Geographical Uniformity of Protein Polymorphisms

Abstract

ELECTROPHORETIC polymorphisms in several species of Drosophila in both North and South America and in Europe show considerable uniformity of allele frequencies over a wide geographical range^1–3. It has been suggested by Kimura and Ohta⁴ that this finding is compatible with the infinite neutral allele hypothesis of Kimura and Crow⁵ as “it is possible that in animal species such as Drosophila, mouse and man well able to migrate, no local population is sufficiently isolated to prevent the entire species or subspecies from forming effectively one panmictic unit”. This claim is supported by reference to the theoretical work of Maruyama^6,7 on the asymptotic rate of decrease of heterozygosity in the absence of mutation, which would seem to be of little relevance to the pattern of variability expected under the joint forces of mutation and genetic drift. Here I show that use of a more appropriate model, which includes the effect of mutation, leads to a quite different conclusion.