TIMID CONSUMERS - SELF-EXTINCTION DUE TO ADAPTIVE CHANGE IN FORAGING AND ANTIPREDATOR EFFORT

We model the evolution of anti-predator ability in a prey species whos e predator has a saturating functional response. Increased anti-predat or ability is assumed to require decreased food intake. The anti-preda tor ability is specified by the value of a continuous trait, whose evo lutionary dynamics are determined by the rate of change of fitness as a function of the trait value. This situation can produce a perpetual evolutionary increase in the anti-predator trait, with a concomitant d ecrease in foraging (or other fitness-enhancing activities); the end r esult of the process is often extinction of the prey species. This out come is most likely if the predator population size is maintained by s ome alternative prey species. Conditions that can promote or counterac t this tendency toward self-extinction are discussed. (C) 1994 Academi c Press, Inc.