ADAPTATION TO FERMENTING RESOURCES IN DROSOPHILA-MELANOGASTER - ETHANOL AND ACETIC-ACID TOLERANCES SHARE A COMMON GENETIC-BASIS

Ethanol and acetic acid tolerances were compared in a French, highly t olerant population, and in a Congolese, very sensitive population. For both tolerances, chromosome substitutions demonstrated a major effect on chromosome 3, a lesser effect on chromosome 2, and no effect on ch romosome 1, except in interactions. Directional selection experiments led to significant increases of tolerance to both toxics. Of greater i nterest, a strong correlated response was observed in each line: incre ased ethanol tolerance was accompanied by higher acetic acid tolerance and vice versa. A high genetic correlation (average value r = 0.77) w as found between the two traits. These data suggest that alcohol dehyd rogenase (ADH) activity does not play a major role in explaining the p hysiological differences known between Afrotropical and European popul ations. The metabolic flux permitting the detoxification of ethanol an d acetic acid seems to be mainly controlled by acetyl-coA synthetase ( ACS) at least in adult dies. Acetic acid adaptation could be as import ant as ethanol adaptation in the ecology of Drosophila melanogaster an d other Drosophila species.