Female-limited variability in mimicry in the swallowtail butterfly papilio polyxenes Fabr.

Abstract

Variation in dorsal and ventral aspects of mimetic wing patterns was measured in the sexually dimorphic swallowtail butterfly Papilio polyxenes, a Batesian mimic of Battus philenor. The pattern on the dorsal surface of the wings makes females better mimics than males and was more variable in females. The pattern on the ventral surface of the hind wings, which provides a similar degree of mimicry in both sexes, was equally variable in both sexes. Full-sib anova indicated that variability in dorsal and ventral patterns was similarily heritable in both sexes, suggesting that the increased variability in females is not simply the result of suppressed expression of genetic variation in males. The results are consistent with the hypothesis that variation in two sets of modifier loci, only one of which is expressed in males, influences the dorsal pattern, resulting in greater variability in females. The nonmimetic dorsal pattern in males is probably maintained as a consequence of sexual selection arising from male-male competition in territorial encounters. The generality of the reduced male variability in the Lepidoptera is discussed. © 1995 The Genetical Society of Great Britain.