Genotypic differences in mating success and the maintenance of the alcohol dehydrogenase polymorphism in Drosophila melanogaster: No evidence for overdominance or rare genotype mating advantage.

Strains of Drosophila melanogaster having different alcohol dehydrogenase (Adh) genotypes (FF, FS, or SS) were assembled in a mating chamber in varying ratios, and the mating successes were recorded. In experiments with a 25:25 ratio, the FF males succeeded in mating more than did FS and SS males, while the FS males surpassed the SS males. As for the females, FF also surpassed SS. In experiments with a 5:45 or 45:5 ratio, some differences from the 25:25 ratio occurred, but in these cases the rare genotypes were at a disadvantage. In one case, female genotypes (FF vs. SS) displayed a difference in mating latency time, but male genotypes did not. The findings did not suggest that rare genotype mating advantage and overdominance in mating success play a role in the maintenance of the Adh polymorphism.