Variation and Covariation of Gene Frequencies in Subdivided Populations

Wahlund (1928) has shown that in a population divided into many small subpopulations, within each of which random mating is made, the frequency of heterozygotes for a locus with two alleles decreases by the amount equal to twice the variance of gene frequency among subpopulations compared with that expected in a single random mating population, while the frequency of homozygotes increases by the same amount. If, however, there are more than two alleles, this simple rule does not hold in the strict sense. Further, if multiple alleles are present, the differentiation of subpopulations may be investigated in terms of the covariation as well as the variation of gene frequencies.