Genetic Differentiation in South Amerindians Is Related to Environmental and Cultural Diversity: Evidence from the Y Chromosome

Abstract

The geographic structure of Y-chromosome variability has been analyzed in native populations of South America, through use of the high-frequency Native American haplogroup defined by the DYS199-T allele and six Y-chromosome-linked microsatellites (DYS19, DYS389A, DYS389B, DYS390, DYS391, and DYS393), analyzed in 236 individuals. The following pattern of within- and among-population variability emerges from the analysis of microsatellite data: (1) the Andean populations exhibit significantly higher levels of within-population variability than do the eastern populations of South America; (2) the spatial-autocorrelation analysis suggests a significant geographic structure of Y-chromosome genetic variability in South America, although a typical evolutionary pattern could not be categorically identified; and (3) genetic-distance analyses and the analysis of molecular variance suggest greater homogeneity between Andean populations than between non-Andean ones. On the basis of these results, we propose a model for the evolution of the male lineages of South Amerindians that involves differential patterns of genetic drift and gene flow. In the western part of the continent, which is associated with the Andean area, populations have relatively large effective sizes and gene-flow levels among them, which has created a trend toward homogenization of the gene pool. On the other hand, eastern populations-settled in the Amazonian region, the central Brazilian plateau, and the Chaco region-have exhibited higher rates of genetic drift and lower levels of gene flow, with a resulting trend toward genetic differentiation. This model is consistent with the linguistic and cultural diversity of South Amerindians, the environmental heterogeneity of the continent, and the available paleoecological data.

BetweenAndes andAmazon: The genetic profile of theArawak‐speakingYanesha

“…In particular, within the Y chromosome native haplogroup Q, the STR haplotypes show very high variance between populations within Amazonia, but greater homogeneity in the Andes, confirming a tendency previously reported (Luiselli et al, 2000;Tarazona-Santos et al, 2001;Fuselli et al, 2003;Barbieri et al, 2011;Bisso-Machado et al, 2012-see Table 2). The NJ tree for the Y chromosome R ST distances (Supporting Information Fig.…”

“…Within South America, genetic structure broadly follows the two contrasts between the environments of the Andes and Amazonia, and their respective cultural trajectories over many millennia (Tarazona-Santos et al, 2001). In particular, within the Y chromosome native haplogroup Q, the STR haplotypes show very high variance between populations within Amazonia, but greater homogeneity in the Andes, confirming a tendency previously reported (Luiselli et al, 2000;Tarazona-Santos et al, 2001;Fuselli et al, 2003;Barbieri et al, 2011;Bisso-Machado et al, 2012-see Table 2).…”

Cultural diversification promotes rapid phenotypic evolution in Xavánte Indians

“…If genotypes are introduced into a population from another population, then the presence of these new genotypes will skew the distribution of genetic effects toward the axis of divergence between populations. However, previous studies in lowland South Amerindian populations suggest that gene flow was a restricted force in comparison with genetic drift (21). Furthermore, ethnographic studies reveal a strong cultural and reproductive isolation between Xavánte and Kayapó, which probably triggered the genetic drift experienced by the Xavánte, despite its linguistic affinity and recent divergence (12,14).…”

Divergent patterns of linkage disequilibrium and haplotype structure across global populations at the interleukin-13 (IL13) locus

“…Only the South American sample shows a Tajima's D statistic significantly higher than expected under models with recombination (r40.002) and exponential population growth (Table 1; 50 In the case of the South Amerindian sample, there is evidence of admixture with European populations as well as a recent population bottleneck. 51 Thus, we cannot easily distinguish between balancing selection or demographic history as an explanation for the observed positive D value.…”

“…We sequenced 3950 bp encompassing the promoter and coding region of IL13 in 132 individuals belonging to 11 worldwide populations from West Africa (14 Igbo, 14 Yoruba and seven Fulani from Nigeria collected by SAT), East Africa (17 Hadza, 10 Maasai from Tanzania collected by SAT), Europe (10 North Europeans and 10 Russians from the Coriell cell repository), Asia (10 Chinese from the Coriell cell repository) and South America (nine Cayapa from Ecuador, 17 Peruvian Quechua from Tayacaja and 13 from San Martin de Pangoa 51,56 ). All samples were collected with informed consent of the donors and the study was performed under Institutional Review Board approval.…”