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Grassland biodiversity is vulnerable to land use change. How to best manage semi-natural grasslands for maintaining biodiversity is still unclear in many cases because land-use processes may depend on environmental conditions and the indirect effects of land-use on biodiversity mediated by altered abiotic and biotic factors are rarely considered. Here we evaluate the relative importance of the direct and indirect effects of grazing intensity on plant communities along an elevational gradient on a large topographic scale in the Eastern Carpathians in Ukraine. We sampled for two years 31 semi-natural grasslands exposed to cattle grazing. Within each grassland site we measured plant community properties such as the number of species, functional groups, and the proportion of species undesirable for grazing. In addition, we recorded cattle density (as a proxy for grazing intensity), soil properties (bare soil exposure, soil organic carbon, and soil pH) and densities of soil decomposers (earthworms and soil microorganisms). We used structural equation modelling to explore the direct and indirect effects of grazing intensity on plant communities along the elevation gradient. We found that cattle density decreased plant species and functional diversity but increased the proportion of undesirable species. Some of these effects were directly linked to grazing intensity (i.e., species richness), while others (i.e., functional diversity and proportion of undesirable species) were mediated via bare soil exposure. Although grazing intensity decreased with elevation, the effects of grazing on the plant community did not change along the elevation gradient. Generally, elevation had a strong positive direct effect on plant species richness as well as a negative indirect effect, mediated via altered soil acidity and decreased decomposer density. Our results indicate that plant diversity and composition are controlled by the complex interplay among grazing intensity and changing environmental conditions along an elevation gradient. Furthermore, we found lower soil pH, organic carbon and decomposer density with elevation, indicating that the effects of grazing on soil and related ecosystem functions and services in semi-natural grasslands may be more pronounced with elevation. This demonstrates that we need to account for environmental gradients when attempting to generalize effects of land-use intensity on biodiversity.

Ultraviolet radiation (UVR) is an environmental stressor in several ecosystems and can affect organisms’ survival and reproduction, and community structure. Rotifers cope with UVR stress adopting preventive behavioral and metabolic mechanisms. However, the demonstration of an immediate behavioral response in rotifers is missing. We investigated the short-term response of rotifers to UVR, by combining video analysis and movement ecology methods, in three common species: Brachionus calyciflorus, Keratella cochlearis, and Keratella quadrata. We recorded the behavior of B. calyciflorus (both sexes), K. quadrata, and K. cochlearis (females) exposed to white light, and to intermittent cycles of UVR (30:30 s). Individual trajectories were extracted from videos with open-source software. We found that B. calyciflorus females exposed to UVR exhibited strong negative phototaxis with increased swimming speed, and a weak positive phototaxis in males. Keratella cochlearis and K. quadrata showed a weaker response. Our study reveals a species-specific behavioral response to UVR in rotifers. Furthermore, we highlight how sexual dimorphism in B. calyciflorus does not only occur in morphology and movement, but also in behavioral traits. Our results help to understand zooplankton community dynamics by providing a mechanistic explanation of UVR response in one major zooplankton taxonomic group.

The research of a generation of ecologists was catalysed by the recognition that the number and identity of species in communities influences the functioning of ecosystems. The relationship between biodiversity and ecosystem functioning (BEF) is most often examined by controlling species richness and randomising community composition. In natural systems, biodiversity changes are often part of a bigger community assembly dynamic. Therefore, focusing on community assembly and the functioning of ecosystems (CAFE), by integrating both species richness and composition through species gains, losses and changes in abundance, will better reveal how community changes affect ecosystem function. We synthesise the BEF and CAFE perspectives using an ecological application of the Price equation, which partitions the contributions of richness and composition to function. Using empirical examples, we show how the CAFE approach reveals important contributions of composition to function. These examples show how changes in species richness and composition driven by environmental perturbations can work in concert or antagonistically to influence ecosystem function. Considering how communities change in an integrative fashion, rather than focusing on one axis of community structure at a time, will improve our ability to anticipate and predict changes in ecosystem function. ISSN:1461-023X ISSN:1461-0248

Made available in DSpace on 2020-12-10T16:59:44Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-11-10 Royal Society of Edinburgh Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Universidad Nacional de Rosario Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Natural Sciences and Engineering Research Council of Canada Carnegie Trust for the Universities of Scotland National Science Foundation International Institute of Tropical Forestry Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Agence Nationale de la Recherche Royal Society Fondation pour la Recherche sur la Biodiversite Centre de synthese et d'analyse sur la biodiversite Saba Conservation Foundation Aim Locally abundant species are usually widespread, and this pattern has been related to properties of the niches and traits of species. However, such explanations fail to account for the potential of traits to determine species niches and often overlook statistical artefacts. Here, we examine how trait distinctiveness determines the abilities of species to exploit either common habitats (niche position) or a range of habitats (niche breadth) and how niche position and breadth, in turn, affect abundance and occupancy. We also examine how statistical artefacts moderate these relationships. Location Sixteen sites in the Neotropics. Time period 1993-2014. Major taxa studied Aquatic invertebrates from tank bromeliads. Methods We measured the environmental niche position and breadth of each species and calculated its trait distinctiveness as the average trait difference from all other species at each site. Then, we used a combination of structural equation models and a meta-analytical approach to test trait-niche relationships and a null model to control for statistical artefacts. Results The trait distinctiveness of each species was unrelated to its niche properties, abundance and occupancy. In contrast, niche position was the main predictor of abundance and occupancy; species that used the most common environmental conditions found across bromeliads were locally abundant and widespread. Contributions of niche breadth to such patterns were attributable to statistical artefacts, indicating that effects of niche breadth might have been overestimated in previous studies. Main conclusions Our study reveals the generality of niche position in explaining one of the most common ecological patterns. The robustness of this result is underscored by the geographical extent of our study and our control of statistical artefacts. We call for a similar examination across other systems, which is an essential task to understand the drivers of commonness across the tree of life. Univ Fed Rio de Janeiro, Inst Biol, Dept Ecol, Rio De Janeiro, RJ, Brazil Univ Fed Rio de Janeiro, Programa Posgrad Ecol, Rio De Janeiro, RJ, Brazil Univ Toulouse, CNRS, ECOLAB, Toulouse, France Univ Toronto, Dept Ecol & Evolutionary Biol, Toronto, ON, Canada Berlin Brandenburg Inst Adv Biodivers Res, Berlin, Germany Univ Salzburg, Dept Biosci, Salzburg, Austria Univ British Columbia, Dept Zool, Vancouver, BC, Canada Univ British Columbia, Biodivers Res Ctr, Vancouver, BC, Canada Univ Estadual Campinas UNICAMP, Inst Biol, Dept Biol Anim, Lab Interacoes Multitrof & Biodiversidade, Campinas, SP, Brazil Univ Andes, Dept Biol Sci, Bogota, Colombia Univ Caldas, Dept Ciencias Biol, Caldas, Colombia Univ British Columbia, Dept Forest & Conservat Sci, Vancouver, BC, Canada Univ Nacl Rosario, CONICET, Inst Invest Ciencias Agr Rosario, Fac Ciencias Agr, Zavalla, Argentina Univ Clermont Auvergne, Lab Microorganismes Genome & Environm, Aubiere, France Univ Fed Rio Grande do Sul, Dept Ecol, Porto Alegre, RS, Brazil Univ Fed Rio Grande do Sul, Programa Posgrad Ecol, Porto Alegre, RS, Brazil INRA, UMR ESE, Ecol & Ecosyst Hlth, Rennes, France Queen Mary Univ London, Sch Biol & Chem Sci, London, England Univ Montpellier, AMAP, IRD, CIRAD,CNRS,INRA, Montpellier, France Univ Antilles, Univ Guyane, EcoFoG, AgroParisTech,CIRAD,CNRS,INRA, Kourou, France Ctr Synth & Anal Biodivers CESAB FRB, Aix En Provence, France Univ Nacl Rosario, Fac Ciencias Agr, Zavalla, Argentina Univ Puerto Rico Rio Piedras, Coll Nat Sci, Inst Trop Ecosyst Studies, Luquillo LTER, San Juan, PR 00931 USA Inst Pasteur Guyane, Unite Entomol Med, Cayenne, France Univ Sao Paulo, Inst Biociencias, Dept Bot, Sao Paulo, SP, Brazil Univ Estadual Paulista, Dept Zool & Bot, Sao Paulo, SP, Brazil Royal Belgian Inst Nat Sci, Aquat & Terr Ecol, Brussels, Belgium Univ Estadual Paulista, Dept Zool & Bot, Sao Paulo, SP, Brazil FAPESP: 2016/01209-9 FAPESP: 2016/09699-5 Universidad Nacional de Rosario: AGR-210 Universidad Nacional de Rosario: AGR-290 CNPq: 301514/2017-8 CNPq: 307689/2014-0 CNPq: 312770/2014-6 CNPq: 401345/2014-9 National Science Foundation: DEB-0218039 National Science Foundation: DEB-0620910 CAPES: 2013/0877 CAPES: 2014/04603-4 Agence Nationale de la Recherche: ANR-10-LABX-25-01 Royal Society: NAF\R2\180791

Organismal movement is ubiquitous and facilitates important ecological mechanisms that drive community and metacommunity composition and hence biodiversity. In most existing ecological theories and models in biodiversity research, movement is represented simplistically, ignoring the behavioural basis of movement and consequently the variation in behaviour at species and individual levels. However, as human endeavours modify climate and land use, the behavioural processes of organisms in response to these changes, including movement, become critical to understanding the resulting biodiversity loss. Here, we draw together research from different subdisciplines in ecology to understand the impact of individual-level movement processes on community-level patterns in species composition and coexistence. We join the movement ecology framework with the key concepts from metacommunity theory, community assembly and modern coexistence theory using the idea of micro-macro links, where various aspects of emergent movement behaviour scale up to local and regional patterns in species mobility and mobile-link-generated patterns in abiotic and biotic environmental conditions. These in turn influence both individual movement and, at ecological timescales, mechanisms such as dispersal limitation, environmental filtering, and niche partitioning. We conclude by highlighting challenges to and promising future avenues for data generation, data analysis and complementary modelling approaches and provide a brief outlook on how a new behaviour-based view on movement becomes important in understanding the responses of communities under ongoing environmental change.

Ecological communities hosted within phytotelmata (plant compartments filled with water) provide an excellent opportunity to test ecological theory and to advance our understanding of how local and global environmental changes affect ecosystems. However, insights from bromeliad phytotelmata communities are currently limited by scarce accounts of microfauna assemblages, even though these assemblages are critical in transferring, recycling, and releasing nutrients in these model ecosystems. Here, we analyzed natural microfaunal communities in leaf compartments of 43 bromeliads to identify the key environmental filters underlying their community structures. We found that microfaunal community richness and abundance were negatively related to canopy openness and vertical height above the ground. These associations were primarily driven by the composition of amoebae and flagellate assemblages and indicate the importance of bottom‐up control of microfauna in bromeliads. Taxonomic richness of all functional groups followed a unimodal relationship with water temperature, peaking at 23–25°C and declining below and above this relatively narrow thermal range. This suggests that relatively small changes in water temperature under expected future climate warming may alter taxonomic richness and ecological structure of these communities. Our findings improve the understanding of this unstudied but crucial component of bromeliad ecosystems and reveal important environmental filters that likely contribute to overall bromeliad community structure and function.

Plant diversity and soil organisms are both widely studied for their contributions to ecosystem functions. It has been recently shown that soil biota may drive the plant species diversity-function relationship in grasslands, while so far studies on plant intraspecific diversity are lacking. To improve the understanding of how ecosystem functions may be influenced by plant intraspecific diversity, soil organisms, and their interactions, we used a field setting to examine the effects of plant intraspecific diversity and functionally dissimilar soil organisms (manipulated by the addition of northern root-knot nematodes, earthworms, and arbuscular mycorrhizal fungi) on aboveground primary production, pollination and shoot herbivory. Plant intraspecific diversity was manipulated by sowing different seed mixtures of Trifolium pratense L. and Lolium perenne L. cultivars. We found a positive effect of plant intraspecific diversity on total aboveground primary production, contributed mostly by T. pratense. The plant intraspecific diversity-productivity effect on T. pratense was mediated by the nematodes, i.e. aboveground biomass was increased by intraspecific diversity only in the nematode treatment. Further, the average floral visitation length was decreased by earthworm addition, while the abundance of pollinators tended to be increased by high plant intraspecific diversity. Leaf damage of T. pratense were not influenced by the treatments. We conclude that plant intraspecific diversity and soil organisms can interactively or independently modify functions such as aboveground primary production and pollination of T. pratense in the field. Specifically, the positive plant intraspecific diversity effect appears to only emerge under conditions of stress (high nematode abundance). This result indicates that plant intraspecific diversity may be important for the maintenance of ecosystem functions, especially in an agricultural context, where pest pressure can be high and can have large detrimental consequences.

International audience; Concern about the functional consequences of unprecedented loss in biodiversity has prompted biodiversity-ecosystem functioning (BEF) research to become one of the most active fields of ecological research in the past 25 years. Hundreds of experiments have manipulated biodiversity as an independent variable and found compelling support that the functioning of ecosystems increases with the diversity of their ecological communities. This research has also identified some of the mechanisms underlying BEF relationships, some context-dependencies of the strength of relationships, as well as implications for various ecosystem services that mankind depends upon. In this paper, we argue that a multitrophic perspective of biotic interactions in random and non-random biodiversity change scenarios is key to advance future BEF research and to address some of its most important remaining challenges. We discuss that the study and the quantification of multitrophic interactions in space and time facilitates scaling up from small-scale biodiversity manipulations and ecosystem function assessments to management-relevant spatial scales across ecosystem boundaries. We specifically consider multitrophic conceptual frameworks to understand and predict the context-dependency of BEF relationships. Moreover, we highlight the importance of the eco-evolutionary underpinnings of multitrophic BEF relationships. We outline that FAIR data (meeting the standards of findability, accessibility, interoperability, and reusability) and reproducible processing will be key to advance this field of research by making it more integrative. Finally, we show how these BEF insights may be implemented for ecosystem management, society, and policy. Given that human well-being critically depends on the multiple services provided by diverse, multitrophic communities, integrating the approaches of evolutionary ecology, community ecology, and ecosystem ecology in future BEF research will be key to refine conservation targets and develop sustainable management strategies.

Recent studies showed that diverse wild bee assemblages are more efficient pollinators than honeybees. In urban ecosystems pollination services are also important, for example for the reproduction of many plant species in parks, for the production of vegetables and fruits in home gardens, as well as other animals depending on bee-pollinated plants. This study investigates the effect of ‘urbanity’ on the abundance, species richness and community structure of wild bees foraging at city trees and quantifies the contribution of wild bees and honeybees to successful pollination. Four common city tree species in Berlin, Germany, were sampled in three parks defined as ‘green spaces’ and compared with trees in more ‘urban areas’. In total, 57 wild bee species foraged at the observed trees representing 19 % of all known species in Berlin. Wild bee species richness showed only small differences between green spaces and urban areas even though social species were found more frequently in green areas. Wild bees visited flowers more frequently in green areas, whereas the numbers of honeybee flower visits were higher in urban areas. Wild bee but not honeybee flower visits showed a positive relationship with the reproductive success of trees. The results suggest that wild bees are important pollinators of city trees that dominate the pollinator community in green spaces. To support wild bee communities green spaces should be preserved and tree species with floral reward should be planted and preserved in urban areas.

Made available in DSpace on 2022-04-28T19:26:17Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-10-01 Carnegie Trust for the Universities of Scotland U.S. Department of Agriculture Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Labex National Science Foundation Royal Society of Edinburgh Functional traits are commonly used in predictive models that link environmental drivers and community structure to ecosystem functioning. A prerequisite is to identify robust sets of continuous axes of trait variation, and to understand the ecological and evolutionary constraints that result in the functional trait space occupied by interacting species. Despite their diversity and role in ecosystem functioning, little is known of the constraints on the functional trait space of invertebrate biotas of entire biogeographic regions. We examined the ecological strategies and constraints underlying the realized trait space of aquatic invertebrates, using data on 12 functional traits of 852 taxa collected in tank bromeliads from Mexico to Argentina. Principal Component Analysis was used to reduce trait dimensionality to significant axes of trait variation, and the proportion of potential trait space that is actually occupied by all taxa was compared to null model expectations. Permutational Analyses of Variance were used to test whether trait combinations were clade-dependent. The major axes of trait variation represented life-history strategies optimizing resource use and antipredator adaptations. There was evidence for trophic, habitat, defence and life-history niche axes. Bromeliad invertebrates only occupied 16%–23% of the potential space within these dimensions, due to greater concentrations than predicted under uniform or normal distributions. Thus, despite high taxonomic diversity, invertebrates only utilized a small number of successful ecological strategies. Empty areas in trait space represented gaps between major phyla that arose from biological innovations, and trait combinations that are unviable in the bromeliad ecosystem. Only a few phylogenetically distant genera were neighbouring in trait space. Trait combinations aggregated taxa by family and then by order, suggesting that niche conservatism was a widespread mechanism in the diversification of ecological strategies. A plain language summary is available for this article. ECOLAB CNRS Université de Toulouse Department of Ecology and Graduate Program in Ecology Universidade Federal do Rio Grande do Sul Department of Zoology & Biodiversity Research Centre University of British Columbia Laboratory of Multitrophic Interactions and Biodiversity Department of Animal Biology Institute of Biology University of Campinas Centre for the Synthesis and Analysis of Biodiversity (CESAB-FRB) Facultad de Ciencias Agrarias Instituto de Investigaciones en Ciencias Agrarias Universidad Nacional de Rosario Laboratoire Microorganismes Génome et Environnement Université Clermont Auvergne AMAP IRD CIRAD CNRS INRA Université de Montpellier ECOFOG Campus Agronomique Department of Biological Sciences Andes University Department of Forest and Conservation Sciences University of British Columbia School of Biological and Chemical Sciences Queen Mary University of London Department of Botany Biosciences Institute University of São Paulo Departamento de Ecologia Instituto de Biologia Universidade Federal do Rio de Janeiro Programa de Pós-Graduação em Ecologia Universidade Federal do Rio de Janeiro Luquillo LTER Institute for Tropical Ecosystem Studies University of Puerto Rico Laboratoire Interdisciplinaire des Environnements Continentaux CNRS Université de Lorraine Department of Ecology and Evolutionary Biology University of Toronto Berlin-Brandenburg Institute of Advanced Biodiversity Research Department of Biosciences University of Salzburg Institut Pasteur de la Guyane Unité d'Entomologie Médicale Department of Zoology and Botany University of São Paulo State Aquatic and Terrestrial Ecology Royal Belgian Institute of Natural Sciences Facultad de Ciencias Agrarias Universidad Nacional de Rosario U.S. Department of Agriculture: 01-1G11120101-001 CNPq: 307689/2014-0 CNPq: 401345/2014-9 Labex: ANR-10-LABX-25-01 National Science Foundation: DEB-0218039 National Science Foundation: DEB-0620910

Biodegradable plastic is gaining attention, also through market regulation by a growing number of countries. The substitution of conventional plastic by these new materials is discussed as one mitigation measure to the ever-growing global problem of marine plastic litter. Modelling showed that the estimated substitution potential on a global scale might be small, with a contribution of only 0.3% to the total marine debris. However, there are huge potentials for substitution on local level, and for single plastic items and applications of one single polymer. In order to assess the environmental risk of new materials such as biodegradable plastics being introduced to the market and potentially also lost to the environment, in-situ studies of the performance under marine conditions have been conducted. Two studies in the Mediterranean Sea are summarized and the role of biofilm formation and fouling on disintegration are highlighted. Preliminary results of ongoing studies in tropical SE Asia are presented.

The increasing amount of plastic littered into the sea may provide a new substratum for benthic organisms. These marine fouling communities on plastic have not received much scientific attention. We present, to our knowledge, the first comprehensive analysis of their macroscopic community composition, their primary production and the polymer degradation comparing conventional polyethylene (PE) and a biodegradable starch-based plastic blend in coastal benthic and pelagic habitats in the Mediterranean Sea. The biomass of the fouling layer increased significantly over time and all samples became heavy enough to sink to the seafloor. The fouling communities, consisting of 21 families, were distinct between habitats, but not between polymer types. Positive primary production was measured in the pelagic, but not in the benthic habitat, suggesting that large accumulations of floating plastic could pose a source of oxygen for local ecosystems, as well as a carbon sink. Contrary to PE, the biodegradable plastic showed a significant loss of tensile strength and disintegrated over time in both habitats. These results indicate that in the marine environment, biodegradable polymers may disintegrate at higher rates than conventional polymers. This should be considered for the development of new materials, environmental risk assessment and waste management strategies.

Fear of predation has been shown to affect prey fitness and behaviour, however, to date little is known about the underlying genetics of responses to predator-associated risk. In an effort to fill this gap we exposed four naïve clones of green peach aphid (Myzus persicae), maintained on the model crop Brassica oleracea, to different types of cues from aphid lion (Chrysoperla carnea). The respective predation risks, we termed Fear Factors, were either lethal (consumption by predator), or non-lethal (non-consumptive predator-associated cues: plant-tethered predator cadavers and homogenised shoot-sprayed or soil-infused blends of predator remains). Our results show that the non-lethal risk cues differentially impeded prey reproductive success that varied by clone, suggesting genotype-specific response to fear of predation. Furthermore, whether plants were perceived as being safe or risky influenced prey responses as avoidance behaviour in prey depended on clone type. Our findings highlight that intra-specific genetic variation underlies prey responses to consumptive and non-consumptive effects of predation. This allows selection to act on anti-predator responses to fear of predation that may ramify and influence higher trophic levels in model agroecosystems.

Ecological communities in forests have been shown to be strongly affected by forest management but a detailed understanding of how different components of management affect insect communities directly and indirectly via environmental variables, how management influences functional trait diversity and composition, and whether these results can be transferred to other functional groups besides insects (e.g. bacteria or nematodes) is still missing. To address these questions we used water-filled tree holes, which provide habitats for insect larvae and other aquatic organisms in forests, as a model system. We mapped all water-filled tree holes in 75 forest plots (1 ha) under different management intensity in three regions of Germany. We measured structural and climatic conditions at different spatial scales, sampled insect communities in 123 tree holes and bacterial and nematode communities in a subset of these. We found that forest management in terms of harvesting intensity and the proportion of non-natural tree species (species not part of the natural vegetation at the sites) negatively affected tree-hole abundance. An increased proportion of non-natural tree species had a positive direct effect on insect richness and functional diversity in the tree holes. However, a structural equation model showed that increasing management intensity had negative indirect effects on insect abundance and richness, operating via environmental variables at stand and tree-hole scale. Functional diversity and trait composition of insect communities similarly responded to changes in management-related variables. In contrast to insects, bacterial and nematode richness were not directly impacted by forest management but by other environmental variables. Our results suggest that forest management may strongly alter insect communities of tree holes, while nematodes and bacteria seem less affected. Most effects in our study were indirect and negative, indicating that management has often complex consequences for forest communities that should be taken into account in forest management schemes.

Initial plant diversity might control subsequent community assembly processes and plant productivity. To study these effects we used a biodiversity experiment (Jena Experiment) with subplots of different sown diversity that were never weeded and spontaneously colonized control plots of different size (3.5 × 3.5 m 20 × 20 m) with and without mowing in an 8 year study. On non sown bare plots without mowing colonizer accumulation depended on plot size resulting in a loss of diversity in large undisturbed (unmown) control plots after initial colonization. On sown plots that were mown twice per year species richness converged to high levels due to the accumulation of internal colonists (species belonging to the experimental pool of sown species) while initially high species richness of external colonists (species not belonging to the experimental pool) and residents (species sown on the plot) declined over time. The convergence of total species richness at higher levels was paralleled by increased taxonomic (Simpson Index QSimp) phylogenetic (QPhylo) and trait (FDQ) diversity whereby FDQ was greatest on plots with low resident species richness after several years. Rates of change in terms of species colonization extinction and community composition decelerated over time irrespective of resident species richness mowing or plot size. While the contribution of residents declined and the contribution of colonists increased community biomass production did not change over time. The biomasses of residents and colonists were greatest at higher levels of species richness partial QPhylo and FDQ of the respective species group but community biomass was consistently weakly related to total species richness and indices of diversity. Our study shows that in contrast to the period of succession “mature” plant communities resulting from natural assembly processes favouring the coexistence of multiple species and thus high biodiversity do no longer show significant relationships between species richness and variables related to ecosystem functioning such as primary productivity.

Forest management could potentially affect organisms in all forest habitats. However, aquatic communities in water-filled tree-holes may be especially sensitive because of small population sizes, the risk of drought and potential dispersal limitation. We set up artificial tree holes in forest stands subject to different management intensities in two regions in Germany and assessed the influence of local environmental properties (tree-hole opening type, tree diameter, water volume and water temperature) as well as regional drivers (forest management intensity, tree-hole density) on tree-hole insect communities (not considering other organisms such as nematodes or rotifers), detritus content, oxygen and nutrient concentrations. In addition, we compared data from artificial tree holes with data from natural tree holes in the same area to evaluate the methodological approach of using tree-hole analogues. We found that forest management had strong effects on communities in artificial tree holes in both regions and across the season. Abundance and species richness declined, community composition shifted and detritus content declined with increasing forest management intensity. Environmental variables, such as tree-hole density and tree diameter partly explained these changes. However, dispersal limitation, indicated by effects of tree-hole density, generally showed rather weak impacts on communities. Artificial tree holes had higher water temperatures (on average 2° C higher) and oxygen concentrations (on average 25% higher) than natural tree holes. The abundance of organisms was higher but species richness was lower in artificial tree holes. Community composition differed between artificial and natural tree holes. Negative management effects were detectable in both tree-hole systems, despite their abiotic and biotic differences. Our results indicate that forest management has substantial and pervasive effects on tree-hole communities and may alter their structure and functioning. We furthermore conclude that artificial tree-hole analogues represent a useful experimental alternative to test effects of changes in forest management on natural communities. Fil: Petermann, Jana S.. University of Salzburg; Austria. Berlin-Brandenburg Institute of Advanced Biodiversity Research; Alemania Fil: Rohland, Anja. Friedrich Schiller University; Alemania Fil: Sichardt, Nora. Friedrich Schiller University; Alemania Fil: Lade, Peggy. Friedrich Schiller University; Alemania Fil: Guidetti, Brenda Yamile. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Friedrich Schiller University; Alemania Fil: Weisser, Wolfgang W.. Friedrich Schiller University; Alemania. Technische Universität München; Alemania Fil: Gossner, Martin M.. Friedrich Schiller University; Alemania. Technische Universität München; Alemania

Arthropod communities in water-filled tree holes may be sensitive to impacts of forest management, for example via changes in environmental conditions such as resource input. We hypothesized that increasing forest management intensity (ForMI) negatively affects arthropod abundance and richness and shifts community composition and trophic structure of tree hole communities. We predicted that this shift is caused by reduced habitat and resource availability at the forest stand scale as well as reduced tree hole size, detritus amount and changed water chemistry at the tree holes scale. We mapped 910 water-filled tree holes in two regions in Germany and studied 199 tree hole inhabiting arthropod communities. We found that increasing ForMI indeed significantly reduced arthropod abundance and richness in water-filled tree holes. The most important indirect effects of management intensity on tree hole community structure were the reduced amounts of detritus for the tree hole inhabiting organisms and changed water chemistry at the tree hole scale, both of which seem to act as a habitat filter. Although habitat availability at the forest stand scale decreased with increasing management intensity, this unexpectedly increased local arthropod abundance in individual tree holes. However, regional species richness in tree holes significantly decreased with increasing management intensity, most likely due to decreased habitat diversity. We did not find that the management-driven increase in plant diversity at the forest stand scale affected communities of individual tree holes, for example via resource availability for adults. Our results suggest that management of temperate forests has to target a number of factors at different scales to conserve diverse arthropod communities in water-filled tree holes.

The importance of competition between similar species in driving community assembly is much debated. Recently, phylogenetic patterns in species composition have been investigated to help resolve this question: phylogenetic clustering is taken to imply environmental filtering, and phylogenetic overdispersion to indicate limiting similarity between species. We used experimental plant communities with random species compositions and initially even abundance distributions to examine the development of phylogenetic pattern in species abundance distributions. Where composition was held constant by weeding, abundance distributions became overdispersed through time, but only in communities that contained distantly related clades, some with several species (i.e., a mix of closely and distantly related species). Phylogenetic pattern in composition therefore constrained the development of overdispersed abundance distributions, and this might indicate limiting similarity between close relatives and facilitation/complementarity between distant relatives. Comparing the phylogenetic patterns in these communities with those expected from the monoculture abundances of the constituent species revealed that interspecific competition caused the phylogenetic patterns. Opening experimental communities to colonization by all species in the species pool led to convergence in phylogenetic diversity. At convergence, communities were composed of several distantly related but species-rich clades and had overdispersed abundance distributions. This suggests that limiting similarity processes determine which species dominate a community but not which species occur in a community. Crucially, as our study was carried out in experimental communities, we could rule out local evolutionary or dispersal explanations for the patterns and identify ecological processes as the driving force, underlining the advantages of studying these processes in experimental communities. Our results show that phylogenetic relations between species provide a good guide to understanding community structure and add a new perspective to the evidence that niche complementarity is critical in driving community assembly.

In order to predict which ecosystem functionsare most at risk from biodiversity loss, meta-analyses havegeneralised results from biodiversity experiments overdifferent sites and ecosystem types. In contrast, comparingthe strength of biodiversity effects across a large number ofecosystem processes measured in a single experimentpermits more direct comparisons. Here, we present ananalysis of 418 separate measures of 38 ecosystem processes.Overall, 45 % of processes were significantlyaffected by plant species richness, suggesting that, whilediversity affects a large number of processes not allrespond to biodiversity. We therefore compared thestrength of plant diversity effects between different categoriesof ecosystem processes, grouping processesaccording to the year of measurement, their biogeochemicalcycle, trophic level and compartment (above- orbelowground) and according to whether they were measuresof biodiversity or other ecosystem processes, biotic orabiotic and static or dynamic. Overall, and for severalindividual processes, we found that biodiversity effectsbecame stronger over time. Measures of the carbon cyclewere also affected more strongly by plant species richnessthan were the measures associated with the nitrogen cycle. In order to predict which ecosystem functions are most at risk from biodiversity loss, meta-analyses have generalised results from biodiversity experiments over different sites and ecosystem types. In contrast, comparing the strength of biodiversity effects across a large number of ecosystem processes measured in a single experiment permits more direct comparisons. Here, we present an analysis of 418 separate measures of 38 ecosystem processes. Overall, 45 % of processes were significantly affected by plant species richness, suggesting that, while diversity affects a large number of processes not all respond to biodiversity. We therefore compared the strength of plant diversity effects between different categories of ecosystem processes, grouping processes according to the year of measurement, their biogeochemical cycle, trophic level and compartment (above- or belowground) and according to whether they were measures of biodiversity or other ecosystem processes, biotic or abiotic and static or dynamic. Overall, and for several individual processes, we found that biodiversity effects became stronger over time. Measures of the carbon cycle were also affected more strongly by plant species richness than were the measures associated with the nitrogen cycle. Further, we found greater plant species richness effects on measures of biodiversity than on other processes. The differential effects of plant diversity on the various types of ecosystem processes indicate that future research and political effort should shift from a general debate about whether biodiversity loss impairs ecosystem functions to focussing on the specific functions of interest and ways to preserve them individually or in combination.

Biodiversity is rapidly declining(1), and this may negatively affect ecosystem processes(2), including economically important ecosystem services(3). Previous studies have shown that biodiversity has positive effects on organisms and processes(4) across trophic levels(5). However, only a few studies have so far incorporated an explicit food-web perspective(6). In an eight-year biodiversity experiment, we studied an unprecedented range of above-and below-ground organisms and multitrophic interactions. A multitrophic data set originating from a single long-term experiment allows mechanistic insights that would not be gained from meta-analysis of different experiments. Here we show that plant diversity effects dampen with increasing trophic level and degree of omnivory. This was true both for abundance and species richness of organisms. Furthermore, we present comprehensive above-ground/below-ground biodiversity food webs. Both above ground and below ground, herbivores responded more strongly to changes in plant diversity than did carnivores or omnivores. Density and richness of carnivorous taxa was independent of vegetation structure. Below-ground responses to plant diversity were consistently weaker than above-ground responses. Responses to increasing plant diversity were generally positive, but were negative for biological invasion, pathogen infestation and hyperparasitism. Our results suggest that plant diversity has strong bottom-up effects on multitrophic interaction networks, with particularly strong effects on lower trophic levels. Effects on higher trophic levels are indirectly mediated through bottom-up trophic cascades. Biodiversity is rapidly declining, and this may negatively affect ecosystem processes, including economically important ecosystem servicesPrevious studies have shown that biodiversity has positive effects on organisms and processesacross trophic levels. However, only a few studies have so far incorporated an explicit food-web perspective6. In an eight-year biodiversity experiment, we studied an unprecedented range of above- and below-ground organisms and multitrophic interactions. A multitrophic data set originating from a single long-term experiment allows mechanistic insights that would not be gained from meta-analysis of different experiments. Here we show that plant diversity effects dampen with increasing trophic level and degree of omnivory. This was true both for abundance and species richness of organisms. Furthermore, we present comprehensive above-ground/below-ground biodiversity food webs. Both above ground and below ground, herbivores responded more strongly to changes in plant diversity than did carnivores or omnivores. Density and richness of carnivorous taxa was independent of vegetation structure. Below-ground responses to plant diversity were consistently weaker than above-ground responses. Responses to increasing plant diversity were generally positive, but were negative for biological invasion, pathogen infestation and hyperparasitism. Our results suggest that plant diversity has strong bottom-up effects on multitrophic interaction networks, with particularly strong effects on lower trophic levels. Effects on higher trophic levels are indirectly mediated through bottom-up trophic cascades.

The consequences of plant species loss are rarely assessed in a multi-trophic context and especially effects on life-history traits of organisms at higher trophic levels have remained largely unstudied. We used a grassland biodiversity experiment and measured the effects of two components of plant diversity, plant species richness and the presence of nitrogen-fixing legumes, on several life-history traits of naturally colonizing aphids and their primary and secondary parasitoids in the field. We found that, irrespective of aphid species identity, the proportion of winged aphid morphs decreased with increasing plant species richness, which was correlated with decreasing host plant biomass. Similarly, emergence proportions of parasitoids decreased with increasing plant species richness. Both, emergence proportions and proportions of female parasitoids were lower in plots with legumes, where host plants had increased nitrogen concentrations. This effect of legume presence could indicate that aphids were better defended against parasitoids in high-nitrogen environments. Body mass of emerged individuals of the two most abundant primary parasitoid species was, however, higher in plots with legumes, suggesting that once parasitoids could overcome aphid defenses, they could profit from larger or more nutritious hosts. Our study demonstrates that cascading effects of plant species loss on higher trophic levels such as aphids, parasitoids and secondary parasitoids begin with changed life-history traits of these insects. Thus, life-history traits of organisms at higher trophic levels may be useful indicators of bottom-up effects of plant diversity on the biodiversity of consumers.