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Food‐web complexity and species richness are predicted to have tremendous effects on ecosystem functioning stability. Yet, our understanding of the relation between diversity and the stability of ecosystem functioning is still mainly limited to single trophic level communities and highly simplified food webs. To start filling this knowledge gap, we model allometric food webs and use structural equation modelling (SEM) to investigate the relations between diversity, food web structure and the temporal variability of total plant and animal biomasses and their components, i.e. synchrony and mean population variability. We find that stability responds differently depending on the metric used. When looking at total biomass variability, higher total biomasses and biomass stored at higher trophic level have the strongest stabilising effects, while species richness has lower impact than previously found. We confirm that synchrony among species is important for the stability of the total plant biomass. However, synchrony only weakly explains variations in the stability of total animal biomass among food webs. Species richness and food web variables often have opposite impacts on synchrony and mean population variability, leading to more ambiguous results for the plant community as synchrony matters only for plant stability. Our approach thus provides new insight on the complexity of the stability of ecosystem functioning in complex food webs. [ABSTRACT FROM AUTHOR]

Climate change and anthropogenic activities are producing a range of new selection pressures, both abiotic and biotic, on marine organisms. Although it is known that climate change can differentially affect fitness‐related traits at different trophic levels of the food web, it is not clear if different trophic levels will respond via phenotypic plasticity in the form of maintenance of phenotypes in the face of abiotic and biotic environmental stress similarly. To answer this question, we combined a mesocosm experiment (120 days) using a food web comprising three gastropod species from two trophic levels (grazers and meso‐predators) and a meta‐analysis including 38 studies to address whether different trophic levels exhibit similar phenotypic responses to abiotic and biotic variables. Abiotic (ocean acidification) and biotic (predation) stress significantly influenced body mass, shell mass, shell thickness and shell strength in both grazers and meso‐predators in the mesocosm experiment, with the magnitude of OA effects greater on the meso‐predator than the grazers; a result supported by the meta‐analysis. In contrast, both mesocosm experiment and meta‐analysis found that predation risk induced stronger responses in shell morphology for grazers compared to meso‐predators. Together, our findings indicate that higher trophic level species are better able to maintain aspects of their phenotype under OA, suggesting that they may show greater tolerance to climate change effects in general, while lower trophic levels express higher levels of plastic inducible defences to maintain function when under threat of predation. By using marine snails as a model, our study provides new knowledge for understanding how changing environmental conditions may alter biological interactions, and increases our understanding of how climate change may affect ecological communities in which gastropods play a key role. [ABSTRACT FROM AUTHOR]

Recent estimates suggest that a quarter of species globally are under threat of extinction. Understanding what happens to ecological networks of interacting organisms when they lose a significant fraction of species is thus essential for assessing, and potentially mediating, the current biodiversity crisis. We introduce and explore a framework for studying the repercussions of mass extinctions in large model ecosystems. This random‐matrix approach reveals the statistical properties of the post‐extinction abundances to exhibit a simple structure, allowing us to determine analytically how susceptibility to secondary extinctions depends on the strength and nature of interspecies interaction. We find, for example, that mutualistic networks are particularly sensitive to species loss and that, for small primary extinctions, realistic food webs suffer fewer secondary extinctions than do random ones. Finally we show how the response to low‐level extinctions can be used to predict the effects of more severe events. [ABSTRACT FROM AUTHOR]

Life on Earth is supported by an infinite number of interactions among organisms. Species interactions in these networks are influenced by latitude, evolutionary history and species traits. We performed a global‐scale literature analysis to build up a database of interactions between anuran communities and their preys, from a wide range of geographical areas, using a network approach. For this purpose, we compiled a total of 55 weighted anuran–prey interaction networks, 39 located in the tropics and 16 in temperate areas. We tested the influence of latitude, as well as anuran taxonomic, functional and phylogenetic richness on network metrics. We found that anuran–prey networks are not nested, exhibit low complementary specialization and modularity and high connectance when compared to other types of networks. The main effects on network metrics were related to latitude, followed by anuran taxonomic, functional and phylogenetic richness, a pattern similar to the emerging in mutualistic networks. Our study is the first integrated analysis of the structural patterns in anuran–prey antagonistic interaction networks in different parts of the world. We suggest that different processes, mediated mainly by latitude, are modeling the architecture of anuran–prey networks across the globe. [ABSTRACT FROM AUTHOR]

Indirect interactions play an essential role in governing population, community and coevolutionary dynamics across a diverse range of ecological communities. Such communities are widely represented as bipartite networks: graphs depicting interactions between two groups of species, such as plants and pollinators or hosts and parasites. For over thirty years, studies have used indices, such as connectance and species degree, to characterise the structure of these networks and the roles of their constituent species. However, compressing a complex network into a single metric necessarily discards large amounts of information about indirect interactions. Given the large literature demonstrating the importance and ubiquity of indirect effects, many studies of network structure are likely missing a substantial piece of the ecological puzzle. Here we use the emerging concept of bipartite motifs to outline a new framework for bipartite networks that incorporates indirect interactions. While this framework is a significant departure from the current way of thinking about bipartite ecological networks, we show that this shift is supported by analyses of simulated and empirical data. We use simulations to show how consideration of indirect interactions can highlight differences missed by the current index paradigm that may be ecologically important. We extend this finding to empirical plant–pollinator communities, showing how two bee species, with similar direct interactions, differ in how specialised their competitors are. These examples underscore the need to not rely solely on network‐ and species‐level indices for characterising the structure of bipartite ecological networks. [ABSTRACT FROM AUTHOR]