LOCAL MOVEMENT AND EDGE EFFECTS ON COMPETITION AND COEXISTENCE IN EPHEMERAL-PATCH MODELS

For insects exploiting spatially structured arrays of resource patches (host plants, fungi, carrion, etc.), the distribution of individuals among patches can have important consequences for the coexistence of c ompetitors. In general, intraspecific aggregation of consumer individu als over the landscape of patches stabilizes competition. Oviposition behavior of individual females can generate aggregation of larvae acro ss patches and, therefore, strongly influences the outcome of competit ion between co-occurring species. We used simulation models to evaluat e the consequences (for the coexistence of competitors) of different m ovement behaviors by females before and between oviposition events. Co existence times increase when females are more likely to travel among neighboring patches than among distant ones. Coexistence times are als o longer when females begin egg laying near the site of their emergenc e. Preoviposition dispersal is, therefore, destabilizing. We also cons idered responses by females to edges of resource arrays. Edge effects are generally stabilizing, delaying competitive exclusion by increasin g larval aggregation, but different responses to edges have dramatical ly different effects on coexistence. The longest coexistence limes occ ur when edges are ''sticky,'' such that females encountering an edge t end to remain there.