Opposing Modes of Selection on the Alcohol Dehydrogenase Locus in Drosophila Melanogaster

Abstract

Three experiments have been carried out which show that exogenous environments of ethanol impose selection on the alcohol dehydrogenase (Adh) locus of D. melanogaster. This locus is widely polymorphic for two alleles, AdhF and Adhs, and AdhF generally produces about twice as much alcohol dehydrogenase activity as Adhs. In the first experiment, AdhF IAdhF and AdhF/Adhs flies survived equally often and Adhs/Adhs flies less frequently after exposure for 7 days to medium impregnated with ethanol. The same pattern of survival differences was found in the second experiment in which flies were exposed for 1 day to an aqueous solution of ethanol and sucrose. In contrast, in the third experiment survival was scored after exposure for 45-min to ethanol fumes, and Adhs/ Adhs flies survived more often than AdhF/Adhs, both these genotypes surviving more frequently than Adh F / Adh F. We doubt whether anyone of the three experiments by itself adequately represents the ecology of natural populations of D. melanogaster exposed to ethanol. It is likely that mixtures of the three experimental conditions approximate more closely the natural environments and therefore we suggest that, overall, selection might favour intermediate levels of alcohol dehydrogenase activity, producing a net advantage for heterozygotes at the Adh locus.

Ethanol tolerance, alcohol-dehydrogenase activity and Adh allozymes in Drosophila melanogaster

“…In experiments where survival in ethanol-supplemented food or exposure to medium impregnated with ethanol is used, the usual situation is that FF has the highest survival which correlates positively with ADH activity (Gibson, 1970;Day et al, 1974;Oakeshott et al, 1980). In addition, Thompson & Kaiser (1977) demonstrated for two strains differing in ADH activity that the strain with the highest activity also shows the highest egg-to-adult survival on food supplemented with alcohols.…”

“…1), although the heterozygote FS complicates the issue being close to SS for ethanol tolerance and between the two homozygotes for enzyme activity. Oakeshott et al (1980) studied adult survival of the three Adh genotypes exposed to ethanol vapour for 45 min and found that the SS flies survived the treatment better than FF flies as in the experiments under discussion, where exposure was in terms of days rather than minutes. In our experiments, the only energy source provided is ethanol, which is normally converted to acetic acid via acetaldehyde (Deltombe-Lietaert et al, 1979).…”

Population genetics of the metabolically related Adh, Gpdh and Tpi polymorphisms in Drosophila melanogaster : II. Temporal and Spatial Variation in an Orchard Population

“…For example, the 2 common alleles at the Adh locus of D. melanogaster differ by a single base substitution (K REITMAN , 1983). This difference has affected the ability of individuals to utilize ethanol-rich environments, at least in the laboratory (V AN D E i.oEN et al, 1978 ;O AKESHOTT et al, 1980). Field studies are essential in the detection of selective factors affecting enzyme polymorphisms (C LARKE , 1975).…”

Fitness components at the octanol dehydrogenase locus in Drosophila melanogaster

“…One of the most suitable systems for such an examination is the polymorphic Odh locus. Series of experiments were set up to study the connection between the "alcohol tolerance and the frequency changes at the Adh locus (Bijlsma-Meeles & Van Delden, 1974;Dorado & Barbancho, 1984;Oakeshott et al, 1980;Sanchez-Canete et al, 1986;Wilson et al, 1982;Van Delden, 1982;Van Herrewege &David, 1980 andVigue et al, 1982). However, few articles have been published on the frequency changes at the Odh locus as an effect of alcoholic stress Nichols, 1971 andWills et al, 1975).…”