Sexual selection and a secondary sexual character in two Drosophila species

Evidence of sexual selection on male body size and on the number and symmetry of sternopleural bristles and of sex comb teeth was sought in natural populations of two Drosophila species. Body size did not differ between mating and non-mating males in either species. Mating male D. simulans had significantly fewer sex comb teeth than did males not found copulating, and mating male D pseudoobscura had more sternopleural bristles. No difference in fluctuating asymmetry of any bilateral trait was found between mating and non-mating males. These observations suggest that generalizations that large body size and symmetry promote mating success are unfounded.