TARGETED SELECTION EXPERIMENTS AND ENZYME POLYMORPHISM: NEGATIVE EVIDENCE FOR OCTANOATE SELECTION AT THE G6PD LOCUS IN DROSOPHILA MELANOGASTER

Walter F. Eanes ¹, Brendan Bingham ¹, Jody Hey ¹, and David Houle ¹

¹ Department of Ecology and Evolution, State University of New York, Stony Brook, New York 11794

Published studies have reported significant selection with respect to the G6pd locus for Drosophila melanogaster reared on Na-octanoate food. We have reexamined the selective effects of Na-octanoate on egg to adult viability with respect to the G6pd polymorphism using specially constructed X chromosomes. Four experiments were carried out using different 6Pgd backgrounds in two recombinant sets of chromosomes segregating for the G6pd locus but constructed so as to minimize variation over most of the X chromosome. In addition, two measures of viability were used, and the size of the experiments and their associated degrees of freedom are approximately double those reported in the former studies. Our results find no evidence for differential selection on G6pd genotypes (males and females) by Na-octanoate and, therefore, do not corroborate the positive results of selection reported by other investigators. The reasons for our different results are discussed.