Selection overrides gene flow to break down maladaptive mimicry

Growing apart Many species that are palatable to predators evolve to resemble unpalatable poisonous species that possess warning coloration. These 'batesian mimics' profit by looking like the dangerous model, and theory predicts that mimics should not occur in areas where their model is absent because predators there would not be under selection to avoid the dangerous species or a look-alike. Yet, in seeming contradiction of this theory, the geographical distributions of many mimics extend far beyond that of their models. The non-venomous scarlet kingsnake is one example, sometimes found hundreds of kilometres outside the range of its model, the venomous eastern coral snake. George Harper and David Pfennig have found an explanation for this apparent paradox that leaves the basis of the theory intact. Initially the harmless mimics occur where coral snakes are absent because of dispersal by male kingsnakes from regions where both snakes are present. Genetic analysis shows that once separated from the coral snakes, natural selection promotes the evolution of kingsnakes that look less like their model.