FLEXIBILITY AND DIVERSITY OF CO-EVOLVING COMMUNITIES

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Effects of predator-specific defense on biodeversity and community complexity in two-trophic-level communities : Antipredator strategies employed by prey may be specific (effective against only one type of predator) or non-specific (effective against all predators). To examine the effects of the specificity of antipredator bahavior on biodiversity and community complexity, we analyze mathematical models including both evolutionary and population dynamics of a system including multiple prey species and multiple predator species. The models assume that all predator species change in their prey choice and all prey species have evolutionary change in their antipredator effort in evolution. The traits of each species change in an adaptive manner, whose rate is proportional to the slope of their fitness function. We calculate community complexity, resource-overlap between predators, an index of biodiversity and other properties of the coevoltionarily stable community for two cases : (1) all prey species have non-specific antipredator behavior and (2) all prey species have predator-specific defense. Predator-specificity in defense increases community complexity, resource-overlap between predators, the total abundance of predators and the ratio of predator to prey abundance. Specific defense also decreases the number of isolated subwebs within the entire foodweb.