The Evolution of Aposematic Coloration in Distasteful Prey: A Family Model

The evolution of bright coloration among distasteful prey has previously been studied almost exclusively from the perspective of Mullerian mimicry. This ignores the question of why unpalatable species appear to advertise themselves to predators. A simple evolutionary model presented here integrates biologically important variables, including both prey population structure and predator learning patterns, to describe the conditions that favor the spread of aposematism in a cryptic distasteful species. Given the assumptions of the model, the conditions are that the aposematic form must not be too readily detected; that the predator must learn to avoid the aposematic form more readily than the cryptic form; and that the density of prey families per predator territory should be low. The model can be tested in various ways, and current evidence indicates that it is biologically realistic. The description of predator avoidance-learning and memory in natural situations seems a promising area for future research on this problem.