TRADE-OFFS AND COEXISTENCE IN CONSUMER-RESOURCE MODELS - IT ALL DEPENDS ON WHAT AND WHERE YOU EAT

The study of interactions between consumers and their resources has le d to three important but largely separate bodies of theory: optimal fo raging theory, density-dependent habitat selection, and consumer-resou rce theory. In this article, we draw on all three to study mechanisms of coexistence, uniting these fields of theory via a set of related mo dels based on Holling's disc equation and four different types and arr angements of resources. Using established rules for optimal behavior a nd habitat selection within a framework of consumer-resource models, w e explore how unavoidable trade-offs in conversion efficiency, handlin g time, and encounter efficiency affect coexistence between species. W hen resources are nutritionally substitutable and spatially mixed, our model predicts that only trade-offs in encounter efficiency can promo te coexistence. For spatially separate substitutable resources, any tr ade-off in encounter, conversion, or handling efficiency allows coexis tence. For essential resources, whether mixed or separate, only trade- offs in conversion efficiency can promote coexistence. Since trade-off s that promote coexistence vary depending on the type of resource, thi s indicates that mechanisms of coexistence can differ depending on how consumers view their resources and how resources are distributed in t he environment.