The evolution of mimicry in the butterfly Papilio dardanus


WHEN Bates put forward the mimicry hypothesis which bears his name, Darwin (1872), although accepting it, had some difficulty in explaining the evolution of the mimetic resemblance of several distinct species to one distasteful model by a series of small changes, a requirement of his general theory of evolution. He said "it is necessary to suppose in some cases that ancient members belonging to several distinct groups, before they had diverged to their present extent, accidentally resembled a member of another and protected group in a sufficient degree to afford some slight protection; this having given the basis for the subsequent acquisition of the most perfect resemblance ". Punnett (1915) realised that the difficulty is even more acute when one is dealing with a polymorphic species whose forms mimic very distantly related models. Knowing that, in those butterflies which had been investigated genetically, the forms differed by single allelomorphs he concluded that the mimicry did not evolve gradually and did not confer any advantage or disadvantage to the individual. He argued that an allelomorph arises at a single step by mutation and that therefore the mimicry also arises by chance at a single step. Goldschmidt (x) although not denying that mimicry confers some advantage to its possessors also maintained that the resemblance arises fully perfected by a single mutation of a gene distinct from that producing the colour pattern in the model, but producing a similar effect in the mimic. Fisher and Ford (see Fisher, 1930; Carpenter and Ford, i; Ford, '953) on the other hand have put forward a view intermediate between the extreme ones of Darwin on the one hand and Goldschmidt on the other. They maintain that a resemblance between the mimic and model as good as that often found in nature cannot reasonably be expected to arise by chance. They therefore suggest that a mutant becomes established which gives a sufficient resemblance to be advantageous and that this is gradually improved by the selection of modifiers which alter the effects produced by the mutant. Ford (i) has raised serious theoretical objections to Goldschmidt's (1945) hypothesis and he pointed out how the validity of each hypothesis can be tested. He notes that a particular mimic usually varies in appearance in parallel with the local race of its model and that on his own hypothesis one would expect these allopatric

DOI: 10.1038/hdy.1960.14
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@article{Clarke1960TheEO, title={The evolution of mimicry in the butterfly Papilio dardanus}, author={Christina A. Clarke and P. M. Sheppard}, journal={Heredity}, year={1960}, volume={14}, pages={163-173} }