A test for rare male mating advantage at an "enzyme locus" in Drosophila.

Matings between Drosophila pseudoobscura strains differing at the amylase (Amy) locus were observed in Elens-Wattiaux chambers. Males homozygous for either Amy1.00 or Amy0.84 alleles in the CH gene arrangement enjoyed a mating advantage when moderately rare, but none when quite rare. The minority male advantage for strains differing at the Amy locus, and other loci linked to it, was comparable in size to that observed between strains carrying the ST or CH gene arrangements, and either alike or different at the Amy locus. Although some features of our results are puzzling, there is evidence that the Amy locus and others for which it serves as a marker have effects on mating behavior which include some degree of rare male mating advantage.