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Geographic variation in sexually selected traits: a role for direct selection or genetic correlation?
Journal of Avian Biology
Geographic variation in sexually selected traits is commonly attributed to geographic variation in the net benefit accrued from bearing such traits. Although natural and sexual selection are potentially important in shaping geographic variation. genetic constraints may also play a role. Although a genetic correlation between two traits may itself be the outcome of natural or sexual selection, it may indirectly reinforce the establishment and maintenance of cline variation with respect to one particular trait when across the cline different values of other traits are selected. Using the barn owl Tyto alba. a species in which the Plumage of females is more reddish-brown and more marked with black spots than that of males, I report results that are consistent with the hypothesis that both direct selection and genetic constraints may help establish and maintain cline variation in sexual dichromatism. In this species, inter-individual variation in plumage coloration and spottiness has a genetic basis, and these traits are not sensitive to the environment. Data, based on the measurernent of skin specimens, is consistent with the hypothesis that the stronger European cline variation in male spottiness than in female spottiness depends oil the combined effects of (1) the similar cline variation in male and female plumage coloration and (2) the more intense phenotypic correlation between plumage coloration and spottiness in males (darker birds are more heavily spotted in the two sexes, but especially males) which is a general feature among the globally distributed barn owls. In northern Europe, male and female T. a. guttata are reddish-brown and heavily spotted, and in Southern Europe male and female T. a. alba are white, but only females display many spots. Here, I discuss the relative importance of direct selection., genetic correlation and the post-ice age invasion of Europe by T. alba, in generating sex-specific cline variation in plumage spottiness and non-sex-specific cline variation in Plumage coloration.
MALE ORNAMENTATION, FEMALE, SIGNALS, RESPECT, TRAITS
Web of science
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