Microsatellite variation in Central Africa: An analysis of intrapopulational and interpopulational genetic diversity

As a part of a research project on molecular variation in Central Africa, w e have analyzed 10 microsatellites (CD4, CSFO, D3S1358, D18S51, D21S11, F13 A1, FES, THO1, TPOX, and VWA) in the Bamileke and Ewondo from Cameroon and the Sanga and Mbenzele Pygmies from the Central African Republic (a total o f 390 chromosomes). A statistically significant trend towards heterozygote deficiency was detected in the Mbenzele Pygmies. This was established throu gh the use of powerful exact tests for the Hardy-Weinberg equilibrium. A ce rtain degree of isolation and a small effective size may explain this findi ng. However, the lack of any substantial reduction in allelic diversity in the Mbenzele does not support the possibility that this group has a smaller effective size in evolutionary terms. A possible explanation based on ethn ographic studies suggests that the gene how from non-Pygmies to Pygmies cou ld have been interrupted only in relatively recent times. The analysis of a ssociation between genotypes at pairs of independent loci indicates that th e level of subheterogeneity is markedly lower in the Bamileke than in other sampled populations. This may be explained by the combined effect of large r population size, more rigid respect of clanic exogamy, and higher matrimo nial mobility of the Bamileke. Finally, we have analyzed interpopulational relationships among our sampled populations and other Central African popul ations. The results are consistent with a previous study of protein loci (S pedini et al. 1999), which suggests the recent history of the Bamileke and Ewondo has led them to aquire a substantial genetic similarity. Furthermore , the Mbenzele Pygmies diverge from Biaka Pygmies, despite their common ori gin and geographical proximity. This is probably due to the differentiating effect of genetic drift, which is enhanced by the small effective size of Pygmy populations. (C) 2000 Wiley-Liss, Inc.