Date Published: June 17, 2019
Publisher: Public Library of Science
Author(s): María Laura Parolin, Ulises F. Toscanini, Irina F. Velázquez, Cintia Llull, Gabriela L. Berardi, Alfredo Holley, Camila Tamburrini, Sergio Avena, Francisco R. Carnese, José L. Lanata, Noela Sánchez Carnero, Lucas F. Arce, Néstor G. Basso, Rui Pereira, Leonor Gusmão, Francesc Calafell.
As in other Latin American populations, Argentinians are the result of the admixture amongst different continental groups, mainly from America and Europe, and to a lesser extent from Sub-Saharan Africa. However, it is known that the admixture processes did not occur homogeneously throughout the country. Therefore, considering the importance for anthropological, medical and forensic researches, this study aimed to investigate the population genetic structure of the Argentinian Patagonia, through the analysis of 46 ancestry informative markers, in 433 individuals from five different localities. Overall, in the Patagonian sample, the average individual ancestry was estimated as 35.8% Native American (95% CI: 32.2–39.4%), 62.1% European (58.5–65.7%) and 2.1% African (1.7–2.4%). Comparing the five localities studied, statistically significant differences were observed for the Native American and European contributions, but not for the African ancestry. The admixture results combined with the genealogical information revealed intra-regional variations that are consistent with the different geographic origin of the participants and their ancestors. As expected, a high European ancestry was observed for donors with four grandparents born in Europe (96.8%) or in the Central region of Argentina (85%). In contrast, the Native American ancestry increased when the four grandparents were born in the North (71%) or in the South (61.9%) regions of the country, or even in Chile (60.5%). In summary, our results showed that differences on continental ancestry contribution have different origins in each region in Patagonia, and even in each locality, highlighting the importance of knowing the origin of the participants and their ancestors for the correct interpretation and contextualization of the genetic information.
Argentina, like many other Latin American countries, has a large proportion of inhabitants with admixed ancestry, with a high Native American and European contribution and to a lesser extent from Africa. Soon after the Spanish conquest in the beginning of the 16th century, and until the first half of the 18th century, the Buenos Aires port received more than 25,000 African slaves, who mainly came from West Africa and Mozambique . The most significant European migration occurred between 1860 and 1950. In that period, Argentina welcomed an estimated 5.5 million migrants, mainly from Spain and Italy [2,3]. According to the 1869 census, the Argentinian population had only 1.8 million inhabitants (National Institute of Statistics and Census of Argentina (INDEC), 2010), placing this migratory event as the most significant worldwide, considering the size of the recipient population. In this context, and for more than a century, the popular imaginary defined Argentina as a “white” country where most of its population was supposed to descend from European immigrants. However, the geographic distribution of the Europeans was strongly biased towards the city of Buenos Aires and the rest of the Central region of Argentina [2,3]. On the other hand, the Argentinian Patagonia was, until the last third of the 19th century, a virtually control-free area of the Republican state, a situation that allowed the native populations to preserve their autonomy for a long period . This region lacked permanent settlings until the late 1800, when the so-called “Conquista del Desierto” (Desert Conquest) annexed the Patagonia to the Argentine Republic.
The genotyping results obtained in the five urban populations from Argentinian Patagonia are shown in S1 Table. Allele frequencies and expected heterozygosities were estimated for the 46 AIM-Indels are presented in S2 and S3 Tables, respectively. Exact test showed no significant deviations to the Hardy-Weinberg equilibrium expectations for all loci in the five populations (p ≥ 0.0038; for a significant level of 0.001, when applying the Bonferroni’s correction for 46 tests performed) .
This study constitutes the first analysis of the genetic ancestry in different populations of the Argentinian Patagonia region, complementing previous information obtained on uniparental and biparental markers. The appropriate representation of the studied samples, both in size and collection strategy, supports the obtained results. Likewise, the 46 AIMs analyzed prove to be robust and reliable for the estimation of population admixture, which has been supported by its strong association with genealogical information, mainly for European ancestry.