Some Crucial Consequences of Adaptive Habitat Selection by Predators and Prey: Apparent Mutualisms, Competitive Ghosts, Habitat Abandonment, and Spatial Structure Douglas

Numerous ecological models evaluate how predators influence the abundance of their prey. Prey dynamics in these models often reflect a compromise between prey reproductive potential, density-dependent competition, and the direct consumption of prey by predators. But predators and prey play a complex evolutionary game where prey behavior, and its effect on distribution and abundance, depends on predation risk. Risk is subsequently modified by adaptive predator responses. Many of the co-adaptive behaviors are likely to involve a spatial component where density-dependent habitat selection can mask prey competition. I explored the consequences of the predator-prey habitat-selection game with numerical simulations of two classical predatorprey models. Two species of prey and their predator attempted to maximize their fitness by choosing between two distinctly different habitats. The simulations included exogenous stochastic effects on prey density and explored large changes in individual parameters. Several common themes emerge from both models. (1) Habitat selection promotes community persistence. (2) Predators and prey often persist at an ideal-free "equilibrium". (3) Single habitats often include only a single food chain (predator and one prey species), whereas pairs of habitats always include the complete web of three species. (4) Habitat selection can cause rapid and occasional reciprocal reversals in predator habitat use and habitat abandonment. ( 5 ) Predators reduce prey numbers. (6) Predators. reinforce prey habitat preferences that further reduce their net competitive interaction. The adaptive behaviors played out in the evolutionary games among interacting species are thereby etched deeply into the dynamics of their populations and the structure of their emergent communities.