Genic variation in marginal populations of Drosophila subobscura

Abstract

The genic variability at 32 enzyme loci in natural populations of Drosophila subobscura has been studied by starch gel electrophoresis. Samples have been collected from eleven populations in southwestern Finland, which represents the northern distribution margin of the species. Of the loci studied 47% are polymorphic with an average heterozygosity per fly of 7.6%. Most of the polymorphisms are geographically undifferentiated and appear to be maintained by a balancing selection. Local differences in allele frequencies exist at some loci. This can be attributed to either differential selection or random drift.