Admixture Dynamics of Hispanics of Antioquia (Colombia)

Admixture dynamics in Hispanics: A shift in the nuclear genetic ancestry of a South American population isolate

Gabriel Bedoya, Patricia Montoya, Jenny Garcia, Ivan Soto, Stephane Bourgeois, Luis Carvajal, Damian Labuda, Victor Alvarez, Jorge Ospina, Philip W. Hedrick, Andres Ruiz-Linares

PNAS: published online April 28, 2006

Abstract:
Although it is well established that Hispanics generally have a mixed Native American, African, and European ancestry, the dynamics of admixture at the foundation of Hispanic populations is heterogeneous and poorly documented. Genetic analyses are potentially very informative for probing the early demographic history of these populations. Here we evaluate the genetic structure and admixture dynamics of a province in northwest Colombia (Antioquia), which prior analyses indicate was founded mostly by Spanish men and native women. We examined surname, Y chromosome, and mtDNA diversity in a geographically structured sample of the region and obtained admixture estimates with highly informative autosomal and X chromosome markers. We found evidence of reduced surname diversity and support for the introduction of several common surnames by single founders, consistent with the isolation of Antioquia after the colonial period. Y chromosome and mtDNA data indicate little population substructure among founder Antioquian municipalities. Interestingly, despite a nearly complete Native American mtDNA background, Antioquia has a markedly predominant European ancestry at the autosomal and X chromosome level, which suggests that, after foundation, continuing admixture with Spanish men (but not with native women) increased the European nuclear ancestry of Antioquia. This scenario is consistent with historical information and with results from population genetics theory.

some interesting lines:
"Because, in populations such as Antioquia, Spanish ancestry has historically been associated with higher social status and probably with greater reproductive success, it is possible that cultural selection also impacted the current genetic makeup of these populations."

, and:
"...continuous gene flow implies higher levels of {LD} than admixture followed by isolation, resulting in a variable density of markers required for mapping in populations with different admixture dynamics."