mtDNA microevolution in Southern Chile's archipelagos

The genetic variability of four predominantly Indian populations of southern Chile's archipelagos was examined by determining the frequencies of four mitochondrial DNA haplogroups that characterize the American Indian populations. Over 90% of the individuals analyzed presented Native American mtDNA haplogroups. By means of an unweighted group pair method with arithmetic mean (UPGMA) dendrogram, a principal component analysis (PCA) derived from a distance matrix of mtDNA, and the exact test of population differentiation, we are able to prove the existence of a North-South cline. The populations in the northern part of the archipelagos are genetically similar to the Huilliche tribe, while the groups from the South are most closely related to the Fueguino tribe from the extreme South of Chile, and secondarily to the Pehuenche and Mapuche, who are found to the North and East of Chiloé archipelago. These results are consistent with a colonization of the southern archipelagos from Tierra del Fuego. We evaluate the evolutionary relationships of the population of the Chiloé area to groups from other geographic areas of Chile, using analysis of molecular variance (AMOVA). Three Amerindian clusters are identified: one formed by the Aymará and Atacameño, a second by the Huilliche, and a third including the Mapuche, Pehuenche, and Fueguino tribes, and the population inhabiting the South of the Chiloé arcipelago. These groups exhibit a North-South gradient in the frequency of haplogroup B, confirmed by F_ST tests.