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Journal Cover Ecology Letters
  [SJR: 8.63]   [H-I: 184]   [218 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1461-023X - ISSN (Online) 1461-0248
   Published by John Wiley and Sons Homepage  [1579 journals]
  • Stoichiometric distribution models: ecological stoichiometry at the
           landscape extent
    • Authors: Shawn J. Leroux; Eric Vander Wal, Yolanda F. Wiersma, Louis Charron, Jonathan D. Ebel, Nichola M. Ellis, Christopher Hart, Emilie Kissler, Paul W. Saunders, Lucie Moudrá, Amy L. Tanner, Semra Yalcin
      Abstract: Human activities are altering the fundamental geography of biogeochemicals. Yet we lack an understanding of how the spatial patterns in organismal stoichiometry affect biogeochemical processes and the tools to predict the impacts of global changes on biogeochemical processes. In this contribution we develop stoichiometric distribution models (StDMs), which allow us to map spatial structure in resource elemental composition across a landscape and evaluate spatial responses of consumers. We parameterise StDMs for a consumer-resource (moose-white birch) system and demonstrate that we can develop predictive models of resource stoichiometry across a landscape and that such models could improve our predictions of consumer space use. With results from our study system application, we argue that explicit consideration of the spatial patterns in organismal elemental composition may uncover emergent individual, population, community and ecosystem properties that are not revealed at the local extents routinely used in ecological stoichiometry. We discuss perspectives for further developments and application of StDMs to advance three emerging frameworks for spatial ecosystem ecology in an era of global change; meta-ecosystem theory, macroecological stoichiometry and remotely sensed biogeochemistry. Progress on these emerging frameworks will allow for the integration of ecological stoichiometry and individual space use and fitness.
      PubDate: 2017-10-12T21:50:53.134718-05:
      DOI: 10.1111/ele.12859
  • Species are not most abundant in the centre of their geographic range or
           climatic niche
    • Authors: Tad Dallas; Robin R. Decker, Alan Hastings
      Abstract: The pervasive idea that species should be most abundant in the centre of their geographic range or centre of their climatic niche is a key assumption in many existing ecological hypotheses and has been declared a general macroecological rule. However, empirical support for decreasing population abundance with increasing distance from geographic range or climatic niche centre (distance–abundance relationships) remains fairly weak. We examine over 1400 bird, mammal, fish and tree species to provide a thorough test of distance–abundance relationships, and their associations with species traits and phylogenetic relationships. We failed to detect consistent distance–abundance relationships, and found no association between distance–abundance slope and species traits or phylogenetic relatedness. Together, our analyses suggest that distance–abundance relationships may be rare, difficult to detect, or are an oversimplification of the complex biogeographical forces that determine species spatial abundance patterns.
      PubDate: 2017-10-12T21:50:34.144196-05:
      DOI: 10.1111/ele.12860
  • Ecological plant epigenetics: Evidence from model and non-model species,
           and the way forward
    • Authors: Christina L. Richards; Conchita Alonso, Claude Becker, Oliver Bossdorf, Etienne Bucher, Maria Colomé-Tatché, Walter Durka, Jan Engelhardt, Bence Gaspar, Andreas Gogol-Döring, Ivo Grosse, Thomas P. van Gurp, Katrin Heer, Ilkka Kronholm, Christian Lampei, Vít Latzel, Marie Mirouze, Lars Opgenoorth, Ovidiu Paun, Sonja J. Prohaska, Stefan A. Rensing, Peter F. Stadler, Emiliano Trucchi, Kristian Ullrich, Koen J. F. Verhoeven
      Abstract: Growing evidence shows that epigenetic mechanisms contribute to complex traits, with implications across many fields of biology. In plant ecology, recent studies have attempted to merge ecological experiments with epigenetic analyses to elucidate the contribution of epigenetics to plant phenotypes, stress responses, adaptation to habitat, and range distributions. While there has been some progress in revealing the role of epigenetics in ecological processes, studies with non-model species have so far been limited to describing broad patterns based on anonymous markers of DNA methylation. In contrast, studies with model species have benefited from powerful genomic resources, which contribute to a more mechanistic understanding but have limited ecological realism. Understanding the significance of epigenetics for plant ecology requires increased transfer of knowledge and methods from model species research to genomes of evolutionarily divergent species, and examination of responses to complex natural environments at a more mechanistic level. This requires transforming genomics tools specifically for studying non-model species, which is challenging given the large and often polyploid genomes of plants. Collaboration among molecular geneticists, ecologists and bioinformaticians promises to enhance our understanding of the mutual links between genome function and ecological processes.
      PubDate: 2017-10-12T21:35:27.554074-05:
      DOI: 10.1111/ele.12858
  • Species reordering, not changes in richness, drives long-term dynamics in
           grassland communities
    • Authors: Sydney K. Jones; Julie Ripplinger, Scott L. Collins
      Abstract: Determining how ecological communities will respond to global environmental change remains a challenging research problem. Recent meta-analyses concluded that most communities are undergoing compositional change despite no net change in local species richness. We explored how species richness and composition of co-occurring plant, grasshopper, breeding bird and small mammal communities in arid and mesic grasslands changed in response to increasing aridity and fire frequency. In the arid system, grassland and shrubland plant and breeding bird communities were undergoing directional change, whereas grasshopper and small mammal communities were stable. In the mesic system, all communities were undergoing directional change regardless of fire frequency. Despite directional change in composition in some communities, species richness of all communities did not change because compositional change resulted more from reordering of species abundances than turnover in species composition. Thus, species reordering, not changes in richness, explains long-term dynamics in these grass and shrub dominated communities.
      PubDate: 2017-10-12T19:50:38.146624-05:
      DOI: 10.1111/ele.12864
  • Ecological generalism facilitates the evolution of sociality in snapping
    • Authors: Katherine C. Brooks; Rafael Maia, J. Emmett Duffy, Kristin M. Hultgren, Dustin R. Rubenstein
      Abstract: Evidence from insects and vertebrates suggests that cooperation may have enabled species to expand their niches, becoming ecological generalists and dominating the ecosystems in which they occur. Consistent with this idea, eusocial species of sponge-dwelling Synalpheus shrimps from Belize are ecological generalists with a broader host breadth and higher abundance than non-eusocial species. We evaluate whether sociality promotes ecological generalism (social conquest hypothesis) or whether ecological generalism facilitates the transition to sociality (social transition hypothesis) in 38 Synalpheus shrimp species. We find that sociality evolves primarily from host generalists, and almost exclusively so for transitions to eusociality. Additionally, sponge volume is more important for explaining social transitions towards communal breeding than to eusociality, suggesting that different ecological factors may influence the independent evolutionary origins of sociality in Synalpheus shrimps. Ultimately, our results are consistent with the social transition hypothesis and the idea that ecological generalism facilitates the transition to sociality.
      PubDate: 2017-10-04T20:10:34.37065-05:0
      DOI: 10.1111/ele.12857
  • Distance-dependent seedling mortality and long-term spacing dynamics in a
           neotropical forest community
    • Authors: Stephen J. Murphy; Thorsten Wiegand, Liza S. Comita
      Abstract: Negative distance dependence (NDisD), or reduced recruitment near adult conspecifics, is thought to explain the astounding diversity of tropical forests. While many studies show greater mortality at near vs. far distances from adults, these studies do not seek to track changes in the peak seedling curve over time, thus limiting our ability to link NDisD to coexistence. Using census data collected over 12 years from central Panama in conjunction with spatial mark-connection functions, we show evidence for NDisD for many species, and find that the peak seedling curve shifts away from conspecific adults over time. We find wide variation in the strength of NDisD, which was correlated with seed size and canopy position, but other life-history traits showed no relationship with variation in NDisD mortality. Our results document shifts in peak seedling densities over time, thus providing evidence for the hypothesized spacing mechanism necessary for diversity maintenance in tropical forests.
      PubDate: 2017-10-04T20:05:57.760062-05:
      DOI: 10.1111/ele.12856
  • Interannual bumble bee abundance is driven by indirect climate effects on
           floral resource phenology
    • Authors: Jane E. Ogilvie; Sean R. Griffin, Zachariah J. Gezon, Brian D. Inouye, Nora Underwood, David W. Inouye, Rebecca E. Irwin
      Abstract: Climate change can influence consumer populations both directly, by affecting survival and reproduction, and indirectly, by altering resources. However, little is known about the relative importance of direct and indirect effects, particularly for species important to ecosystem functioning, like pollinators. We used structural equation modelling to test the importance of direct and indirect (via floral resources) climate effects on the interannual abundance of three subalpine bumble bee species. In addition, we used long-term data to examine how climate and floral resources have changed over time. Over 8 years, bee abundances were driven primarily by the indirect effects of climate on the temporal distribution of floral resources. Over 43 years, aspects of floral phenology changed in ways that indicate species-specific effects on bees. Our study suggests that climate-driven alterations in floral resource phenology can play a critical role in governing bee population responses to global change.
      PubDate: 2017-09-28T23:05:02.771882-05:
      DOI: 10.1111/ele.12854
  • Ice ages leave genetic diversity ‘hotspots’ in Europe but not
           in Eastern North America
    • Authors: Candice Y. Lumibao; Sean M. Hoban, Jason McLachlan
      Abstract: After the last glacial cycle, temperate European trees migrated northward, experiencing genetic bottlenecks and founder effects, which left high haplotype endemism in southern populations and clines in genetic diversity northward. These patterns are thought to be ubiquitous across temperate forests, and are therefore used to anticipate the potential genetic consequences of future warming. We compared existing and new phylogeographic data sets (chloroplast DNA) from 14 woody taxa in Eastern North America (ENA) to data sets from 21 ecologically similar European species to test for common impacts of Quaternary climate swings on genetic diversity across diverse taxa and between continents. Unlike their European counterparts, ENA taxa do not share common southern centres of haplotype endemism and they generally maintain high genetic diversity even at their northern range limits. Differences between the genetic impacts of Quaternary climate cycles across continents suggest refined lessons for managing genetic diversity in today's warming world.
      PubDate: 2017-09-24T18:55:28.011929-05:
      DOI: 10.1111/ele.12853
  • Evidence of developmental niche construction in dung beetles: effects on
           growth, scaling and reproductive success
    • Authors: Daniel B. Schwab; Sofia Casasa, Armin P. Moczek
      Abstract: Niche construction occurs when organisms modify their environments and alter selective conditions through their physiology and behaviours. Such modifications can bias phenotypic variation and enhance organism–environment fit. Yet few studies exist that experimentally assess the degree to which environmental modifications shape developmental and fitness outcomes, how their influences may differ among species and identify the underlying proximate mechanisms. Here, we experimentally eliminate environmental modifications from the developmental environment of Onthophagus dung beetles. We show that these modifications (1) differentially influence growth among species, (2) consistently shape scaling relationships in fitness-related traits, (3) are necessary for the maintenance of sexual dimorphism, (4) influence reproductive success among females of at least one species and (5) implicate larval cultivation of an external rumen as a possible mechanism for environmental modification. Our results present evidence that Onthophagus larvae engage in niche construction, and that this is a fundamental component of beetle development and fitness.
      PubDate: 2017-09-24T18:50:27.883025-05:
      DOI: 10.1111/ele.12830
  • Opposing mechanisms affect taxonomic convergence between tree assemblages
           during tropical forest succession
    • Authors: Natalia Norden; Vanessa Boukili, Anne Chao, K. H. Ma, Susan G. Letcher, Robin L. Chazdon
      Abstract: Whether successional forests converge towards an equilibrium in species composition remains an elusive question, hampered by high idiosyncrasy in successional dynamics. Based on long-term tree monitoring in second-growth (SG) and old-growth (OG) forests in Costa Rica, we show that patterns of convergence between pairs of forest stands depend upon the relative abundance of species exhibiting distinct responses to the successional gradient. For instance, forest generalists contributed to convergence between SG and OG forests, whereas rare species and old-growth specialists were a source of divergence. Overall, opposing trends in taxonomic similarity among different subsets of species nullified each other, producing a net outcome of stasis over time. Our results offer an explanation for the limited convergence observed between pairwise communities and suggest that rare species and old-growth specialists may be prone to dispersal limitation, while the dynamics of generalists and second-growth specialists are more predictable, enhancing resilience in tropical secondary forests.
      PubDate: 2017-09-20T18:30:32.365134-05:
      DOI: 10.1111/ele.12852
  • Species richness effects on grassland recovery from drought depend on
           community productivity in a multisite experiment
    • Authors: Juergen Kreyling; Jürgen Dengler, Julia Walter, Nikolay Velev, Emin Ugurlu, Desislava Sopotlieva, Johannes Ransijn, Catherine Picon-Cochard, Ivan Nijs, Pauline Hernandez, Behlül Güler, Philipp Gillhaussen, Hans J. De Boeck, Juliette M.G. Bloor, Sigi Berwaers, Carl Beierkuhnlein, Mohammed A.S. Arfin Khan, Iva Apostolova, Yasin Altan, Michaela Zeiter, Camilla Wellstein, Marcelo Sternberg, Andreas Stampfli, Giandiego Campetella, Sándor Bartha, Michael Bahn, Anke Jentsch
      Abstract: Biodiversity can buffer ecosystem functioning against extreme climatic events, but few experiments have explicitly tested this. Here, we present the first multisite biodiversity × drought manipulation experiment to examine drought resistance and recovery at five temperate and Mediterranean grassland sites. Aboveground biomass production declined by 30% due to experimental drought (standardised local extremity by rainfall exclusion for 72–98 consecutive days). Species richness did not affect resistance but promoted recovery. Recovery was only positively affected by species richness in low-productive communities, with most diverse communities even showing overcompensation. This positive diversity effect could be linked to asynchrony of species responses. Our results suggest that a more context-dependent view considering the nature of the climatic disturbance as well as the productivity of the studied system will help identify under which circumstances biodiversity promotes drought resistance or recovery. Stability of biomass production can generally be expected to decrease with biodiversity loss and climate change.
      PubDate: 2017-09-20T18:25:42.885918-05:
      DOI: 10.1111/ele.12848
  • Biodiversity and ecosystem functioning relations in European forests
           depend on environmental context
    • Authors: Sophia Ratcliffe; Christian Wirth, Tommaso Jucker, Fons der Plas, Michael Scherer-Lorenzen, Kris Verheyen, Eric Allan, Raquel Benavides, Helge Bruelheide, Bettina Ohse, Alain Paquette, Evy Ampoorter, Cristina C. Bastias, Jürgen Bauhus, Damien Bonal, Olivier Bouriaud, Filippo Bussotti, Monique Carnol, Bastien Castagneyrol, Ewa Chećko, Seid Muhie Dawud, Hans De Wandeler, Timo Domisch, Leena Finér, Markus Fischer, Mariangela Fotelli, Arthur Gessler, André Granier, Charlotte Grossiord, Virginie Guyot, Josephine Haase, Stephan Hättenschwiler, Hervé Jactel, Bogdan Jaroszewicz, François-Xavier Joly, Stephan Kambach, Simon Kolb, Julia Koricheva, Mario Liebersgesell, Harriet Milligan, Sandra Müller, Bart Muys, Diem Nguyen, Charles Nock, Martina Pollastrini, Oliver Purschke, Kalliopi Radoglou, Karsten Raulund-Rasmussen, Fabian Roger, Paloma Ruiz-Benito, Rupert Seidl, Federico Selvi, Ian Seiferling, Jan Stenlid, Fernando Valladares, Lars Vesterdal, Lander Baeten
      Abstract: The importance of biodiversity in supporting ecosystem functioning is generally well accepted. However, most evidence comes from small-scale studies, and scaling-up patterns of biodiversity–ecosystem functioning (B-EF) remains challenging, in part because the importance of environmental factors in shaping B-EF relations is poorly understood. Using a forest research platform in which 26 ecosystem functions were measured along gradients of tree species richness in six regions across Europe, we investigated the extent and the potential drivers of context dependency of B-EF relations. Despite considerable variation in species richness effects across the continent, we found a tendency for stronger B-EF relations in drier climates as well as in areas with longer growing seasons and more functionally diverse tree species. The importance of water availability in driving context dependency suggests that as water limitation increases under climate change, biodiversity may become even more important to support high levels of functioning in European forests.
      PubDate: 2017-09-18T19:40:45.086286-05:
      DOI: 10.1111/ele.12849
  • Modelling time to population extinction when individual reproduction is
    • Authors: Aline Magdalena Lee; Bernt-Erik Sæther, Stine Svalheim Markussen, Steinar Engen
      Abstract: In nature, individual reproductive success is seldom independent from year to year, due to factors such as reproductive costs and individual heterogeneity. However, population projection models that incorporate temporal autocorrelations in individual reproduction can be difficult to parameterise, particularly when data are sparse. We therefore examine whether such models are necessary to avoid biased estimates of stochastic population growth and extinction risk, by comparing output from a matrix population model that incorporates reproductive autocorrelations to output from a standard age-structured matrix model that does not. We use a range of parameterisations, including a case study using moose data, treating probabilities of switching reproductive class as either fixed or fluctuating. Expected time to extinction from the two models is found to differ by only small amounts (under 10%) for most parameterisations, indicating that explicitly accounting for individual reproductive autocorrelations is in most cases not necessary to avoid bias in extinction estimates.
      PubDate: 2017-09-18T19:30:48.878961-05:
      DOI: 10.1111/ele.12834
  • Plant resistance to drought depends on timely stomatal closure
    • Authors: Nicolas Martin-StPaul; Sylvain Delzon, Hervé Cochard
      Abstract: Stomata play a significant role in the Earth's water and carbon cycles, by regulating gaseous exchanges between the plant and the atmosphere. Under drought conditions, stomatal control of transpiration has long been thought to be closely coordinated with the decrease in hydraulic capacity (hydraulic failure due to xylem embolism). We tested this hypothesis by coupling a meta-analysis of functional traits related to the stomatal response to drought and embolism resistance with simulations from a soil–plant hydraulic model. We report here a previously unreported phenomenon: the existence of an absolute limit by which stomata closure must occur to avoid rapid death in drought conditions. The water potential causing stomatal closure and the xylem pressure at the onset of embolism formation were equal for only a small number of species, and the difference between these two traits (i.e. safety margins) increased continuously with increasing embolism resistance. Our findings demonstrate the need to revise current views about the functional coordination between stomata and hydraulic traits and provide a mechanistic framework for modeling plant mortality under drought conditions.
      PubDate: 2017-09-18T17:05:02.131564-05:
      DOI: 10.1111/ele.12851
  • Combined effects of agrochemicals and ecosystem services on crop yield
           across Europe
    • Authors: Vesna Gagic; David Kleijn, András Báldi, Gergely Boros, Helene Bracht Jørgensen, Zoltán Elek, Michael P. D. Garratt, G. Arjen Groot, Katarina Hedlund, Anikó Kovács-Hostyánszki, Lorenzo Marini, Emily Martin, Ines Pevere, Simon G. Potts, Sarah Redlich, Deepa Senapathi, Ingolf Steffan-Dewenter, Stanislaw Świtek, Henrik G. Smith, Viktória Takács, Piotr Tryjanowski, Wim H. van der Putten, Stijn van Gils, Riccardo Bommarco
      Abstract: Simultaneously enhancing ecosystem services provided by biodiversity below and above ground is recommended to reduce dependence on chemical pesticides and mineral fertilisers in agriculture. However, consequences for crop yield have been poorly evaluated. Above ground, increased landscape complexity is assumed to enhance biological pest control, whereas below ground, soil organic carbon is a proxy for several yield-supporting services. In a field experiment replicated in 114 fields across Europe, we found that fertilisation had the strongest positive effect on yield, but hindered simultaneous harnessing of below- and above-ground ecosystem services. We furthermore show that enhancing natural enemies and pest control through increasing landscape complexity can prove disappointing in fields with low soil services or in intensively cropped regions. Thus, understanding ecological interdependences between land use, ecosystem services and yield is necessary to promote more environmentally friendly farming by identifying situations where ecosystem services are maximised and agrochemical inputs can be reduced.
      PubDate: 2017-09-12T21:11:03.585657-05:
      DOI: 10.1111/ele.12850
  • Native insect herbivory overwhelms context dependence to limit complex
           invasion dynamics of exotic weeds
    • Authors: Emily L. Schultz; James O. Eckberg, Sergey S. Berg, Svata M. Louda, Tom E. X. Miller
      Abstract: Understanding the role of consumers in density-dependent plant population dynamics is a long-standing goal in ecology. However, the generality of herbivory effects across heterogeneous landscapes is poorly understood due to the pervasive influence of context-dependence. We tested effects of native insect herbivory on the population dynamics of an exotic thistle, Cirsium vulgare, in a field experiment replicated across eight sites in eastern Nebraska. Using hierarchical Bayesian analysis and density-dependent population models, we found potential for explosive low-density population growth (λ > 5) and complex density fluctuations under herbivore exclusion. However, herbivore access drove population decline (λ 
      PubDate: 2017-09-12T21:06:04.636301-05:
      DOI: 10.1111/ele.12833
  • No consistent pollinator-mediated impacts of alien plants on natives
    • Authors: Julia A. Charlebois; Risa D. Sargent
      Abstract: The introduction of an alien plant is widely assumed to have negative consequences for the pollinator-mediated fitness of nearby natives. Indeed, a number of studies, including a highly cited meta-analysis, have concluded that the trend for such interactions is competitive. Here we provide evidence that publication bias and study design have obscured our ability to assess the pollinator-mediated impacts of alien plants. In a meta-analysis of 76 studies, we demonstrate that alien/native status does not predict the outcome of pollinator-mediated interactions among plants. Moreover, we found no evidence that similarity in floral traits or phylogenetic distance between species pairs influences the outcome of pollinator-mediated interactions. Instead, we report that aspects of study design, such as distance between the control and nearest neighbour, and/or the arrangement of study plants better predict the impact of a neighbour than does alien/native status. Our study sheds new light on the role that publication bias and experimental design play in the evaluation of key patterns in ecology. We conclude that, due to the absence of clear, generalisable pollinator-mediated impacts of alien species, management schemes should base decisions on community-wide assessments of the impacts of individual alien plant species, and not solely on alien/native status itself.
      PubDate: 2017-09-12T21:05:51.443222-05:
      DOI: 10.1111/ele.12831
  • A ‘dynamic’ landscape of fear: prey responses to spatiotemporal
           variations in predation risk across the lunar cycle
    • Authors: M. S. Palmer; J. Fieberg, A. Swanson, M. Kosmala, C. Packer
      Abstract: Ambiguous empirical support for ‘landscapes of fear’ in natural systems may stem from failure to consider dynamic temporal changes in predation risk. The lunar cycle dramatically alters night-time visibility, with low luminosity increasing hunting success of African lions. We used camera-trap data from Serengeti National Park to examine nocturnal anti-predator behaviours of four herbivore species. Interactions between predictable fluctuations in night-time luminosity and the underlying risk-resource landscape shaped herbivore distribution, herding propensity and the incidence of ‘relaxed’ behaviours. Buffalo responded least to temporal risk cues and minimised risk primarily through spatial redistribution. Gazelle and zebra made decisions based on current light levels and lunar phase, and wildebeest responded to lunar phase alone. These three species avoided areas where likelihood of encountering lions was high and changed their behaviours in risky areas to minimise predation threat. These patterns support the hypothesis that fear landscapes vary heterogeneously in both space and time.
      PubDate: 2017-09-12T19:05:02.630917-05:
      DOI: 10.1111/ele.12832
  • Age-specific infectious period shapes dynamics of pneumonia in bighorn
    • Authors: Raina K. Plowright; Kezia R. Manlove, Thomas E. Besser, David J. Páez, Kimberly R. Andrews, Patrick E. Matthews, Lisette P. Waits, Peter J. Hudson, E. Frances Cassirer
      Abstract: Superspreading, the phenomenon where a small proportion of individuals contribute disproportionately to new infections, has profound effects on disease dynamics. Superspreading can arise through variation in contacts, infectiousness or infectious periods. The latter has received little attention, yet it drives the dynamics of many diseases of critical public health, livestock health and conservation concern. Here, we present rare evidence of variation in infectious periods underlying a superspreading phenomenon in a free-ranging wildlife system. We detected persistent infections of Mycoplasma ovipneumoniae, the primary causative agent of pneumonia in bighorn sheep (Ovis canadensis), in a small number of older individuals that were homozygous at an immunologically relevant genetic locus. Interactions among age-structure, genetic composition and infectious periods may drive feedbacks in disease dynamics that determine the magnitude of population response to infection. Accordingly, variation in initial conditions may explain divergent population responses to infection that range from recovery to catastrophic decline and extirpation.
      PubDate: 2017-09-04T19:05:02.424713-05:
      DOI: 10.1111/ele.12829
  • Direct fitness benefits explain mate preference, but not choice, for
           similarity in heterozygosity levels
    • Authors: Lies Zandberg; Gerrit Gort, Kees Oers, Camilla A. Hinde
      Abstract: Under sexual selection, mate preferences can evolve for traits advertising fitness benefits. Observed mating patterns (mate choice) are often assumed to represent preference, even though they result from the interaction between preference, sampling strategy and environmental factors. Correlating fitness with mate choice instead of preference will therefore lead to confounded conclusions about the role of preference in sexual selection. Here we show that direct fitness benefits underlie mate preferences for genetic characteristics in a unique experiment on wild great tits. In repeated mate preference tests, both sexes preferred mates that had similar heterozygosity levels to themselves, and not those with which they would optimise offspring heterozygosity. In a subsequent field experiment where we cross fostered offspring, foster parents with more similar heterozygosity levels had higher reproductive success, despite the absence of assortative mating patterns. These results support the idea that selection for preference persists despite constraints on mate choice.
      PubDate: 2017-09-03T23:40:23.487019-05:
      DOI: 10.1111/ele.12827
  • Interactions among symbionts operate across scales to influence parasite
    • Authors: Fletcher W. Halliday; James Umbanhowar, Charles E. Mitchell
      Abstract: Parasite epidemics may be influenced by interactions among symbionts, which can depend on past events at multiple spatial scales. Within host individuals, interactions can depend on the sequence in which symbionts infect a host, generating priority effects. Across host individuals, interactions can depend on parasite phenology. To test the roles of parasite interactions and phenology in epidemics, we embedded multiple cohorts of sentinel plants, grown from seeds with and without a vertically transmitted symbiont, into a wild host population, and tracked foliar infections caused by three common fungal parasites. Within hosts, parasite growth was influenced by coinfections, but coinfections were often prevented by priority effects among symbionts. Across hosts, parasite phenology altered host susceptibility to secondary infections, symbiont interactions and ultimately the magnitude of parasite epidemics. Together, these results indicate that parasite phenology can influence parasite epidemics by altering the sequence of infection and interactions among symbionts within host individuals.
      PubDate: 2017-09-03T23:26:16.649348-05:
      DOI: 10.1111/ele.12825
  • Soil fertility shapes belowground food webs across a regional climate
    • Authors: Etienne Laliberté; Paul Kardol, Raphael K. Didham, François P. Teste, Benjamin L. Turner, David A. Wardle
      Abstract: Changes in soil fertility during pedogenesis affect the quantity and quality of resources entering the belowground subsystem. Climate governs pedogenesis, yet how climate modulates responses of soil food webs to soil ageing remains unexplored because of the paucity of appropriate model systems. We characterised soil food webs along each of four retrogressive soil chronosequences situated across a strong regional climate gradient to show that belowground communities are predominantly shaped by changes in fertility rather than climate. Basal consumers showed hump-shaped responses to soil ageing, which were propagated to higher-order consumers. There was a shift in dominance from bacterial to fungal energy channels with increasing soil age, while the root energy channel was most important in intermediate-aged soils. Our study highlights the overarching importance of soil fertility in regulating soil food webs, and indicates that belowground food webs will respond more strongly to shifts in soil resources than climate change.
      PubDate: 2017-08-29T18:26:21.271206-05:
      DOI: 10.1111/ele.12823
  • Metabolic compensation constrains the temperature dependence of gross
           primary production
    • Authors: Daniel Padfield; Chris Lowe, Angus Buckling, Richard Ffrench-Constant, , Simon Jennings, Felicity Shelley, Jón S. Ólafsson, Gabriel Yvon-Durocher
      Abstract: Gross primary production (GPP) is the largest flux in the carbon cycle, yet its response to global warming is highly uncertain. The temperature dependence of GPP is directly linked to photosynthetic physiology, but the response of GPP to warming over longer timescales could also be shaped by ecological and evolutionary processes that drive variation in community structure and functional trait distributions. Here, we show that selection on photosynthetic traits within and across taxa dampens the effects of temperature on GPP across a catchment of geothermally heated streams. Autotrophs from cold streams had higher photosynthetic rates and after accounting for differences in biomass among sites, biomass-specific GPP was independent of temperature in spite of a 20 °C thermal gradient. Our results suggest that temperature compensation of photosynthetic rates constrains the long-term temperature dependence of GPP, and highlights the importance of considering physiological, ecological and evolutionary mechanisms when predicting how ecosystem-level processes respond to warming.
      PubDate: 2017-08-29T18:21:56.306357-05:
      DOI: 10.1111/ele.12820
  • Boom-bust dynamics in biological invasions: towards an improved
           application of the concept
    • Authors: David L. Strayer; Carla M. D'Antonio, Franz Essl, Mike S. Fowler, Juergen Geist, Sabine Hilt, Ivan Jarić, Klaus Jöhnk, Clive G. Jones, Xavier Lambin, Alexander W. Latzka, Jan Pergl, Petr Pyšek, Peter Robertson, Menja Schmalensee, Robert A. Stefansson, Justin Wright, Jonathan M. Jeschke
      Abstract: Boom-bust dynamics – the rise of a population to outbreak levels, followed by a dramatic decline – have been associated with biological invasions and offered as a reason not to manage troublesome invaders. However, boom-bust dynamics rarely have been critically defined, analyzed, or interpreted. Here, we define boom-bust dynamics and provide specific suggestions for improving the application of the boom-bust concept. Boom-bust dynamics can arise from many causes, some closely associated with invasions, but others occurring across a wide range of ecological settings, especially when environmental conditions are changing rapidly. As a result, it is difficult to infer cause or predict future trajectories merely by observing the dynamic. We use tests with simulated data to show that a common metric for detecting and describing boom-bust dynamics, decline from an observed peak to a subsequent trough, tends to severely overestimate the frequency and severity of busts, and should be used cautiously if at all. We review and test other metrics that are better suited to describe boom-bust dynamics. Understanding the frequency and importance of boom-bust dynamics requires empirical studies of large, representative, long-term data sets that use clear definitions of boom-bust, appropriate analytical methods, and careful interpretations.
      PubDate: 2017-08-17T20:00:59.8713-05:00
      DOI: 10.1111/ele.12822
  • Decoupled responses of soil bacteria and their invertebrate consumer to
           warming, but not freeze–thaw cycles, in the Antarctic Dry Valleys
    • Authors: Matthew A. Knox; Walter S. Andriuzzi, Heather N. Buelow, Cristina Takacs-Vesbach, Byron J. Adams, Diana H. Wall
      Abstract: Altered temperature profiles resulting in increased warming and freeze–thaw cycle (FTC) frequency pose great ecological challenges to organisms in alpine and polar ecosystems. We performed a laboratory microcosm experiment to investigate how temperature variability affects soil bacterial cell numbers, and abundance and traits of soil microfauna (the microbivorous nematode Scottnema lindsayae) from McMurdo Dry Valleys, Antarctica. FTCs and constant freezing shifted nematode body size distribution towards large individuals, driven by higher mortality among smaller individuals. FTCs reduced both bacterial and nematode abundance, but bacterial cell numbers also declined under warming, demonstrating decoupled consumer–prey responses. We predict that higher occurrence of FTCs in cold ecosystems will select for large body size within soil microinvertebrates and overall reduce their abundance. In contrast, warm temperatures without FTCs could lead to divergent responses in soil bacteria and their microinvertebrate consumers, potentially affecting energy and nutrient transfer rates in soil food webs of cold ecosystems.
      PubDate: 2017-08-10T18:25:40.353433-05:
      DOI: 10.1111/ele.12819
  • Rainfall variability and fine-scale life history tradeoffs help drive
           niche partitioning in a desert annual plant community
    • Authors: Robert K. Shriver
      Abstract: Tradeoffs have long been an essential part of the canon explaining the maintenance of species diversity. Despite the intuitive appeal of the idea that no species can be a master of all trades, there has been a scarcity of linked demographic and physiological evidence to support the role of resource use tradeoffs in natural systems. Using five species of Chihuahuan desert summer annual plants, I show that demographic tradeoffs driven by short-term soil moisture variation act as a mechanism to allow multiple species to partition a limiting resource. Specifically, by achieving highest fitness in either rainfall pulse or interpulse periods, variability reduces fitness differences through time that could promote coexistence on a limiting resource. Differences in fitness are explained in part by the response of photosynthesis to changing soil moisture. My results suggest that increasing weather variability, as predicted under climate change, could increase the opportunity for coexistence in this community.
      PubDate: 2017-08-03T19:56:14.995246-05:
      DOI: 10.1111/ele.12818
  • Issue Information
    • Pages: 1217 - 1218
      PubDate: 2017-09-17T22:03:31.185727-05:
      DOI: 10.1111/ele.12683
  • Trophic interaction modifications: an empirical and theoretical framework
    • Authors: J. Christopher D. Terry; Rebecca J. Morris, Michael B. Bonsall
      Pages: 1219 - 1230
      Abstract: Consumer–resource interactions are often influenced by other species in the community. At present these ‘trophic interaction modifications’ are rarely included in ecological models despite demonstrations that they can drive system dynamics. Here, we advocate and extend an approach that has the potential to unite and represent this key group of non-trophic interactions by emphasising the change to trophic interactions induced by modifying species. We highlight the opportunities this approach brings in comparison to frameworks that coerce trophic interaction modifications into pairwise relationships. To establish common frames of reference and explore the value of the approach, we set out a range of metrics for the ‘strength’ of an interaction modification which incorporate increasing levels of contextual information about the system. Through demonstrations in three-species model systems, we establish that these metrics capture complimentary aspects of interaction modifications. We show how the approach can be used in a range of empirical contexts; we identify as specific gaps in current understanding experiments with multiple levels of modifier species and the distributions of modifications in networks. The trophic interaction modification approach we propose can motivate and unite empirical and theoretical studies of system dynamics, providing a route to confront ecological complexity.
      PubDate: 2017-09-17T22:03:26.226679-05:
      DOI: 10.1111/ele.12824
  • Opportunistic attachment assembles plant–pollinator networks
    • Authors: Lauren C. Ponisio; Marilia P. Gaiarsa, Claire Kremen
      Pages: 1261 - 1272
      Abstract: Species and interactions are being lost at alarming rates and it is imperative to understand how communities assemble if we have to prevent their collapse and restore lost interactions. Using an 8-year dataset comprising nearly 20 000 pollinator visitation records, we explore the assembly of plant–pollinator communities at native plant restoration sites in an agricultural landscape. We find that species occupy highly dynamic network positions through time, causing the assembly process to be punctuated by major network reorganisations. The most persistent pollinator species are also the most variable in their network positions, contrary to what preferential attachment – the most widely studied theory of ecological network assembly – predicts. Instead, we suggest assembly occurs via an opportunistic attachment process. Our results contribute to our understanding of how communities assembly and how species interactions change through time while helping to inform efforts to reassemble robust communities.
      PubDate: 2017-09-17T22:03:27.859364-05:
      DOI: 10.1111/ele.12821
  • Soil microbial communities drive the resistance of ecosystem
           multifunctionality to global change in drylands across the globe
    • Authors: Manuel Delgado-Baquerizo; David J. Eldridge, Victoria Ochoa, Beatriz Gozalo, Brajesh K. Singh, Fernando T. Maestre
      Pages: 1295 - 1305
      Abstract: The relationship between soil microbial communities and the resistance of multiple ecosystem functions linked to C, N and P cycling (multifunctionality resistance) to global change has never been assessed globally in natural ecosystems. We collected soils from 59 dryland ecosystems worldwide to investigate the importance of microbial communities as predictor of multifunctionality resistance to climate change and nitrogen fertilisation. Multifunctionality had a lower resistance to wetting–drying cycles than to warming or N deposition. Multifunctionality resistance was regulated by changes in microbial composition (relative abundance of phylotypes) but not by richness, total abundance of fungi and bacteria or the fungal: bacterial ratio. Our results suggest that positive effects of particular microbial taxa on multifunctionality resistance could potentially be controlled by altering soil pH. Together, our work demonstrates strong links between microbial community composition and multifunctionality resistance in dryland soils from six continents, and provides insights into the importance of microbial community composition for buffering effects of global change in drylands worldwide.
      PubDate: 2017-09-17T22:03:27.498235-05:
      DOI: 10.1111/ele.12826
  • Shifts of community composition and population density substantially
           affect ecosystem function despite invariant richness
    • Authors: Jurg W. Spaak; Jan M. Baert, Donald J. Baird, Nico Eisenhauer, Lorraine Maltby, Francesco Pomati, Viktoriia Radchuk, Jason R. Rohr, Paul J. Van den Brink, Frederik De Laender
      Pages: 1315 - 1324
      Abstract: There has been considerable focus on the impacts of environmental change on ecosystem function arising from changes in species richness. However, environmental change may affect ecosystem function without affecting richness, most notably by affecting population densities and community composition. Using a theoretical model, we find that, despite invariant richness, (1) small environmental effects may already lead to a collapse of function; (2) competitive strength may be a less important determinant of ecosystem function change than the selectivity of the environmental change driver and (3) effects on ecosystem function increase when effects on composition are larger. We also present a complementary statistical analysis of 13 data sets of phytoplankton and periphyton communities exposed to chemical stressors and show that effects on primary production under invariant richness ranged from −75% to +10%. We conclude that environmental protection goals relying on measures of richness could underestimate ecological impacts of environmental change.
      PubDate: 2017-09-17T22:03:28.647134-05:
      DOI: 10.1111/ele.12828
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