ESTIMATION, VARIANCE AND OPTIMAL SAMPLING OF GENE DIVERSITY .1. HAPLOID LOCUS

An extension of Nei's analysis of diversity in a subdivided population is proposed for a haploid locus. The differentiation G(ST) becomes a natural extension of Wright's F-ST and generalizes Weir and Cockerham' s parameter of co-ancestry by relaxing the assumption of identical cor relation for all the alleles. Inter- and intrapopulation variances of the estimated diversities and differentiation are derived. Finally, th e optimal sampling strategy for measuring G(ST) when a fixed number of individuals can be analysed is considered. It is shown that, at a giv en locus, there is a unique sample size per population which yields th e smallest variance of G(ST), regardless of the number of populations studied. These theoretical developments are illustrated with an analys is of chloroplast DNA diversity in a forest tree. The results emphasiz e the necessity of sampling many populations, rather than many individ uals per population, for an accurate measurement of the subdivision of gene diversity at a single locus.