Allozyme polymorphism at the αGpdh and Adh loci and fitness in Drosophila melanogaster

We have studied in Drosophila melanogaster the effects of allozyme variation at the αGpdh and Adh loci on the following fitness components: female fecundity, egg hatchability, egg-to-adult survival under near-optimal and competitive conditions, rate of development under near-optimal and competitive conditions, and mating capacity of males. Significant effects of the αGpdh locus on rate of development under competitive conditions ( SS > FS> SS ), and of the Adh locus on egg hatchability ( FF = SS > FS ) and egg-to-adult survival under competitive conditions ( FF > SS = FS ) were revealed. Possible natural selection mechanisms involved in the maintenance of allozyme polymorphisms at the αGpdh and Adh loci are described. These mechanisms and the fitness of In(2L)t may account for the persistence and clinal distribution of the two allozyme polymorphisms in nature.