PERTURBATION OF GENE-FREQUENCIES IN A NATURAL-POPULATION OF DROSOPHILA-MELANOGASTER - EVIDENCE FOR SELECTION AT THE ADH LOCUS

The cellar population of Drosophila melanogaster at the Chateau Tahbil k Winery (Victoria, Australia) was perturbed for alcohol dehydrogenase (Adh) gene frequencies. Phenol oxidase (Phox) frequencies were also p erturbed and monitored as a control. Subsequent gene frequency changes , together with information on population structure, indicated that se lection acted on the chromosome regions of both loci. Adh gene frequen cies returned to preperturbation levels in a predictable manner. A mod el in which the relative fitness of Adh phenotypes was determined by t emperature-dependent specific activities of enzymes of Adh genotypes a dequately accounts for the rate of gene frequency change at this locus . Thus temperature behaves as a selective agent in modulating Adh gene frequencies in this cellar environment.