THE APPORTIONMENT OF DINUCLEOTIDE REPEAT DIVERSITY IN NATIVE-AMERICANS AND EUROPEANS - A NEW APPROACH TO MEASURING GENE IDENTITY REVEALS ASYMMETRIC PATTERNS OF DIVERGENCE

The purpose of this paper is to assess the extent of gene identity and differentiation at 33 dinucleotide repeat loci (377 total alleles) wi thin acid among three European and three Native American populations. In order to do this, we show that a maximum-likelihood method proposed for phylogenetic trees (Cavalli-Sforza and Piazza 1975) can be used t o estimate gene identity (Nei 1987) with respect to any hierarchical s tructure. This method allows gene differentiation to be evaluated with respect to any internal node of a hierarchy, It also allows a general ization of F- and G-statistics to situations with unequal expected lev els of differentiation. Our principal finding is that levels of geneti c differentiation are unique to specific populations and levels of nes ting. The populations of European origin show very little internal dif ferentiation; moreover, their continental average is close to the tota l population defined by the aggregate of Europeans and Native American s. By contrast, the Native American populations show moderate levels o f internal differentiation, and a great distance between their contine ntal average and the total. The results of analyses of subsets of loci that were selected to have high gene diversities in either Europeans or Native Americans closely parallel those from the total set of loci. This suggests that the principal results are unlikely to be caused by a European ascertainment bias in locus selection. In summary, our fin dings demonstrate that partitions of gene diversity into within- and b etween-populations components are heavily biased by the populations an alyzed and the models fitted. Optimistically, however, more informatio n is available to analyze population history and evolution by quantify ing, as we have done, the uniqueness of patterns of differentiation.