Journal Cover Ecology
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   ISSN (Print) 0012-9658 - ISSN (Online) 1939-9170
   Published by John Wiley and Sons Homepage  [1579 journals]
  • Fighting an uphill battle: the recovery of frogs in Australia's Wet
           Tropics
    • Authors: Donald T. McKnight; Ross A. Alford, Conrad J. Hoskin, Lin Schwarzkopf, Sasha E. Greenspan, Kyall R. Zenger, Deborah S. Bower
      PubDate: 2017-11-15T13:42:33.767097-05:
      DOI: 10.1002/ecy.2019
       
  • Thaw circles around tree trunks provide spring ephemeral plants with a big
           head start on the growing season
    • Authors: Mark Vellend; Amanda B. Young, Gabriel Letendre, Sébastien Rivest
      PubDate: 2017-11-15T13:40:28.618221-05:
      DOI: 10.1002/ecy.2024
       
  • Books and Monographs Received through July 2017
    • PubDate: 2017-11-14T14:40:26.684738-05:
      DOI: 10.1002/ecy.1985
       
  • An introduction to appreciation of soil
    • Authors: Mac A. Callaham
      PubDate: 2017-11-14T14:40:23.5147-05:00
      DOI: 10.1002/ecy.1986
       
  • Importance of citizen science for science, individuals, communities, and
           the planet
    • Authors: Kerry E. Grimm
      PubDate: 2017-11-14T14:40:22.222385-05:
      DOI: 10.1002/ecy.1987
       
  • Recent Publications of Interest
    • PubDate: 2017-11-14T14:40:20.67879-05:0
      DOI: 10.1002/ecy.1989
       
  • 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
           herbivores
    • 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:
           Reply
    • 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
           diversity
    • 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
       
  • Carbon dioxide and submersed macrophytes in lakes: linking functional
           ecology to community composition
    • Authors: John E. Titus; Angela M. Pagano
      Abstract: Evaluating plant community response to atmospheric CO2 rise is critical to predicting ecosystem level change. Freshwater lakes offer a model system for examining CO2 effects as submersed macrophyte species differ greatly in their growth responses to CO2 enrichment, and free CO2 concentrations among these habitats show a wide range of natural, spatial variation. We determined free CO2 concentrations in the water column and sediment porewater in littoral zones with pH
      PubDate: 2017-10-24T00:25:27.969227-05:
      DOI: 10.1002/ecy.2030
       
  • Trait-fitness relationships determine how trade-off shapes affect species
           coexistence
    • Authors: Elias Ehrlich; Lutz Becks, Ursula Gaedke
      Abstract: Trade-offs between functional traits are ubiquitous in nature and can promote species coexistence depending on their shape. Classic theory predicts that convex trade-offs facilitate coexistence of specialized species with extreme trait values (extreme species) while concave trade-offs promote species with intermediate trait values (intermediate species). We show here that this prediction becomes insufficient when the traits translate non-linearly into fitness which frequently occurs in nature, e.g. an increasing length of spines reduces grazing losses only up to a certain threshold resulting in a saturating or sigmoid trait-fitness function. We present a novel, general approach to evaluate the effect of different trade-off shapes on species coexistence. We compare the trade-off curve to the invasion boundary of an intermediate species invading the two extreme species. At this boundary the invasion fitness is zero. Thus, it separates trait combinations where invasion is or is not possible. The invasion boundary is calculated based on measurable trait-fitness relationships. If at least one of these relationships is not linear, the invasion boundary becomes non-linear implying that convex and concave trade-offs not necessarily lead to different coexistence patterns. Therefore, we suggest a new ecological classification of trade-offs into extreme-favouring and intermediate-favouring which differs from a purely mathematical description of their shape. We apply our approach to a well-established model of an empirical predator-prey system with competing prey types facing a trade-off between edibility and half-saturation constant for nutrient uptake. We show that the survival of the intermediate prey depends on the convexity of the trade-off. Overall, our approach provides a general tool to make a priori predictions on the outcome of competition among species facing a common trade-off in dependence of the shape of the trade-off and the shape of the trait-fitness relationships.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-15T22:35:22.396488-05:
      DOI: 10.1002/ecy.2047
       
  • 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
       
  • Climate drives phenological reassembly of a mountain wildflower meadow
           community
    • Authors: Elli J. Theobald; Ian Breckheimer, Janneke HilleRisLambers
      Abstract: Spatial community reassembly driven by changes in species abundances or habitat occupancy is a well-documented response to anthropogenic global change, but communities can also reassemble temporally if the environment drives differential shifts in the timing of life events across community members. Much like spatial community reassembly, temporal reassembly could be particularly important when critical species interactions are temporally concentrated (e.g., plant-pollinator dynamics during flowering). Previous studies have documented species-specific shifts in phenology driven by climate change, implying that temporal reassembly, a process we term “phenological reassembly,” is likely. However, few studies have documented changes in the temporal co-occurrence of community members driven by environmental change, likely because few datasets of entire communities exist. We addressed this gap by quantifying the relationship between flowering phenology and climate for 48 co-occurring subalpine wildflower species at Mount Rainier (Washington, USA) in a large network of plots distributed across Mt. Rainier's steep environmental gradients; large spatio-temporal variability in climate over the 6 yr of our study (including the earliest and latest snowmelt year on record) provided robust estimates of climate-phenology relationships for individual species. We used these relationships to examine changes to community co-flowering composition driven by ‘climate change analog’ conditions experienced at our sites in 2015. We found that both the timing and duration of flowering of focal species was strongly sensitive to multiple climatic factors (snowmelt, temperature, and soil moisture). Some consistent responses emerged, including earlier snowmelt and warmer growing seasons driving flowering phenology earlier for all focal species. However, variation among species in their phenological sensitivities to these climate drivers was large enough that phenological reassembly occurred in the climate change analog conditions of 2015. An unexpected driver of phenological reassembly was fine-scale variation in the direction and magnitude of climatic change, causing phenological reassembly to be most apparent early and late in the season and in topographic locations where snow duration was shortest (i.e., at low elevations and on ridges in the landscape). Because phenological reassembly may have implications for many types of ecological interactions, failing to monitor community-level repercussions of species-specific phenological shifts could underestimate climate change impacts.
      PubDate: 2017-10-11T15:51:10.745265-05:
      DOI: 10.1002/ecy.1996
       
  • Explaining ecosystem multifunction with evolutionary models
    • Authors: Marc W. Cadotte; Stuart W. Livingstone, Simone-Louise E. Yasui, Russell Dinnage, Jin-tian Li, Robin Marushia, James Santangelo, Wensheng Shu
      Abstract: Ecosystem function is the outcome of species interactions, traits, and niche overlap –all of which are influenced by evolution. However, it is not well understood how the tempo and mode of niche evolution can influence ecosystem function. In evolutionary models where either species differences accumulate through random drift in a single trait or species differences accumulate through divergent selection among close relatives, we should expect that ecosystem function is strongly related to diversity. However, when strong selection causes species to converge on specific niches or when novel traits that directly affect function evolve in some clades but not others, the relationship between diversity and ecosystem function might not be very strong. We test these ideas using a field experiment that established plant mixtures with differing phylogenetic diversities and we measured ten different community functions. We show that some functions were strongly predicted by species richness and mean pairwise phylogenetic distance (MPD, a measure of phylogenetic diversity), including biomass production and the reduction of herbivore and pathogen damage in polyculture, while other functions had weaker (litter production and structural complexity) or nonsignificant relationships (e.g., flower production and arthropod abundance) with MPD and richness. However, these divergent results can be explained by different models of niche evolution. These results show that diversity-ecosystem function relationships are the product of evolution, but that the nature of how evolution influences ecosystem function is complex.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-11T02:00:19.55202-05:0
      DOI: 10.1002/ecy.2045
       
  • Fungi reduce preference and performance of insect herbivores on challenged
           plants
    • 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
       
  • Multiple dimensions of intraspecific diversity affect biomass of eelgrass
           and its associated community
    • Authors: Jessica M. Abbott; Rick K. Grosberg, Susan L. Williams, John J. Stachowicz
      Abstract: Genetic diversity within key species can play an important role in the functioning of entire communities. However, the extent to which different dimensions of diversity (e.g., the number of genotypes vs. the extent of genetic differentiation among those genotypes) best predicts functioning is unknown and may yield clues into the different mechanisms underlying diversity effects. We explicitly test the relative influence of genotypic richness and genetic relatedness on eelgrass productivity, biomass, and the diversity of associated invertebrate grazers in a factorial field experiment using the seagrass species, Zostera marina (eelgrass). Genotypic richness had the strongest effect on eelgrass biomass accumulation, such that plots with more genotypes at the end of the experiment attained a higher biomass. Genotypic diversity (richness + evenness) was a stronger predictor of biomass than richness alone, and both genotype richness and diversity were positively correlated with trait diversity. The relatedness of genotypes in a plot reduced eelgrass biomass independently of richness. Plots containing eelgrass with greater trait diversity also had a higher abundance of invertebrate grazers, while the diversity and relatedness of eelgrass genotypes had little effect on invertebrate abundance or richness. Our work extends previous findings by explicitly relating genotypic diversity to trait diversity, thus mechanistically connecting genotypic diversity to plot-level yields. We also show that other dimensions of diversity, namely relatedness, influence eelgrass performance independent of trait differentiation. Ultimately, richness and relatedness captured fundamentally different components of intraspecific variation and should be treated as complementary rather than competing dimensions of biodiversity affecting ecosystem functioning.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-06T00:40:30.716495-05:
      DOI: 10.1002/ecy.2037
       
  • The causes of disproportionate non-random mortality among life-cycle
           stages
    • 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
       
  • Termites and large herbivores influence seed removal rates in an African
           savanna
    • Authors: Erik Francis Acanakwo; Douglas Sheil, Stein R. Moe
      Abstract: Seed removal can influence plant community dynamics, composition and resulting vegetation characteristics. In the African savanna, termites and large herbivores influence vegetation in various ways, likely including indirect effects on seed predators and secondary dispersers. However, the intensity and variation of seed removal rates in African savannas has seldom been studied. We experimentally investigated whether termites and large herbivores were important factors in the mechanisms driving observed patterns in tree species composition on and off mounds, in Lake Mburo National Park, Uganda. Within fenced (excluding large herbivores) and unfenced termite mounds and adjacent savanna plots, we placed seeds of nine native tree species within small open “cages”, accessed by all animals, roofed cages which only allowed access to small vertebrates and invertebrates, and closed cages which permitted access by smaller invertebrates only (5 mm wire mesh). We found that mean seed removal rate was high (up to 87.3% per three days). Mound habitats experienced significantly higher removal rates than off mound habitats. The mean removal rate of native seeds from closed cages was 11.1% per 3 days compared with 19.4% and 23.3% removed per 3 days in the roofed and open cages, respectively. Smaller seeds experienced higher removal rates than larger seeds. Large herbivore exclusion on mounds reduced native seed removal rates by a mean of 8.8% in the open cages, but increased removal rates by 1.7% in the open cages when off-mound habitats were fenced. While removal rates from open cages were higher on active mounds (30.9%) than on inactive mounds (26.7%), the removal rates from closed cages were lower on active versus inactive mounds (6.1% versus 11.6%, respectively). Thus, we conclude that large herbivores and Macrotermes mounds influence seed removal rates, though these effects appear indirect.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-04T13:45:20.020556-05:
      DOI: 10.1002/ecy.2038
       
  • Ant-plant mutualism: a dietary by-product of a tropical ant's
           macronutrient requirements
    • Authors: Lina M. Arcila Hernández; Jon G. Sanders, Gabriel A. Miller, Alison Ravenscraft, Megan E. Frederickson
      Abstract: Many arboreal ants depend on myrmecophytic plants for both food and shelter; in return, these ants defend their host plants against herbivores, which are often insects. Ant-plant and other mutualisms do not necessarily involve the exchange of costly rewards or services; they may instead result from by-product benefits, or positive outcomes that do not entail a cost for one or both partners. Here, we examined whether the plant-ant Allomerus octoarticulatus pays a short-term cost to defend their host plants against herbivores, or whether plant defense is a by-product benefit of ant foraging for insect prey. Because the food offered by ant-plants is usually nitrogen-poor, arboreal ants may balance their diets by consuming insect prey or associating with microbial symbionts to acquire nitrogen, potentially shifting the costs and benefits of plant defense for the ant partner. To determine the effect of ant diet on an ant-plant mutualism, we compared the behavior, morphology, fitness, stable isotope signatures, and gaster microbiomes of A. octoarticulatus ants nesting in Cordia nodosa trees maintained for nearly a year with or without insect herbivores. At the end of the experiment, ants from herbivore exclosures preferred protein-rich baits more than ants in the control (i.e., herbivores-present) treatment. Furthermore, workers in the control treatment were heavier than in the herbivore-exclusion treatment, and worker mass predicted reproductive output, suggesting that foraging for insect prey directly increased ant colony fitness. The gaster microbiome of ants was not significantly affected by the herbivore exclusion treatment. We conclude that the defensive behavior of some phytoecious ants is a by-product of their need for external protein sources; thus, the consumption of insect herbivores by ants benefits both the ant colony and the host plant.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-04T13:40:20.473308-05:
      DOI: 10.1002/ecy.2036
       
  • Why are nitrogen-fixing trees rare at higher compared to lower
           latitudes'
    • Authors: Duncan N. L. Menge; Sarah A. Batterman, Lars O. Hedin, Wenying Liao, Stephen W. Pacala, Benton N. Taylor
      Abstract: Symbiotic nitrogen (N) fixation provides a dominant source of new N to the terrestrial biosphere, yet in many cases the abundance of N-fixing trees appears paradoxical. N-fixing trees, which should be favored when N is limiting, are rare in higher-latitude forests where N limitation is common, but are abundant in lower-latitude forests where N limitation is rare. Here, we develop a graphical and mathematical model to resolve the paradox. We use the model to demonstrate that N fixation is not necessarily cost-effective under all degrees of N limitation, as intuition suggests. Rather, N fixation is only cost-effective when N limitation is sufficiently severe. This general finding, specific versions of which have also emerged from other models, would explain sustained moderate N limitation because N-fixing trees would either turn N fixation off or be outcompeted under moderate N limitation. From this finding, four general hypothesis classes emerge to resolve the apparent paradox of N limitation and N-fixing tree abundance. The first hypothesis is that N limitation is less common at higher latitudes. This hypothesis contradicts prevailing evidence, so is unlikely, but the following three hypotheses all seem likely. The second hypothesis, which is new, is that even if N limitation is more common at higher latitudes, more severe N limitation might be more common at lower latitudes because of the capacity for higher N demand. Third, N fixation might be cost-effective under milder N limitation at lower latitudes but only under more severe N limitation at higher latitudes. This third hypothesis class generalizes previous hypotheses and suggests new specific hypotheses. For example, greater tradeoffs between N fixation and N use efficiency, soil N uptake, or plant turnover at higher compared to lower latitudes would make N fixation cost-effective only under more severe N limitation at higher latitudes. Fourth, N-fixing trees might adjust N fixation more at lower than at higher latitudes. This framework provides new hypotheses to explain the latitudinal abundance distribution of N-fixing trees, and also provides a new way to visualize them. Therefore, it can help explain the seemingly paradoxical persistence of N limitation in many higher latitude forests.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-04T10:05:32.655345-05:
      DOI: 10.1002/ecy.2034
       
  • Serendipity in a salt marsh: detecting frequent sea otter haul outs in a
           marsh ecosystem
    • Authors: Ron Eby; Robert Scoles, Brent Bancroft Hughes, Kerstin Wasson
      PubDate: 2017-09-28T09:41:23.224512-05:
      DOI: 10.1002/ecy.1965
       
  • Does energy flux predict density-dependence' An empirical field test
    • Authors: Giulia Ghedini; Craig R. White, Dustin J. Marshall
      Abstract: Changes in population density alter the availability, acquisition and expenditure of resources by individuals, and consequently their contribution to the flux of energy in a system. Whilst both negative and positive density-dependence have been well studied in natural populations, we are yet to estimate the underlying energy flows that generate these patterns and the ambivalent effects of density make prediction difficult. Ultimately, density-dependence should emerge from the effects of conspecifics on rates of energy intake (feeding) and expenditure (metabolism) at the organismal level, thus determining the discretionary energy available for growth. Using a model system of colonial marine invertebrates, we measured feeding and metabolic rates across a range of population densities to calculate how discretionary energy per colony changes with density and test whether this energy predicts observed patterns in organismal size across densities. We found that both feeding and metabolic rates decline with density but that feeding declines faster, and that this discrepancy is the source of density-dependent reductions in individual growth. Importantly, we could predict the size of our focal organisms after 8 weeks in the field based on our estimates of energy intake and expenditure. The effects of density on both energy intake and expenditure overwhelmed the effects of body size; even though higher density populations had smaller colonies (with higher mass-specific biological rates), density effects meant that these smaller colonies had lower mass-specific rates overall. Thus, to predict the contribution of organisms to the flux of energy in populations it seems necessary not only to quantify how rates of energy intake and expenditure scale with body size, but also how they scale with density given that this ecological constraint can be a stronger driver of energy use than the physiological constraint of body size.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-26T10:40:47.35472-05:0
      DOI: 10.1002/ecy.2033
       
  • Phytoplankton size-scaling of net-energy flux across light and biomass
           gradients
    • Authors: Martino E. Malerba; Craig R. White, Dustin J. Marshall
      Abstract: Many studies examine how body size mediates energy use, but few examine how size simultaneously regulates energy acquisition. Furthermore, rarely energy fluxes are examined while accounting for the role of biotic and abiotic factors in which they are nested. These limitations contribute to an incomplete understanding of how size affects the transfer of energy through individuals, populations, and communities. Here we characterized photosynthesis-irradiance (P-I) curves and per-cell net-energy use for 21 phytoplankton species spanning across 4 orders of magnitude of size and 7 phyla, each measured across 6 light intensities and 4 population densities. We then used phylogenetic mixed models to quantify how body size influences the energy turnover rates of a species, and how this changes across environments. Rate-parameters for the P-I curve and net-energy budgets were mostly highly correlated and consistent with an allometric size-scaling exponent of less than 1. The energy flux of a cell decreased with population density and increased with light intensity, but the effect of size remained constant across all combinations of treatment levels (i.e. no size X population density interaction). The negative effect of population density on photosynthesis and respiration is mostly consistent with an active downregulation of metabolic rates following a decrease in per-cell resource availability, possibly as an adaptive strategy to reduce the minimum requirements of a cell and improve its competitive ability. Also, because an increase in body size corresponds to a less-than-proportional increase in net-energy (i.e. exponent
      PubDate: 2017-09-22T10:25:19.103086-05:
      DOI: 10.1002/ecy.2032
       
  • Increased grassland arthropod production with mammalian herbivory and
           eutrophication: A test of mediation pathways
    • Authors: Eric M. Lind; Kimberly J. La Pierre, Eric W. Seabloom, Juan Alberti, Oscar Iribarne, Jennifer Firn, Daniel S. Gruner, Adam D. Kay, Jesus Pascal, Justin P. Wright, Louie Yang, Elizabeth T. Borer
      Abstract: Increases in nutrient availability and alterations to mammalian herbivore communities are a hallmark of the Anthropocene, with consequences for the primary producer communities in many ecosystems. While progress has advanced understanding of plant community responses to these perturbations, the consequences for energy flow to higher trophic levels in the form of secondary production are less well understood. We quantified arthropod biomass after manipulating soil nutrient availability and wild mammalian herbivory, using identical methods across 13 temperate grasslands. Of experimental increases in nitrogen, phosphorus, and potassium, only treatments including nitrogen resulted in significantly increased arthropod biomass. Wild mammalian herbivore removal had a marginal, negative effect on arthropod biomass, with no interaction with nutrient availability. Path analysis including all sites implicated nutrient content of the primary producers as a driver of increased arthropod mean size, which we confirmed using 10 sites for which we had foliar nutrient data. Plant biomass and physical structure mediated the increase in arthropod abundance, while the nitrogen treatments accounted for additional variation not explained by our measured plant variables. The mean size of arthropod individuals was 2.5 times more influential on the plot-level total arthropod biomass than was the number of individuals. The eutrophication of grasslands through human activity, especially nitrogen deposition, thus may contribute to higher production of arthropod consumers through increases in nutrient availability across trophic levels.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-21T03:50:54.580506-05:
      DOI: 10.1002/ecy.2029
       
  • Pre-damage biomass allocation and not invasiveness predicts tolerance to
           damage in seedlings of woody species in Hawaii
    • Authors: Matthew H. Lurie; Kasey E. Barton, Curtis C. Daehler
      Abstract: Plant-herbivore interactions have been predicted to play a fundamental role in plant invasions, although support for this assertion from previous research is mixed. While plants may escape from specialist herbivores in their introduced ranges, herbivory from generalists is common. Tolerance traits may allow non-native plants to mitigate the negative consequences of generalist herbivory that they cannot avoid in their introduced range. Here we address whether tolerance to herbivory, quantified as survival and compensatory growth, is associated with plant invasion success in Hawaii and investigate traits that may enhance tolerance in seedlings, the life stage most susceptible to herbivory. In a greenhouse experiment, we measured seedling tolerance to simulated herbivory through mechanical damage (50% leaf removal) of 16 non-native woody plant species differing in invasion status (invasive vs. non-invasive). Seedlings were grown for two weeks following damage and analyzed for biomass to determine whether damaged plants could fully compensate for the lost leaf tissue. Over 99% of all seedlings survived defoliation. Although species varied significantly in their levels of compensation, there was no consistent difference between invasive and non-invasive species. Seedlings of 11 species undercompensated and remained substantially smaller than control seedlings two weeks after damage; four species were close to compensating, while one species overcompensated. Across species, compensation was positively associated with an increased investment in potential storage reserves, specifically cotyledons and roots, suggesting that these organs provide resources that help seedlings re-grow following damage. Our results add to a growing consensus that pre-damage growth patterns determine tolerance to damage, even in young seedlings which have relatively low biomass. The lack of higher tolerance in highly invasive species may suggest that invaders overcome herbivory barriers to invasion in other ways, such as resistance traits, or that herbivory does not play an important role in the seedling invasion dynamics of these woody species in Hawaii.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-21T03:50:29.488008-05:
      DOI: 10.1002/ecy.2031
       
  • The Native-Exotic species richness relationship varies with spatial grain
           of measurement and environmental conditions
    • Authors: Dennis D. Tarasi; Robert K. Peet
      Abstract: Biological invasions can have dramatic impacts on communities and biodiversity, and are critical considerations in conservation and management decisions. We present a novel analysis to determine how exotic species success varies with community richness and scale of measurement. Using 5022 plots representing natural vegetation of the Carolinas, we calculated native and exotic species richness of all vascular plants at five grain sizes. To avoid spatial pseudoreplication, we randomly selected unique subplots from each larger plot, re-selecting 100 times to develop an empirical distribution of the native-exotic richness relationship (NERR). Because observed NERRs vary with spatial scale, we developed separate scale-specific null-model distributions to compare to the empirical data. For each spatial scale, we compared the empirical distribution of 100 slopes to the null distribution containing 99 permutations of species origin per empirical slope. We also analyzed the dataset according to broad assignments corresponding to environmental conditions, using the formation type assigned to each community. The plots followed across most scales the general trend that exotic richness increases with native richness. At the smallest scale, however, the NERR was negative. The slope of the NERR is significantly higher than the null model at the largest observed scale and significantly lower than the null model at the smallest two observed scales. The NERR for most formations follows the general pattern with scale for the entire dataset. Warm temperate forests expressed essentially 0 slope at the largest spatial grain, decreasing to a negative relationship at 1 m2 and smaller. Temperate freshwater marshes and wet meadows and shrublands expressed a positive relationship at all spatial grains, demonstrating that unique environmental and biogeographic conditions differentially affect exotic species. Further, these results indicate that exotic species are unevenly distributed across natural communities and that community assembly processes vary with scale.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-21T03:45:39.682947-05:
      DOI: 10.1002/ecy.2028
       
  • 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
       
  • Physical calculations of resistance to water loss improve species range
           models: Reply
    • Authors: Eric A. Riddell; Michael W. Sears
      Abstract: Christian et al. (2017) proposed several possible flaws in the methods and logic presented by Riddell et al. (2017) that included potential activity of salamanders during measurements, trimming of the agar model's legs, misinterpretations of the empirical data, limitations on agar models, and the relationship between body size and skin resistance to water loss (ri). We argue that these criticisms are easily addressable, and here, we reinforce our original claim that the agar method for determination of resistance to water loss is flawed. Before responding to these individual critiques, we begin with a deeper criticism of the agar model method and general methodology for determining resistance to water loss that has resulted in the reification of the boundary layer's ecological and physiological importance.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-13T10:45:19.086603-05:
      DOI: 10.1002/ecy.2022
       
  • Quantity and quality limit detritivore growth: mechanisms revealed by
           ecological stoichiometry and co-limitation theory
    • Authors: Halvor M. Halvorson; Erik Sperfeld, Michelle A. Evans-White
      Abstract: Resource quantity and quality are fundamental bottom-up constraints on consumers. Best understood in autotroph-based systems, co-occurrence of these constraints may be common but remains poorly studied in detrital-based systems. Here, we used a laboratory growth experiment to test limitation of the detritivorous caddisfly larvae Pycnopsyche lepida across a concurrent gradient of oak litter quantity (food supply) and quality (phosphorus:carbon, P:C ratios). Growth increased simultaneously with quantity and quality, indicating co-limitation across the resource gradients. We merged approaches of ecological stoichiometry and co-limitation theory, showing how co-limitation reflected shifts in C and P acquisition throughout homeostatic regulation. Increased growth was best explained by elevated consumption rates and improved P assimilation, which both increased with elevated quantity and quality. Notably, C assimilation efficiencies remained unchanged and achieved maximum 18% at low quantity despite pronounced C-limitation. Detrital C recalcitrance and substantive post-assimilatory C losses probably set a minimum quantity threshold to achieve positive C balance. Above this threshold, greater quality enhanced larval growth probably by improving P assimilation toward P-intensive growth. We suggest this interplay of C and P acquisition contributes to detritivore co-limitation, highlighting quantity and quality as potential simultaneous bottom-up controls in detrital-based ecosystems, including under anthropogenic change like nutrient enrichment.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-13T10:15:31.636898-05:
      DOI: 10.1002/ecy.2026
       
  • Biodiversity maintenance may be lower under partial niche differentiation
           than under neutrality
    • Authors: Rafael D'Andrea; Annette Ostling
      Abstract: Niche differentiation is normally regarded as a promoter of species coexistence in competitive systems, as it stabilizes species abundances. One might therefore expect lower extinction rates and higher species richness and local persistence times in niche-differentiated communities than in neutral assemblages. Here we compare stochastic niche and neutral dynamics in simulated assemblages, and find that when local dynamics combine with immigration from a regional pool, the effect of niches can be more complex. Trait variation that lessens competition between species will not necessarily give all immigrating species their own niche to occupy. Such partial niche differentiation protects certain species from local extinction, but expedites exclusion of others. Differences in regional abundances and intrinsic growth rates have similar impacts on the distribution of persistence times as niche differentiation and blur the distinction between niche and neutral dynamical patterns, though niche dynamics will influence which species persist longer. Ultimately, unless the number of niches available to species is sufficiently high, niches may actually heighten extinction rates and lower species richness and local persistence times. Our results help make sense of recent observations of community dynamics, and point to the dynamical observations needed to discern the influence of niche differentiation.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-12T06:00:23.528654-05:
      DOI: 10.1002/ecy.2020
       
  • Orthogonal fitness benefits of nitrogen and ants for nitrogen-limited
           plants in the presence of herbivores
    • Authors: Elizabeth G. Pringle; Ian Ableson, Jennifer Kerber, Rachel L. Vannette, Leiling Tao
      Abstract: Predictable effects of resource availability on plant growth-defense strategies provide a unifying theme in theories of direct anti-herbivore defense, but it is less clear how resource availability modulates plant indirect defense. Ant-plant-hemipteran interactions produce mutualistic trophic cascades when hemipteran-tending ants reduce total herbivory, and these interactions are a key component of plant indirect defense in most terrestrial ecosystems. Here we conducted an experiment to test how ant-plant-hemipteran interactions depend on nitrogen (N) availability by manipulating the presence of ants and aphids under different N fertilization treatments. Ants increased plant flowering success by decreasing the densities of herbivores, and the effects of ants on folivores were positively related to the density of aphids. Unexpectedly, N fertilization produced no changes in plant N concentrations. Plants grown in higher N grew and flowered more, but aphid honeydew chemistry stayed the same, and neither the density of aphids nor the rate of ant attraction per aphid changed with N addition. The positive effects of ants and N addition on plant fitness were thus independent of one another. We conclude that N was the plant's limiting nutrient and propose that addition of the limiting nutrient is unlikely to alter the strength of mutualistic trophic cascades.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-09T09:15:27.323804-05:
      DOI: 10.1002/ecy.2013
       
  • Influence of littoral periphyton on whole-lake metabolism relates to
           littoral vegetation in humic lakes
    • Authors: Jussi Vesterinen; Shawn P. Devlin, Jari Syväranta, Roger I. Jones
      Abstract: The role of littoral habitats in lake metabolism has been underrated, especially in humic lakes, based on an assumption of low benthic primary production (PP) due to low light penetration into water. This assumption has been challenged by recent recognition of littoral epiphyton dominance of whole-lake PP in a small highly humic lake and of epiphyton as an important basal food source for humic lake biota. However, as these studies have mostly concerned single lakes, there is a need to test their wider generality. We studied the whole-lake PP and community respiration (CR) in eight small humic lakes in southern Finland during July 2015 using 14C incorporation to measure pelagic PP and the changes in dissolved inorganic carbon in light and dark in situ incubations to measure CR and littoral PP by epiphyton. Changes in O2 concentration in both pelagic and littoral surface water were measured periodically from each lake and, additionally, continuously with a data logger from one lake during the study period. The results revealed that the littoral dominated whole-lake net primary production (NPP) in five of the eight lakes, which was supported by observed O2 supersaturation in the littoral surface water in most of the lakes. Calculated pelagic:littoral ratios by area correlated negatively with both littoral NPP and littoral contribution to whole-lake NPP. Moreover, there was a significant positive relationship between littoral proportion of whole-lake NPP and the fraction of lake surface area covered by littoral aquatic vegetation. This demonstrates that increased aquatic littoral vegetation cover increases the overall importance of the littoral to whole-lake PP in highly humic lakes. Littoral NPP also correlated strongly with littoral O2 saturation, and the continuously measured O2 revealed substantial temporal variation in O2 saturation, particularly in the littoral zone. Whole-lake gross primary production:community respiration (GPP:CR) ratios revealed that accounting for littoral metabolism produced a marked shift towards lake metabolic balance, although all the eight lakes remained net heterotrophic. This study emphasizes that littoral metabolism needs to be accounted for when estimating whole-lake C fluxes in all lakes, even in highly colored humic waters.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-09T09:10:28.70721-05:0
      DOI: 10.1002/ecy.2012
       
  • The little things that run: a general scaling of invertebrate exploratory
           speed with body mass
    • Authors: Myriam R. Hirt; Tobias Lauermann, Ulrich Brose, Lucas P.J.J. Noldus, Anthony I. Dell
      Abstract: Speed is a key trait of animal movement, and while much is already known about vertebrate speed and how it scales with body mass, studies on invertebrates are sparse, especially across diverse taxonomic groups. Here, we used automated image-based tracking to characterize the exploratory (voluntary) speed of 173 invertebrates comprising 57 species across 6 taxonomic groups (Arachnida, Chilopoda, Diplopoda, Entognatha, Insecta, Malacostraca) and 4 feeding types (carnivore, detritivore, herbivore, omnivore). Across all individuals, exploratory speed scaled with body mass following a power-law relationship with a scaling exponent of 0.19 (±0.04 standard error) and an intercept of 14.33 (±1.2). These parameters varied substantially with taxonomic group and feeding type. For the first time, we provide general empirically-derived allometric scaling relationships of exploratory speed across broad taxonomic groups of invertebrates. As exploratory speed drives key components of species interactions – such as encounter and attack rates, or competition – our study contributes to a deeper understanding of the role of individual movement in population and community level processes.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-08T20:45:30.539817-05:
      DOI: 10.1002/ecy.2006
       
  • Long-Term Research in Ecology and Evolution (LTREE): 2015 survey data
    • Authors: Mark A. Bradford; Anthony Leiserowitz, Geoffrey Feinberg, Seth A. Rosenthal, Jennifer A. Lau
      Abstract: To systematically assess views on contributions and future activities for long-term research in ecology and evolution (LTREE), we conducted and here provide data responses and associated metadata for a survey of ecological and evolutionary scientists. The survey objectives were to: 1) Identify and prioritize research questions that are important to address through long-term, ecological field experiments; and 2) Understand the role that these experiments might play in generating and applying ecological and evolutionary knowledge. The survey was developed adhering to the standards of the American Association for Public Opinion Research. It was administered online using Qualtrics Survey Software. Survey creation was a multi-step process, with questions and format developed and then revised with, for example, input from an external advisory committee comprising senior and junior ecological and evolutionary researchers. The final questionnaire was released to ~100 colleagues to ensure functionality and then fielded two days later (January 7th 2015). Two professional societies distributed it to their membership, including the Ecological Society of America, and it was posted to three list serves. The questionnaire was available through February 8th 2015 and completed by 1,179 respondents. The distribution approach targeted practicing ecologists and evolutionary biologists in the U.S. Quantitative (both ordinal and categorical) closed-ended questions used a pre-defined set of response categories, facilitating direct comparison across all respondents. Qualitative, open-ended questions, provided respondents the opportunity to develop their own answers. We employed quantitative questions to score views on the extent to which long-term experimental research has contributed to understanding in ecology and evolutionary biology; its role compared to other approaches (e.g. short-term experiments); justifications for and caveats to long-term experiments; and the relative importance of incentives for conducting long-term research. Qualitative questions were used to assess community views on the most important topics and questions for long-term research to address, and primary incentives and challenges to realizing this work. Finally, demographic data were collected to determine if views were conditional on such things as years of experience and field of expertise. The final questionnaire and all responses are provided for unrestricted use.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-08T01:25:27.465656-05:
      DOI: 10.1002/ecy.1999
       
  • Live long and prosper: plant-soil feedback, lifespan and landscape
           abundance covary
    • Authors: Andrew Kulmatiski; Karen H. Beard, Jeanette Norton, Justin Heavilin, Leslie Forero, Josephine Grenzer
      Abstract: Plant soil feedbacks (PSFs) are thought to be important to plant growth and species coexistence, but most support for these hypotheses is derived from short-term greenhouse experiments. Here we use a seven-year, common garden experiment to measure PSFs for seven native and six non-native species common to the western USA. We use these long-term, field-based estimates to test correlations between PSF and plant landscape abundance, species origin, functional type and lifespan. To assess potential PSF mechanisms, we also measured soil microbial community composition, root biomass, nitrogen cycling, bulk density, penetration resistance, and shear strength. Plant abundance on the landscape and plant lifespan were positively correlated with PSFs, though this effect was due to the relationships for native plants. PSFs were correlated with indices of soil microbial community composition. Soil nutrient and physical traits and root biomass differed among species but were not correlated with PSF. While results must be taken with caution because only 13 species were examined, these species represent most of the dominant plant species in the system. Results suggest that native plant abundance is associated with the ability of long-lived plants to create positive plant-soil microbe interactions, while short-lived non-native plants maintain dominance by avoiding soil-borne antagonists, increasing nitrogen cycling and dedicating resources to aboveground growth and reproduction rather than to belowground growth. Broadly, results suggest that PSFs are correlated with a suite of traits that determine plant abundance.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-07T05:55:23.799412-05:
      DOI: 10.1002/ecy.2011
       
  • Drivers of synchrony of acorn production in the valley oak (Quercus
           lobata) at two spatial scales
    • Authors: Walter D. Koenig; Johannes M. H. Knops, Mario B. Pesendorfer, David N. Zaya, Mary V. Ashley
      Abstract: We investigated spatial synchrony of acorn production by valley oaks (Quercus lobata) among individual trees at the within-population, local level and at the among-population, statewide level spanning the geographic range of the species. At the local level, the main drivers of spatial synchrony were water availability and flowering phenology of individual trees, while proximity, temperature differences between trees, and genetic similarity failed to explain a significant proportion of variance in spatial synchrony. At the statewide level, annual rainfall was the primary driver, while proximity was significant by itself but not when controlling for rainfall; genetic similarity was again not significant. These results support the hypothesis that environmental factors—the Moran effect—are key drivers of spatial synchrony in acorn production at both small and large geographic scales. The specific environmental factors differed depending on the geographic scale, but were in both cases related to water availability. In addition, flowering phenology, potentially affecting either density-independent pollination failure (the pollination Moran effect) or density-dependent pollination efficiency (pollen coupling), plays a key role in driving spatial synchrony at the local geographic scale.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-07T05:50:19.802177-05:
      DOI: 10.1002/ecy.2010
       
  • Drivers of nitrogen transfer in stream food webs across continents
    • Authors: B. C. Norman; M. R. Whiles, S. M. Collins, A. S. Flecker, S. K. Hamilton, S. L. Johnson, E. J. Rosi-Marshall, L. R. Ashkenas, W. B. Bowden, C. L. Crenshaw, T. Crowl, W. K. Dodds, R. O. Hall, R. El-Sabaawi, N. A. Griffiths, E. Marti, W. H. McDowell, S. D. Peterson, H. M. Rantala, T. Riis, K. S. Simon, J. L. Tank, S. A. Thomas, D. von Schiller, J. R. Webster
      Abstract: Studies of trophic-level material and energy transfers are central to ecology. The use of isotopic tracers has now made it possible to measure trophic transfer efficiencies of important nutrients and to better understand how these materials move through food webs. We analyzed data from thirteen 15N-ammonium tracer addition experiments to quantify N transfer from basal resources to animals in headwater streams with varying physical, chemical, and biological features. N transfer efficiencies from primary uptake compartments (PUCs; heterotrophic microorganisms and primary producers) to primary consumers was lower (mean: 11.5%, range: 100%). Total N transferred (as a rate) was greater in streams with open compared to closed canopies and overall N transfer efficiency generally followed a similar pattern, although was not statistically significant. We used principal component analysis to condense a suite of site characteristics into two environmental components. Total N uptake rates among trophic levels were best predicted by the component that was correlated with latitude, DIN:SRP, GPP:ER, and % canopy cover. N transfer efficiency did not respond consistently to environmental variables. Our results suggest that canopy cover influences N movement through stream food webs because light availability and primary production facilitate N transfer to higher trophic levels.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-07T04:20:29.652809-05:
      DOI: 10.1002/ecy.2009
       
  • Influence of neighboring plants on the dynamics of an ant-acacia
           protection mutualism
    • Authors: Todd M. Palmer; Corinna Riginos, Rachel E. Damiani, Natalya Morgan, John S. Lemboi, James Lengingiro, Juan Carlos Ruiz-Guajardo, Robert M. Pringle
      Abstract: Ant-plant protection symbioses, in which plants provide food and/or shelter for ants in exchange for protection from herbivory, are model systems for understanding the ecology of mutualism. While interactions between ants, host plants, and herbivores have been intensively studied, we know little about how plant-plant interactions influence the dynamics of these mutualisms—despite strong evidence that plants compete for resources, that hosting ants can be costly, and that host-plant provisioning to ants can therefore be constrained by resource availability. We used field experiments in a semi-arid Kenyan savanna to examine interactions between the ant-plant Acacia drepanolobium, neighboring grasses, and two species of symbiotic acacia-ants with divergent behaviors: Crematogaster mimosae, an aggressive symbiont that imposes high costs to host trees via consumption of extrafloral nectar, and Tetraponera penzigi, a less-protective symbiont that imposes lower costs because it does not consume nectar. We hypothesized that by competing with acacias for resources, neighboring grasses (a) reduce hosts’ ability to support costly C. mimosae, while having little or no effect on the ability of hosts to support low-cost T. penzigi, and (b) reduce sapling growth rates irrespective of ant occupant. We factorially manipulated the presence/absence of grasses and the identity of ant occupants on saplings and evaluated effects on colony survivorship and sapling growth rates over 40 weeks. Contrary to prediction, the high-cost/high-reward nectar-dependent mutualist C. mimosae had higher colony-survival rates on saplings with grass neighbors present. Grasses appear to have indirectly facilitated the survival of C. mimosae by reducing water stress on host plants; soils under saplings shaded by grasses had higher moisture content, and these saplings produced more active nectaries than grass-removal saplings. Consistent with prediction, survival of low-cost/low-reward T. penzigi did not differ significantly between grass-removal treatments. Saplings occupied by low-cost/low-reward T. penzigi grew 100% more on average than saplings occupied by high-cost/high-reward C. mimosae, demonstrating that mutualist-partner identity strongly and differentially influences demographic rates of young plants. In contrast, contrary to prediction, grass neighbors had no significant net impact on sapling growth rates. Our results suggest that neighboring plants can exert strong and counterintuitive effects on ant-plant protection symbioses, highlighting the need to integrate plant-plant interactions into our understanding of these mutualisms.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-06T03:05:31.817263-05:
      DOI: 10.1002/ecy.2008
       
  • Abundance of small mammals in the Atlantic Forest (ASMAF): a data set for
           analyzing tropical community patterns
    • Authors: Marcos S. L. Figueiredo; Camila S. Barros, Ana C. Delciellos, Edú B. Guerra, Pedro Cordeiro-Estrela, Maja Kajin, Martin R. Alvarez, Paulo H. Asfora, Diego Astúa, Helena G. Bergallo, Rui Cerqueira, Lena Geise, Rosana Gentile, Carlos Eduardo V. Grelle, Gilson E. Iack-Ximenes, Leonardo C. Oliveira, Marcelo Weksler, Marcus V. Vieira
      Abstract: Local abundance results from the interaction between populational and environmental processes. The abundance of the species in a community is also one of the most basic descriptors of its structure. Despite its importance, information about species abundances is fragmentary, creating a knowledge gap about species abundances known as Prestonian Shortfall. Here we present a comprehensive dataset of small mammal abundance in the Atlantic Forest. Data were extracted from 114 published sources and from unpublished data collected by our research groups spanning from 1943 to 2017. The data set includes 1,902 records of at least 111 species in 155 localities, totaling 42,617 individuals represented. We selected studies that (i) were conducted in forested habitats of the Atlantic Forest, (ii) had a minimum sampling effort of at least 500 trap-nights, and (iii) contained species abundance data in detail. For each study, we recorded (i) latitude and longitude, (ii) name of the locality, (iii) employed sampling effort, (iv) type of traps used, (v) study year, (vi) country, and (vii) species name with (viii) its respective abundances. For every locality, we also obtained information regarding its (ix) ecoregion, (x) predominant vegetation type, and (xi) biogeographic subdivision. Whenever necessary, we also (xii) updated the species names as new species were described and some genera suffered taxonomic revision since the publication. The localities are spread across the Atlantic Forest and most of the small mammal species known for to occur in Atlantic Forest are present in the data set, making it representative of communities of the entire biome. This data set can be used to address various patterns in community ecology and geographical ecology, as the relation between local abundance and environmental suitability, hypothesis regarding local and regional factors on community structuring, species abundance distributions (SAD), and functional and phylogenetic mechanisms on community assembling.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-06T03:01:28.874285-05:
      DOI: 10.1002/ecy.2005
       
  • ATLANTIC BATS: a dataset of bat communities from the Atlantic Forests of
           South America
    • Authors: Renata Lara Muylaert; Richard D. Stevens, Carlos Eduardo Lustosa Esbérard, Marco Aurelio Ribeiro Mello, Guilherme Siniciato Terra Garbino, Luiz H. Varzinczak, Deborah Faria, Marcelo Moraes Weber, Patricia Kerches Rogeri, André Luis Regolin, Hernani Fernandes Magalhães Oliveira, Luciana de Moraes Costa, Marília A. S. Barros, Gilberto Sabino-Santos, Mara Ariane Crepaldi de Morais, Vinicius Silva Kavagutti, Fernando C. Passos, Emma-Liina Marjakangas, Felipe Gonçalves Motta Maia, Milton Cezar Ribeiro, Mauro Galetti
      Abstract: Bats are the second most diverse mammal order and they provide vital ecosystem functions (e.g., pollination, seed dispersal, and nutrient flux in caves) and services (e.g., crop pest suppression). Bats are also important vectors of infectious diseases, harboring more than 100 different virus types. In the present study, we compiled information on bat communities from the Atlantic Forests of South America, a species-rich biome that are highly threatened by habitat loss and fragmentation. ATLANTIC BATS dataset comprises 135 quantitative studies carried out in 205 sites, which cover most vegetation types of the tropical and subtropical Atlantic Forest: dense ombrophilous forest, mixed ombrophilous forest, semideciduous forest, deciduous forest, savanna, steppe, and open ombrophilous forest. The dataset includes information on more than 90,000 captures of 98 bat species of 8 families. Species richness averaged 12.1 per site, with a median value of 10 species (ranging from 1 to 53 species). Six species occurred in more than 50% of the communities: Artibeus lituratus, Carollia perspicillata, Sturnira lilium, Artibeus fimbriatus, Glossophaga soricina, and Platyrrhinus lineatus. The number of captures divided by sampling effort, a proxy for abundance, varied from 0.000001 to 0.77 individuals/hour*m2 (0.04+0.007 individuals/hour*m2). Our dataset reveals a hyper-dominance of eight species that together that comprise 80% of all captures: Platyrrhinus lineatus (2.3%), Molossus molossus (2.8%), Artibeus obscurus (3.4%), Artibeus planirostris (5.2%), Artibeus fimbriatus (7%), Sturnira lilium (14.5%), Carollia perspicillata (15.6%), and Artibeus lituratus (29.2%).This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-06T03:00:35.699505-05:
      DOI: 10.1002/ecy.2007
       
  • Increased consumer density reduces the strength of neighborhood effects in
           a model system
    • Authors: Andrew C. Merwin; Nora Underwood, Brian D. Inouye
      Abstract: An individual's susceptibility to attack can be influenced by conspecific and heterospecifics neighbors. Predicting how these neighborhood effects contribute to population-level processes such as competition and evolution requires an understanding of how the strength of neighborhood effects is modified by changes in the abundances of both consumers and neighboring resource species. We show for the first time that consumer density can interact with the density and frequency of neighboring organisms to determine the magnitude of neighborhood effects. We used the bean beetle, Callosobruchus maculatus, and two of its host beans, Vigna unguiculata and V. radiata, to perform a response-surface experiment with a range of resource densities and three consumer densities. At low beetle density, damage to beans was reduced with increasing conspecific density (i.e. resource dilution) and damage to the less preferred host, V. unguiculata, was reduced with increasing V. radiata frequency (i.e. frequency-dependent associational resistance). As beetle density increased, however, neighborhood effects were reduced; at the highest beetle densities neither focal nor neighboring resource density nor frequency influenced damage. These findings illustrate the importance of consumer density in mediating indirect effects among resources, and suggest that accounting for consumer density may improve our ability to predict population-level outcomes of neighborhood effects and to use them in applications such as mixed-crop pest management.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-04T13:57:17.692794-05:
      DOI: 10.1002/ecy.2004
       
  • Genetic variation of a foundation rockweed species affects associated
           communities
    • Authors: Veijo Jormalainen; Maria Danelli, Karine Gagnon, Helmut Hillebrand, Eva Rothäusler, Juha-Pekka Salminen, Joakim Sjöroos
      Abstract: Genetic variation in a foundation species may affect the composition of associated communities as well as modify ecosystem function. While the ecological consequences of genetic diversity of foundation species have been widely reported, the ability of individual genotypes to support dissimilar communities has been documented only in forest ecosystems. Here, for the first time in a marine ecosystem, we test whether the different genotypes of the rockweed Fucus vesiculosus harbor distinct community phenotypes and whether the genetic similarity of individual genotypes or their defensive compound content can explain the variation of the associated communities. We reared replicated genotypes in a common garden in the sea and analyzed their associated communities of periphytic algae and invertebrates as well as determined their contents of defense compounds, phlorotannins, and genetic distance based on neutral molecular markers. The periphytic community was abundant in mid-summer and its biovolume, diversity and community composition varied among the rockweed genotypes. The diversity of the periphytic community decreased with its increasing biovolume. In autumn, when grazers were abundant, periphytic community biomass was lower and less variable among rockweed genotypes, indicating different relative importance of bottom-up regulation through heritable variation of the foundation species and top-down regulation through grazing intensity. Similarly, composition of the invertebrate community varied among the rockweed genotypes. Although the genotype explained about 10 - 18% of the variation in associated communities, the variation was explained neither by the genetic distance nor the phlorotannin content. Thus, neither neutral genetic markers nor a single phenotypic trait could provide a mechanistic understanding of the genetic basis of community specificity. Therefore, a more comprehensive mapping of quantitative trait variation is needed to understand the underlying mechanisms. The community specificity implies that genetic variation within a foundation species is crucial for the biodiversity and assembly of associated organisms and, thus, for the functioning of associated communities. The result highlights the importance of ensuring the genetic variation of foundation species as a conservation target.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-04T13:50:56.192203-05:
      DOI: 10.1002/ecy.2002
       
  • Plant diversity maintains long-term ecosystem productivity under frequent
           drought by increasing short-term variation
    • Authors: Cameron Wagg; Michael J. O'Brien, Anja Vogel, Michael Scherer-Lorenzen, Nico Eisenhauer, Bernhard Schmid, Alexandra Weigelt
      Abstract: Increasing frequency of extreme climatic events can disrupt ecosystem processes and destabilize ecosystem functioning. Biodiversity may dampen these negative effects of environmental perturbations to provide greater ecosystem stability. We assessed the effects of plant diversity on the resistance, recovery and stability of experimental grassland ecosystems in response to recurring summer drought over seven years. Plant biomass production was reduced during the summer drought treatment compared with control plots. However, the negative effect of drought was relatively less pronounced at high than at low plant diversity, demonstrating that biodiversity increased ecosystem resistance to environmental perturbation. Furthermore, more diverse plant communities compensated for the reduced productivity during drought by increasing spring productivity compared to control plots. The drought-induced compensatory recovery led to increased short-term variations in productivity across growing seasons in more diverse communities that stabilized the longer-term productivity across years. Our findings show that short-term variation between seasons in the face of environmental perturbation can lead to longer-term stability of annual productivity in diverse ecosystems compared to less diverse ecosystems.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-04T13:50:54.25827-05:0
      DOI: 10.1002/ecy.2003
       
  • Deciphering the Enigma of Undetected Species, Phylogenetic, and Functional
           Diversity Based on Good-Turing Theory
    • Authors: Anne Chao; Chun-Huo Chiu, Robert K. Colwell, Luiz Fernando S. Magnago, Robin L. Chazdon, Nicholas J. Gotelli
      Abstract: Estimating the species, phylogenetic, and functional diversity of a community is challenging because rare species are often undetected, even with intensive sampling. The Good-Turing frequency formula, originally developed for cryptography, estimates in an ecological context the true frequencies of rare species in a single assemblage based on an incomplete sample of individuals. Until now, this formula has never been used to estimate undetected species, phylogenetic, and functional diversity. Here, we first generalize the Good-Turing formula to incomplete sampling of two assemblages. The original formula and its two-assemblage generalization provide a novel and unified approach to notation, terminology, and estimation of undetected biological diversity. For species richness, the Good-Turing framework offers an intuitive way to derive the non-parametric estimators of the undetected species richness in a single assemblage, and of the undetected species shared between two assemblages. For phylogenetic diversity, the unified approach leads to an estimator of the undetected Faith's phylogenetic diversity (PD, the total length of undetected branches of a phylogenetic tree connecting all species), as well as a new estimator of undetected PD shared between two phylogenetic trees. For functional diversity based on species traits, the unified approach yields a new estimator of undetected Walker et al.'s functional attribute diversity (FAD, the total species-pairwise functional distance) in a single assemblage, as well as a new estimator of undetected FAD shared between two assemblages. Although some of the resulting estimators have been previously published (but derived with traditional mathematical inequalities), all taxonomic, phylogenetic, and functional diversity estimators are now derived under the same framework. All the derived estimators are theoretically lower bounds of the corresponding undetected diversities; our approach reveals the sufficient conditions under which the estimators are nearly unbiased, thus offering new insights. Simulation results are reported to numerically verify the performance of the derived estimators. We illustrate all estimators and assess their sampling uncertainty with an empirical dataset for Brazilian rain forest trees. These estimators should be widely applicable to many current problems in ecology, such as the effects of climate change on spatial and temporal beta diversity and the contribution of trait diversity to ecosystem multi-functionality.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-04T13:45:52.880007-05:
      DOI: 10.1002/ecy.2000
       
  • A geographic cline in the ability to self-fertilize is unrelated to the
           pollination environment
    • Authors: Matthew H. Koski; Dena L. Grossenbacher, Jeremiah W. Busch, Laura F. Galloway
      Abstract: The reproductive assurance (RA) hypothesis predicts that the ability to autonomously self-fertilize (hereafter, autonomy) in plants should be favored in environments where a lack of mates or pollinators limits outcross reproduction. Because such limits to outcrossing are predicted to be most severe at range edges, elevated autonomy in peripheral populations is often attributed to RA. We test this hypothesis in 24 populations spanning the range of Campanula americana, including range interior and populations at three geographic range edges. We scored autonomous fruit set in a pollinator-free environment and detected clinal variation—autonomy increased linearly from the southern to the northern edge, and from the eastern to the western edge. We then address whether the cline reflects the contemporary pollination environment. We measured population size, plant density, pollinator visitation, outcross pollen limitation and RA in natural populations over two years. Most populations were pollen limited, and those that experienced higher visitation rates by bumblebees had reduced pollen limitation. Reproductive assurance, however, was generally low across populations and was unrelated to pollen limitation or autonomy. Neither pollen limitation nor RA displayed geographic clines. Finally, autonomy was not associated with pollinator visitation rates or mate availability. Thus, the data do not support the RA hypothesis; clinal variation in autonomy is unrelated to the current pollination environment. Therefore, geographic patterns of autonomy are likely the result of historical processes rather than contemporary natural selection for RA.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-04T13:45:41.430537-05:
      DOI: 10.1002/ecy.2001
       
  • ATLANTIC-CAMTRAPS: a dataset of medium and large terrestrial mammal
           communities in the Atlantic Forest of South America
    • Authors: Fernando Lima; Gabrielle Beca, Renata de Lara Muylaert, Clinton N. Jenkins, Miriam Lucia Lages Perilli, Ana Maria de Oliveira Paschoal, Rodrigo Lima Massara, Adriano Pereira Paglia, Adriano Garcia Chiarello, Maurício Eduardo Graipel, Jorge José Cherem, André Luis Regolin, Luiz Gustavo Rodrigues Oliveira Santos, Carlos Rodrigo Brocardo, Agustín Paviolo, Mario S. Di Bitetti, Leandro Moraes Scoss, Fabiana Lopes Rocha, Roberto Fusco-Costa, Clarissa Alves da Rosa, Marina Xavier da Silva, Ludmila Hufnagel, Paloma Marques Santos, Gabriela Teixeira Duarte, Luiza Neves Guimarães, Larissa Lynn Bailey, Flávio Henrique Guimarães Rodrigues, Heitor Morais Cunha, Felipe Moreli Fantacini, Graziele Oliveira Batista, Juliano André Bogoni, Marco Adriano Tortato, Micheli Ribeiro Luiz, Nivaldo Peroni, Pedro Volkmer de Castilho, Thiago Bernardes Maccarini, Vilmar Picinatto Filho, Carlos De Angelo, Paula Cruz, Verónica Quiroga, María Eugenia Iezzi, Diego Varela, Sandra Maria Cintra Cavalcanti, Alexandre Camargo Martensen, Erica Vanessa Maggiorini, Fabíola Ferreira Keesen, André Valle Nunes, Gisele Mendes Lessa, Pedro Cordeiro-Estrela, Mayara Guimarães Beltrão, Anna Carolina Figueiredo de Albuquerque, Bianca Ingberman, Camila Righetto Cassano, Laury Cullen Junior, Milton Cezar Ribeiro, Mauro Galetti
      Abstract: Our understanding of mammal ecology has always been hindered by the difficulties of observing species in closed tropical forests. Camera trapping has become a major advance for monitoring terrestrial mammals in biodiversity rich ecosystems. Here we compiled one of the largest datasets of inventories of terrestrial mammal communities for the Neotropical region based on camera trapping studies. The dataset comprises 170 surveys of medium to large terrestrial mammals using camera traps conducted in 144 areas by 74 studies, covering six vegetation types of tropical and subtropical Atlantic Forest of South America (Brazil and Argentina), and present data on species composition and richness. The complete dataset comprises 53,438 independent records of 83 species of mammals, includes 10 species of marsupials, 15 rodents, 20 carnivores, 8 ungulates and 6 armadillos. Species richness averaged 13 species (± 6.07 SD) per site. Only six species occurred in more than 50% of the sites: the domestic dog Canis familiaris, crab-eating fox Cerdocyon thous, tayra Eira barbara, south American coati Nasua nasua, crab-eating raccoon Procyon cancrivorus and the nine-banded armadillo Dasypus novemcinctus. The information contained in this dataset can be used to understand macroecological patterns of biodiversity, community, and population structure, but also to evaluate the ecological consequences of fragmentation, defaunation, and trophic interactions.This article is protected by copyright. All rights reserved.
      PubDate: 2017-08-31T02:30:34.505186-05:
      DOI: 10.1002/ecy.1998
       
  • Remotely sensed canopy height reveals three pantropical ecosystem states:
           comment
    • 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
       
  • The southernmost parakeet might be enhancing pollination of a dioecious
           conifer
    • Authors: Gabriela Gleiser; Sergio A. Lambertucci, Karina L. Speziale, Fernando Hiraldo, José L. Tella, Marcelo A. Aizen
      PubDate: 2017-08-28T13:46:33.258823-05:
      DOI: 10.1002/ecy.1938
       
  • A historical perspective of nutrient change impact on an infectious
           disease in Daphnia
    • Authors: Lien Reyserhove; Giovanni Samaey, Koenraad Muylaert, Vincent Coppé, Willem Van Colen, Ellen Decaestecker
      Abstract: Changes in food quality can play a substantial role in the vulnerability of hosts to infectious diseases. In this study, we focused on the genetic differentiation of the water flea Daphnia magna towards food of different quality (by manipulating C:N:P ratios) and its impact on the interaction with a virulent infectious disease, “White Fat Cell Disease (WFCD)”. Via a resurrection ecology approach, we isolated two Daphnia subpopulations from different depths in a sediment core, which were exposed to parasites and a nutrient ratio gradient in a common garden experiment. Our results showed a genetic basis for sensitivity towards food deprivation. Both fecundity and host survival was differently affected when fed with low-quality food. This strongly impacted the way both subpopulations interacted with this parasite. A historical reconstruction of nutrient changes in a sediment core reflected an increase in organic material and phosphorus concentration (more eutrophic conditions) over time in the studied pond. These results enable us to relate patterns of genetic differentiation in sensitivity towards food deprivation to an increasing level of eutrophication of the subpopulations, which ultimately impacts parasite virulence effects. This finding was confirmed via a dynamic energy budgets (DEB), in which energy was partitioned for the host and the parasite. The model was tailored to our study by integrating (i) increased growth and a fecundity shift in the host upon parasitism and (ii) differences of food assimilation in the subpopulations showing that a reduced nutrient assimilation resulted in increased parasite virulence. The combination of our experiment with the DEB model shows that it is important to consider genetic diversity when studying the impact of nutritional stress on species interactions, especially in the context of changing environments and emerging infectious diseases.This article is protected by copyright. All rights reserved.
      PubDate: 2017-08-28T03:20:56.510857-05:
      DOI: 10.1002/ecy.1994
       
  • An arthropod survival strategy in a frequently burned forest
    • Authors: Jane Dell; Joseph O'Brien, Lydia Doan, Lora Richards, Lee Dyer
      PubDate: 2017-08-24T14:50:33.110609-05:
      DOI: 10.1002/ecy.1939
       
  • Macroevolutionary constraints to tolerance: trade-offs with drought
           tolerance and phenology, but not resistance
    • Authors: Ian S. Pearse; Jessica Aguilar, John Schroder, Sharon Y. Strauss
      Abstract: Plant tolerance of herbivory, i.e., the ability to recover after damage, is an important component of how plants cope with herbivores. Tolerance has long been hypothesized to be constrained evolutionarily by plant resistance to herbivores, traits that allow plants to cope with stressful growing conditions, and traits that influence the timing of damage in relation to reproduction. Variation in tolerance and resistance can be caused by differences in the identity of the plant (e.g. genotype, species, clade) and by the context of the herbivore threat (e.g. identity of the herbivore, type of damage it causes, abiotic conditions in which the plant is growing). To date, the vast majority of studies have explored trade-offs with tolerance within species. Here, we test hypotheses of constraints on tolerance using comparative approaches in a clade of mustards, emphasizing the variety of contexts in which damage is realistically tolerated. We estimated tolerance to leaf damage, tolerance to apical clipping at the bolting stage– simulating browsing–, and resistance to a specialist and generalist lepidopteran herbivore for a group of native mustards, grown in field soils unique to each population and in a common potting soil. Resistance to herbivores was soil dependent, while surprisingly, tolerance was not. Phylogenetic signal in resistance to specialist and generalist lepidopteran herbivores was present, but only when plants were grown in field soils. Tolerance had low phylogenetic signal. Tolerance to leaf damage was unrelated to tolerance to simulated browse. We found no evidence for a resistance-tolerance trade-off, and some evidence for a soil-dependent positive correlation between tolerance and resistance to both herbivores. Drought-tolerant species had poorer ability to tolerate browse damage, and earlier flowering species tended to be less tolerant to leaf damage. Our results suggest that tolerance trades off with traits that allow mostly annual, monocarpic Streptanthus (s.l.) to persist in drought-prone conditions but is largely unrelated to resistance to herbivores. Our study highlights a need for a new framework for tolerance to herbivory that explicitly acknowledges that the relationship between tolerance, resistance, and traits that ameliorate abiotic stress.This article is protected by copyright. All rights reserved.
      PubDate: 2017-08-24T00:10:24.573393-05:
      DOI: 10.1002/ecy.1995
       
  • LCE: Leaf carbon exchange dataset for tropical, temperate, and boreal
           species of North and Central America
    • Authors: Nicholas G. Smith; Jeffrey S. Dukes
      Abstract: Leaf canopy carbon exchange processes, such as photosynthesis and respiration, are substantial components of the global carbon cycle. Climate models base their simulations of photosynthesis and respiration on an empirical understanding of the underlying biochemical processes, and the responses of those processes to environmental drivers. As such, data spanning large spatial scales are needed to evaluate and parameterize these models. Here, we present data on four important biochemical parameters defining leaf carbon exchange processes from 626 individuals of 98 species at 12 North and Central American sites spanning ~53° of latitude. The four parameters are the maximum rate of Rubisco carboxylation (Vcmax), the maximum rate of electron transport for the regeneration of Ribulose-1,5,-bisphosphate (Jmax), the maximum rate of phosphoenolpyruvate carboxylase carboxylation (Vpmax), and leaf dark respiration (Rd). The raw net photosynthesis by intercellular CO2 (A/Ci) data used to calculate Vcmax, Jmax, and Vpmax rates are also presented. Data were gathered on the same leaf of each individual (one leaf per individual), allowing for the examination of each parameter relative to others. Additionally, the dataset contains a number of covariates for the plants measured. Covariate data include (a) leaf-level traits (leaf mass, leaf area, leaf nitrogen and carbon content, predawn leaf water potential), (b) plant-level traits (plant height for herbaceous individuals and diameter at breast height for trees), (c) soil moisture at the time of measurement, (d) air temperature from nearby weather stations for the day of measurement and each of the 90 days prior to measurement, and (e) climate data (growing season mean temperature, precipitation, photosynthetically active radiation, vapor pressure deficit, and aridity index). We hope that the data will be useful for obtaining greater understanding of the abiotic and biotic determinants of these important biochemical parameters and for evaluating and improving large-scale models of leaf carbon exchange.This article is protected by copyright. All rights reserved.
      PubDate: 2017-08-20T21:35:30.552664-05:
      DOI: 10.1002/ecy.1992
       
  • Demographic drivers of functional composition dynamics
    • Authors: Robert Muscarella; Madelon Lohbeck, Miguel Martínez-Ramos, Lourens Poorter, Jorge Enrique Rodríguez-Velázquez, Michiel van Breugel, Frans Bongers
      Abstract: Mechanisms of community assembly and ecosystem function are often analyzed using community-weighted mean trait values (CWMs). We present a novel conceptual framework to quantify the contribution of demographic processes (i.e., growth, recruitment, and mortality) to temporal changes in CWMs. We used this framework to analyze mechanisms of secondary succession in wet tropical forests in Mexico. Seed size increased over time, reflecting a trade-off between colonization by small seeds early in succession, to establishment by large seeds later in succession. Specific leaf area (SLA) and leaf phosphorus content decreased over time, reflecting a trade-off between fast growth early in succession versus high survival late in succession. On average, CWM shifts were driven mainly (70%) by growth of surviving trees that comprise the bulk of standing biomass, then mortality (25%), and weakly by recruitment (5%). Trait shifts of growing and recruiting trees mirrored the CWM trait shifts, and traits of dying trees did not change during succession, indicating that these traits are important for recruitment and growth, but not for mortality, during the first 30 years of succession. Identifying the demographic drivers of functional composition change links population dynamics to community change, and enhances insights into mechanisms of succession.This article is protected by copyright. All rights reserved.
      PubDate: 2017-08-20T21:30:24.729527-05:
      DOI: 10.1002/ecy.1990
       
  • Gaps contribute tree diversity to a tropical floodplain forest
    • Authors: John Terborgh; Nohemi Huanca Nuñez, Patricia Alvarez Loayza, Fernando Cornejo Valverde
      Abstract: Treefall gaps have long been a central feature of discussions about the maintenance of tree diversity in both temperate and tropical forests. Gaps expose parts of the forest floor to direct sunlight and create a distinctive microenvironment that can favor the recruitment into the community of so-called gap pioneers. This traditional view enjoys strong empirical support yet has been cast into doubt by a much-cited article claiming that gaps are inherently “neutral” in their contribution to forest dynamics. We present concurrent data on seedfall and sapling recruitment into gaps vs. under a vertically structured canopy in an Amazonian floodplain forest in Perú. Our results strongly uphold the view of gaps as important generators of tree diversity. Our methods differed significantly from those employed by the neutralist group and can explain the contrasting outcomes. We found that seedfall into gaps differs both quantitatively and qualitatively from that falling under a multi-tiered canopy, being greatly enriched in wind-dispersed and autochorus species and sharply deficient in all types of zoochorous seeds. Despite a reduced input of zoochorous seeds, zoochorous species made up 79% of saplings recruiting into gaps, whereas wind-dispersed species made up only 1%. Cohorts of saplings recruiting into gaps are less diverse than those recruiting under a closed canopy (Fisher's alpha = 40 vs. 100) and compositionally distinct, containing many light-demanding species that rarely, if ever, recruit under shaded conditions. Saplings recruiting into gaps appear to represent a variable mix of shade-tolerant survivors of the initiating treefall and sun-demanding species that germinate subsequently.This article is protected by copyright. All rights reserved.
      PubDate: 2017-08-20T21:30:21.546063-05:
      DOI: 10.1002/ecy.1991
       
  • Physical calculations of resistance to water loss improve predictions of
           species range models: Comment
    • Authors: Keith A. Christian; Christopher R. Tracy, C.Richard Tracy
      Abstract: In an attempt to improve estimates of evaporative water loss (EWL) as a component of species distribution models, Riddell et al. (2017) compared the traditional method for empirically measuring skin resistance (ri) to that determined by a mathematical model based in physics. They argued that the resulting differences between these two approaches had implications for estimates of species range.This article is protected by copyright. All rights reserved.
      PubDate: 2017-08-08T06:01:09.438065-05:
      DOI: 10.1002/ecy.1982
       
  • Bottom-up processes influence the demography and life-cycle phenology of
           Hawaiian bird communities
    • Authors: Jared D. Wolfe; C.John Ralph, Andrew Wiegardt
      Abstract: Changes in climate can indirectly regulate populations at higher trophic levels by influencing the availability of food resources in the lower reaches of the food web. As such, species that rely on fruit and nectar food resources may be particularly sensitive to these bottom-up perturbations due to the strength of their trophic linkages with climatically-influenced plants. To measure the influence of climatically-mediated, bottom-up processes, we used climate, bird capture, bird count, and plant phenology data from the Big Island of Hawaii to construct a series of structural equation and abundance models. Our results suggest that fruit and nectar-eating birds arrange life cycle events around climatically-influenced food resources, while some of these same food resources also influence seasonal patterns of abundance. This trend was particularly strong for two native nectarivores, ‘I'iwi and ‘Apapane, where we found that the dissimilar timing of molting and breeding activity was associated with peak abundance of the two most common flowers at our study site which, in turn, were each driven by dissimilar climatic cues. Given the rapidly changing Hawaiian climate, we suggest that determining behavioral plasticity, or evolutionary capacity of birds to mitigate changes in climatically-influenced food resources, should be recognized as a future research priority.This article is protected by copyright. All rights reserved.
      PubDate: 2017-08-05T06:45:20.307455-05:
      DOI: 10.1002/ecy.1981
       
  • Increased duration of aquatic resource pulse alters community and
           ecosystem responses in a subarctic plant community
    • Authors: Claudio Gratton; David Hoekman, Jamin Dreyer, Randall D. Jackson
      Abstract: Allochthonous resource movement across ecosystem boundaries creates episodic linkages between ecosystems. The sensitivity of the community to external resources of varying duration can alter the baseline upon which future pulses of allochthony can act. We explored the terrestrial ecosystem response to pulsed inputs of lake-derived resources with a manipulative experiment in a subarctic heathland where we assessed plant community and nutrient availability responses to additions of midge carcasses (Diptera: Chironomidae). Insect carcasses were added as either a one-time pulse or a 4-year press to simulate differing durations of allochthony, which is common in the area. We found that midge pulses significantly elevated soil inorganic [N] in the first year (7× over background levels) but were significantly diminished (1.5×) by the second year after the initial pulse. The press treatment continued to elevate total soil inorganic [N] to 13× over background levels by the fourth year of midge additions, but then declined to 3.6× background in year 5 when experimental midge additions had ceased. In contrast to the soil inorganic N response, plant biomass was similar in pulse-addition and control plots over the course of the experiment. However, by the second year of the study plant biomass in press-addition plots were significantly higher than controls (>50%), and continued to increase over the 4 years of the press treatment. Midge addition stimulated dominance of graminoids and thatch litter in plots that had previously been primarily heathland vegetation, a response that persisted four years post-midge addition. Our findings suggest that soil and plant community responses to persistent insect carcass deposition (e.g., press) into heathland vegetation has the potential to carry forward in a way that modifies the baseline ecosystem conditions upon which additional allochthony may act.This article is protected by copyright. All rights reserved.
      PubDate: 2017-08-03T10:50:28.168029-05:
      DOI: 10.1002/ecy.1977
       
  • Parallel environmental factors drive variation in insect density and plant
           resistance in the native and invaded ranges
    • Authors: Yuzu Sakata; Timothy P. Craig, Joanne K. Itami, Michimasa Yamasaki, Takayuki Ohgushi
      Abstract: Geographic variation in the traits of a species is shaped by variation in abiotic conditions, biotic interactions, and evolutionary history of its interactions with other species. We studied the geographic variation in the density of the lace bug, Corythucha marmorata, and the resistance of tall goldenrod Solidago altissima to the lace bug herbivory in their native range in the USA and invaded range in Japan. We conducted field surveys and reciprocal transplant experiments to examine what abiotic and biotic factors influence variation in lace bug density, and what ecological and evolutionary factors predict the resistance of the host plant between and within the native and invaded ranges. Lace bug density was higher throughout the invaded range than in the native range, higher in populations with warmer climates, and negatively affected by foliage damage by other insects in both ranges. The higher lace bug density in warmer climates was explained by the shorter developmental time of the lace bugs at higher temperatures. The resistance of S. altissima to lace bugs was higher in populations with lace bugs compared to populations without lace bugs in both native and invaded ranges, indicating that the evolutionary history of the interaction with the lace bugs was responsible for the variation in S. altissima resistance in both ranges. The present study revealed that abiotic and biotic factors, including temperature and other herbivorous insects, can drive the geographic variation in lace bug density, which in turn selects for variation in plant resistance in both in the native and invaded ranges. We conclude that the novel combination of factors such as higher temperature and lower number of other herbivorous insects is responsible for the higher lace bug density in the invaded range than in the native range.This article is protected by copyright. All rights reserved.
      PubDate: 2017-08-03T10:45:24.770317-05:
      DOI: 10.1002/ecy.1978
       
  • Allocation, not male resistance, increases male frequency during
           epidemics: A case study in facultatively sexual hosts
    • Authors: Jessica L. Hite; Rachel M. Penczykowski, Marta S. Shocket, Katherine Griebel, Alexander T. Strauss, Meghan A. Duffy, Carla E. Cáceres, Spencer R. Hall
      Abstract: Why do natural populations vary in the frequency of sexual reproduction' Virulent parasites may help explain why sex is favored during disease epidemics. To illustrate, we show a higher frequency of males and sexually produced offspring in natural populations of a facultative parthenogenetic host during fungal epidemics. In a multi-year survey of 32 lakes, the frequency of males (an index of sex) was higher in populations of zooplankton hosts with larger epidemics. A lake mesocosm experiment established causality: experimental epidemics produced a higher frequency of males relative to disease-free controls. One common explanation for such a pattern involves Red Queen (RQ) dynamics. However, this particular system lacks key genetic specificity mechanisms required for the RQ, so we evaluated two other hypotheses. First, individual females, when stressed by infection, could increase production of male offspring vs. female offspring (a tenant of ‘Abandon Ship’ theory). Data from a life table experiment supports this mechanism. Second, higher male frequency during epidemics could reflect a purely demographic process (illustrated with a demographic model): males could resist infection more than females (via size-based differences in resistance and mortality). However, we found no support for this resistance mechanism. A size-based model of resistance, parameterized with data, revealed why: higher male susceptibility negated the lower exposure (a size-based advantage) of males. These results suggest that parasite-mediated increases in allocation to sex by individual females, rather than male resistance, increased the frequency of sex during larger disease epidemics.This article is protected by copyright. All rights reserved.
      PubDate: 2017-08-02T03:35:27.757728-05:
      DOI: 10.1002/ecy.1976
       
  • Warming effects on permafrost ecosystem carbon fluxes associated with
           plant nutrients
    • Authors: Fei Li; Yunfeng Peng, Susan M. Natali, Kelong Chen, Tianfeng Han, Guibiao Yang, Jinzhi Ding, Dianye Zhang, Guanqin Wang, Jun Wang, Jianchun Yu, Futing Liu, Yuanhe Yang
      Abstract: Large uncertainties exist in carbon (C)-climate feedback in permafrost regions, partly due to an insufficient understanding of warming effects on nutrient availabilities and their subsequent impacts on vegetation C sequestration. Although a warming climate may promote a substantial release of soil C to the atmosphere, a warming-induced increase in soil nutrient availability may enhance plant productivity, thus offsetting C loss from microbial respiration. Here, we present evidence that the positive temperature effect on carbon dioxide (CO2) fluxes may be weakened by reduced plant nitrogen (N) and phosphorous (P) concentrations in a Tibetan permafrost ecosystem. Although experimental warming initially enhanced ecosystem CO2 uptake, the increased rate disappeared after the period of peak plant growth during the early growing season, even though soil moisture was not a limiting factor in this swamp meadow ecosystem. We observed that warming did not significantly affect soil extractable N or P during the period of peak growth, but decreased both N and P concentrations in the leaves of dominant plant species, likely caused by accelerated plant senescence in the warmed plots. The attenuated warming effect on CO2 assimilation during the late growing season was associated with lowered leaf N and P concentrations. These findings suggest that warming-mediated nutrient changes may not always benefit ecosystem C uptake in permafrost regions, making our ability to predict the C balance in these warming-sensitive ecosystems more challenging than previously thought.This article is protected by copyright. All rights reserved.
      PubDate: 2017-08-02T03:30:47.472617-05:
      DOI: 10.1002/ecy.1975
       
  • Predicting coexistence in species with continuous ontogenetic niche shifts
           and competitive asymmetry
    • Authors: Ronald D. Bassar; Joseph Travis, Tim Coulson
      Abstract: A longstanding problem in ecology is whether structured life cycles impede or facilitate coexistence between species. Theory based on populations with only two discrete stages in the life-cycle indicates that for two species to coexist, at least one must shift its niche between stages and each species must be a better competitor in one of the niches. However, in many cases, niche shifts are associated with changes in an underlying continuous trait like body size and we have few predictions concerning conditions for coexistence for such a widespread form of ontogenetic development. We develop a framework for analyzing species coexistence based on Integral Projection Models (IPMs) that incorporates continuous ontogenetic changes in both the resource niche and competitive ability. We parameterize the model using experimental data from Trinidadian guppies and show how niche shifts and competitive symmetries impact species coexistence. Overall, our results show that the effects of competition on fitness depend upon trait-mediated niche-separation, trait-mediated competitive asymmetry in the part of the niche that is shared across body sizes, and the sensitivity of fitness to body size. Interactions among these processes generate multiple routes to coexistence. We discuss how our modelling framework expands results from two-stage models to mutli-stage or continuous stage models and allows for deriving predictions that can be tested in populations displaying continuous changes in niche use and competitive ability.This article is protected by copyright. All rights reserved.
      PubDate: 2017-08-02T03:20:33.892351-05:
      DOI: 10.1002/ecy.1969
       
  • Detecting population-environmental interactions with mismatched time
           series data
    • Authors: Jake M. Ferguson; Brian E. Reichert, Robert J. Fletcher, Henriëtte I. Jager
      Abstract: Time series analysis is an essential method for decomposing the influences of density and exogenous factors such as weather and climate on population regulation. However, there has been little work focused on understanding how well commonly collected data can reconstruct the effects of environmental factors on population dynamics. We show that analogous to similar scale issues in spatial data analysis, coarsely sampled temporal data can fail to detect covariate effects when interactions occur on timescales that are fast relative to the survey period. We propose a method for modeling mismatched time series data that couples high-resolution environmental data to low-resolution abundance data. We illustrate our approach with simulations and by applying it to Florida's southern snail kite population. Our simulation results show that our method can reliably detect linear environmental effects and that detecting nonlinear effects requires high-resolution covariate data even when the population turnover rate is slow. In the snail kite analysis our approach performed among the best in a suite of previously used environmental covariates explaining snail kite dynamics and was able to detect a potential phenological shift in the environmental dependence of snail kites. Our work provides a statistical framework for reliably detecting population-environment interactions from coarsely surveyed time series. An important implication of this work is that the low predictability of animal population growth by weather variables found in previous studies may be due, in part, to how these data are utilized as covariates.
      PubDate: 2017-07-31T10:45:20.132625-05:
      DOI: 10.1002/ecy.1966
       
  • Spatial and temporal drivers of avian population dynamics across the
           annual cycle
    • Authors: Clark S. Rushing; Jeffrey A. Hostetler, T. Scott Sillett, Peter P. Marra, James A. Rotenberg, Thomas B. Ryder
      Abstract: Untangling the spatial and temporal processes that influence population dynamics of migratory species is challenging, because changes in abundance are shaped by variation in vital rates across heterogeneous habitats and throughout the annual cycle. We developed a full-annual-cycle, integrated population model and used demographic data collected between 2011 and 2014 in southern Indiana and Belize to estimate stage-specific vital rates of a declining migratory songbird, the Wood Thrush (Hylocichla mustelina). Our primary objective was to understand how spatial and temporal variation in demography contributes to local and regional population growth. Our full-annual-cycle model allowed us to estimate: 1) age-specific, seasonal survival probabilities, including latent survival during both spring and autumn migration, and 2) how the relative contribution of vital rates to population growth differed among habitats. Wood Thrushes in our study populations experienced the lowest apparent survival rates during migration and apparent survival was lower during spring migration than during fall migration. Both mortality and high dispersal likely contributed to low apparent survival during spring migration. Population growth in high-quality habitat was most sensitive to variation in fecundity and apparent survival of juveniles during spring migration, whereas population growth in low-quality sites was most sensitive to adult apparent breeding-season survival. These results elucidate how full-annual-cycle vital rates, particularly apparent survival during migration, interact with spatial variation in habitat quality to influence population dynamics in migratory species.
      PubDate: 2017-07-30T06:20:23.792169-05:
      DOI: 10.1002/ecy.1967
       
  • Issue Information
    • Pages: 2739 - 2742
      PubDate: 2017-11-01T11:10:20.68479-05:0
      DOI: 10.1002/ecy.2046
       
  • Digging for roots
    • Authors: William Jordan
      Pages: 2982 - 2984
      PubDate: 2017-11-01T11:10:17.959298-05:
      DOI: 10.1002/ecy.1971
       
  • Meet mazaalai: the most critically endangered bear on the planet
    • Authors: Roberta K. Newbury
      Pages: 2984 - 2985
      PubDate: 2017-11-01T11:10:14.456455-05:
      DOI: 10.1002/ecy.1972
       
  • Longterm ecosystem change
    • Authors: Clifford A. White
      Pages: 2986 - 2987
      PubDate: 2017-11-01T11:10:18.086208-05:
      DOI: 10.1002/ecy.1974
       
  • Recent Publications of Interest
    • Pages: 2988 - 2989
      PubDate: 2017-11-01T11:10:19.050366-05:
      DOI: 10.1002/ecy.1973
       
  • Books and Monographs Received through June 2017
    • Pages: 2988 - 2988
      PubDate: 2017-11-01T11:10:14.062295-05:
      DOI: 10.1002/ecy.1970
       
 
 
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