EFFECTS OF PREDATOR-SPECIFIC DEFENSE ON COMMUNITY COMPLEXITY

Some properties of community structure are explored using co-evolution ary theory. We consider mathematical models of food webs in which all species in a community adopt foraging behaviours and antipredator beha viours that maximize individual fitness. If the antipredator behaviour of a prey is effective against all its enemies, the number of prey-pr edator links in a food web must be less than the sum of the numbers of prey and predator species. However, if an increase in a prey's attent ion to one type of predator decreases its attention to another type of predator, there may be no limit on the number of predator species usi ng a common set of prey species. Predator-specific defence allows a mu ch more complex community structure than non-specific defence. Predato r-specific defence more frequently allows a large niche overlap betwee n predators than does non-specific defence. The high connectivity of s ome fish communities in Lake Tanganyika may be an example of this phen omenon.