Prey Communities in Patchy Environments

Abstract

Individuals should exploit a spatially variable environment so as to increase their Darwinian fitness. Predators should aggregate in patches with relatively high densities of high-quality prey, and prey should in turn seek refuges providing protection from predators. This paper explores some of the consequences of such behavior for the coexistence of prey species in a patchy environment. It is argued that an aggregative predator response can lead to indirect interactions among otherwise non-interacting prey species co-occurring in a patch. In many circumstances, the interaction should be (-,-) (apparent competition), although in some situations other interactions may occur. If refuges are in short supply, then prey may compete for occupancy of refuges. Several models of such competition are presented. If predators act as density-independent mortality agents on prey outside refuges, it is shown for a simple model that two prey species cannot coexist when competing for a single refuge. Coexistence may be permitted if: (1) each prey has an exclusive refuge, (2) the dominant prey species experiences strong intraspecific interference, (3) there are trade-offs in competitive ability for refuges and for food resources, (4) the predator has a numerical response, and the prey that is subordinate in competition for refuge can better withstand predation (i.e., is superior in apparent competition). These models highlight the potential importance of spatial heterogeneity for understanding prey community structure.