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The twin crises of climate change and biodiversity loss define a strong need for functional diversity monitoring. While the availability of high-quality ecological monitoring data is increasing, the quantification of functional diversity so far requires the identification of species traits, for which data is harder to obtain. However, the traits that are relevant for the ecological function of a species also shape its performance in the environment and hence should be reflected indirectly in its spatio-temporal distribution. Thus it may be possible to reconstruct these traits from a sufficiently extensive monitoring dataset. Here we use diffusion maps, a deterministic and de-facto parameter-free analysis method, to reconstruct a proxy representation of the species' traits directly from monitoring data and use it to estimate functional diversity. We demonstrate this approach both with simulated data and real-world phytoplankton monitoring data from the Baltic sea. We anticipate that wider application of this approach to existing data could greatly advance the analysis of changes in functional biodiversity., Comment: 37 pages, main text ends on page 13, color figures

Biodiversity is expected to change in response to future global warming. However, it is difficult to predict how species will track the ongoing climate change. Here we use the fossil record of planktonic foraminifera to assess how biodiversity responded to climate change with a magnitude comparable to future anthropogenic warming. We compiled time series of planktonic foraminifera assemblages, covering the time from the last ice age across the deglaciation to the current warm period. Planktonic foraminifera assemblages shifted immediately when temperature began to rise at the end of the last ice age and continued to change until approximately 5,000 years ago, even though global temperature remained relatively stable during the last 11,000 years. The biotic response was largest in the mid latitudes and dominated by range expansion, which resulted in the emergence of new assemblages without analogues in the glacial ocean. Our results indicate that the plankton response to global warming was spatially heterogeneous and did not track temperature change uniformly over the past 24,000 years. Climate change led to the establishment of new assemblages and possibly new ecological interactions, which suggests that current anthropogenic warming may lead to new, different plankton community composition.

Increasing human impact on the environment is causing drastic changes in disturbance regimes and how they prevail over time. Of increasing relevance is to further our understanding on biological responses to pulse disturbances (short duration) and how they interact with other ongoing press disturbances (constantly present). Because the temporal and spatial contexts of single experiments often limit our ability to generalize results across space and time, we conducted a modularized mesocosm experiment replicated in space (five lakes along a latitudinal gradient in Scandinavia) and time (two seasons, spring and summer) to generate general predictions on how the functioning and composition of multitrophic plankton communities (zoo-, phyto- and bacterioplankton) respond to pulse disturbances acting either in isolation or combined with press disturbances. As pulse disturbance, we used short-term changes in fish presence, and as press disturbance, we addressed the ongoing reduction in light availability caused by increased cloudiness and lake browning in many boreal and subarctic lakes. First, our results show that the top-down pulse disturbance had the strongest effects on both functioning and composition of the three trophic levels across sites and seasons, with signs for interactive impacts with the bottom-up press disturbance on phytoplankton communities. Second, community composition responses to disturbances were highly divergent between lakes and seasons: temporal accumulated community turnover of the same trophic level either increased (destabilization) or decreased (stabilization) in response to the disturbances compared to control conditions. Third, we found functional recovery from the pulse disturbances to be frequent at the end of most experiments. In a broader context, these results demonstrate that top-down, pulse disturbances, either alone or with additional constant stress upon primary producers caused by bottom-up disturbances, can induce profound but often functionally reversible changes across multiple trophic levels, which are strongly linked to spatial and temporal context dependencies. Furthermore, the identified dichotomy of disturbance effects on the turnover in community composition demonstrates the potential of disturbances to either stabilize or destabilize biodiversity patterns over time across a wide range of environmental conditions.

Ecological stability encompasses multiple dimensions of functional and compositional responses to environmental change. Though no single stability dimension used in isolation can fully reflect the overall response to environmental change, a common vulnerability assessment that integrates simultaneously across multiple stability components is highly desirable for ecological risk assessment. We develop both functional and compositional counterparts of a novel, integrative metric of overall ecological vulnerability (OEV). We test the framework with data from a modularized experiment replicated in five lakes over two seasons, examining functional and compositional responses to both pulse and press disturbances across three trophic groups. OEV is measured as the area under the curve integrated over the entire observation period, with the curve delimiting the difference between the disturbance treatment and undisturbed parallel controls, expressed either as the log response ratio of biomass (functional OEV) or community dissimilarity index (compositional OEV). Both, functional and compositional OEV correlated negatively with functional and compositional ‘resistance’, ‘temporal stability’ and ‘final/extent of recovery’ following both pulse and press disturbances, though less so with ‘resilience’ following a pulse disturbance. We also found a positive correlation between functional and compositional OEV, which reveals the potential to also evaluate the intricate linkage between biodiversity and functional change. Our findings demonstrate that OEV comprises a robust framework to: (a) capture simultaneously multiple functional and compositional stability components, and (b) quantify the functional consequences of biodiversity change. Our results provide the basis for an overarching framework for quantifying the overall vulnerability of ecosystems to environmental change, opening new possibilities for ecological risk assessment and management. Synthesis. Ecological stability comprises multiple dimensions that together encapsulate how ecosystems respond to environmental change. Considering these multiple aspects of stability simultaneously often poses a problem in environmental assessments, which frequently require overarching indicators of risk or vulnerability. While an analysis of multiple dimensions allows for deeper exploration of mechanisms, here we develop and test a new univariate indicator that integrates stability aspects under a broad range of disturbance regimes. Using a modularized experiment in Swedish lakes, we show that this integrative measure captures multiple stability dimensions reflecting compositional and functional vulnerability and their relationships between them.

Whereas the anthropogenic impact on marine biodiversity is undebated, the quantification and prediction of this change are not trivial. Simple traditional measures of biodiversity (e.g. richness, diversity indices) do not capture the magnitude and direction of changes in species or functional composition. In this paper, we apply recently developed methods for measuring biodiversity turnover to time-series data of four broad taxonomic groups from two coastal regions: the southern North Sea (Germany) and the South African coast. Both areas share geomorphological features and ecosystem types, allowing for a critical assessment of the most informative metrics of biodiversity change across organism groups. We found little evidence for directional trends in univariate metrics of diversity for either the effective number of taxa or the amount of richness change. However, turnover in composition was high (on average nearly 30% of identities when addressing presence or absence of species) and even higher when taking the relative dominance of species into account. This turnover accumulated over time at similar rates across regions and organism groups. We conclude that biodiversity metrics responsive to turnover provide a more accurate reflection of community change relative to conventional metrics (absolute richness or relative abundance) and are spatially broadly applicable. This article is part of the theme issue ‘Integrative research perspectives on marine conservation’.

Estimates of biodiversity change are essential for the management and conservation of ecosystems. Accurate estimates rely on selecting representative sites, but monitoring often focuses on sites of special interest. How such site-selection biases influence estimates of biodiversity change is largely unknown. Site-selection bias potentially occurs across four major sources of biodiversity data, decreasing in likelihood from citizen science, museums, national park monitoring, and academic research. We defined site-selection bias as a preference for sites that are either densely populated (i.e., abundance bias) or species rich (i.e., richness bias). We simulated biodiversity change in a virtual landscape and tracked the observed biodiversity at a sampled site. The site was selected either randomly or with a site-selection bias. We used a simple spatially resolved, individual-based model to predict the movement or dispersal of individuals in and out of the chosen sampling site. Site-selection bias exaggerated estimates of biodiversity loss in sites selected with a bias by on average 300-400% compared with randomly selected sites. Based on our simulations, site-selection bias resulted in positive trends being estimated as negative trends: richness increase was estimated as 0.1 in randomly selected sites, whereas sites selected with a bias showed a richness change of -0.1 to -0.2 on average. Thus, site-selection bias may falsely indicate decreases in biodiversity. We varied sampling design and characteristics of the species and found that site-selection biases were strongest in short time series, for small grains, organisms with low dispersal ability, large regional species pools, and strong spatial aggregation. Based on these findings, to minimize site-selection bias, we recommend use of systematic site-selection schemes; maximizing sampling area; calculating biodiversity measures cumulatively across plots; and use of biodiversity measures that are less sensitive to rare species, such as the effective number of species. Awareness of the potential impact of site-selection bias is needed for biodiversity monitoring, the design of new studies on biodiversity change, and the interpretation of existing data.Efectos del Sesgo en la Selección de Sitio sobre las Estimaciones del Cambio en la Biodiversidad Resumen Las estimaciones del cambio en la biodiversidad son esenciales para el manejo y la conservación de los ecosistemas. Las estimaciones precisas dependen de la selección de sitios representativos pero su monitoreo con frecuencia se enfoca en los sitios de interés especial. En su mayoría se desconoce cómo influyen tales sesgos en la selección de sitios sobre las estimaciones del cambio en la biodiversidad. El sesgo en la selección de sitios ocurre potencialmente en cuatro fuentes principales de datos sobre biodiversidad, disminuyendo en probabilidad cuando los datos vienen de la ciencia ciudadana, museos, el monitoreo de los parques nacionales y la investigación académica. Definimos al sesgo en la selección de sitios como la preferencia por sitios que están densamente poblados (es decir, sesgo por abundancia) o que son ricos en especies (es decir, sesgo por riqueza). Simulamos el cambio en la biodiversidad en un paisaje virtual y le dimos seguimiento a la biodiversidad observada en un sitio muestreado. El sitio fue seleccionado al azar o con un sesgo en la selección de sitio. Usamos un modelo simple basado en los individuos y resuelto espacialmente para predecir el movimiento o la dispersión de los individuos dentro y fuera del sitio de muestreo elegido. El sesgo en la selección de sitio exageró las estimaciones de la pérdida de la biodiversidad en los sitios seleccionados con un sesgo en promedio de 300-400% en comparación con sitios seleccionados al azar. Con base en nuestras simulaciones, el sesgo en la selección de sitio derivó en que las tendencias positivas se estimaran como tendencias negativas: se estimó que el incremento en la riqueza fue de 0.1 en sitios seleccionados al azar, mientras que en los sitios seleccionados con un sesgo mostraron un cambio en la riqueza de −0.1 a −0.2 en promedio. Así, el sesgo en la selección de sitio puede indicar erróneamente la existencia de disminuciones en la biodiversidad. Variamos el diseño del muestreo y las características de las especies y encontramos que los sesgos en la selección de sitio estaban más consolidados en las series de tiempo corto, para los granos pequeños, organismos con una baja habilidad de dispersión, grandes patrimonios genéticos de especies regionales y una agregación espacial fuerte. Con base en estos resultados, para lograr minimizar el sesgo en la selección de sitio, recomendamos usar esquemas sistemáticos de selección de sitio; maximizar el área de muestreo; calcular las medidas de biodiversidad acumulativamente en los lotes; y usar las medidas de biodiversidad que son menos sensibles a las especies raras, como el número efectivo de especies. Se necesita tener conciencia sobre el impacto potencial del sesgo en la selección de sitio para el monitoreo de la biodiversidad, el diseño de nuevos estudios sobre el cambio en la biodiversidad y la interpretación de los datos existentes.估计生物多样性变化对于生态系统的管理和保护至关重要。准确的估计依赖于选择代表性位点, 但监测却往往集中于研究者特别感兴趣的位点。这种位点选择的偏倚如何影响对生物多样性变化的估计, 在很大程度上仍不清楚。位点选择偏倚可能出现在四种来源的生物多样性数据中, 按可能性从大到小排序依次为公民科学、博物馆、国家公园监测和学术研究。我们将位点选择偏倚定义为种群密度大 (即丰度偏倚) 和物种丰富 (丰富度偏倚) 两种类型。本研究在虚拟景观中模拟了生物多样性的变化, 并在一个采样点持续记录观察到的生物多样性。位点是随机选择或有偏倚地选择的。接下来, 我们使用基于个体的简单空间解析模型来预测个体在选定采样位点内外的移动或扩散。与随机选择位点相比, 偏倚性地选择位点对生物多样性损失的估计平均夸大了 300-400% 。根据我们的模拟, 位点选择偏倚会导致正趋势被估计为负趋势: 在随机选择的位点, 丰富度增加被估计为 0.1, 而偏倚性选择的位点, 丰富度平均变化为 −0.1到−0.2 。因此, 位点选择偏倚可能错误地表明生物多样性减少。我们改变了采样设计和物种特征, 结果发现在时间序列短、粒度小、生物扩散能力低、区域物种库较大和空间聚集较强的情况下, 位点选择偏倚最明显。基于以上发现, 为了最大程度地减少位点选择偏倚, 我们建议采用系统的位点选择方案、最大化采样区域、累积计算地块间的生物多样性, 以及使用对稀有物种不敏感的生物多样性指标, 例如有效物种数量。在生物多样性监测、生物多样性变化研究设计以及对现有数据的解释中, 都应认识到位点选择偏倚的潜在影响。翻译: 胡怡思; 审校: 聂永刚.

Aim Biodiversity dynamics comprise evolutionary and ecological changes on multiple temporal scales from millions of years to decades, but they are often interpreted within a single time frame. Planktonic foraminifera communities offer a unique opportunity for analysing the dynamics of marine biodiversity over different temporal scales. Our study aims to provide a baseline for assessments of biodiversity patterns over multiple time-scales, which is urgently needed to interpret biodiversity responses to increasing anthropogenic pressure. Location Global (26 sites). Time period Five time-scales: multi-million-year (0-7 Myr), million-year (0-0.5 Myr), multi-millennial (0-15 thousand years), millennial (0-1,100 years) and decadal (0-32 years). Major taxa studied Planktonic foraminifera. Methods We analysed community composition of planktonic foraminifera at five time-scales, combining measures of standing diversity (richness and effective number of species, ENS) with measures of temporal community turnover (presence-absence-based, dominance-based). Observed biodiversity patterns were compared with the outcome of a neutral model to separate the effects of sampling resolution (the highest in the shortest time series) from biological responses. Results Richness and ENS decreased from multi-million-year to millennial time-scales, but higher standing diversity was observed on the decadal scale. As predicted by the neutral model, turnover in species identity and dominance was strongest at the multi-million-year time-scale and decreased towards the millennial scale. However, contrary to the model predictions, modern time series show rapid decadal variation in the dominance structure of foraminifera communities, which is of comparable magnitude as over much longer time periods. Community turnover was significantly correlated with global temperature change, but not on the shortest time-scale. Main conclusions Biodiversity patterns can be to some degree predicted from the scaling effects related to different durations of time series, but changes in the dominance structure observed over the last few decades reach higher magnitude, probably forced by anthropogenic effects, than those observed over much longer durations.

Most ecosystems are affected by anthropogenic or natural pulse disturbances, which alter the community composition and functioning for a limited period of time. Whether and how quickly communities recover from such pulses is central to our understanding of biodiversity dynamics and ecosystem organisation, but also to nature conservation and management. Here, we present a meta-analysis of 508 (semi-)natural field experiments globally distributed across marine, terrestrial and freshwater ecosystems. We found recovery to be significant yet incomplete. At the end of the experiments, disturbed treatments resembled controls again when considering abundance (94%), biomass (82%), and univariate diversity measures (88%). Most disturbed treatments did not further depart from control after the pulse, indicating that few studies showed novel trajectories induced by the pulse. Only multivariate community composition on average showed little recovery: disturbed species composition remained dissimilar to the control throughout most experiments. Still, when experiments revealed a higher compositional stability, they tended to also show higher functional stability. Recovery was more complete when systems had high resistance, whereas resilience and resistance were negatively correlated. The overall results were highly consistent across studies, but significant differences between ecosystems and organism groups appeared. Future research on disturbances should aim to understand these differences, but also fill obvious gaps in the empirical assessments for regions (especially the tropics), ecosystems and organisms. In summary, we provide general evidence that (semi-)natural communities can recover from pulse disturbances, but compositional aspects are more vulnerable to long-lasting effects of pulse disturbance than the emergent functions associated to them.

While there is a lot of data on interactive effects of eutrophication and warming, to date, we lack data to generate reliable predictions concerning possible effects of nutrient decrease and temperature increase on community composition and functional responses. In recent years, a wide‐ranging trend of nutrient decrease (re‐oligotrophication) was reported for freshwater systems. Small lakes and ponds, in particular, show rapid responses to anthropogenic pressures and became model systems to investigate single as well as synergistic effects of warming and fertilization in situ and in experiments. Therefore, we set up an experiment to investigate the single as well as the interactive effects of nutrient reduction and gradual temperature increase on a natural freshwater phytoplankton community, using an experimental indoor mesocosm setup. Biomass production initially increased with warming but decreased with nutrient depletion. If nutrient supply was constant, biomass increased further, especially under warming conditions. Under low nutrient supply, we found a sharp transition from initially positive effects of warming to negative effects when resources became scarce. Warming reduced phytoplankton richness and evenness, whereas nutrient reduction at ambient temperature had positive effects on diversity. Our results indicate that temperature effects on freshwater systems will be altered by nutrient availability. These interactive effects of energy increase and resource decrease have major impacts on biodiversity and ecosystem function and thus need to be considered in environmental management plans.

1. A resampling of 38 small farmland ponds in Belgium after 10 years revealed a high temporal species turnover for both phytoplankton and zooplankton communities, associated with substantial changes in abiotic factors, especially a reduction in total phosphorus concentration. 2. Across ponds, phytoplankton biomass decreased while evenness and richness increased between the samplings in 2003 and 2013. By contrast, the zooplankton assemblage was characterised by lower biomass, richness and evenness in 2013. Ponds experiencing larger environmental change showed stronger changes in phytoplankton richness and evenness. 3. Resource use efficiency (RUE) of zooplankton increased with greater environmental change and zooplankton evenness, which points to a switch towards species with higher RUE or greater variety in food sources in higher trophic levels. 4. As ponds are important habitats for freshwater biodiversity and ecosystems services, the strong but predictable species turnover and the opposing effects of environmental change on different trophic levels need to be embedded in conservation and management plans.

Global concern about human impact on biological diversity has triggered an intense research agenda on drivers and consequences of biodiversity change in parallel with international policy seeking to conserve biodiversity and associated ecosystem functions. Quantifying the trends in biodiversity is far from trivial, however, as recently documented by meta-analyses, which report little if any net change in local species richness through time.Here, we summarise several limitations of species richness as a metric of biodiversity change and show that the expectation of directional species richness trends under changing conditions is invalid. Instead, we illustrate how a set of species turnover indices provide more information content regarding temporal trends in biodiversity, as they reflect how dominance and identity shift in communities over time.We apply these metrics to three monitoring datasets representing different ecosystem types. In all datasets, nearly complete species turnover occurred, but this was disconnected from any species richness trends. Instead, turnover was strongly influenced by changes in species presence (identities) and dominance (abundances). We further show that these metrics can detect phases of strong compositional shifts in monitoring data and thus identify a different aspect of biodiversity change decoupled from species richness.Synthesis and applications: Temporal trends in species richness are insufficient to capture key changes in biodiversity in changing environments. In fact, reductions in environmental quality can lead to transient increases in species richness if immigration or extinction has different temporal dynamics. Thus, biodiversity monitoring programmes need to go beyond analyses of trends in richness in favour of more meaningful assessments of biodiversity change.Synthesis and applications:Temporal trends in species richness are insufficient to capture key changes in biodiversity in changing environments. In fact, reductions in environmental quality can lead to transient increases in species richness if immigration or extinction has different temporal dynamics. Thus, biodiversity monitoring programmes need to go beyond analyses of trends in richness in favour of more meaningful assessments of biodiversity change.

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

Biodiversity ensures ecosystem functioning and provisioning of ecosystem services, but it remains unclear how biodiversity-ecosystem multifunctionality relationships depend on the identity and number of functions considered. Here, we demonstrate that ecosystem multifunctionality, based on 82 indicator variables of ecosystem functions in a grassland biodiversity experiment, increases strongly with increasing biodiversity. Analysing subsets of functions showed that the effects of biodiversity on multifunctionality were stronger when more functions were included and that the strength of the biodiversity effects depended on the identity of the functions included. Limits to multifunctionality arose from negative correlations among functions and functions that were not correlated with biodiversity. Our findings underline that the management of ecosystems for the protection of biodiversity cannot be replaced by managing for particular ecosystem functions or services and emphasize the need for specific management to protect biodiversity. More plant species from the experimental pool of 60 species contributed to functioning when more functions were considered. An individual contribution to multifunctionality could be demonstrated for only a fraction of the species.

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.

The paradigmatic hypothesis for the effect of fertilisation on plant diversity represents a one-dimensional trade-off for plants competing for below-ground nutrients (generically) and above-ground light: fertilisation reduces competition for nutrients while increasing biomass and thereby shifts competition for depleted available light. The essential problem of this simple paradigm is that it misses both the multivariate and mechanistic nature of the factors that determine biodiversity as well as their causal relationships. We agree that light limitation, as DeMalach and Kadmon argue, can indeed be an important factor associated with diversity loss, and we presented it as an integral part of our tests of the niche dimension hypothesis. We disagree with DeMalach and Kadmon that light is the ‘main’ factor explaining diversity, because this misrepresents the causal structure represented in the design of our experiment in which multiple nutrient addition was the ultimate causal driver of a suite of correlated responses that included diversity and light, and especially live and dead biomass, which are the factors that control light depletion. Our findings highlight that multiple nutrient limitations can structure plant diversity and composition independently of changes in light and biomass. For example, approximately one-third of our sites showed no significant increase in biomass with greater number of added nutrients yet still lost diversity when nutrients were added. The important message is that while light limitation can be an important contributor to diversity loss, it is not a necessary mechanism. Fil: Harpole, W. Stanley. Helmholtz Center for Environmental Research; Alemania Fil: Sullivan, Lauren L.. University of Minnesota; Estados Unidos Fil: Lind, Eric M.. University of Minnesota; Estados Unidos Fil: Firn, Jennifer. Queensland University of Technology; Australia Fil: Adler, Peter B.. State University of Utah; Estados Unidos Fil: Borer, Elizabeth T.. University of Minnesota; Estados Unidos Fil: Chase, Jonathan. Martin Luther University Halle Wittenberg; Alemania Fil: Fay, Philip A.. USDA-ARS Grassland Soil and Water Research Lab; Estados Unidos Fil: Hautier, Yann. Utrecht University; Países Bajos Fil: Hillebrand, Helmut. University of Oldenburg; Alemania Fil: MacDougall, Andrew S.. University of Guelph; Canadá Fil: Seabloom, Eric W.. University of Minnesota; Estados Unidos Fil: Bakker, Jonathan D.. University of Washington; Estados Unidos Fil: Cadotte, Marc W.. University of Toronto; Canadá Fil: Chaneton, Enrique Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía; Argentina Fil: Chu, Chengjin. Sun Yat-sen University; China Fil: Hagenah, Nicole. University of KwaZulu-Natal; Sudáfrica Fil: Kirkman, Kevin. University of KwaZulu-Natal; Sudáfrica Fil: La Pierre, Kimberly J.. Smithsonian Environmental Research Center; Estados Unidos Fil: Moore, Joslin L.. Monash University; Australia Fil: Morgan, John W.. La Trobe University; Australia Fil: Prober, Suzanne M.. CSIRO Land and Water; Australia Fil: Risch, Anita C.. Swiss Federal Institute for Forest, Snow and Landscape Research; Suiza Fil: Schuetz, Martin. Swiss Federal Institute for Forest, Snow and Landscape Research; Suiza Fil: Stevens, Carly J.. Lancaster University; Reino Unido

Consumer diversity effects on ecosystem functioning are highly context dependent and are determined by consumer specialization and other consumer and prey specific traits such as growth and grazing rates. Despite complex reciprocal interactions between consumers and their prey, few experimental studies have focused on prey diversity effects on consumer dynamics and trophic transfer. In microbial microcosms, we investigated effects of algal prey diversity (one, two and four species) on the production, evenness and grazing rates of 4 ciliate consumers, differing in grazing preferences and rates. Prey diversity increased prey biovolume in the absence of consumers and had opposing effects on different consumers, depending on their specialization and their preferred prey. Consumers profited from prey mixtures compared to monocultures of non-preferred prey, but responded negatively if preferred prey species were offered together with other species. Prey diversity increased consumer evenness by preventing dominance of specific consumers, demonstrating that the loss of prey species may have cascading effects resulting in reduced consumer diversity. Our study emphasizes that not only the degree of specialization but also the selectivity for certain prey species within the dietary niche may alter the consequences of changing prey diversity in a food web context.

Summary 1.Niche complementarity and competitive disparity are driving mechanisms behind plant community assembly and productivity. Consequently, there is great interest in predicting species complementarity and their competitive differences from their functional traits as dissimilar species may compete less and result in more complete use of resources. 2.Here we assessed the role of trait dissimilarities on species complementarity and competitive disparities within an experimental gradient of plant species richness and functional trait dissimilarity. Communities were assembled using three pools of grass and forb species based on a priori knowledge of traits related to (1) above- and belowground spatial differences in resource acquisition, (2) phenological differences, or (3) both. Complementarity and competitive disparities were assessed by partitioning the overyielding in mixed species communities into species complementarity and dominance effects. 3.Community overyielding and the underlying complementarity and competitive dominance varied strongly among the three plant species pools. Overyielding and complementarity was greatest among species that were assembled based on their variation in both spatial and phenological traits. Competitive dominance was greatest when species were assembled based on spatial resource-acquisition traits alone. 4.In communities that were assembled based on species variation in only spatial or phenological traits greater competitive dominance was predicted by greater differences SLA and flowering initiation respectively, while greater complementarity was predicted by greater dissimilarity in leaf area and flowering senescence, respectively. Greater differences in leaf area could also be linked to greater species complementarity in communities assembled based on variation in both phenological and spatial traits, but trait dissimilarity was unrelated to competitive dominance in these communities. 5.Our results indicate that complementarity and competitive disparity among species are both driven by trait dissimilarities. However, the identity of the traits that drives the complementarity and competitive disparity depends on the trait variation among species that comprise the community. Moreover, we demonstrate that communities assembled with the greater variation in both spatial and phenological traits show the greatest complementarity among species. This article is protected by copyright. All rights reserved.

Climatic warming is a primary driver of change in ecosystems worldwide. Here, we synthesize responses of species richness and evenness from 187 experimental warming studies in a quantitative meta-analysis. We asked 1) whether effects of warming on diversity were detectable and consistent across terrestrial, freshwater and marine ecosystems, 2) if effects on diversity correlated with intensity, duration, and experimental unit size of temperature change manipulations, and 3) whether these experimental effects on diversity interacted with ecosystem types. Using multilevel mixed linear models and model averaging, we also tested the relative importance of variables that described uncontrolled environmental variation and attributes of experimental units. Overall, experimental warming reduced richness across ecosystems (mean log-response ratio = -0.091, 95% bootstrapped CI: -0.13, -0.05) representing an 8.9% decline relative to ambient temperature treatments. Richness did not change in response to warming in freshwater systems, but was more strongly negative in terrestrial (-11.8%) and marine (-10.5%) experiments. In contrast, warming impacts on evenness were neutral overall and in aquatic systems, but weakly negative on land (7.6%). Intensity and duration of experimental warming did not explain variation in diversity responses, but negative effects on richness were stronger in smaller experimental units, particularly in marine systems. Model-averaged parameter estimation confirmed these main effects while accounting for variation in latitude, ambient temperature at the sites of manipulations, venue (field versus lab), community trophic type, and whether experiments were open or closed to colonization. These analyses synthesize extensive experimental evidence showing declines in local richness with increased temperature, particularly in terrestrial and marine communities. However, the more variable effects of warming on evenness were better explained by the random effect of site identity, suggesting that effects on species' relative abundances were contingent on local species composition.

Food-chain length (FCL) is a fundamental ecosystem attribute, integrating information on both food web composition and ecosystem processes. It remains untested whether FCL also reflects the history of community assembly known to affect community composition and ecosystem functioning. Here, we performed microcosm experiments with a copepod (top predator), two ciliate species (intermediate consumers), and bacteria (producers), and modified the sequence of species introduction into the microcosm at four productivity levels to jointly test the effects of historical contingency and productivity on FCL. FCL increased when the top predator was introduced last; thus, the trophic position of the copepod reflected assembly history. A shorter FCL occurred at the highest productivity level, probably because the predator switched to feeding at the lower trophic levels because of the abundant basal resource. Thus, we present empirical evidence that FCL was determined by historical contingency, likely caused by priority effects, and by productivity., Hideyuki Doi and Helmut Hillebrand investigate how the sequence of species immigration affects food-chain length and whether the effect depends on productivity. Using a microcosm experiment including a copepod predator, ciliate species, and bacteria, they find that food chains are longest when the top predator is added last and that high productivity reduces food-chain length.

The relationship between biodiversity and ecosystem functioning (BEF) is a topic of considerable interest to scientists and managers because a better understanding of its underlying mechanisms may help us mitigate the consequences of biodiversity loss on ecosystems. Our current knowledge of BEF relies heavily on theoretical and experimental studies, typically conducted on a narrow range of spatio-temporal scales, environmental conditions, and trophic levels. Hence, whether a relationship holds in the natural environment is poorly understood, especially in exploited marine ecosystems. Using large-scale observations of marine fish communities, we applied a structural equation modelling framework to investigate the existence and significance of BEF relationships across northwestern European seas. We find that ecosystem functioning, here represented by spatial patterns in total fish biomass, is unrelated to species richness—the most commonly used diversity metric in BEF studies. Instead, community evenness, differences in species composition, and abiotic variables are significant drivers. In particular, we find that high fish biomass is associated with fish assemblages dominated by a few generalist species of a high trophic level, who are able to exploit both the benthic and pelagic energy pathway. Our study provides a better understanding of the mechanisms behind marine ecosystem functioning and allows for the integration of biodiversity into management considerations.

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.

Whereas the conservation and management of biodiversity has become a key issue in environmental sciences and policy in general, the conservation of marine biodiversity faces additional challenges such as the challenges of accessing field sites (e.g. polar, deep sea), knowledge gaps regarding biodiversity trends, high mobility of many organisms in fluid environments, and ecosystem-specific obstacles to stakeholder engagement and governance. This issue comprises contributions from a diverse international group of scientists in a benchmarking volume for a common research agenda on marine conservation. We begin by addressing information gaps on marine biodiversity trends through novel approaches and technologies, then linking such information to ecosystem functioning through a focus on traits. We then leverage the knowledge of these relationships to inform theory aiming at predicting the future composition and functioning of marine communities. Finally, we elucidate the linkages between marine ecosystems and human societies by examining economic, management and governance approaches that contribute to effective marine conservation in practice. This article is part of the theme issue ‘Integrative research perspectives on marine conservation’.

International audience; Human actions challenge nature in many ways. Ecological responses are ineluctably complex, demanding measures that describe them succinctly. Collectively, these measures encapsulate the overall ‘stability’ of the system. Many international bodies, including the Intergovernmental Science‐Policy Platform on Biodiversity and Ecosystem Services, broadly aspire to maintain or enhance ecological stability. Such bodies frequently use terms pertaining to stability that lack clear definition. Consequently, we cannot measure them and so they disconnect from a large body of theoretical and empirical understanding. We assess the scientific and policy literature and show that this disconnect is one consequence of an inconsistent and one‐dimensional approach that ecologists have taken to both disturbances and stability. This has led to confused communication of the nature of stability and the level of our insight into it. Disturbances and stability are multidimensional. Our understanding of them is not. We have a remarkably poor understanding of the impacts on stability of the characteristics that define many, perhaps all, of the most important elements of global change. We provide recommendations for theoreticians, empiricists and policymakers on how to better integrate the multidimensional nature of ecological stability into their research, policies and actions.

Plant diversity is an important driver of nitrogen and phosphorus stocks in aboveground plant biomass of grassland ecosystems, but plant diversity effects on other elements also important for plant growth are less understood. We tested whether plant species richness, functional group richness or the presence/absence of particular plant functional groups influences the Si and Ca concentrations (mmol g(-1)) and stocks (mmol m(-2)) in aboveground plant biomass in a large grassland biodiversity experiment (Jena Experiment). In the experiment including 60 temperate grassland species, plant diversity was manipulated as sown species richness (1, 2, 4, 8, 16) and richness and identity of plant functional groups (1-4; grasses, small herbs, tall herbs, legumes). We found positive species richness effects on Si as well as Ca stocks that were attributable to increased biomass production. The presence of particular functional groups was the most important factor explaining variation in aboveground Si and Ca stocks (mmol m(-2)). Grass presence increased the Si stocks by 140 % and legume presence increased the Ca stock by 230 %. Both the presence of specific plant functional groups and species diversity altered Si and Ca stocks, whereas Si and Ca concentration were affected mostly by the presence of specific plant functional groups. However, we found a negative effect of species diversity on Si and Ca accumulation, by calculating the deviation between mixtures and mixture biomass proportions, but in monoculture concentrations. These changes may in turn affect ecosystem processes such as plant litter decomposition and nutrient cycling in grasslands.

Environmental change can result in substantial shifts in community composition. The associated immigration and extinction events are likely constrained by the spatial distribution of species. Still, studies on environmental change typically quantify biotic responses at single spatial (time series within a single plot) or temporal (spatial beta diversity at single time points) scales, ignoring their potential interdependence. Here, we use data from a global network of grassland experiments to determine how turnover responses to two major forms of environmental change - fertilisation and herbivore loss - are affected by species pool size and spatial compositional heterogeneity. Fertilisation led to higher rates of local extinction, whereas turnover in herbivore exclusion plots was driven by species replacement. Overall, sites with more spatially heterogeneous composition showed significantly higher rates of annual turnover, independent of species pool size and treatment. Taking into account spatial biodiversity aspects will therefore improve our understanding of consequences of global and anthropogenic change on community dynamics.

Biodiversity is declining in many local communities while also becoming increasingly homogenized across space. Experimentsshow that local plant species loss reduces ecosystem functioning and services, but the role of spatial homogenization of communitycomposition and the potential interaction between diversity at different scales in maintaining ecosystem functioningremains unclear, especially when many functions are considered (ecosystem multifunctionality). We present an analysis ofeight ecosystem functions measured in 65 grasslands worldwide. We find that more diverse grasslands?those with both species-rich local communities (α-diversity) and large compositional differences among localities (β-diversity)?had higher levelsof multifunctionality. Moreover, α- and β-diversity synergistically affected multifunctionality, with higher levels of diversity at one scale amplifying the contribution to ecological functions at the other scale. The identity of species influencing ecosystem functioning differed among functions and across local communities, explaining why more diverse grasslands maintained greater functionality when more functions and localities were considered. These results were robust to variation in environmental drivers. Our findings reveal that plant diversity, at both local and landscape scales, contributes to the maintenance of multiple ecosystem services provided by grasslands. Preserving ecosystem functioning therefore requires conservation of biodiversity both within and among ecological communities. Fil: Hautier, Yann. University of Utrecht; Países Bajos Fil: Isbell, Forest. University of Minnesota; Estados Unidos Fil: Borer, Elizabeth T.. University of Minnesota; Estados Unidos Fil: Seabloom, Eric W.. University of Minnesota; Estados Unidos Fil: Harpole, Stanley. Martin Luther University Halle-Wittenberg; Alemania Fil: Lind, Eric M.. University of Minnesota; Estados Unidos Fil: MacDougall, Andrew. University of Guelph; Canadá Fil: Stevens, Carly. Lancaster University, ; Reino Unido Fil: Adler, Peter. Utah State University; Estados Unidos Fil: Alberti, Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Bakker, Jonathan D. University of Washington, ; Estados Unidos Fil: Brudvig, Lars A. Michigan State University; Estados Unidos Fil: Buckley, Yvonne M. Trinity College Dublin; Irlanda Fil: Cadotte, Marc. University of Toronto Scarborough,; Canadá Fil: Caldeira, María C. University of Lisbon; Portugal Fil: Chaneton, Enrique Jose. Universidad de Buenos Aires; Argentina Fil: Chu, Chengjin. Sun Yat-sen University; China Fil: Daleo, Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Dickman, Christopher R. The University of Sydney; Australia Fil: Dwyer, John M. The University of Queensland; Australia Fil: Eskelinen, Anu. University of Oulu; Finlandia Fil: Fay, Philip. USDA-ARS, Grassland Soil and Water Lab; Estados Unidos Fil: Firn, Jennifer. Queensland University of Technology; Australia Fil: Hagenah, Nicole. University of KwaZulu-Natal; Sudáfrica Fil: Hillebrand, Helmut. University Oldenburg; Alemania Fil: Iribarne, Oscar Osvaldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Kirkman, Kevin P.. University of KwaZulu-Natal; Sudáfrica Fil: Knops, Johannes M. H. University of Nebraska, Lincoln; Estados Unidos Fil: La Pierre, Kimberly J. Smithsonian Environmental Research Center; Estados Unidos Fil: McCulley, Rebecca L. University of Kentucky; Estados Unidos Fil: Morgan, John W.. La Trobe University; Australia Fil: Pärtel, Meelis. University of Tartu; Estonia Fil: Pascual, Jesus Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Price, Jodi N. Charles Sturt University; Australia Fil: Prober, Suzanne M. CSIRO Land and Water; Australia Fil: Risch, Anita C. Swiss Federal Institute of Forest, Snow and Landscape Research; Suiza Fil: Sankaran, Mahesh. National Centre for Biological Sciences; India Fil: Schuetz, Martin. Swiss Federal Institute of Forest, Snow and Landscape Research; Suiza Fil: Standish, Rachel J. Murdoch University; Australia Fil: Virtanen, Risto. University of Oulu; Finlandia Fil: Wardle, Glenda M. The University of Sydney; Australia Fil: Yahdjian, María Laura. UBA; Argentina Fil: Hector, Andy. University of Oxford; Reino Unido

There is growing interest in the integration of macroecology and palaeoecology towards a better understanding of past, present, and anticipated future biodiversity dynamics. However, the empirical basis for this integration has thus far been limited. Here we review prospects for a macroecology–palaeoecology integration in biodiversity analyses with a focus on marine microfossils [i.e. small (or small parts of) organisms with high fossilization potential, such as foraminifera, ostracodes, diatoms, radiolaria, coccolithophores, dinoflagellates, and ichthyoliths]. Marine microfossils represent a useful model system for such integrative research because of their high abundance, large spatiotemporal coverage, and good taxonomic and temporal resolution. The microfossil record allows for quantitative cross-scale research designs, which help in answering fundamental questions about marine biodiversity, including the causes behind similarities in patterns of latitudinal and longitudinal variation across taxa, the degree of constancy of observed gradients over time, and the relative importance of hypothesized drivers that may explain past or present biodiversity patterns. The inclusion of a deep-time perspective based on high-resolution microfossil records may be an important step for the further maturation of macroecology. An improved integration of macroecology and palaeoecology would aid in our understanding of the balance of ecological and evolutionary mechanisms that have shaped the biosphere we inhabit today and affect how it may change in the future.

Humans dominate many important Earth system processes including the nitrogen (N) cycle. Atmospheric N deposition affects fundamental processes such as carbon cycling, climate regulation, and biodiversity, and could result in changes to fundamental Earth system processes such as primary production. Both modelling and experimentation have suggested a role for anthropogenically altered N deposition in increasing productivity, nevertheless, current understanding of the relative strength of N deposition with respect to other controls on production such as edaphic conditions and climate is limited. Here we use an international multiscale data set to show that atmospheric N deposition is positively correlated to aboveground net primary production (ANPP) observed at the 1-m 2 level across a wide range of herbaceous ecosystems. N deposition was a better predictor than climatic drivers and local soil conditions, explaining 16% of observed variation in ANPP globally with an increase of 1 kg Nha � 1 � yr � 1 increasing ANPP by 3%. Soil pH explained 8% of observed variation in ANPP while climatic drivers showed no significant relationship. Our results illustrate that the incorporation of global N deposition patterns in Earth system models are likely to substantially improve estimates of primary production in herbaceous systems. In herbaceous systems across the world, humans appear to be partially driving local ANPP through impacts on the N cycle.

In this chapter, the effects of temperature change—as a main aspect of climate change—on marine biodiversity are assessed. Starting from a general discussion of species responses to temperature, the chapter presents how species respond to warming. These responses comprise adaptation and phenotypic plasticity as well as range shifts. The observed range shifts show more rapid shifts at the poleward range edge than at the equator-near edge, which probably reflects more rapid immigration than extinction in a warming world. A third avenue of changing biodiversity is change in species interactions, which can be altered by temporal and spatial shifts in interacting species. We then compare the potential changes in biodiversity to actual trends recently addressed in empirical synthesis work on local marine biodiversity, which lead to conceptual issues in quantifying the degree of biodiversity change. Finally we assess how climate change impacts the protection of marine environments.

International audience; We examined the relationship between species richness (S) and evenness (J) within a novel, community assembly framework. We hypothesized that environmental stress leads to filtering (increasing the proportional abundance of tolerant species) and taxonomic dispersion (decreasing the number of species within genera and families). Environmental filtering would cause a decline in S by eliminating some stress-sensitive species and a reduction of J by allowing only tolerant species to maintain large populations. Taxonomic relatedness may influence both S and J by controlling the nature of interspecific interactions—positive under taxonomic dispersion versus negative under taxonomic clustering. Therefore, the S–J relationship may be a product of environmental filtering and taxonomic relatedness. We tested this framework with redundancy analyses and structural equation models using continental stream diatom and fish data. We confirmed that (i) environmental stress, defined by watershed forest cover, slope, and temperature, caused filtering (lower sensitive:tolerant species abundance ratios) and taxonomic dispersion (elevated genus:species richness and family:species richness ratios); (ii) S and J, which declined with filtering and taxonomic dispersion, exhibited a positive relationship; and (iii) the role of filtering on J was pronounced only under stressful conditions, while taxonomic dispersion remained an important predictor of J across stressful and favorable environments.

In the past two decades, a large number of studies have investigated the relationship between biodiversity and ecosystem functioning, most of which focussed on a limited set of ecosystem variables. The Jena Experiment was set up in 2002 to investigate the effects of plant diversity on element cycling and trophic interactions, using a multi-disciplinary approach. Here, we review the results of 15 years of research in the Jena Experiment, focussing on the effects of manipulating plant species richness and plant functional richness. With more than 85,000 measures taken from the plant diversity plots, the Jena Experiment has allowed answering fundamental questions important for functional biodiversity research.[br/] First, the question was how general the effect of plant species richness is, regarding the many different processes that take place in an ecosystem. About 45% of different types of ecosystem processes measured in the 'main experiment', where plant species richness ranged from 1 to 60 species, were significantly affected by plant species richness, providing strong support for the view that biodiversity is a significant driver of ecosystem functioning. Many measures were not saturating at the 60-species level, but increased linearly with the logarithm of species richness. There was, however, great variability in the strength of response among different processes. One striking pattern was that many processes, in particular belowground processes, took several years to respond to the manipulation of plant species richness, showing that biodiversity experiments have to be long-term, to distinguish trends from transitory patterns. In addition, the results from the Jena Experiment provide further evidence that diversity begets stability, for example stability against invasion of plant species, but unexpectedly some results also suggested the opposite, e.g. when plant communities experience severe perturbations or elevated resource availability. This highlights the need to revisit diversity-stability theory.[br/] Second, we explored whether individual plant species or individual plant functional groups, or biodiversity itself is more important for ecosystem functioning, in particular biomass production. We found strong effects of individual species and plant functional groups on biomass production, yet these effects mostly occurred in addition to, but not instead of, effects of plant species richness.[br/] Third, the Jena Experiment assessed the effect of diversity on multitrophic interactions. The diversity of most organisms responded positively to increases in plant species richness, and the effect was stronger for above-than for belowground organisms, and stronger for herbivores than for carnivores or detritivores. Thus, diversity begets diversity. In addition, the effect on organismic diversity was stronger than the effect on species abundances.[br/] Fourth, the Jena Experiment aimed to assess the effect of diversity on N, P and C cycling and the water balance of the plots, separating between element input into the ecosystem, element turnover, element stocks, and output from the ecosystem. While inputs were generally less affected by plant species richness, measures of element stocks, turnover and output were often positively affected by plant diversity, e.g. carbon storage strongly increased with increasing plant species richness. Variables of the N cycle responded less strongly to plant species richness than variables of the C cycle.[br/] Fifth, plant traits are often used to unravel mechanisms underlying the biodiversity-ecosystem functioning relationship. In the Jena Experiment, most investigated plant traits, both above-and belowground, were plastic and trait expression depended on plant diversity in a complex way, suggesting limitation to using database traits for linking plant traits to particular functions.[br/] Sixth, plant diversity effects on ecosystem processes are often caused by plant diversity effects on species interactions. Analyses in the Jena Experiment including structural equation modelling suggest complex interactions that changed with diversity, e.g. soil carbon storage and greenhouse gas emission were affected by changes in the composition and activity of the belowground microbial community. Manipulation experiments, in which particular organisms, e.g. belowground invertebrates, were excluded from plots in split-plot experiments, supported the important role of the biotic component for element and water fluxes.[br/] Seventh, the Jena Experiment aimed to put the results into the context of agricultural practices in managed grasslands. The effect of increasing plant species richness from 1 to 16 species on plant biomass was, in absolute terms, as strong as the effect of a more intensive grassland management, using fertiliser and increasing mowing frequency. Potential bioenergy production from high-diversity plots was similar to that of conventionally used energy crops. These results suggest that diverse 'High Nature Value Grasslands' are multifunctional and can deliver a range of ecosystem services including production-related services.[br/] A final task was to assess the importance of potential artefacts in biodiversity-ecosystem functioning relationships, caused by the weeding of the plant community to maintain plant species composition. While the effort ( in hours) needed to weed a plot was often negatively related to plant species richness, species richness still affected the majority of ecosystem variables. Weeding also did not negatively affect monoculture performance; rather, monocultures deteriorated over time for a number of biological reasons, as shown in plant-soil feedback experiments.[br/] To summarize, the Jena Experiment has allowed for a comprehensive analysis of the functional role of biodiversity in an ecosystem. A main challenge for future biodiversity research is to increase our mechanistic understanding of why the magnitude of biodiversity effects differs among processes and contexts. It is likely that there will be no simple answer. For example, among the multitude of mechanisms suggested to underlie the positive plant species richness effect on biomass, some have received limited support in the Jena Experiment, such as vertical root niche partitioning. However, others could not be rejected in targeted analyses. Thus, from the current results in the Jena Experiment, it seems likely that the positive biodiversity effect results from several mechanisms acting simultaneously in more diverse communities, such as reduced pathogen attack, the presence of more plant growth promoting organisms, less seed limitation, and increased trait differences leading to complementarity in resource uptake. Distinguishing between different mechanisms requires careful testing of competing hypotheses. Biodiversity research has matured such that predictive approaches testing particular mechanisms are now possible.

Disentangling the mechanisms that maintain the stability of communities and ecosystem properties has become a major research focus in ecology in the face of anthropogenic environmental change. Dispersal plays a pivotal role in maintaining diversity in spatially subdivided communities, but only a few experiments have simultaneously investigated how dispersal and environmental fluctuation affect community dynamics and ecosystem stability. We performed an experimental study using marine phytoplankton species as model organisms to test these mechanisms in a metacommunity context. We established three levels of dispersal and exposed the phytoplankton to fluctuating light levels, where fluctuations were either spatially asynchronous or synchronous across patches of the metacommunity. Dispersal had no effect on diversity and ecosystem function (biomass), while light fluctuations affected both evenness and community biomass. The temporal variability of community biomass was reduced by fluctuating light and temporal beta diversity was influenced interactively by dispersal and fluctuation, whereas spatial variability in community biomass and beta diversity were barely affected by treatments. Along the establishing gradient of species richness and dominance, community biomass increased but temporal variability of biomass decreased, thus highest stability was associated with species-rich but highly uneven communities and less influenced by compensatory dynamics. In conclusion, both specific traits (dominance) and diversity (richness) affected the stability of metacommunities under fluctuating conditions.

Plant functional characteristics may drive plant species richness effects on ecosystem processes. Consequently, the focus of biodiversity–ecosystem functioning (BEF) experiments has expanded from the manipulation of plant species richness to manipulating functional trait composition. Involving ecophysiological plant traits in the experimental design might allow for a better understanding of how species loss alters ecosystem processes. Here we provide the theoretical background, design and first results of the ‘Trait-Based Biodiversity Experiment’ (TBE), established in 2010 that directly manipulates the trait composition of experimental plant communities. Analysis of six plant traits related to resource acquisition and use were analyzed using principal component analysis of 60 grassland species. The resulting two main axes describe gradients in functional similarity, and were used as the basis for designing plant communities with different functional and species diversity levels. Using such an approach allowed us to manipulate different levels of complementarity in spatial and temporal plant resource acquisition. In contrast to previous biodiversity experiments, the TBE is designed according to more realistic scenarios of non-random species loss along orthogonal axes of species trait dissimilarities. This allows us to tease apart the relative importance of selection and complementarity effects on multiple ecosystem processes, and to mechanistically study the consequences of plant community simplification.

One of the most controversially discussed topics in current biodiversity-ecosystem function research is the transfer of results from experimental and theoretical studies to natural ecosystems. At the same time, monitoring data on biodiversity are requested as key indicators for the state of an ecosystem in most environmental evaluation frameworks. We analyse two monitoring data sets comprising information on abundance and biomass of macrozoobenthos communities in the German Wadden Sea in order to evaluate how much information monitoring data on biodiversity provide concerning ecosystem functioning and what implications this information (or the lack thereof) has for future monitoring programmes. Our results show a positive correlation between number of species of macrozoobenthos and its standing stock. Despite differences in overall biomass and individual size in different functional groups, this correlation remained consistent for different feeding guilds and therefore is likely to be independent of certain species traits. Moreover, functional turnover analyses indicate that increasing species richness is needed to maintain biomass levels over increasing periods of time. Whereas our data thus corroborate predictions from theory, we could not determine any causal relationships, because monitoring data commonly include only vague proxies for very few functional parameters, in our case standing biomass as a proxy for production. As to the use of diversity as an indicator for ecosystem functioning, we advise that management decisions are to be based on verified causal relationships and therefore strongly suggest the general incorporation of unambiguous proxies for functional parameters in the measuring campaigns of monitoring programmes.

The linkages between biological communities and ecosystem function remain poorly understood along gradients of human-induced stressors. We examined how resource provisioning (nutrient recycling), mediated by native freshwater mussels, influences the structure and function of benthic communities by combining observational data and a field experiment. We compared the following: (1) elemental and community composition (algal pigments and macroinvertebates) on live mussel shells and on nearby rocks across a gradient of catchment agriculture and (2) experimental colonisation of benthic communities on live vs. sham shells controlling for initial community composition and colonisation duration. We show that in near pristine systems, nutrient heterogeneity mediated by mussels relates to greater biodiversity of communities, which supports the notion that resource heterogeneity can foster biological diversity. However, with increased nutrients from the catchment, the relevance of mussel-provisioned nutrients was nearly eliminated. While species can persist in disturbed systems, their functional relevance may be diminished or lost.

Plant growth can be limited by resource acquisition and defence against consumers, leading to contrasting trade-off possibilities. The competition-defence hypothesis posits a trade-off between competitive ability and defence against enemies (e.g. herbivores and pathogens). The growth-defence hypothesis suggests that strong competitors for nutrients are also defended against enemies, at a cost to growth rate. We tested these hypotheses using observations of 706 plant populations of over 500 species before and following identical fertilisation and fencing treatments at 39 grassland sites worldwide. Strong positive covariance in species responses to both treatments provided support for a growth-defence trade-off: populations that increased with the removal of nutrient limitation (poor competitors) also increased following removal of consumers. This result held globally across 4 years within plant life-history groups and within the majority of individual sites. Thus, a growth-defence trade-off appears to be the norm, and mechanisms maintaining grassland biodiversity may operate within this constraint.

Two decades of biodiversity-ecosystem func tioning research have not yet led to consensus view on how local dominance and bio diversity affect the stability of ecosystems in the presence of disturbances. As natural systems are usually affected by multiple stressors, we tested the diversity−stability hypothesis on phytoplankton commu nities subjected to combinations of 2 stressors (pH reduction and simulated grazing). Monocultures revealed uncorrelated species’ sensitivities to the 2 stressors and the presence of a best-performing species (Scenedesmus obliquus). We thus selected 2 experimental species combinations, either (A) including or (B) excluding S. obliquus, and inoculated at 3 diversity levels (2, 4, 8 species). Both stressors induced significant biovolume loss and increased temporal biovolume variation, but the effect on final biomass (Btot) differed between combinations and with richness. The fast recovery of S. obliquus precluded long-term disturbance effects on Btot in Combination A. Correspondingly, these communities showed slower recovery rates and lower Btot with more species present, since the strong performance of S. obliquus was diluted by more species being present. More species-rich assemblages in Combination B lost more biovolume after stressor application, whereas the recovery rates showed a more complex pattern, depending on stressor sequence and species richness. Our study suggests that the stability of communities in the face of multiple disturbances cannot be predicted from a general diversity−stability relationship alone, but depends on the correlation between species sensitivities to different stressors and on the population dynamics of a well-performing species when dominant.

Niche dimensionality provides a general theoretical explanation for biodiversity-more niches, defined by more limiting factors, allow for more ways that species can coexist. Because plant species compete for the same set of limiting resources, theory predicts that addition of a limiting resource eliminates potential trade-offs, reducing the number of species that can coexist. Multiple nutrient limitation of plant production is common and therefore fertilization may reduce diversity by reducing the number or dimensionality of belowground limiting factors. At the same time, nutrient addition, by increasing biomass, should ultimately shift competition from belowground nutrients towards a one-dimensional competitive trade-off for light. Here we show that plant species diversity decreased when a greater number of limiting nutrients were added across 45 grassland sites from a multi-continent experimental network. The number of added nutrients predicted diversity loss, even after controlling for effects of plant biomass, and even where biomass production was not nutrient-limited. We found that elevated resource supply reduced niche dimensionality and diversity and increased both productivity and compositional turnover. Our results point to the importance of understanding dimensionality in ecological systems that are undergoing diversity loss in response to multiple global change factors. Fil: Harpole, W. Stanley. Martin Luther University Halle-Wittenberg; Alemania Fil: Sullivan, Lauren L.. University of Minnesota; Estados Unidos Fil: Lind, Eric M.. University of Minnesota; Estados Unidos Fil: Firn, Jennifer. Queensland University of Technology; Australia Fil: Adler, Peter B.. State University of Utah; Estados Unidos Fil: Borer, Elizabeth T.. University of Minnesota; Estados Unidos Fil: Chase, Jonathan. Martin Luther University Halle-Wittenberg; Alemania Fil: Fay, Philip A.. USDA-ARS Grassland Soil and Water Research Lab; Estados Unidos Fil: Hautier, Yann. Utrecht University; Países Bajos Fil: Hillebrand, Helmut. University of Oldenburg; Alemania Fil: MacDougall, Andrew S.. University of Guelph; Canadá Fil: Seabloom, Eric W.. University of Minnesota; Estados Unidos Fil: Williams, Ryan. University of Iowa; Estados Unidos Fil: Bakker, Jonathan D.. University of Washington; Estados Unidos Fil: Cadotte, Marc W.. University of Toronto; Canadá Fil: Chaneton, Enrique Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía; Argentina Fil: Chu, Chengjin. Sun Yat-sen University; China Fil: Cleland, Elsa E.. University of California at San Diego; Estados Unidos Fil: D'Antonio, Carla. University of California; Estados Unidos Fil: Davies, Kendi F.. University of Colorado; Estados Unidos Fil: Gruner, Daniel S.. University of Maryland; Estados Unidos Fil: Hagenah, Nicole. University of KwaZulu-Natal; Sudáfrica Fil: Kirkman, Kevin. University of KwaZulu-Natal; Sudáfrica Fil: Knops, Johannes M. H.. Universidad de Nebraska - Lincoln; Estados Unidos Fil: La Pierre, Kimberly J.. University of California at Berkeley; Estados Unidos Fil: McCulley, Rebecca L.. University of Kentucky; Estados Unidos Fil: Moore, Joslin L.. Monash University; Australia Fil: Morgan, John W.. La Trobe University; Australia Fil: Prober, Suzanne M.. CSIRO Land and Water; Australia Fil: Risch, Anita C.. Swiss Federal Institute for Forest, Snow and Landscape Research; Suiza Fil: Schuetz, Martin. Swiss Federal Institute for Forest, Snow and Landscape Research; Suiza Fil: Stevens, Carly J.. Lancaster University; Reino Unido Fil: Wragg, Peter D.. University of Yale; Estados Unidos

There is still considerable debate about which mechanisms drive the relationship between biodiversity and ecosystem function (BEF). Although most scientists agree on the existence of two underlying mechanisms, complementarity and selection, experimental studies keep producing contrasting results on the relative contributions of the two effects. We present a spatially explicit resource competition model and investigate how the strength of these effects is influenced by trait and environmental variability, resource distribution, and species pool size. Our results demonstrate that the increase of biomass production with increasing species numbers depends on the concurrence of environmental and trait variability: BEF relationships are stronger if functionally different species coexist in a landscape with heterogeneous resource supply. These large biodiversity effects arise from complementarity effects, whereas selection effects are maximized when broad trait ranges coincide with narrow ranges of resource supply ratios. Our results will therefore help to resolve the debate on complementarity and selection mechanisms.

The relationship between biodiversity and ecosystem functioning (BEF) and its consequence for ecosystem services has predominantly been studied by controlled, short-term and small-scale experiments under standardized environmental conditions and constant community compositions. However, changes in biodiversity occur in real-world ecosystems with varying environments and a dynamic community composition. In this theme issue, we present novel research on BEF in such dynamic communities. The contributions are organized in three sections on BEF relationships in (i) multi-trophic diversity, (ii) non-equilibrium biodiversity under disturbance and varying environmental conditions, and (iii) large spatial and long temporal scales. The first section shows that multi-trophic BEF relationships often appear idiosyncratic, while accounting for species traits enables a predictive understanding. Future BEF research on complex communities needs to include ecological theory that is based on first principles of species-averaged body masses, stoichiometry and effects of environmental conditions such as temperature. The second section illustrates that disturbance and varying environments have direct as well as indirect (via changes in species richness, community composition and species' traits) effects on BEF relationships. Fluctuations in biodiversity (species richness, community composition and also trait dominance within species) can severely modify BEF relationships. The third section demonstrates that BEF at larger spatial scales is driven by different variables. While species richness per se and community biomass are most important, species identity effects and community composition are less important than at small scales. Across long temporal scales, mass extinctions represent severe changes in biodiversity with mixed effects on ecosystem functions. Together, the contributions of this theme issue identify new research frontiers and answer some open questions on BEF relationships in dynamic communities of real-world landscapes.

Fraser et al. (Reports, 17 July 2015, p. 302) report a unimodal relationship between productivity and species richness at regional and global scales, which they contrast with the results of Adler et al. (Reports, 23 September 2011, p. 1750). However, both data sets, when analyzed correctly, show clearly and consistently that productivity is a poor predictor of local species richness. EEA Santa Cruz Fil: Tredennick, Andrew T. Utah State University. Department of Wildland Resources and the Ecology Center; Estados Unidos Fil: Adler, Peter B. Utah State University. Department of Wildland Resources and the Ecology Center; Estados Unidos Fil: Grace, James B. U.S. Geological Survey, Wetland and Aquatic Research Center; Estados Unidos Fil: Harpole, W. Stanley. Helmholtz Center for Environmental Research – UFZ. Department of Physiological Diversity; Alemania Fil: Borer, Elizabeth T. University of Minnesota. Department of Ecology, Evolution, and Behavior; Estados Unidos Fil: Seabloom, Eric W. University of Minnesota. Department of Ecology, Evolution, and Behavior; Estados Unidos Fil: Anderson, T. Michael. Wake Forest University. Department of Biology; Estados Unidos Fil: Bakker, Jonathan D. University of Washington. School of Environmental and Forest Sciences; Estados Unidos Fil: Biederman, Lori A. lowa State University Ecology. Evolution and Organismal Biology; Estados Unidos Fil: Brown, Cynthia S. Colorado State University. Department of Bioagricultural Sciences and Pest Management; Estados Unidos Fil: Buckley, Yvonne M. University of Dublin. School of Natural Sciences. Trinity College Dublin. Zoology; Irlanda. Fil: Chu, Chengjin. Sun Yat-sen University. School of Life Sciences; China. Fil: Collins, Scott L. University of New Mexico. Department of Biology; Estados Unidos Fil: Crawley, Michael J. Imperial College London. Department of Biology; Reino Unido Fil: Fay, Philip A. USDA-ARS. Grassland, Soil, and Water Research Laboratory; Estados Unidos Fil: Firn, Jennifer. Queensland University of Technology. School of Earth, Environmental and Biological Sciences; Australia. Fil: Gruner, Daniel S. University of Maryland. Department of Entomology. Plant Sciences; Estados Unidos Fil: Hagenah, Nicole. University of KwaZulu-Natal. School of Life Sciences; Sudáfrica Fil: Hautier, Yann. Utrecht University. Department of Biology, Ecology and Biodiversity group; Países Bajos Fil: Hector, Andy. University of Oxford. Department of Plant Sciences; Reino Unido Fil: Hillebrand, Helmut. Carl-von-Ossietzky University. Institute for Chemistry and Biology of the Marine Environment; Alemania Fil: Kirkman, Kevin. University of KwaZulu-Natal. School of Life Sciences; Sudáfrica Fil: Knops, Johannes M. H. University of Nebraska. School of Biological Sciences; Estados Unidos Fil: Laungani, Ramesh. Doane College. Biology Department; Estados Unidos Fil: Lind, Eric M. University of Minnesota. Department of Ecology, Evolution and Behavior; Estados Unidos. Fil: MacDougall, Andrew S. University of Guelph. Department of Integrative Biology; Canadá. Fil: McCulley, Rebecca L. University of Kentucky. Department of Plant and Soil Science; Estados Unidos Fil: Mitchell, Charles E. University of North Carolina at Chapel Hill. Department of Biology; Estados Unidos Fil: Moore, Joslin L. Monash University. School of Biological Sciences; Australia. Fil: Morgan, John W. La Trobe University. Department of Ecology, Environment and Evolution; Australia. Fil: Orrock, John L. University of Wisconsin. Department of Zoology; Estados Unidos Fil: Peri, Pablo Luis. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Santa Cruz; Argentina. Fil: Peri, Pablo Luis. Universidad Nacional de la Patagonia Austral; Argentina. Fil: Peri, Pablo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Fil: Prober, Suzanne M. Commonwealth Scientific and Industrial Research Organisation Land and Water; Australia. Fil: Risch, Anita C. Swiss Federal Institute for Forest, Snow and Landscape Research. Community Ecology; Suiza Fil: Schütz, Martin. Swiss Federal Institute for Forest, Snow and Landscape Research. Community Ecology; Suiza Fil: Speziale, Karina L. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Biodiversidad y Medioambiente (INIBIOMA). Universidad Nacional del Comahue; Argentina. Fil: Standish, Rachel J. Murdoch University. School of Veterinary and Life Sciences; Australia. Fil: Sullivan, Lauren L. University of Minnesota. Department of Ecology, Evolution and Behavior; Estados Unidos Fil: Wardle, Glenda M. University of Sydney. School of Biological Sciences; Australia. Fil: Williams, Ryan J. Iowa State University. Agricultural and Biosystems Engineering; Estados Unidos Fil: Yang, Louie H. University of California. Department of Entomology and Nematology; Estados Unidos

Numerous studies show that increasing species richness leads to higher ecosystem productivity. This effect is often attributed to more efficient portioning of multiple resources in communities with higher numbers of competing species, indicating the role of resource supply and stoichiometry for biodiversity–ecosystem functioning relationships. Here, we merged theory on ecological stoichiometry with a framework of biodiversity–ecosystem functioning to understand how resource use transfers into primary production. We applied a structural equation model to define patterns of diversity–productivity relationships with respect to available resources. Meta-analysis was used to summarize the findings across ecosystem types ranging from aquatic ecosystems to grasslands and forests. As hypothesized, resource supply increased realized productivity and richness, but we found significant differences between ecosystems and study types. Increased richness was associated with increased productivity, although this effect was not seen in experiments. More even communities had lower productivity, indicating that biomass production is often maintained by a few dominant species, and reduced dominance generally reduced ecosystem productivity. This synthesis, which integrates observational and experimental studies in a variety of ecosystems and geographical regions, exposes common patterns and differences in biodiversity–functioning relationships, and increases the mechanistic understanding of changes in ecosystems productivity.

The North Sea region contains a vast number of lakes; from shallow, highly eutrophic water bodies in agricultural areas to deep, oligotrophic systems in pristine high-latitude or high-altitude areas. These freshwaters and the biota they contain are highly vulnerable to climate change. As largely closed systems, lakes are ideally suited to studying climate-induced effects via changes in ice cover, hydrology and temperature, as well as via biological communities (phenology, species and size distribution, food-web dynamics, life-history traits, growth and respiration, nutrient dynamics and ecosystem metabolism). This chapter focuses on change in natural lakes and on parameters for which their climate-driven responses have major impacts on ecosystem properties such as productivity, community composition, metabolism and biodiversity. It also points to the importance of addressing different temporal scales and variability in driving and response variables along with threshold-driven responses to environmental forces. Exceedance of critical thresholds may result in abrupt changes in particular elements of an ecosystem. Modelling climate-driven physical responses like ice-cover duration, stratification periods and thermal profiles in lakes have shown major advances, and the chapter provide recent achievements in this field for northern lakes. Finally, there is a tentative summary of the level of certainty for key climatic impacts on freshwater ecosystems. Wherever possible, data and examples are drawn from the North Sea region.

Predator diversity and abundance are under strong human pressure in all types of ecosystems. Whereas predator potentially control standing biomass and species interactions in food webs, their effects on prey biomass and especially prey biodiversity have not yet been systematically quantified. Here, we test the effects of predation in a cross-system meta-analysis of prey diversity and biomass responses to local manipulation of predator presence. We found 291 predator removal experiments from 87 studies assessing both diversity and biomass responses. Across ecosystem types, predator presence significantly decreased both biomass and diversity of prey across ecosystems. Predation effects were highly similar between ecosystem types, whereas previous studies had shown that herbivory or decomposition effects differed fundamentally between terrestrial and aquatic systems based on different stoichiometry of plant material. Such stoichiometric differences between systems are unlikely for carnivorous predators, where effect sizes on species richness strongly correlated to effect sizes on biomass. However, the negative predation effect on prey biomass was ameliorated significantly with increasing prey richness and increasing species richness of the manipulated predator assemblage. Moreover, with increasing richness of the predator assemblage present, the overall negative effects of predation on prey richness switched to positive effects. Our meta-analysis revealed strong general relationships between predator diversity, prey diversity and the interaction strength between trophic levels in terms of biomass. This study indicates that anthropogenic changes in predator abundance and diversity will potentially have strong effects on trophic interactions across ecosystems.

Biological diversity comprises both species richness, i.e., the number of species in a community, and evenness, measuring how similar species are in their abundances. The relationship between species richness and evenness (RRE) across communities remains, however, a controversial issue in ecology because no consistent pattern has been reported. We conducted a systematic meta-review of RRE in aquatic ecosystems along regional to continental gradients and across trophic groups, differing in body size by 13 orders of magnitude. Hypotheses that RRE responded to latitudinal and scale variability across trophic groups were tested by regression analyses. Significant correlations of species richness and evenness only existed in 71 out of 229 datasets. Among the RRE, 89 were negative and 140 were positive. RRE did not vary with latitude but showed a positive response to scale. In a meta-analysis with ecosystem type as a single explaining variable, RRE did not vary among ecosystem types, i.e. between marine and freshwater. Finally, autotrophs had more positive RRE than heterotrophs. The weak RRE in many aquatic datasets suggests that richness and evenness often reflect independent components of biodiversity, highlighting that richness alone may be an incomplete surrogate for biodiversity. Our results further elucidate that RRE is driven by organismal and environmental properties, both of which must be considered to gain a deeper understanding of large-scale patterns of biodiversity.

The information on temperature-mediated changes in biodiversity in local assemblages is scarce and mainly addresses the change in species richness. However, warming may have more consistent effects on species turnover than on the number of species. Moreover, very few studies extended the analysis of changes in biodiversity and species composition to questions of associated ecosystem functions such as primary production. Here, we synthesize 4 case studies employing microalgal microcosms within the Aquashift priority program to ask (1) do warming-related shifts in species richness correspond to changes in the rate of biomass production, (2) do similar relationships prevail for evenness, and (3) do warming-related shifts in species turnover stabilize or destabilize biomass production? Two of the four cases are previously unpublished, and for a third case, the link between diversity and functional consequences of temperature was not analyzed before. We found accelerated loss of species with warming in all cases. Biomass production was lower with lower species richness in most cases but increased with lower evenness. Most importantly, the relation between functional and compositional stability was different between cases: More rapid extinction resulted in more variable biomass in 2 cases conducted with a limited species pool, indicating that compositional destabilization relates to functional variability. By contrast, the only experiment with a large species pool (30 species) allowed previously rare species to become dominant in the community and showed more stable biomass at high turnover, indicating that compensatory dynamics (turnover) can promote functional stability. These 4 independent experiments highlight the need to consider both compositional and functional consequences of altered temperature regimes.

Global predictions of increasing mean temperature and its variance result in concerns about the fate of biodiversity under future climatic conditions. On the local scale of interacting species, the response of diversity to warming will depend much on the change in interspecific interactions such as competition or predation. Using a phytoplankton model community, we conducted a 2 × 2 × 2 factorial long-term microcosm experiment (16 months) with an underlying seasonal temperature profile. We manipulated the mean temperature (T mean ), the temperature variance (T var ), and the presence of consumers (ciliates) and monitored treatment effects on algal biomass, species composition and species richness. Temperature effects on algal biomass depended on the seasonal development and consumer presence. Algal biomass decreased with increasing T mean at consumer absence, but increased at consumer presence. Overall, algal biomass decreased with increasing T var . Consumer presence reduced algal biomass from summer to winter, but then ciliates and the consumer effect disappeared. Almost all treatment combinations collapsed to monocultures after 16 months, but extinction occurred faster at higher T mean (especially at consumer absence) and slower at consumer presence (especially at higher T mean ). Contrasting our predictions, increasing T var reduced richness and increased extinction rate. The treatment effects on biomass and richness were not independent, as algal species richness and biomass were positively correlated. Moreover, accelerated loss of species was consistently correlated to higher temporal variability in biomass. In conclusion, altered temperature regimes strongly affected algal biomass and diversity by interdependently altering competitive and consumer interactions.

It is an exciting time to be an ecologist. Over the past several decades, our discipline has matured from one focused on the assembly of case studies based on natural history, to one that has seen improved conceptual frameworks and mathematical models that help explain ecological phenomena from species coexistence to elemental cycling. The maturation of our discipline has been fostered by many things, including improved technology, increased availability of data, and emergent methods for analyzing large data sets. One factor that has played a central role in the modern synthesis is metaanalyses. Gurevitch et al. (1992) introduced metaanalyses to ecologists and catalyzed their entrance into the ecological literature as a powerful statistical means to assess the generality of pattern and process. Soon after, the U.S. National Science Foundation established the National Center for Ecological Analysis and Synthesis (NCEAS) whose mission it is to bring together ecological data sets so that we could synthesize pattern and process using meta-analysis and many other analytical tools. NCEAS was so successful that it was soon after mimicked by other scientific disciplines (e.g., NESCent, the National Evolutionary Synthesis Center). However, when our initial honeymoon with ‘‘synthesis’’ was over, criticisms began to surface, exposing the inherent warts and flaws of a growing discipline. Some argued that data sets were now being analyzed, and syntheses performed, by researchers who knew little about (or perhaps had never even seen) the systems they were trying to understand. Such ‘‘remote ecology’’ reduces an appreciation for natural history, and may lead to incorrect conclusions because one doesn’t understand the intricacies and contingencies of each system that reveal how pattern is linked to process. Some argued that meta-analyses were proliferating more rapidly than the methods needed for quality control, and that the concatenation of data sets was leading to a propagation of errors.