:
      DOI: 10.1002/ecy.2122
  • The interaction of drought and habitat explain space-time patterns of
           establishment in saguaro (Carnegiea gigantea)
    • Authors: Daniel E. Winkler; Joshua L. Conver, Travis E. Huxman, Don E. Swann
      Abstract: The long-lived columnar saguaro cactus (Carnegiea gigantea) is among the most studied plants in the world. Long-term studies have shown saguaro establishment to be generally episodic and strongly influenced by precipitation and temperature. Water limitation through lower-than-average seasonal rainfall and elevated temperatures increasing evaporative loss can reduce survivorship of recent germinates. Thus, multi-year, extended drought could cause populations to decline as older saguaros die without replacement. Previous studies have related establishment to temporal variation in rainfall, but most studies have been on non-randomized plots in ideal habitat and thus might not have captured the full variability within the local area. We studied how saguaro establishment varied in space and which habitat features may buffer responses to drought on 36, 4 ha plots located randomly across an elevation gradient, including substantial replication in landscape position (bajada, foothills, and slopes) in the two disjunct districts of Saguaro National Park in southern Arizona, USA. Recent, severe drought coincided with drastic declines in saguaro establishment across this ca. 25,000 ha area. Establishment patterns derived from the park-wide dataset was strongly correlated with drought, but the Park's two districts and diversity of plots demonstrated substantially different population outcomes. Saguaro establishment was best explained by the interaction of drought and habitat type; establishment in bajada and foothill plots dropped to near-zero under the most severe periods of water limitation but remained higher in slope plots during the same time span. Combined with saguaro density estimates, these data suggest that the most suitable habitat type for saguaro establishment shifted to higher elevations during the time span of the recent drought. These results place into context the extent to which historical patterns of demography provide insight into future population dynamics in a changing climate and reveal the importance of understanding dynamics across the distribution of possible local habitat types with response to variation in weather.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-27T13:45:26.413972-05:
      DOI: 10.1002/ecy.2124
  • Can overcompensation increase crop production'
    • Authors: Katja Poveda; María F. Díaz, Augusto Ramirez
      Abstract: The two most pressing challenges to agriculture worldwide are feeding a rapidly growing human population and developing more sustainable agricultural practices that do not threaten human and ecosystem health. We address these challenges through research in plant-herbivore interactions, specifically overcompensatory responses in potato to herbivore damage. While herbivory is usually detrimental to most crops, some potato cultivars can overcompensate and increase crop productivity up to two-fold in response to herbivore damage. However, biotic and abiotic factors are known to influence compensatory responses. Here we tested if compensatory plant responses to herbivory increase productivity of potatoes under field conditions along gradients of altitude and landscape simplification in 15 different farms. Our results suggest that compensatory plant responses could double the mean productivity of a potato farm in relation to the productivity of undamaged plants. The compensatory response is best predicted by pest pressure on a farm with potato plants having the maximum productivity when 10% of the tubers are damaged and decreasing in productivity as pest pressure increases. To a lesser extent an interaction between altitude and landscape simplification did affect the compensatory response, suggesting that abiotic factors play an important role in compensation. Our results suggest that overcompensation-based management practices could be used to maximize yields on working potato farms. Further research is required to determine action thresholds (i.e. the damage levels at which pest control needs to be enacted to maximize yields and minimize insecticide use) to develop more sustainable ways of increasing yields in the future.
      PubDate: 2017-12-27T09:57:26.740649-05:
      DOI: 10.1002/ecy.2088
  • Size, growth, and density data for shallow-water sea urchins from Mexico
           to the Aleutian Islands, Alaska, 1956–2016
    • Authors: Thomas A. Ebert; Louis M. Barr, James L. Bodkin, Dirk Burcham, Dominique Bureau, Henry S. Carson, Nancy L Caruso, Jennifer E. Caselle, Jeremy T. Claisse, Sabrina Clemente, Kathryn Davis, Paul M. Detwiler, John D. Dixon, David O. Duggins, John M. Engle, James A. Estes, Scott D. Groth, Benjamin M. Grupe, Peter Halmay, Kyle P. Hebert, José C. Hernández, Laura J. Jurgens, Peter E. Kalvass, Michael C. Kenner, Brenda Kenner, David J. Kushner, Lynn C. Lee, David L. Leighton, Gabriela Montaño-Moctezuma, J. Eric Munk, Irma Olguin, Julio S. Palleiro, David O. Parker, John S. Pearse, Daniel J. Pondella, Laura Rogers-Bennett, Stephen C. Schroeter, A. Ole Shelton, Jorge Sonnenholzner, Ian K. Taniguchi, Glenn R. VanBlaricom, Jane C. Watson, Benjamin P. Weitzman, Jonathan P. Williams, Jennifer Yakimishyn, Zane Zhang
      Abstract: Size, growth, and density have been studied for North American Pacific coast sea urchins Strongylocentrotus purpuratus, S. droebachiensis, S. polyacanthus, Mesocentrotus (Strongylocentrotus) franciscanus, Lytechinus pictus, Centrostephanus coronatus, and Arbacia stellata by various workers at diverse sites and for varying lengths of time from 1956 to present. Numerous peer-reviewed publications have used some of these data but some data have appeared only in graduate theses or the gray literature. There also are data that have never appeared outside original data sheets. Motivation for studies has included fisheries management and environmental monitoring of sewer and power plant outfalls as well as changes associated with disease epidemics. Studies also have focused on kelp restoration, community effects of sea otters, basic sea urchin biology, and monitoring. The data sets presented here are a historical record of size, density and growth for a common group of marine invertebrates in intertidal and nearshore environments that can be used to test hypotheses concerning future changes associated with fisheries practices, shifts of predator distributions, climate and ecosystem changes, and ocean acidification along the Pacific Coast of North America and islands of the north Pacific. No copyright restrictions apply. Please credit this paper when using the data.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-27T08:35:56.781472-05:
      DOI: 10.1002/ecy.2123
  • Emma Lucy Braun's forest plots in eastern North America
    • Authors: Robert E. Ricklefs
      Abstract: Relative abundances of tree species are presented for the 348 forest plots described in E. Lucy Braun's (1950) book, Deciduous Forests of Eastern North America (Hafner, New York, facsimile reprint 1972). Information about the plots includes forest type, location with latitude and longitude, WorldClim climate variables, and sources of original studies where applicable. No copyright restrictions are associated with the use of this data set. Please cite this article when the data are used in other publications.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-21T10:40:19.711741-05:
      DOI: 10.1002/ecy.2121
  • Litter P content drives consumer production in detritus-based streams
           spanning an experimental N:P gradient
    • Authors: Lee M. Demi; Jonathan P. Benstead, Amy D. Rosemond, John C. Maerz
      Abstract: Ecological stoichiometry theory (EST) is a key framework for predicting how variation in N:P supply ratios influences biological processes, at molecular to ecosystem scales, by altering the availability of C, N and P relative to organismal requirements. We tested EST predictions by fertilizing five forest streams at different dissolved molar N:P ratios (2, 8, 16, 32, 128) for two years and tracking responses of macroinvertebrate consumers to the resulting steep experimental gradient in basal resource stoichiometry (leaf litter %N, %P and N:P). Nitrogen and P content of leaf litter, the dominant basal resource, increased in all five streams following enrichment, with steepest responses in litter %P and N:P ratio. Additionally, increases in primary consumer biomass and production occurred in all five streams following N and P enrichment (averages across all streams: biomass by 1.2×, production by 1.6×). Patterns of both biomass and production were best predicted by leaf litter N:P and %P and were unrelated to leaf litter %N. Primary consumer production increased most in streams where decreases in leaf litter N:P were largest. Macroinvertebrate predator biomass and production were also strongly positively related to litter %P, providing robust experimental evidence for the primacy of P limitation at multiple trophic levels in these ecosystems. However, production of predatory macroinvertebrates was not related directly to primary consumer production, suggesting the importance of additional controls for macroinvertebrates at upper trophic positions. Our results reveal potential drivers of animal production in detritus-based ecosystems, including the relative importance of resource quality vs. quantity. Our study also sheds light on the more general impacts of variation in N:P supply ratio on nutrient-poor ecosystems, providing strong empirical support for predictions that nutrient enrichment increases food web productivity whenever large elemental imbalances between basal resources and consumer demand are reduced.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-21T10:25:28.803-05:00
      DOI: 10.1002/ecy.2118
  • ATLANTIC BIRDS: a dataset of bird species from the Brazilian Atlantic
    • Authors: Érica Hasui; Jean Paul Metzger, Rafael Guerra Pimentel, Luís Fábio Silveira, Alex Augusto de Abreu Bovo, Alexandre Camargo Martensen, Alexandre Uezu, André Luis Regolin, Arthur Ângelo Bispo de Oliveira, Cassiano Augusto Ferreira Rodrigues Gatto, Charles Duca, Christian Borges Andretti, Cristina Banks-Leite, Daniela Luz, Daniele Mariz, Eduardo Roberto Alexandrino, Fabio Monteiro de Barros, Felipe Martello, Iolanda Maria da Silva Pereira, José Nilton da Silva, Katia Maria Paschoaletto Micchi de Barros Ferraz, Luciano Nicolas Naka, Luiz dos Anjos, Márcio Amorim Efe, Marco Aurélio Pizo, Mauro Pichorim, Maycon Sanyvan Sigales Gonçalves, Paulo Henrique Chaves Cordeiro, Rafael Antunes Dias, Renata de Lara Muylaert, Rodolpho Credo Rodrigues, Thiago Vernaschi Vieira da Costa, Vagner Cavarzere, Vinicius Rodrigues Tonetti, Wesley Rodrigues Silva, Clinton N. Jenkins, Mauro Galetti, Milton Cezar Ribeiro
      Abstract: South America holds 30% of the world's avifauna, with the Atlantic Forest representing one of the richest region of the Neotropics. Here we compiled a dataset on Brazilian Atlantic Forest bird occurrence (150,423) and abundance samples (N=832 bird species; 33,119) using multiple methods, including qualitative surveys, mist-nets, point counts, and line transects). We used four main sources of data: museum collections, on-line databases, literature sources, and unpublished reports. The dataset comprises 4,122 localities and data from 1815 to 2017. Most studies were conducted in the “Florestas de Interior” (N=1510 localities) and “Serra do Mar” (1280) biogeographic sub-regions. Considering the three main quantitative methods (mist net, point count, and line transect), we compiled abundance data for 745 species in 576 communities. In the dataset, the most frequent species were Basileuterus culicivorus, Cyclaris gujanensis and Conophaga lineata. There were 71 singletons, such as Lipaugus conditus and Calyptura cristata. We suggest that these small number of records reinforce the critical situation of these taxa in the Atlantic Forest. The information provided in this dataset can be used for macroecological studies, and to foster conservation strategies in this biodiversity hotspot. No copyright restrictions are associated with the data set. Please cite this Data Paper if data are used in publications and teaching events.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-21T02:59:59.105084-05:
      DOI: 10.1002/ecy.2119
  • Active and colorful life under lake ice
    • Authors: Guillaume Grosbois; Milla Rautio
      PubDate: 2017-12-19T09:56:18.287121-05:
      DOI: 10.1002/ecy.2074
  • How to be a bee hunter
    • Authors: David E. Hibbs
      PubDate: 2017-12-18T10:41:12.563205-05:
      DOI: 10.1002/ecy.2083
  • Books and Monographs Received through October 2017
    • PubDate: 2017-12-18T10:41:11.592396-05:
      DOI: 10.1002/ecy.2082
  • The curious nature of a raptor researcher
    • Authors: Stan D. Rullman
      PubDate: 2017-12-18T10:40:35.976567-05:
      DOI: 10.1002/ecy.2085
  • Synthesizing stream fish community dynamics in the southern Great Plains
           and beyond
    • Authors: Joshuah S. Perkin
      PubDate: 2017-12-18T10:40:34.802008-05:
      DOI: 10.1002/ecy.2084
  • Recent Publications of Interest
    • PubDate: 2017-12-18T10:40:27.640543-05:
      DOI: 10.1002/ecy.2086
  • Holy flux: spatial and temporal variation in massive pulses of emerging
           insect biomass from western U.S. rivers
    • Authors: David M. Walters; Jeff S. Wesner, Robert E. Zuellig, Dan A. Kowalski, Matt C. Kondratieff
      PubDate: 2017-12-14T10:20:51.604439-05:
      DOI: 10.1002/ecy.2023
  • Our common blood
    • Authors: G. A. Bradshaw
      PubDate: 2017-12-12T10:26:45.105044-05:
      DOI: 10.1002/ecy.2057
  • Our next, better parks
    • Authors: Kevin Van Tighem
      PubDate: 2017-12-12T10:26:43.845715-05:
      DOI: 10.1002/ecy.2059
  • Recent Publications of Interest
    • PubDate: 2017-12-12T10:26:23.408414-05:
      DOI: 10.1002/ecy.2061
  • Books and Monographs Received through September 2017
    • PubDate: 2017-12-12T10:26:21.76121-05:0
      DOI: 10.1002/ecy.2060
  • Documenting a regional forest journey
    • Authors: Mark E. Swanson
      PubDate: 2017-12-12T10:26:20.681021-05:
      DOI: 10.1002/ecy.2058
  • Mapping multi-scale vascular plant richness in a forest landscape with
           integrated LiDAR and hyperspectral remote-sensing
    • Authors: C.R Hakkenberg; K Zhu, R.K Peet, C. Song
      Abstract: The central role of floristic diversity in maintaining habitat integrity and ecosystem function has propelled efforts to map and monitor its distribution across forest landscapes. While biodiversity studies have traditionally relied largely on ground-based observations, the immensity of the task of generating accurate, repeatable, and spatially-continuous data on biodiversity patterns at large scales has stimulated the development of remote-sensing methods for scaling up from field plot measurements. One such approach is through integrated LiDAR and hyperspectral remote-sensing. However, despite their efficiencies in cost and effort, LiDAR-hyperspectral sensors are still highly constrained in structurally- and taxonomically-heterogeneous forests - especially when species’ cover is smaller than the image resolution, intertwined with neighboring taxa, or otherwise obscured by overlapping canopy strata. In light of these challenges, this study goes beyond the remote characterization of upper canopy diversity to instead model total vascular plant species richness in a continuous-cover North Carolina Piedmont forest landscape. We focus on two related, but parallel, tasks. First, we demonstrate an application of predictive biodiversity mapping, using nonparametric models trained with spatially-nested field plots and aerial LiDAR-hyperspectral data, to predict spatially-explicit landscape patterns in floristic diversity across seven spatial scales between 0.01m2–900m2. Second, we employ bivariate parametric models to test the significance of individual, remotely-sensed predictors of plant richness to determine how parameter estimates vary with scale. Cross-validated results indicate that predictive models were able to account for 15-70% of variance in plant richness, with LiDAR-derived estimates of topography and forest structural complexity, as well as spectral variance in hyperspectral imagery explaining the largest portion of variance in diversity levels. Importantly, bivariate tests provide evidence of scale-dependence among predictors, such that remotely-sensed variables significantly predict plant richness only at spatial scales that sufficiently subsume geolocational imprecision between remotely-sensed and field data, and best align with stand components including plant size and density, as well as canopy gaps and understory growth patterns. Beyond their insights into the scale-dependent patterns and drivers of plant diversity in Piedmont forests, these results highlight the potential of remotely-sensible essential biodiversity variables for mapping and monitoring landscape floristic diversity from air- and space-borne platforms.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-12T10:02:16.368422-05:
      DOI: 10.1002/ecy.2109
  • Symbioses with nitrogen-fixing bacteria: nodulation and phylogenetic data
           across legume genera
    • Authors: Michelle E. Afkhami; D. Luke Mahler, Jean H. Burns, Marjorie G. Weber, Martin F. Wojciechowski, Janet Sprent, Sharon Y. Strauss
      Abstract: How species interactions shape global biodiversity and influence diversification is a central – but also data-hungry – question in evolutionary ecology. Microbially-based mutualisms are widespread and could cause diversification by ameliorating stress and thus allowing organisms to colonize and adapt to otherwise unsuitable habitats. Yet the role of these interactions in generating species diversity has received limited attention, especially across large taxonomic groups. In the massive angiosperm family Leguminosae, plants often associate with root-nodulating bacteria that ameliorate nutrient stress by fixing atmospheric nitrogen. These symbioses are ecologically-important interactions, influencing community assembly, diversity, and succession, contributing ~100-290 million tons of N annually to natural ecosystems, and enhancing growth of agronomically-important forage and crop plants worldwide. In recent work attempting to determine whether mutualism with N-fixing bacteria led to increased diversification across legumes, we were unable to definitively resolve the relationship between diversification and nodulation. We did, however, succeed in compiling a very large searchable, analysis-ready database of nodulation data for 749 legume genera (98% of Leguminosae genera; LPWG 2017), which, along with associated phylogenetic information, will provide a valuable resource for future work addressing this question and others. For each legume genus, we provide information about the species richness, frequency of nodulation, subfamily association, and topological correspondence with an additional data set of 100 phylogenetic trees curated for database compatibility. We found 386 legume genera were confirmed nodulators (i.e., all species examined for nodulation nodulated), 116 were non-nodulating, 4 were variable (i.e., containing both confirmed nodulators and confirmed non-nodulators), and 243 had not been examined for nodulation in published studies. Interestingly, data exploration revealed that nodulating legume genera are ~3× more species-rich than non-nodulating genera, but we did not find evidence that this difference in diversity was due to differences in net diversification rate. Our metadata file describes in more detail the structure of these data that provide a foundational resource for future work as more nodulation data become available, and as greater phylogenetic resolution of this ca. 19,500-species family comes into focus.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-11T01:55:22.702192-05:
      DOI: 10.1002/ecy.2110
  • Unique preening behavior may use light and heat to facilitate ectoparasite
           removal in green herons (Butorides virescens)
    • Authors: Loren Merrill
      PubDate: 2017-12-05T12:50:03.491643-05:
      DOI: 10.1002/ecy.2040
  • Recent Publications of Interest
    • PubDate: 2017-12-04T15:59:24.513596-05:
      DOI: 10.1002/ecy.2018
  • Surveying the relative wild
    • Authors: Jason Kirkey
      PubDate: 2017-12-04T15:59:23.541395-05:
      DOI: 10.1002/ecy.2016
  • Nature's heroes
    • Authors: David W. Orr
      PubDate: 2017-12-04T15:59:18.708763-05:
      DOI: 10.1002/ecy.2017
  • Books and Monographs Received through August 2017
    • PubDate: 2017-12-04T15:59:17.665742-05:
      DOI: 10.1002/ecy.2014
  • A transboundary approach to parsing plains bison (Bison bison bison)
           ecology and restoration
    • Authors: Cristina Eisenberg
      PubDate: 2017-12-04T15:59:16.670738-05:
      DOI: 10.1002/ecy.2015
  • The “jack-in-the-box” stamens of Heliconia wagneriana
    • Authors: Dustin G. Gannon; Urs G. Kormann, Adam S. Hadley, Matthew G. Betts, Franklin Andrew Jones
      PubDate: 2017-12-04T11:06:45.741383-05:
      DOI: 10.1002/ecy.2042
  • Growing competitive or tolerant' Significance of apical dominance in
           the overcompensating herb Gentianella campestris
    • Authors: Tommy Lennartsson; Satu Ramula, Juha Tuomi
      Abstract: As a compensatory response to herbivory, plants may branch vigorously when the growth of dormant meristems is triggered by shoot damage. Undamaged plants, on the other hand, often restrain branching, and this limitation on growth can be considered a cost of tolerance to herbivory. Restrained branching is caused by apical dominance and may, alternatively, be associated with fitness benefits in competitive environments that favor fast vertical growth. To test these hypotheses regarding selection for restrained branching, we compared the performance of two subspecies of the biennial grassland herb Gentianella campestris; the tall, apically dominant ssp. campestris and the short, multi-stemmed ssp. islandica, which shows reduced apical dominance. For both subspecies, we manipulated the height of surrounding vegetation (competition) and damage intensity in grasslands of differing productivity (high, medium, low), and examined population growth rates using matrix population models combined with life table response experiments (LTREs). In the absence of damage, ssp. campestris exhibited a higher population growth rate than ssp. islandica in the tallest vegetation, however with the growth rate still being below one. In the medium and low productivity environments where the vegetation was shorter, the population growth rate of ssp. islandica was considerably higher than that of ssp. campestris as long as no more than about 50% of the plants were damaged. When plants were damaged, the apically dominant ssp. campestris showed a positive population growth rate (λ> 1) and often overcompensatory seed production in all productivity levels, while ssp. islandica showed no compensation and therefore the population was predicted to decline (λ < 1). We conclude that restrained branching in Gentianella cannot be selected for by competition alone, but that episodes of apical damage are required to maintain the trait. Furthermore, because of the costs of restrained branching, apical dominance should be selected against in grasslands where competition and disturbance are low.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-02T10:32:52.586589-05:
      DOI: 10.1002/ecy.2101
  • Fitness consequences of occasional outcrossing in a functionally asexual
           plant (Oenothera biennis)
    • Authors: John L. Maron; Marc T.J. Johnson, Amy P. Hastings, Anurag A. Agrawal
      Abstract: Many clonal organisms occasionally outcross, but the long-term consequences of such infrequent events are often unknown. During five years, representing three to five plant generations, we followed 16 experimental field populations of the forb, Oenothera biennis, originally planted with the same 18 original genotypes. Oenothera biennis usually self-fertilizes, which due to its genetic system (Permanent Translocation Heterozygosity), results in seeds that are clones of the maternal plant. However, rare outcrossing produces genetically novel offspring (but without recombination or increased heterozygosity). We sought to understand whether novel genotypes produced through natural outcrossing had greater fecundity or different multigenerational dynamics compared to our original genotypes. We further assessed whether any differences in fitness or abundances through time between original and novel genotypes were exaggerated in the presence versus absence of insect herbivores. Over the course of the experiment, we genotyped>12,500 plants using microsatellite DNA markers to identify and track the frequency of specific genotypes and estimated fecundity on a subset (>3000) of plants. The effective outcrossing rate was 7.3% in the first year and ultimately 50% of the plants were of outcrossed origin by the final year of the experiment. Lifetime fruit production per plant was on average 32% higher across all novel genotypes produced via outcrossing compared to the original genotypes, and this fecundity advantage was significantly enhanced in populations lacking herbivores. Among 43 novel genotypes that were abundant enough to phenotype with replication, plants produced nearly 30% more fruits than the average of their specific two parental genotypes, and marginally more fruits (8%) than their most fecund parent. Mean per capita fecundity of novel genotypes predicted their relative frequencies at the end of the experiment. Novel genotypes increased more dramatically in herbivore-present compared to suppressed populations (45% vs. 27% of all plants), countering the increased competition from dandelions (Taraxacum officinale) that resulted from herbivore suppression. Increased interspecific competition likely also lead to the lower realized fitness of novel versus original genotypes in herbivore-suppressed populations. These results demonstrate that rare outcrossing and the generation of novel genotypes can create high-fecundity progeny, with the biotic environment influencing the dynamical outcome of such advantages.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-02T10:27:49.731969-05:
      DOI: 10.1002/ecy.2099
  • Phosphorus limitation of aboveground production in northern hardwood
    • Authors: Shinjini Goswami; Melany C. Fisk, Matthew A. Vadeboncoeur, Mariann Garrison-Johnston, Ruth D Yanai, Timothy J. Fahey
      Abstract: Forest productivity on glacially derived soils with weatherable phosphorus (P) is expected to be limited by nitrogen (N), according to theories of long-term ecosystem development. However, recent studies and model simulations based on resource optimization theory indicate that productivity can be co-limited by N and P. We conducted a full factorial N x P fertilization experiment in 13 northern hardwood forest stands of three age classes in central New Hampshire, USA, to test the hypothesis that forest productivity is co-limited by N and P. We also asked whether the response of productivity to N and P addition differs among species and whether differential species responses contribute to community-level co-limitation. Plots in each stand were fertilized with 30 kg N ha−1 yr−1, 10 kg P ha−1yr−1, N+P together, or neither nutrient (control) for four growing seasons. The productivity response to treatments was assessed using per-tree annual relative basal area increment (RBAI) as an index of growth. RBAI responded significantly to P (P=0.02) but not to N (P=0.73). However, evidence for P limitation was not uniform among stands. RBAI responded to P fertilization in mid-age (P = 0.02) and mature (P = 0.07) stands, each taken as a group, but was greatest in N-fertilized plots of two stands in these age classes, and there was no significant effect of P in the young stands. Both white birch (Betula papyrifera Marsh.) and beech (Fagus grandifolia Ehrh.) responded significantly to P; no species responded significantly to N. We did not find evidence for N and P co-limitation of tree growth. The response to N+P did not differ from that to P alone, and there was no significant N x P interaction (P=0.68). Our P limitation results support neither the N limitation prediction of ecosystem theory nor the N and P co-limitation prediction of resource optimization theory, but could be a consequence of long-term anthropogenic N deposition in these forests. Inconsistencies in response to P suggest that successional status and variation in site conditions influence patterns of nutrient limitation and recycling across the northern hardwood forest landscape.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-02T10:22:47.457107-05:
      DOI: 10.1002/ecy.2100
  • Can mesophotic reefs replenish shallow reefs' Reduced coral
           reproductive performance casts a doubt
    • Authors: Tom Shlesinger; Mila Grinblat, Hanna Rapuano, Tal Amit, Yossi Loya
      Abstract: Mesophotic coral ecosystems (i.e. deep coral reefs at 30-120 m depth) appear to be thriving while many shallow reefs in the world are declining. Amidst efforts to understand and manage their decline, it was suggested that mesophotic reefs might serve as natural refuges and a possible source of propagules for the shallow reefs. However, our knowledge of how reproductive performance of corals alters with depth is sparse. Here, we present a comprehensive study of the reproductive phenology, fecundity and abundance of seven reef-building conspecific corals in shallow and mesophotic habitats. Significant differences were found in the synchrony and timing of gametogenesis and spawning between shallow and mesophotic coral populations. Thus, mesophotic populations exhibited delayed or protracted spawning events, which led to spawning of the mesophotic colonies in large proportions at times where the shallow ones had long been depleted of reproductive material. All species investigated demonstrated a substantial reduction in fecundity and/or oocyte sizes at mesophotic depths (40–60 m). Two species (Seriatopora hystrix and Galaxea fascicularis) displayed a reduction in both fecundity and oocyte size at mesophotic depths. Turbinaria reniformis had only reduced fecundity and Acropora squarrosa and Acropora valida only reduced oocyte size. In Montipora verrucosa, reduced fecundity was found during one annual reproductive season while in the following year only reduced oocyte size was found. In contrast, reduced oocyte size in mesophotic populations of Acropora squarrosa was consistent along three studied years. One species, Acropora pharaonis, was found to be infertile at mesophotic depths along two studied years. The above indicate that reproductive performance decreases with depth; and that although some species are capable of reproducing at mesophotic depths, their contribution to the replenishment of shallow reefs may be inconsequential. Reduced reproductive performance with depth, combined with the possible narrower tolerance to environmental factors further suggests that mesophotic corals may in fact be more vulnerable than previously conceived. Furthermore, we posit that the observed temporal segregation in reproduction could lead to assortative mating, and this, in turn, may facilitate adaptive divergence across depth.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-02T10:17:45.406416-05:
      DOI: 10.1002/ecy.2098
  • Why do some birds carry their chicks'
    • Authors: Bruce Lyon
      PubDate: 2017-11-27T14:05:37.006959-05:
      DOI: 10.1002/ecy.2025
  • Variation in range size and dispersal capabilities of microbial taxa
    • Authors: Mallory J. Choudoir; Albert Barberán, Holly L. Menninger, Rob R. Dunn, Noah Fierer
      Abstract: Geographic range size can span orders of magnitude for plant and animal species, with the study of why range sizes vary having preoccupied biogeographers for decades. In contrast, there have been few comparable studies of how range size varies across microbial taxa and what traits may be associated with this variation. We determined the range sizes of 74,134 bacterial and archaeal taxa found in settled dust collected from 1,065 locations across the United States. We found that most microorganisms have small ranges and few have large ranges, a pattern similar to the range size distributions commonly observed for macrobes. However, contrary to expectations, those microbial taxa which were locally abundant did not necessarily have larger range sizes. The observed differences in microbial range sizes were generally predictable from taxonomic identity, phenotypic traits, genomic attributes, and habitat preferences, findings that provide insight into the factors shaping patterns of microbial biogeography.This article is protected by copyright. All rights reserved.
      PubDate: 2017-11-21T11:25:30.156169-05:
      DOI: 10.1002/ecy.2094
  • Identifiability in N-mixture models: a large-scale screening test with
           bird data
    • Authors: Marc Kéry
      Abstract: Binomial N-mixture models have proven very useful in ecology, conservation and monitoring: they allow estimation and modeling of abundance separately from detection probability using simple counts. Recently, doubts about parameter identifiability have been voiced. I conducted a large-scale screening test with 137 bird data sets from 2,037 sites. I found virtually no identifiability problems for Poisson and zero-inflated Poisson (ZIP) binomial N-mixture models, but negative-binomial (NB) models had problems in 25% of all data sets. The corresponding multinomial N-mixture models had no problems. Parameter estimates under Poisson and ZIP binomial and multinomial N-mixture models were extremely similar. Identifiability problems became a little more frequent with smaller sample sizes (267 and 50 sites), but were unaffected by whether the models did or did not include covariates. Hence, binomial N-mixture model parameters with Poisson and ZIP mixtures typically appeared identifiable. In contrast, NB mixtures were often unidentifiable, which is worrying since these were often selected by AIC. Identifiability of binomial N-mixture models should always be checked. If problems are found, simpler models, integrated models which combine different observation models or the use of external information via informative priors or penalized likelihoods may help.This article is protected by copyright. All rights reserved.
      PubDate: 2017-11-21T01:46:02.430017-05:
      DOI: 10.1002/ecy.2093
  • Large-scale bleaching of corals on the Great Barrier Reef
    • Authors: T. P. Hughes; J. T. Kerry, T. Simpson
      Abstract: In 2015–2016, record temperatures triggered a pan-tropical episode of coral bleaching. In the southern hemisphere summer of March–April 2016, we used aerial surveys to measure the level of bleaching on 1,156 individual reefs throughout the 2,300 km length of the Great Barrier Reef, the world's largest coral reef system. The accuracy of the aerial scores was ground-truthed with detailed underwater surveys of bleaching at 260 sites (104 reefs), allowing us to compare aerial and underwater bleaching data with satellite-derived temperatures and with associated model predictions of bleaching. The severity of bleaching on individual reefs in 2016 was tightly correlated with the level of local heat exposure: the southernmost region of the Great Barrier Reef escaped with only minor bleaching because summer temperatures there were close to average. Gradients in nutrients and turbidity from inshore to offshore across the Great Barrier Reef had minimal effect on the severity of bleaching. Similarly, bleaching was equally severe on reefs that are open or closed to fishing, once the level of satellite-derived heat exposure was accounted for. The level of post-bleaching mortality, measured underwater after 7–8 months, was tightly correlated with the aerial scores measured at the peak of bleaching. Similarly, reefs with a high aerial bleaching score also experienced major shifts in species composition due to extensive mortality of heat-sensitive species. Reefs with low bleaching scores did not change in composition, and some showed minor increases in coral cover. Two earlier mass bleaching events occurred on the Great Barrier Reef in 1998 and 2002, that were less severe than 2016. In 2016, less than 9% of scored reefs had no bleaching, compared to 42% in 2002 and 44% in 1998. Conversely, the proportion of reefs that were severely bleached (>60% of corals affected) was four times higher in 2016. The geographic footprint of each of the three events is distinctive, and matches satellite-derived sea surface temperature patterns. Our aerial surveys indicate that past exposure to bleaching in 1998 and 2002 did not lessen the severity of bleaching in 2016. This dataset of aerial bleaching scores provides a historical baseline for comparison with future bleaching events. No copyright restrictions apply to the use of this data set other than citing this publication.This article is protected by copyright. All rights reserved.
      PubDate: 2017-11-20T10:55:22.118212-05:
      DOI: 10.1002/ecy.2092
  • The China Plant Trait Database: towards a comprehensive regional
           compilation of functional traits for land plants
    • Authors: Han Wang; Sandy P. Harrison, I. Colin Prentice, Yanzheng Yang, Fan Bai, Henrique Furstenau Togashi, Meng Wang, Shuangxi Zhou, Jian Ni
      Abstract: Plant functional traits provide information about adaptations to climate and environmental conditions, and can be used to explore the existence of alternative plant strategies within ecosystems. Trait data are also increasingly being used to provide parameter estimates for vegetation models. Here we present a new database of plant functional traits from China. Most global climate and vegetation types can be found in China, and thus the database is relevant for global modelling. The China Plant Trait Database contains information on morphometric, physical, chemical and photosynthetic traits from 122 sites spanning the range from boreal to tropical, and from deserts and steppes through woodlands and forests, including montane vegetation. Data collection at each site was based either on sampling the dominant species or on a stratified sampling of each ecosystem layer. The database contains information on 1215 unique species, though many species have been sampled at multiple sites. The original field identifications have been taxonomically standardized to the Flora of China. Similarly, derived photosynthetic traits, such as electron-transport and carboxylation capacities, were calculated using a standardized method. To facilitate trait-environment analyses, the database also contains detailed climate and vegetation information for each site. The dataset is released under a Creative Commons BY licence. When using the dataset, we kindly request that you cite this article, recognizing the hard work that went into collecting the data and the authors’ willingness to make it publicly available.This article is protected by copyright. All rights reserved.
      PubDate: 2017-11-20T10:50:21.656184-05:
      DOI: 10.1002/ecy.2091
  • Subterranean flowers of Aspidistra elatior are mainly pollinated by not
           terrestrial amphipods but fungus gnats
    • Authors: Kenji Suetsugu; Masahiro Sueyoshi
      PubDate: 2017-11-14T10:15:37.518521-05:
      DOI: 10.1002/ecy.2021
  • Hemiparasites can transmit indirect effects from their host plants to
    • Authors: Nathan L. Haan; Jonathan D. Bakker, M. Deane Bowers
      Abstract: Parasitic plants can serve as critical intermediaries between their hosts and other organisms; however these relationships are not well understood. To investigate the relative importance of plant traits in such interactions, we studied the role of the root hemiparasite, Castilleja levisecta (Orobanchaceae), as a mediator of interactions between the host plants it parasitizes and the lepidopteran herbivore Euphydryas editha (Nymphalidae), whose caterpillars feed on Castilleja and sequester iridoid glycosides from it. We tested whether the hemiparasite's size, leaf N concentration, and iridoid glycoside concentrations were influenced by the identity of its host plant, and then whether these traits influenced outcomes for the herbivore.We found that the hemiparasite's size and leaf N depended on the host it parasitized, and these traits in turn affected outcomes for E. editha. Specifically, Euphydryas editha survival increased with hemiparasite size and caterpillar mass increased with leaf N; caterpillars with greater mass were more likely to survive during diapause. We also found preliminary evidence that host identity influenced iridoid glycoside sequestration by the herbivore. Mean iridoid glycoside concentrations in caterpillars ranged from 1-12% depending on the host being parasitized by Castilleja. This study demonstrates that root parasitism can result in strong indirect effects on higher trophic levels, influencing organisms’ survival, growth, and chemical interactions.This article is protected by copyright. All rights reserved.
      PubDate: 2017-11-13T07:45:43.454143-05:
      DOI: 10.1002/ecy.2087
  • Analyzing community-weighted trait means across environmental gradients:
           should phylogeny stay or should it go'
    • Authors: Leandro D. S. Duarte; Vanderlei Julio Debastiani, Marcos Bergmann Carlucci, José Alexandre Felizola Diniz-Filho
      Abstract: Functional traits mediate ecological responses of organisms to the environment, determining community structure. Community-weighted trait means (CWM) are often used to characterize communities by combining information on species traits and distribution. Relating CWM variation to environmental gradients allows for evaluating species sorting across the metacommunity, either based on correlation tests or ordinary least squares (OLS) models. Yet, it is not clear if phylogenetic signal in both traits and species distribution affect those analyses. On one hand, phylogenetic signal might indicate niche conservatism along clade evolution, reinforcing the environmental signal in trait assembly patterns. On the other hand, it might introduce phylogenetic autocorrelation to mean trait variation among communities. Under this latter scenario, phylogenetic signal might inflate type I error in analysis relating CWM variation to environmental gradients. We explore multiple ways phylogenetic history may influence analysis relating CWM to environmental gradients. We propose the concept of neutral trait diffusion, which predicts that for a functional trait x, CWM variation among local communities does not deviate from the expectation that x evolved according to a neutral evolutionary process. Based on this framework we introduce a graphical tool called neutral trait diffusion representation (NTDR) that allows for the evaluation of whether it is necessary to carry out phylogenetic correction in the trait prior to analyzing the association between CWM and environmental gradients. We illustrate the NTDR approach using simulated traits, phylogenies and metacommunities. We show that even under moderate phylogenetic signal in both the trait used to define CWM and species distribution across communities, OLS models relating CWM variation to environmental gradients lead to inflated type I error when testing the null hypothesis of no association between CWM and environmental gradient. To overcome this issue, we propose a phylogenetic correction for OLS models and evaluate its statistical performance (type I error and power). Phylogeny-corrected OLS models successfully control for type I error in analysis relating CWM variation to environmental gradients but may show decreased power. Combining the exploratory tool of NTDR and phylogenetic correction in traits, when necessary, guarantees more precise inferences about the environmental forces driving trait-mediated species sorting across metacommunities.This article is protected by copyright. All rights reserved.
      PubDate: 2017-11-09T13:50:22.553632-05:
      DOI: 10.1002/ecy.2081
  • Dynamic preferential allocation to arbuscular mycorrhizal fungi explains
           fungal succession and coexistence
    • Authors: Benedicte Bachelot; Charlotte T. Lee
      Abstract: Evidence accumulates about the role of arbuscular mycorrhizal (AM) fungi in shaping plant communities, but little is known about the factors determining the biomass and coexistence of several types of AM fungi in a plant community. Here, using a consumer-resource framework that treats the relationship between plants and fungi as simultaneous, reciprocal exploitation, we investigated what patterns of dynamic preferential plant carbon allocation to empirically-defined fungal types (on-going partner choice) would be optimal for plants, and how these patterns depend on successional dynamics. We found that ruderal AM fungi can dominate under low steady-state nutrient availability, and competitor AM fungi can dominate at higher steady-state nutrient availability; these are conditions characteristic of early and late succession, respectively. We also found that dynamic preferential allocation alone can maintain a diversity of mutualists, suggesting that on-going partner choice is a new coexistence mechanism for mutualists. Our model can therefore explain both mutualist coexistence and successional strategy, providing a powerful tool to derive testable predictions.This article is protected by copyright. All rights reserved.
      PubDate: 2017-11-09T13:45:29.780083-05:
      DOI: 10.1002/ecy.2080
  • Multiple mechanisms of early plant community assembly with stochasticity
           driving the process
    • Authors: Bryndís Marteinsdóttir; Kristín Svavarsdóttir, Thóra Ellen Thórhallsdóttir
      Abstract: Initial plant establishment is one of the most critical phases in ecosystem development, where an early suite of physical (environmental filtering), biological (seed limitation, species interactions) and stochastic factors may affect successional trajectories and rates. While functional traits are commonly used to study processes that influence plant community assembly in late successional communities, few studies have applied them to primary succession. The objective here was to determine the importance of these factors in shaping early plant community assembly on a glacial outwash plain, Skeiðarársandur, in SE Iceland using a trait based approach. We used data on vascular plant assemblages at two different spatial scales (community and neighbourhood) sampled in 2005 and 2012, and compiled a dataset on seven functional traits linked to species dispersal abilities, establishment and persistence for all species within these assemblages. Trait-based null model analyses were used to determine the processes that influenced plant community assembly from the regional species pool into local communities, and to determine if the importance of these processes in community assembly was dependent on local environment or changed with time. On the community scale, for most traits, random processes dominated the assembly from the regional species pool. However, in some communities, there was evidence of non – random assembly in relation to traits linked to species dispersal abilities, persistence and establishment. On the neighborhood scale, assembly was mostly random. The relative importance of different processes varied spatially and temporally and the variation was linked to local soil conditions. While stochasticity dominated assembly patterns of our early successional communities, there was evidence of both seed limitation and environmental filtering. Our results indicated that as soil conditions improved, environmental constraints on assembly became weaker and the assembly became more dependent on species availability.This article is protected by copyright. All rights reserved.
      PubDate: 2017-11-09T13:45:22.576324-05:
      DOI: 10.1002/ecy.2079
  • Remotely sensed canopy height reveals three pantropical ecosystem states:
    • Authors: Chi Xu; Arie Staal, Stijn Hantson, Milena Holmgren, Egbert H. van Nes, Marten Scheffer
      Abstract: The idea that the tropics may have alternative vegetation states of forest, savanna and treeless has gained growing support from both theoretical and empirical studies over the past years (Hirota et al. 2011, Staver et al. 2011, Van Nes et al. 2014, Wuyts et al. 2017). In our previous work, we combined multi-sourced remote sensing data to demonstrate correspondence between multimodal distributions of tree cover and canopy height, and further suggested that at a global scale, tropical forest, savanna and treeless landscapes represent distinct vegetation states separated by tipping points at 600, 1500 and 2000 mm mean annual precipitation (Xu et al. 2016). In their comment, Synodinos et al. (2017) acknowledge the value of incorporating canopy height as an additional defining ecosystem variable that is complementary to tree cover, but question our observed pattern of the treeless-savanna transition. Synodinos et al.This article is protected by copyright. All rights reserved.
      PubDate: 2017-11-07T15:00:18.93377-05:0
      DOI: 10.1002/ecy.2077
  • Resource availability underlies the plant-fungal diversity relationship in
           a grassland ecosystem
    • Authors: Lauren C. Cline; Sarah E. Hobbie, Michael Madritch, Christopher R. Buyarski, David Tilman, Jeannine M. Cavender-Bares
      Abstract: It is commonly assumed that microbial communities are structured by ‘bottom-up’ ecological forces, although few experimental manipulations have rigorously tested the mechanisms by which resources structure soil communities. We investigated how plant substrate availability might structure fungal communities and belowground processes along an experimental plant richness gradient in a grassland ecosystem. We hypothesized that variation in total plant-derived substrate inputs, plant functional group diversity, as well as the relative abundance of C4 grasses and legumes would modulate fungal α- and β-diversity and their rates of soil carbon (C) and nitrogen (N) cycling. To test these predictions, we molecularly characterized fungal communities, as well as potential extracellular enzyme activity, net N mineralization, and soil organic matter respiration. We found higher fungal richness was associated with increasing aboveground plant biomass; whereas, fungal β-diversity was explained by contributions from C4 grass and legume relative dominance, plant functional group diversity, as well as plant biomass. Furthermore, aboveground plant biomass consistently shaped the richness and composition of individual fungal trophic modes (i.e., saprotrophs, symbiotrophs, pathotrophs). Finally, variation in extracellular enzyme activity, net N mineralization rates, and soil organic matter respiration was significantly explained by fungal β-diversity when fungi were functionally classified. Via changes in the supply and composition of organic substrates entering soil, our study demonstrates that changes in the plant species richness and functional composition collectively influence fungal communities and rates of soil C and N cycling.This article is protected by copyright. All rights reserved.
      PubDate: 2017-11-06T10:15:29.687889-05:
      DOI: 10.1002/ecy.2075
  • Navigational efficiency in a biased and correlated random walk model of
           individual animal movement
    • Authors: Joseph D. Bailey; Jamie Wallis, Edward A. Codling
      Abstract: Understanding how an individual animal is able to navigate through its environment is a key question in movement ecology that can give insight into observed movement patterns and the mechanisms behind them. Efficiency of navigation is important for behavioural processes at a range of different spatio-temporal scales, including foraging and migration. Random walk models provide a standard framework for modelling individual animal movement and navigation. Here we consider a vector-weighted biased and correlated random walk (BCRW) model for directed movement (taxis), where external navigation cues are balanced with forward persistence. We derive a mathematical approximation of the expected navigational efficiency for any BCRW of this form and confirm the model predictions using simulations. We demonstrate how the navigational efficiency is related to the weighting given to forward persistence and external navigation cues, and highlight the counter-intuitive result that for low (but realistic) levels of error on forward persistence, a higher navigational efficiency is achieved by giving more weighting to this indirect navigation cue rather than direct navigational cues. We discuss and interpret the relevance of these results for understanding animal movement and navigation strategies.This article is protected by copyright. All rights reserved.
      PubDate: 2017-11-06T10:15:22.672679-05:
      DOI: 10.1002/ecy.2076
  • Freshwater eutrophication drives sharp reductions in temporal beta
    • Authors: Stephen C. Cook; Lauren Housley, Jeffrey A. Back, Ryan S. King
      Abstract: Eutrophication has become one of the most widespread anthropogenic forces impacting freshwater biological diversity. One potentially important mechanism driving biodiversity changes in response to eutrophication is the alteration of seasonal patterns of succession, particularly among species with short, synchronous life cycles. We tested the hypothesis that eutrophication reduces seasonally driven variation in species assemblages by focusing on an understudied aspect of biodiversity: temporal beta diversity (βt). We estimated the effect of eutrophication on βt by sampling benthic macroinvertebrate assemblages bimonthly for 2 years across 35 streams spanning a steep gradient of total phosphorus (P) and benthic algal biomass (as chlorophyll-a; chl-a). Two widely used metrics of β diversity both declined sharply in response to increasing P and chl-a, regardless of covariates. The most parsimonious explanatory model for βt included an interaction between P and macroinvertebrate biomass, which revealed that βt was lower when macroinvertebrate biomass was relatively high. Macroinvertebrate biomass explained a greater amount of deviance in βt at lower to moderate concentrations of P, providing additional explanatory power where P concentration alone was unable to fully explain declines in βt. Chl-a explained similar amounts of deviance in βt in comparison to the best P model, but only when temperature variability, which was positively related to βt, also was included in the model. Declines in βt suggest that nutrient enrichment decreases the competitive advantage that specialists gain by occupying particular temporal niches, which leads to assemblages dominated by generalists that exhibit little seasonal turnover. The collapse of seasonal variation in assemblage composition we observed in our study suggests that treating dynamic communities as static assemblages is a simplification that may fail to detect the full impact of anthropogenic stressors. Our results show that eutrophication leads to more temporally homogenous communities and therefore degrades a fundamental facet of biodiversity.This article is protected by copyright. All rights reserved.
      PubDate: 2017-11-05T20:58:48.532704-05:
      DOI: 10.1002/ecy.2069
  • Life history traits and functional processes generate multiple pathways to
           ecological stability
    • Authors: John P. DeLong; Torrance C. Hanley, Jean P. Gibert, Linda M. Puth, David M. Post
      Abstract: Stability contributes to the persistence of ecological communities, yet the interactions among different stabilizing forces are poorly understood. We assembled mesocosms with an algal resource and 1-8 different clones of the consumer Daphnia ambigua and tracked algal and Daphnia abundances through time. We then fitted coupled ordinary differential equations (ODEs) to the consumer-resource time series. We show that variation in different components of stability (local stability and the magnitude of population fluctuations) across mesocosms arises through variation in life history traits and the functional processes represented by ODE model parameters. Local stability was enhanced by increased algal growth rate and Daphnia mortality and foraging rate. Population fluctuations were dampened by high Daphnia conversion efficiency and lower interaction strengths, low algal growth rate, high Daphnia death rate, and low Daphnia foraging. These results indicate that 1) stability in consumer-resource systems may arise through the net effect of multiple related stabilizing pathways, and 2) different aspects of stability can vary independently and may respond in opposite directions to the same forces.This article is protected by copyright. All rights reserved.
      PubDate: 2017-11-01T21:15:43.137262-05:
      DOI: 10.1002/ecy.2070
  • Synergistic effects of parental and embryonic exposure to predation risk
           on prey offspring size at emergence
    • Authors: Sarah C. Donelan; Geoffrey C. Trussell
      Abstract: Cues signaling predation risk can strongly influence prey phenotypes both within and between generations. Parental and embryonic effects have been shown to operate independently in response to predation risk, but how they interact to shape offspring life history traits remains largely unknown. Here, we conducted experiments to examine the synergistic impacts of parental and embryonic experiences with predation risk on offspring size at emergence in the snail, Nucella lapillus, which is an ecologically important intermediate consumer on rocky intertidal shores. We found that when embryos were exposed to predation risk, the offspring of risk-experienced parents emerged larger than those of parents that had no risk experience. This response was not the result of increased development time, greater resource availability, or fewer emerging offspring, but may have occurred because both parental and embryonic experiences with risk increased growth efficiency, perhaps by reducing embryonic respiration rates under risk. Our results highlight the potential for organisms to be influenced by a complex history of environmental signals with important consequences for individual fitness and predator-prey interactions.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-30T10:05:39.751098-05:
      DOI: 10.1002/ecy.2067
  • Frequency-dependent seed predation by rodents on Sonoran Desert winter
           annual plants
    • Authors: Jonathan L. Horst; D.Lawrence Venable
      Abstract: Numerous mechanisms may allow species to coexist. We tested for frequency-dependent predation, a mechanism predicted by theory and established as a foraging behavior for many types of animals. Our field test included multiple prey species exposed in situ to multiple predator species and individuals to determine whether the prey species experienced predation patterns that were frequency-dependent. The prey were seeds of three species of Sonoran Desert winter annual plants while the predator species were a guild of nocturnal seed foraging heteromyid and murid rodents that co-occur naturally in the same community as the desert annuals at Tumamoc Hill near Tucson. Seeds of one species were much preferred over the other two. Nonetheless, we found the net effect of rodent foraging to be positively frequency-dependent (the preference for each species is higher when it is common than when it is uncommon) as has been previously hypothesized. This frequency-dependent predation should function as a species coexistence promoting mechanism in concert with the storage effect which has been previously demonstrated for this system.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-30T10:00:24.192813-05:
      DOI: 10.1002/ecy.2066
  • Stabilizing effects in temporal fluctuations: management, traits and
           species richness in high-diversity communities
    • Authors: Jan Lepš; Maria Májeková, Alena Vítová, Jiří Doležal, Francesco de Bello
      Abstract: The loss of biodiversity is thought to have adverse effects on multiple ecosystem functions, including the decline of community stability. Decreased diversity reduces the strength of the portfolio effect, a mechanism stabilizing community temporal fluctuations. Community stability is also expected to decrease with greater variability in individual species populations and with synchrony of their fluctuations. In semi-natural meadows, eutrophication is one of the most important drivers of diversity decline; it is expected to increase species fluctuations and synchrony among them, all effects leading to lower community stability. With a 16 year time series of biomass data from a temperate species-rich meadow with fertilization and removal of the dominant species, we assessed population biomass temporal (co)variation under different management types and competition intensity, and in relation to species functional traits and to species diversity. Whereas the effect of dominant removal was relatively small (with a tendency towards lower stability), fertilization markedly decreased community stability (i.e. increased coefficient of variation in the total biomass) and species diversity. On average, the fluctuations of individual populations were mutually independent, with a slight tendency towards synchrony in unfertilized plots, and a tendency towards compensatory dynamics in fertilized plots and no effects of removal. The marked decrease of synchrony with fertilization, contrary to the majority of the results reported previously, follows the predictions of increased compensatory dynamics with increased asymmetric competition for light in a more productive environment. Synchrony increased also with species functional similarity stressing the importance of shared ecological strategies in driving similar species responses to weather fluctuations. As expected, the decrease of temporal stability of total biomass was mainly related to the decrease of species richness, with its effect remaining significant also after accounting for fertilization. The weakening of the portfolio effect with species richness decline is a crucial driver of community destabilization. However, the positive effect of species richness on temporal stability of total biomass was not due to increased compensatory dynamics, since synchrony increased with species richness. This shows that the negative effect of eutrophication on community stability does not operate through increasing synchrony, but through the reduction of diversity.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-30T09:55:40.469216-05:
      DOI: 10.1002/ecy.2065
  • Latitude, temperature and habitat complexity predict predation pressure in
           eelgrass beds across the Northern Hemisphere
    • Authors: Pamela L. Reynolds; John J. Stachowicz, Kevin Hovel, Christoffer Boström, Katharyn Boyer, Mathieu Cusson, Johan S. Eklöf, Friederike G. Engel, Aschwin H. Engelen, Britas Klemens Eriksson, F.Joel Fodrie, John N. Griffin, Clara Hereu, Masakazu Hori, Torrance Hanley, Mikhail Ivanov, Pablo Jorgensen, Claudia Kruschel, Kun-Seop Lee, Karen McGlathery, Per Olav Moksnes, Masahiro Nakaoka, Mary I. O'Connor, Nessa O'Connor, Robert J. Orth, Francesca Rossi, Jennifer Ruesink, Erik Sotka, Fiona Tomas, Richard K.F. Unsworth, Matthew A. Whalen, J.Emmett Duffy
      Abstract: Latitudinal gradients in species interactions are widely cited as potential causes or consequences of global patterns of biodiversity. However, mechanistic studies documenting changes in interactions across broad geographic ranges are limited. We surveyed predation intensity on common prey (live amphipods and gastropods) in communities of eelgrass (Zostera marina) at 48 sites across its Northern Hemisphere range, encompassing over 370 of latitude and four continental coastlines. Predation on amphipods declined with latitude on all coasts but declined more strongly along western ocean margins where temperature gradients are steeper. Whereas in situ water temperature at the time of the experiments was uncorrelated with predation, mean annual temperature strongly positively predicted predation, suggesting a more complex mechanism than simple increased metabolic activity at the time of predation. This large-scale biogeographic pattern was modified by local habitat characteristics; predation declined with higher shoot density both among and within sites. Predation rates on gastropods, by contrast, were uniformly low and varied little among sites. The high replication and geographic extent of our study not only provides additional evidence to support biogeographic variation in intensity, but also insight into the mechanisms that relate temperature and biogeographic gradients in species interactions.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-30T09:50:21.858931-05:
      DOI: 10.1002/ecy.2064
  • Interaction frequency, network position, and the temporal persistence of
           interactions in a plant-pollinator network
    • Authors: Natacha P. Chacoff; Julian Resasco, Diego P. Vázquez
      Abstract: Ecological interactions are highly dynamic in time and space. Previous studies of plant-animal mutualistic networks have shown that the occurrence of interactions varies substantially across years. We analyzed inter-annual variation of a quantitative mutualistic network, in which links are weighted by interaction frequency. The network was sampled over six consecutive years, representing one of the longest time series for a community-wide mutualistic network. We estimated the inter-annual similarity in interactions and assessed the determinants of their persistence. The occurrence of interactions varied greatly among years, with most interactions seen in only one year (64%) and few (20%) in more than two years. This variation was associated with the frequency and position of interactions relative to the network core, so that the network consisted of a persistent core of frequent interactions and many peripheral, infrequent interactions. Null model analyses suggest that species abundances play a substantial role in generating these patterns. Our study represents an important step in the study of ecological networks, furthering our mechanistic understanding of the ecological processes driving the temporal persistence of interactions.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-30T03:15:24.210647-05:
      DOI: 10.1002/ecy.2063
  • Opposite effects of daytime and nighttime warming on top-down control of
           plant diversity
    • Authors: Brandon T. Barton; Oswald J. Schmitz
      Abstract: Ecological analyses of climate warming explore how rising mean temperature will affect the species composition of communities and their associated functioning. Experimentation usually presumes that warming arises from simultaneous increase in daily maximum (daytime) and minimum (nighttime) temperatures. Yet evidence shows that mean warming arises largely from increasing nighttime temperatures. We report on a three-year experiment that compared the effects of daytime and nighttime warming on a community comprising herbaceous plants, grasshopper herbivores and predatory spiders. We warmed experimental mesocosms 3-4˚ C above ambient control treatments during the daytime (06:00-18:00 h) or nighttime (18:00-06:00 h). Daytime warming caused spiders to seek a thermal refuge low in the plant canopy and away from grasshopper prey, which allowed grasshoppers to spend more time feeding on a competitively dominant plant species. Nighttime had the opposite effect, where spider activity increased causing grasshoppers to reduce feeding. Two consecutive years of daytime warming resulted in a suppression of the competitive dominant plant and increased the diversity and evenness of the plant community, whereas nighttime warming had opposite effects. These results show that ignoring the nuanced effects of asymmetrical warming may lead to inaccurate conclusions about the net effects of climate change on ecosystems.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-28T10:35:30.189846-05:
      DOI: 10.1002/ecy.2062
  • Larval body condition regulates predator-induced life-history variation in
           a dragonfly
    • Authors: Michael P. Moore; Cassandra Lis, Ryan A. Martin
      Abstract: Organisms with complex life cycles commonly exhibit adaptive plasticity in the timing of transitions between life stages. While the threat of predation is predicted to induce earlier transitions, empirical support has been equivocal. When predation risk affects both the propensity to transition to the next life stage and the ability to reach the energetic thresholds necessary to complete the transition, only those individuals in the best physiological condition may be able to accelerate development and emerge earlier. To test this hypothesis, we followed uniquely marked dragonfly larvae (Pachydiplax longipennis) through emergence in pools where we factorially manipulated the presence of a large heterospecific predator (Anax junius) and cannibalism risk via conspecific size variation. Consistent with our hypothesis, high-condition larvae were more likely to emerge in the presence of the heterospecific predator than in its absence, and low-condition larvae were more likely to emerge in its absence than in its presence. Moreover, high-condition larvae emerged earlier when cannibalism risk was high than when it was low. Predation risk therefore has condition-dependent effects on emergence. As predation risk frequently affects resource accumulation, similar mechanisms across taxa could commonly underlie the incongruence between empirical results and theoretical expectations for predator-induced life-history variation.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-25T07:05:45.859938-05:
      DOI: 10.1002/ecy.2056
  • Comparing chemistry and bioactivity of burned versus decomposed plant
           litter: different pathways but same result'
    • Authors: Giuliano Bonanomi; Guido Incerti, Ahmed M. Abd El-Gawad, Gaspare Cesarano, Tushar C. Sarker, Luigi Saulino, Virginia Lanzotti, Antonio Saracino, Francisco C. Rego, Stefano Mazzoleni
      Abstract: Litter burning and biological decomposition are oxidative processes co-occurring in many terrestrial ecosystems, producing organic matter with different chemical properties and differently affecting plant growth and soil microbial activity. We tested the chemical convergence hypothesis i.e. materials with different initial chemistry converge towards a common profile, with similar biological effects, as the oxidative process advances, for burning and decomposition. We compared the molecular composition, assessed by 13C NMR, of 7 plant litter types either fresh, decomposed for 30, 90, 180 days in a microcosms incubation experiment, or heated at 100, 200, 300, 400, 500 °C for thirty minutes. We used litter water extracts (5% dw) as treatments in bioassays on plant (Lepidium sativum) and fungal (Aspergillus niger) growth, and a washed quartz sand amended with litter (0.5% dw) to assess heterotrophic respiration by flux chamber (i.e. μg of CO2 released per g of added litter per day). We observed different molecular variations for materials either burning (i.e. a sharp increase of aromatic C and a decrease of other fractions above 200 °C) or decomposing (i.e. early increase of alkyl, methoxyl and N-alkyl C and decrease of O-alkyl and di-O-alkyl C fractions). Soil respiration and fungal growth decreased with litter age and heating severity, down to 20% relative to fresh litter. Plant was inhibited on fresh litter (on average 13% of the control), but recovered on aged (180 days) and heated (30 minutes at 500°C) materials, up to 126% and 63% of the control, respectively. Correlation between the intensity of 13C NMR signals in litter spectra and bioassay results showed that O-alkyl, methoxyl, and aromatic C fractions are crucial to understand organic matter effects, with plant response negatively affected by labile C but positively associated to lignification and pyrogenic C. The pattern of association of soil respiration and fungal growth to these C fractions was essentially opposite to that observed for plant root growth. Our findings suggest a functional convergence of decomposed and burnt organic substrates, emerging from the balance between the bioavailability of labile C sources and the presence of recalcitrant and pyrogenic compounds, oppositely affecting different trophic levels.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-24T11:04:24.624609-05:
      DOI: 10.1002/ecy.2053
  • Changing contributions of stochastic and deterministic processes in
           community assembly over a successional gradient
    • Authors: Inger Elisabeth Måren; Jutta Kapfer, Per Arild Aarrestad, John-Arvid Grytnes, Vigdis Vandvik
      Abstract: Successional dynamics in plant community assembly may result from both deterministic and stochastic ecological processes. The relative importance of different ecological processes is expected to vary over the successional sequence, between different plant functional groups, and with the disturbance levels and land-use management regimes of the successional systems. We evaluate the relative importance of stochastic and deterministic processes in bryophyte and vascular plant community assembly after fire in grazed and un-grazed anthropogenic coastal heathlands in Northern Europe. A replicated series of post-fire successions (n = 12) were initiated under grazed and un-grazed conditions, and vegetation data were recorded in permanent plots over 13 years. We used redundancy analysis (RDA) to test for deterministic successional patterns in species composition repeated across the replicate successional series and analyses of co-occurrence to evaluate to what extent species respond synchronously along the successional gradient. Change in species co-occurrences over succession indicates stochastic successional dynamics at the species level (i.e., species equivalence), whereas constancy in co-occurrence indicates deterministic dynamics (successional niche differentiation). The RDA shows high and deterministic vascular plant community compositional change, especially early in succession. Co-occurrence analyses indicate stochastic species-level dynamics the first two years, which then give way to more deterministic replacements. Grazed and un-grazed successions are similar, but the early-stage stochasticity is higher in un-grazed areas. Bryophyte communities in un-grazed successions resemble vascular plant communities. In contrast, bryophytes in grazed successions showed consistently high stochasticity and low determinism in both community composition and species co-occurrence. In conclusion, stochastic and individualistic species responses early in succession give way to more niche-driven dynamics in later successional stages. Grazing reduces predictability in both successional trends and species-level dynamics, especially in plant functional groups that are not well adapted to disturbance.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-24T11:04:12.109158-05:
      DOI: 10.1002/ecy.2052
  • Increased Energy Differentially Increases Richness and Abundance of
           Optimal Body Sizes in Deep-Sea Wood-Falls
    • Authors: Craig R. McClain; James P. Barry, Thomas J. Webb
      Abstract: Theoretical and empirical studies suggest that the total energy available in natural communities influences body size as well as patterns of abundance and diversity. But the precise mechanisms underlying relationships or how these three ecological properties relate remain elusive. We identify five hypotheses relating energy availability, body size distributions, abundance, and species richness within communities, and we use experimental deep sea wood fall communities to test their predicted effects both on descriptors describing the species richness-body size distribution, and on trends in species richness within size classes over an energy gradient (size class-richness relationships). Invertebrate communities were taxonomically identified, weighed, and counted from 32 Acacia sp. logs ranging in size from 0.6 to 20.6 kg (corresponding to different levels of energy available) which were deployed at 3203 m in the Northeast Pacific Ocean for between 5 and 7 years. Trends in both the species richness-body size distribution and the size class-richness distribution with increasing wood fall size provide support for the Increased Packing hypothesis: species richness increases with increasing wood fall size but only in the modal size class. Furthermore, species richness of body size classes reflected the abundance of individuals in that size class. Thus, increases in richness in the modal size class with increasing energy were concordant with increases in abundance within that size class. The results suggest that increases in species richness occurring as energy availability increases may be isolated to specific niches, e.g. the body size classes, especially in communities developing on discrete and energetically isolated resources such as deep sea wood falls.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-24T11:03:54.79549-05:0
      DOI: 10.1002/ecy.2055
  • Sampling scales define occupancy and underlying occupancy-abundance
           relationships in animals
    • Authors: Robin Steenweg; Mark Hebblewhite, Jesse Whittington, Paul Lukacs, Kevin McKelvey
      Abstract: Occupancy-abundance (OA) relationships are a foundational ecological phenomenon and field of study, and occupancy models are increasingly used to track population trends and understand ecological interactions. However, these two fields of ecological inquiry remain largely isolated, despite growing appreciation of the importance of integration. For example, using occupancy models to infer trends in abundance is predicated on positive OA relationships. Many occupancy studies collect data that violate geographical closure assumptions due to the choice of sampling scales and application to mobile organisms, which may change how occupancy and abundance are related. Little research, however, has explored how different occupancy sampling designs affect OA relationships. We develop a conceptual framework for understanding how sampling scales affect the definition of occupancy for mobile organisms, which drives OA relationships. We explore how spatial and temporal sampling scales, and the choice of sampling unit (areal-, vs. point-sampling), affect OA relationships. We develop predictions using simulations, and test them using empirical occupancy data from remote cameras on 11 medium-large mammals. Surprisingly, our simulations demonstrate that when using point sampling, OA relationships are unaffected by spatial sampling grain (i.e. cell size). In contrast, when using areal-sampling (e.g. species atlas data), OA relationships are affected by spatial grain. Furthermore, OA relationships are also affected by temporal sampling scales, where the curvature of the OA relationship increases with temporal sampling duration. Our empirical results support these predictions, showing that at any given abundance, the spatial grain of point sampling does not affect occupancy estimates, but longer surveys do increase occupancy estimates. For rare species (low occupancy), estimates of occupancy will quickly increase with longer surveys, even while abundance remains constant. Our results also clearly demonstrate that occupancy for mobile species without geographical closure is not true occupancy. The independence of occupancy estimates from spatial sampling grain depends on the sampling unit. Point-sampling surveys can, however, provide unbiased estimates of occupancy for multiple species simultaneously, irrespective of home-range size. The use of occupancy for trend monitoring needs to explicitly articulate how the chosen sampling scales define occupancy and affect the occupancy-abundance relationship.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-24T11:03:50.42199-05:0
      DOI: 10.1002/ecy.2054
  • Born at the right time' A conceptual framework linking reproduction,
           development, and settlement in reef fish
    • Authors: J. S. Shima; E. G. Noonburg, S. E. Swearer, S. H. Alonzo, C. W. Osenberg
      Abstract: Parents are expected to make decisions about reproductive timing and investment that maximize their own fitness, even if this does not maximize the fitness of each individual offspring. When offspring survival is uncertain, selection typically favors iteroparity, which means that offspring born at some times can be disadvantaged, while others get lucky. The eventual fate of offspring may be further modified by their own decisions. Are fates of offspring set by birthdates (i.e., determined by parents), or can offspring improve upon the cards they've been dealt' If so, do we see adaptive plasticity in the developmental timing of offspring' We evaluate these questions for a coral reef fish (the sixbar wrasse, Thalassoma hardwicke) that is characterized by extreme iteroparity and flexible larval development. Specifically, we monitored larval settlement to 192 small reefs over 11 lunar months and found that most fish settled during new moons of a lunar cycle (consistent with preferential settlement on dark nights). Settlement was significantly lower than expected by chance during the full moon and last quarter of the lunar cycle (consistent with avoidance of bright nights). Survival after settlement was greatest for fish that settled during times of decreasing lunar illumination (from last quarter to new moon). Fish that settled on the last quarter of the lunar cycle were ~10% larger than fish that settled during other periods, suggesting larvae delay settlement to avoid the full moon. These results are consistent with a numerical model that predicts plasticity in larval development time that enables avoidance of settlement during bright periods. Collectively, our results suggest that fish with inauspicious birthdates may alter their developmental trajectories to settle at better times. We speculate that such interactions between parent and offspring strategies may reinforce the evolution of extreme iteroparity and drive population dynamics, by increasing the survival of offspring born at the “wrong” time by allowing them to avoid the riskiest times of settlement.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-14T23:15:23.477091-05:
      DOI: 10.1002/ecy.2048
  • Woody plant encroachment amplifies spatial heterogeneity of soil
           phosphorus to considerable depth
    • Authors: Yong Zhou; Thomas W Boutton, X Ben Wu
      Abstract: The geographically extensive phenomenon of woody plant encroachment into grass-dominated ecosystems has strong potential to influence biogeochemical cycles at ecosystem to global scales. Previous research has focused almost exclusively on quantifying pool sizes and flux rates of soil carbon and nitrogen (N), while few studies have examined the impact of woody encroachment on soil phosphorus (P) cycling. Moreover, little is known regarding the impact of woody encroachment on the depth distribution of soil total P at the landscape scale. We quantified patterns of spatial heterogeneity in soil total P along a soil profile by taking spatially-explicit soil cores to a depth of 120 cm across a subtropical savanna landscape that has undergone encroachment by Prosopis glandulosa (an N2-fixer) and other tree/shrub species during the past century. Soil total P increased significantly following woody encroachment throughout the entire 120 cm soil profile. Large groves (> 100 m2) and small discrete clusters (< 100 m2) accumulated 53 and 10 g P m−2 more soil P, respectively, compared to grasslands. This P accumulation in soils beneath woody patches is most likely attributable to P uplift by roots located deep in the soil profile (> 120 cm) and transfer to upper portions of the profile via litterfall and root turnover. Woody encroachment also altered patterns of spatial heterogeneity in soil total P in the horizontal plane, with highest values at the centers of woody patches, decreasing towards the edges, and reaching lowest values in the surrounding grassland matrix. These spatial patterns were evident throughout the upper 1.2 m of the soil profile, albeit at reduced magnitude deeper in the soil profile. Spatial generalized least squares models indicated that fine root biomass explained a significant proportion of the variation in soil total P both across the landscape and throughout the profile. Our findings suggest that transfer of P from deeper soil layers enlarges the P pool in upper soil layers where it is more actively cycled may be a potential strategy for encroaching woody species to satisfy their P demands.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-14T10:35:20.916388-05:
      DOI: 10.1002/ecy.2051
  • Fear affects parental care which predicts juvenile survival and
           exacerbates the total cost of fear on demography
    • Authors: Blair P. Dudeck; Michael Clinchy, Marek C. Allen, Liana Y. Zanette
      Abstract: Fear itself (perceived predation risk) can affect wildlife demography, but the cumulative impact of fear on population dynamics is not well understood. Parental care is arguably what most distinguishes birds and mammals from other taxa, yet only one experiment on wildlife has tested fear effects on parental food provisioning and the repercussions this has for the survival of dependent offspring, and only during early-stage care. We tested the effect of fear on late-stage parental care of mobile dependent offspring, by locating radio-tagged song sparrow fledglings and broadcasting predator or non-predator playbacks in their vicinity, measuring their parent's behaviour and their own, and tracking the offspring's survival to independence. Fear significantly reduced late-stage parental care, and parental fearfulness (as indexed by their reduction in provisioning when hearing predators) significantly predicted their offspring's condition and survival. Combining results from this experiment with that on early-stage care, we project that fear itself is powerful enough to reduce late-stage survival by 24%, and cumulatively reduce the number of young reaching independence by more than half, 53%. Experiments in invertebrate and aquatic systems demonstrate that fear is commonly as important as direct killing in affecting prey demography, and we suggest focusing more on fear effects and on offspring survival will reveal the same for wildlife.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-14T10:15:20.184697-05:
      DOI: 10.1002/ecy.2050
  • Fungi reduce preference and performance of insect herbivores on challenged
    • Authors: Pilar Fernandez-Conradi; Hervé Jactel, Cécile Robin, Ayco J. M. Tack, Bastien Castagneyrol
      Abstract: Although insect herbivores and fungal pathogens frequently share the same individual host plant, we lack general insights in how fungal infection affects insect preference and performance. We addressed this question in a meta-analysis of 1,113 case studies gathered from 101 primary papers that compared preference or performance of insect herbivores on control vs. fungus challenged plants. Generally, insects preferred, and performed better on, not challenged plants, regardless of experimental conditions. Insect response to fungus infection significantly differed according to fungus lifestyle, insect feeding guild and the spatial scale of the interaction (local/distant). Insect performance was reduced on plants challenged by biotrophic pathogens or endophytes but not by necrotrophic pathogens. For both chewing and piercing-sucking insects, performance was reduced on challenged plants when interactions occurred locally but not distantly. In plants challenged by biotrophic pathogens, both preference and performance of herbivores were negatively impacted, whereas infection by necrotrophic pathogens reduced herbivore preference more than performance and endophyte infection reduced only herbivore performance. Our study demonstrates that fungi are may be important but hitherto overlooked drivers of plant-herbivore interactions, suggesting both direct and plant-mediated effects of fungi on insect's behavior and development.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-11T01:50:27.89435-05:0
      DOI: 10.1002/ecy.2044
  • Bi-dimensional null model analysis of presence-absence binary matrices
    • Authors: Giovanni Strona; Werner Ulrich, Nicholas J. Gotelli
      Abstract: Comparing the structure of presence/absence (i.e. binary) matrices with those of randomized counterparts is a common practice in ecology. However, differences in the randomization procedures (null models) can affect the results of the comparisons, leading matrix structural patterns to appear either ‘random’ or not. Subjectivity in the choice of one particular null model over another makes it often advisable to compare the results obtained using several different approaches. Yet, available algorithms to randomize binary matrices differ substantially in respect to the constraints they impose on the discrepancy between observed and randomized row and column marginal totals, which complicates the interpretation of contrasting patterns. This calls for new strategies both to explore intermediate scenarios of restrictiveness in-between extreme constraint assumptions, and to properly synthesize the resulting information. Here we introduce a new modeling framework based on a flexible matrix randomization algorithm (named the ‘Tuning Peg’ algorithm) that addresses both issues. The algorithm consists of a modified swap procedure in which the discrepancy between the row and column marginal totals of the target matrix and those of its randomized counterpart can be ‘tuned’ in a continuous way by two parameters (controlling, respectively, row and column discrepancy). We show how combining the Tuning Peg with a wise random walk procedure makes it possible to explore the complete null space embraced by existing algorithms. This exploration allows researchers to visualize matrix structural patterns in an innovative bi-dimensional landscape of significance/effect size. We demonstrate the rational and potential of our approach with a set of simulated and real matrices, showing how the simultaneous investigation of a comprehensive and continuous portion of the null space can be extremely informative, and possibly key to resolving longstanding debates in the analysis of ecological matrices.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-11T01:45:37.244904-05:
      DOI: 10.1002/ecy.2043
  • Testing the keystone community concept: effects of landscape, patch
           removal, and environment on metacommunity structure
    • Authors: Emlyn Resetarits; Sara Cathey, Mathew Leibold
      Abstract: Although the influence of regional processes on local patches is well studied, the influence of local patches and their spatial arrangement on regional processes is likely to be complex. One interesting idea is the keystone community concept (KCC); this posits that there may be some patches that have a disproportionately large effect on the metacommunity compared to other patches. We experimentally test the KCC by using replicate protist microcosm metacommunities with single-patch removals. Removing single patches had no effect on average community richness, evenness and biomass of our metacommunities, but did cause metacommunities to be assembled significantly less by local environmental conditions and more by spatial effects related to stochastic factors. Overall our results show that local patch removal can have large regional effects on structural processes, but indicate that more experiments are needed to find evidence of keystone communities.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-09T02:06:01.707075-05:
      DOI: 10.1002/ecy.2041
  • The causes of disproportionate non-random mortality among life-cycle
    • Authors: Peter T. Green; Kyle E. Harms
      Abstract: The emergent properties of the collection of species in a natural community, such as diversity and the distribution of relative abundances, are influenced by both niche-based and neutral (stochastic) processes. This pluralistic view of the natural world reconciles theory with empirical observations better than does either a strictly niche- or neutrality-based perspective. Even so, rules (or rules-of-thumb) that govern the relative contributions that niche-based and stochastic processes make as communities assemble remain only vaguely formulated and incompletely tested. For example, the translation of non-random (non-neutral) ecological processes – that differentially sort among species within a community – into species-compositional patterns may occur more influentially within some demographic subsets of organisms than within others. In other words, the relative contributions of niche vs. neutral processes may vary among age-, size-, or stage-classes. For example, non-random patterns of mortality that occur among seedlings in a rainforest, or among newly-settled juveniles in communities of sessile marine communities, could be more influential than non-random mortality during later stages in determining overall community diversity.We propose two alternative, mutually compatible, hypotheses to account for different levels of influence from mortality among life-cycle stages towards producing non-random patterns in organismal communities. The Turnover Model simply posits that those demographic classes characterized by faster rates of turnover contribute greater influence in the short-term as sufficient mortality gives rise to non-random changes to the community, as well as over the longer-term as multiple individuals of a given fast-turnover demographic class transition into later classes compared to each individual that ratchets from a slow-turnover starting class into a later class. The Turnover Model should apply to most communities of organisms. The Niche Model, which posits that niche-based processes are more influential in some demographic classes relative to others, may alternatively or additionally apply to communities. We also propose several alternative mechanisms, especially relevant to forest trees, that could cause dynamics consistent with the Niche Model. These mechanisms depend on differences among demographic classes in the extent of demographic variation that individual organisms experience through their trait values or neighborhood conditions.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-04T13:50:19.995363-05:
      DOI: 10.1002/ecy.2039
  • Indirect effects of larvae dispersal following mass mortality events
    • Authors: Marcus A. Lashley; Heather R. Jordan, Jeffery K. Tomberlin, Brandon T. Barton
      Abstract: Mass mortality events are characterized by rapid die-offs of many individuals within a population at a specific location. These events produce a high concentration of remains within a given locale and the frequency and magnitude of these events may be increasing (Fey et al. 2015). Mass mortality events may be caused by physical (e.g., lightning strikes, fire), chemical (e.g., pollutants, hypoxia), or biological processes (e.g., disease, phenological mismatch with food source).This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-15T06:47:05.720516-05:
      DOI: 10.1002/ecy.2027
  • Remotely sensed canopy height reveals three pantropical ecosystem states:
    • Authors: Alexis D. Synodinos; David Eldridge, Katja Geißler, Florian Jeltsch, Dirk Lohmann, Guy Midgley, Niels Blaum
      Abstract: Xu et al. (2016) recently demonstrated the existence of three ecosystem states in the tropics: forest, savanna and ‘treeless’. Using remotely sensed tree cover and canopy height measurements, they conclude that 1) savannas and forest represent alternative states due to their climatic overlap in moist conditions (1,500-2,000 mm mean annual precipitation (MAP)), and 2) that ‘treeless’ and savanna ecosystems do not occur in the same MAP range, and that an abrupt shift from one ecosystem state to the other occurs at 600 mm MAP. While the first conclusion accords with existing studies (Hirota et al. 2011, Staver et al. 2011, Ratajczak and Nippert 2012), the second one contradicts our own observations from Africa and Australia as well as empirical data from published studies (February et al. 2007, Ward et al. 2013, Dohn et al. 2017), all of which indicate that savanna ecosystems certainly do occur within this dry rainfall range (
      PubDate: 2017-08-29T03:22:00.641566-05:
      DOI: 10.1002/ecy.1997
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