French Guiana Amerindian demographic history as revealed by autosomal and Y-chromosome STRs.

BACKGROUND: Previous investigations of French Guiana Amerindians performed by this group included blood group and protein genetic markers, mitochondrial DNA and Y-chromosome investigations. Molecular autosomal data and more extensive Y-chromosome determinations were lacking. SUBJECTS AND METHODS: The genetic variability of 15 autosome (ASTRs) and 17 Y-chromosome (YSTRs) microsatellite loci was studied in four French Guiana (Emerillon, Palikur, Wayampi, Kali'na) and one Brazilian (Apalai) Amerindian populations. A sixth group, the Peruvian Matsiguenga of the Maipurean linguistic family, was included in the data analysis since they could provide information about the past migration of people from that linguistic stock into northeastern Amazonia. RESULTS: Marked ASTR and YSTR variability was found, with 96% of the YSTR haplotypes being found in one population only. There was excellent agreement between the present and previous autosomal or uniparental results. Multidimensional scaling based on F(ST) genetic distances and population structure analysis revealed heterogeneity in gene distribution, with a clear difference between the Matsiguenga and Emerillon and the other groups. In the latter, Wilcoxon sign-rank test between observed and expected heterozygosity and the mode of allele frequency distribution revealed clues of a significant past genetic bottleneck. The Wayampi stand genetically closer to the Apalai, Palikur and Kali'na when examined for the autosome but not the Y-chromosome panel of markers, suggesting preferential female gene flow. CONCLUSION: The new data provided additional important information about the biological history of people from a remote South American region, indicating how gene diversity analyses can be used to increase understanding of human microevolutionary processes.

Autosomal STR genetic variability in the Gran Chaco native population: Homogeneity or heterogeneity?

To investigate the population structure and variation in Gran Chaco's Amerindian population, data from 15 short tandem repeats (STRs) were determined in 128 individuals from three tribes of the Argentinean part of this region. STR genotypic differences, structure analysis, and multidimensional plot for the D(A) distances indicated that (1) Wichí from the Chaco Province are genetically distinct from the other populations, but still preserve a fair amount of genetic similarity with Wichí from Formosa; (2) the Toba populations studied are genetically indistinguishable; and (3) Toba subjects from Formosa are similar to the Pilagá of the same linguistic group (Guaykurú) and to the Wichí from Formosa who speak a Mataco language. This similarity could be due to their past mobility and the custom of absorbing females taken as prisoners from groups raided by them. Language, geography, and genetics seem to play similar roles in determining the population structure of these groups. Analyses of molecular variance and G(ST)' values calculated considering three South American regions indicated that the Argentinean Chaco is genetically homogeneous; addition of the Ayoreo Amerindians of the Paraguayan Chaco, however, led to diversity values that are not much different from those of South Amerindians in general. The present data contribute to efforts that try to understand in what way groups with diverse sociocultural settings (tribal, agricultural, and industrial) differ in genetic structure.