Diversity, Complexity, and Persistence in Large Model Ecosystems

Research on how vast numbers of interacting species manage to coexist in nature reveals a deep disparity between the ubiquity of complex ecosystems and their theoretical improbability. Here, we show how integrating models of food-web structure and nonlinear bioenergetic dynamics bridges this disparity and helps elucidate ecological complexity. Network constraints including the trophic hierarchy, contiguity, and looping formalized by the “niche model” are shown to greatly increase persistence in complex model ecosystems. Behavioral nonlinearities including interference between consumers and reduced consumption of rare resources formalized by predator interference and new “type II.2” functional responses further increase the diversity of dynamically interacting species. Integrating these empirically observed regularities yields remarkably comprehensive, extensible, and ecologically realistic models that revise the role of omnivory and emphasize the importance of network structure, short food chains, and behavioral ecology. These models also provide a powerful framework for adding non-trophic effects and developing field experiments and hypotheses.