Local Adaptation of Male Sexual Fitness in Drosophila melanogaster.

Abstract

Mate competition gives rise to sexual selection, and healthier, more vigorous males are likely to be superior competitors. Because most genes are likely to impact an individual's vigor, sexual selection should act across much of the genome to favor the same alleles as natural selection, thereby promoting adaptation. On the other side of the coin, adaptation to an environment should enhance male sexual fitness in that environment because it is likely to increase the overall vigor of individuals within a population. Surprisingly, there are few tests of this latter prediction and results are mixed. Taking advantage of a long-term evolution experiment involving replicate populations of Drosophila melanogaster, we performed a reciprocal transplant in which the sexual fitness of males was compared when raised in an environment to which they were well adapted and in one to which they were not. Male sexual fitness was a comprehensive measure that included pre- and post-copulatory reproductive success in a competitive assay performed under conditions that closely mirrored those to which the populations had been evolving. The results add support to the idea that local adaptation to the abiotic environment enhances male sexual fitness.