[Study on genetic polymorphism of isozyme in natural populations of Drosophila virilis]

Using techniques of polyacrylamide slab electrophoresis and agarose electrophoresis, we have detected genetic variation at 6 loci which coding for enzymes in 4 local samples from natural population of Drosophila virilis. We found 50% of the loci detected are polymorphic, depending on the criterion of polymorphism used. An individual is heterozygotes on the average at 27.13% of its loci. The amount of genetic variation fluctuates widely from locus to locus. At Est-alpha, Est-beta, Amy, most of the individuals are heterozygotes. At the other extreme , Mdh, aGpdh, Acph, few individuals are heterozygotes. For Mdh, we have measured the thermostability at 53 degrees C. No more genetic variation was found. We have measured the amount of genetic differentiation between different local populations. The result showed that there is no relationship between geographical distance and genetic distance. The results are discussed in the light of the continuing controversy over selection and natural theories of genetic variation. We think that both selection and stochastic processes must operate simultaneously in most systems.