||Jul 6, 2017
Dr. Kazuhiro Takemoto,
Department of Bioscience and Bioinformatics,
Kyushu Institute of Technology, Japan
Stability of ecological communities: A network perspective
Network structure and dynamics are significant in ecology. The structure-stability relationship is a long-standing question. For example, mutualistic networks (e.g., plant-pollinator and seed-dispersal networks) exhibit a nested architecture. The architecture is believed to increase ecological stability. However, definite conclusions have not yet been reached because previous studies are mainly based on numerical simulations. We reveal a mathematical architecture in the relationship between ecological networks and local stability based on spectral graph analysis . In particular, we propose a theoretical method for estimating the dominant eigenvalue (i.e., spectral radius) of weighted bipartite networks by extending spectral graph theory, and provide a theoretical prediction that the heterogeneity of node degrees and link weights primarily determines the local stability; on the other hand, nestedness additionally affects it. Given that environmental factors can be sources of perturbation (e.g., climate change), it would be expected that ecological networks have an optimal structure that maximizes ecosystem stability against such perturbations. We constructed a large dataset of mutualistic networks, and used a spatial analysis approach to examine the effects of climate change and human activities on the structural patterns of mutualistic networks . We found that network structure is globally affected by climate change and human impacts. The results indicate that mutualistic networks form in such a way as to enhance ecosystem stability against environmental changes or perturbations. Network science enhances our understanding of the ecological communities, and it is useful for environmental assessment.
 Feng W, Takemoto K. Heterogeneity in ecological mutualistic networks dominantly determines community stability. Sci. Rep. 4, 5912 (2014).
 Takemoto K, Kajihara K. Human impacts and climate change influence nestedness and modularity in food-web and mutualistic networks. PLoS ONE 11, e0157929 (2016).