Abstract
Theoretical studies have indicated that nestedness and modularity—non-random structural patterns of ecological networks—influence the stability of ecosystems against perturbations; as such, climate change and human activity, as well as other sources of environmental perturbations, affect the nestedness and modularity of ecological networks. However, the effects of climate change and human activities on ecological networks are poorly understood. Here, we used a spatial analysis approach to examine the effects of climate change and human activities on the structural patterns of food webs and mutualistic networks, and found that ecological network structure is globally affected by climate change and human impacts, in addition to current climate. In pollination networks, for instance, nestedness increased and modularity decreased in response to increased human impacts. Modularity in seed-dispersal networks decreased with temperature change (i.e., warming), whereas food web nestedness increased and modularity declined in response to global warming. Although our findings are preliminary owing to data-analysis limitations, they enhance our understanding of the effects of environmental change on ecological communities.
Highlights
Many species interact with one another via antagonistic and mutualistic relationships, and they compose ecological communities that are often represented as networks [1,2], or ecological networks
[29], we demonstrated that climate seasonality affects ecological networks, and that the type of climatic seasonality influencing network structure differs among ecosystems; for example, network properties in freshwater ecosystems were mainly affected by rainfall seasonality but primarily by temperature seasonality in terrestrial ecosystems
No relationship was detected between temperature-change velocity and nestedness/modularity in either mainland or island networks (S4–S7 Tables). These results suggest that nestedness and modularity in pollination networks are influenced by human impacts rather than temperature-change velocity, a discrepancy that may exist for several reasons
Summary
Many species interact with one another via antagonistic (e.g., prey–predator) and mutualistic (e.g., plant–pollinator) relationships, and they compose ecological communities that are often represented as networks [1,2], or ecological networks. A significant amount of data on real-world ecological networks have been collected and are available from such sources as GlobalWeb [9], the Interaction Web DataBase, and the Web-of-Life Database, among others (see Materials and Methods). Empirical ecological networks are known to display two non-random structural patterns. One is nested architecture (nestedness) [10], a hierarchical structure in which the interaction.
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