SEXMEME

In sexual organisms, males and females share most of their genomes but often respond to distinct selective pressures. Theory predicts that males evolve to be more reproductively persistent and females to be more resistant to males’ manipulations. This can lead to a phenomenon known as intra-locus sexual conflict (IASC), in which a genetic allele advantageous in one sex is deleterious in the opposite sex. IASC can be resolved by restricting the expression of alleles to the sex for which they are advantageous. However, the consequences of unresolved IASC are still unclear. We posit that unresolved IASC can be evolutionarily maintained and increase sexual diversity if it leads to a reciprocal sexual mimicry syndrome, wherein each sex is polymorphic for different traits and the selectively advantageous morph mimics the phenotype of the opposite sex. We will test this hypothesis in the fly Drosophila erecta where conspicuous sex-specific differences in color and odor are controlled by a single short genetic element regulating distinct genes. Female morphs mimicking males gain an advantage by reducing sexual harassment whereas male morphs mimicking females have higher mating success by luring females or reducing competition. We will (i) identify the genetic variants responsible for each trait and how they are regulated in each sex, (ii) assess the sexual selective advantage of mimicry alleles, (iii) evaluate sex-specific differences in allele frequencies in wild populations, and (iv) trace the evolution of the regulatory element in the lineage leading to D. erecta through analyses of allied species. Because most genes in sexually reproducing organisms are not restricted to one sex, unresolved IASC may be more widespread than currently appreciated. We therefore expect our results to significantly elucidate the role of IASC as a major source of the evolution and maintenance of diversity within and between the sexes.