Is the genetic structure of Gran Chaco populations unique? Interregional perspectives on Native South American mitochondrial DNA variation

CABANA G, MERRIWETHER AD, HUNLEY KL. DEMARCHI DA

AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY

Wiley-Liss

Año: 2006 vol. 131 p. 108 - 119

0002-9483

This study reevaluates the hypothesis in Demarchi et al. ([2001] Am. J. Phys. Anthropol. 115:199?203) that Gran Chaco peoples demonstrate a unique pattern of genetic diversity due to a distinct regional population history. Specifically, they found populations in the central part of the Gran Chaco, or Central Chaco, to have higher within- and lower between-population mitochondrial DNA (mtDNA) haplogroup frequency variation compared to populations in other South American regions. To test this hypothesis of regional uniqueness, we applied analytical and simulation methods to mtDNA first hypervariable (HVI) region sequence data from a broad set of comparative South and Central American population samples. Contrary to the results of Demarchi et al. ([2001] Am. J. Phys. Anthropol. 115:199?203), we found that the Gran Chaco?s regional within-population diversity is about average among regions, and populationsare highly differentiated from each other. When we limited the scale of analysis to the Central Chaco, a more localized subregion of the Gran Chaco, our results fell more in line with the original findings of Demarchi et al. ([2001] Am. J. Phys. Anthropol. 115:199?203). Still,we conclude that neither the Gran Chaco regional pattern, nor the Central Chaco subregional pattern, is unique within South America. Nonetheless, the Central Chaco pattern accords well with the area?s history, including pre-European contact lifeways and the documented historical use of the area as an interregional crossroads. However, we cannot exclude post-Europeancontact disruption of traditional mating networks as an equally plausible explanation for the observed diversity pattern. Finally, these results additionally inform broader models of South American genetic diversity. While other researchers proposed an east-west continentaldivision in patterns of genetic variation (e.g., Fuselli et al. [2003] Mol. Biol. Evol.  20:1682?1691]), we found that in the geographically intermediate Central Chaco, astrict east-west divide in genetic variation breaks down. We suggest that future genetic characterizations of the continent, and subsequent interpretations of evolutionary history, involve a broad regional sampling of South American populations.