Probable evolutionary mechanism underlying octanol dehydrogenase isozyme patterns in the genus drosophila

Abstract

A comparative species study of octanol dehydrogenase (ODH) isozyme patterns of members of the genusDrosophila and six related genera has shown a rough correlation of these with taxonomic grouping at the level of subgenus or section within the subgeneraPholadoris, Sophophora, andDrosophila. Extensive polymorphism of ODH patterns occurs in thequinaria section of the subgenusDrosophila. In polymorphic strains ofD. pellewae andD. metzii, ODH pattern types of single females were shown to occur in frequencies expected on the hypothesis of a Hardy-Weinberg distribution of morphs depending on alleles at a single locus. However, patterns of homozygous B and A variants extracted from such populations differ from those expected if variants are due to alleles at a structural locus and indicate that such variants differ in alleles affecting the levels of particular isozymes. ODH patterns of monomorphic species strikingly resemble those of homozygous B, D, or A variants extracted from polymorphic populations ofD. pellewae, D. metzii, orD. albirostris which have been studied genetically by Pipkin (1968a, 1969) and Ogonji (1971). Based on these findings and previous work indicating that the ODH molecule is a polymer, an hypothesis is proposed that species differences in ODH patterns depend on differential activity of several ODH structural genes.