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 the relationship between ecological complexity and stability. Network structure constraints, including trophic hierarchy, niche contiguity, and looping formalized by the “niche model,” greatly increase persistence in complex model ecosystems. Behavioral nonlinearities, particularly competition among consumers and reduced consumption of rare resources, formalized by predator interference and new “Type II.2” functional responses, further encourage persistence of species in complex food webs. Trophic dynamics are also shown to feed back to network structure, resulting in more accurate topologies than those achieved by simple structural models alone. Thus, integrating structure and dynamics of ecological networks yields remarkably comprehensive and ecologically plausible models that highlight the