A comparison of the roles of intra and intersexual selection in the evolution of sex-limited mimicry in two swallowtail butterflies. Both black and tiger swallowtails (Papilio polyxenes and P. glaucus) exhibit mimicry of the distasteful pipevine swallowtail (Battus philenor) that is limited to females. Selection against novel mimetic coloration in males results either from mating preferences for typical males by females or the reduced success of novel males in direct competition with typical males. Using a series of parallel experiments, the investigators will compare the impact of female intersexual selection with that of male intrasexual selection on the maintenance of the ancestral color in males. The profound differences in the mating systems of these related butterflies will aid in distinguishing between the alternatives. Intrasexual selection may be very important in the black swallowtail, where males are aggregated and aggressively territorial, but is unlikely to be important in the tiger swallowtail, where males are dispersed and patrol widely for females. The influence of coloration will be evaluated by altering the appearance of males to resemble females, then comparing their success in courtship, copulation, territorial defense and mate location with unaltered males. Observed effects will be attributable to either inter- or intrasexual selection. The results of this research will improve our understanding of the evolution of mimicry and protective coloration. It will provide the first experimental test of the alternative sexual selection hypotheses and estimate the relative importance of each. From the applied viewpoint, the research will indicate the potential to control or alter mating success in visually oriented insect pest species. In addition, knowing the mechanisms of reproductive isolation will aid us in understanding gene flow in these species. This could be important in predicting the movement of resistance genes to natural plant toxins or pesticides in natural or pest populations.
