WILKINSON, Gerald S.; AMITIN, Emily G.; JOHNS, Philip M.; Univ. of Maryland, College Park: Correlated responses to long-term artificial sexual selection in stalk-eyed flies

Coevolutionary models of sexual selection by female choice predict that an ornamental trait in males should become genetically correlated with female preferences for that trait. This prediction motivated a long-term artificial selection study on male eye stalk length in Cyrtodiopsis dalmanni, a sexually dimorphic stalk-eyed fly. After 22 generations of bidirectional selection, we discovered correlated responses in progeny sex ratio among replicate lines. Sex ratios changed due to changes in the frequency of an X chromosome meiotic drive system and linkage between the drive system and eye stalk genes. In this talk we will report on unexpected correlated changes in the reproductive anatomy of male and female flies. We will also provide evidence to discriminate among the following explanations for these changes. Some reproductive traits, such as testes size, might exhibit correlated response to selection on eyestalks if there is competition for resources during metamorphosis. Alternatively, the selection regime might alter the likelihood of multiple mating and sperm competition, compared to field conditions, thereby inadvertently selecting for alternative female reproductive tract morphologies. Finally, traits with X-linked inheritance might exhibit correlated response to selection as a consequence of restricted recombination on the X chromosome. We will discuss these changes in light of dramatic differences that exist in many of these traits among related species of stalk-eyed flies.