Insights into the Y chromosome human diversity in Uruguay

BACKGROUND

With regard to the origin of its population and microevolutionary processes, Uruguay exhibits distinctive features that distinguish it from other countries in Latin America, while at the same time sharing several similarities. In this article, we will focus on the variability of paternal genetic lineages in two geographical regions with different histories that can be considered as examples of distinct populations for the continent. In general terms, the genetic diversity is a result of different demographic processes related to the American conquest and colonisation. These resulted in distinct ancestral components which vary geographical and depend on the distribution by sex within these components. In Uruguay, native maternal haplogroups are significantly more frequent in the North. Although there are several studies about the geneticvariability of Uruguay, little is known about male genetic lineages.

AIMS

The aim of this work is to present an updated study of the male genetic variability of the Uruguayan population.

METHODS

We analyzed 13 biallelic markers and 27 STRs located in the male-specific region of the Y chromosome for 157 males: 98 from the capital, Montevideo, and 59 from Tacuarembó.

RESULTS

Almost all haplogroups found in both locations are European (99% and 93.2% respectively). One Sub-Saharan African haplogroup was found in Montevideo (1%) and 2 in Tacuarembó (3%), while Native haplogroups were found only in Tacuarembó, evidencing a strong sex-biased admixture. By crossing genetic and genealogical information we could relate European haplogroups with different waves and times of migrations.

DISCUSSION

Network analysis indicated a very diverse male population, suggesting that European migrants came from heterogeneous geographic locations and in different waves. Tacuarembó has closer population affinities with Iberian populations while Montevideo is more diverse. Male population expansion expansion, can be explained by the large number of migrants that arrived during the XIX century and the first half of the XX century.

CONCLUSIONS

The Uruguayan male gene pool is the result of several migration waves with diverse origins, with strong sex-biased admixture that can be explained by the European migration, the violence against the indigenous males, and the segregation of the Africansadmixture that can be explained due to European migration, violence against Natives, and segregation against African males.admixture that can be explained due to European migration, violence against Natives, and segregation against African males.admixture that can be explained due to European migration, violence against Natives, and segregation against African males.admixture that can be explained due to European migration, violence against Natives, and segregation of hte Africans.

Ancient and modern mitogenomes from Central Argentina: new insights into population continuity, temporal depth and migration in South America

The inverted triangle shape of South America places Argentina territory as a geographical crossroads between the two principal peopling streams that followed either the Pacific or the Atlantic coasts, which could have then merged in Central Argentina (CA). Although the genetic diversity from this region is therefore crucial to decipher past population movements in South America, its characterization has been overlooked so far. We report 92 modern and 22 ancient mitogenomes spanning a temporal range of 5000 years, which were compared with a large set of previously reported data. Leveraging this dataset representative of the mitochondrial diversity of the subcontinent, we investigate the maternal history of CA populations within a wider geographical context. We describe a large number of novel clades within the mitochondrial DNA tree, thus providing new phylogenetic interpretations for South America. We also identify several local clades of great temporal depth with continuity until the present time, which stem directly from the founder haplotypes, suggesting that they originated in the region and expanded from there. Moreover, the presence of lineages characteristic of other South American regions reveals the existence of gene flow to CA. Finally, we report some lineages with discontinuous distribution across the Americas, which suggest the persistence of relic lineages likely linked to the first population arrivals. The present study represents to date the most exhaustive attempt to elaborate a Native American genetic map from modern and ancient complete mitochondrial genomes in Argentina and provides relevant information about the general process of settlement in South America.

The structure and migration patterns of the population of Uruguay through isonymy

Surname distribution can be a useful tool for studying the genetic structure of a human population. In South America, the Uruguay population has traditionally been considered to be of European ancestry, despite its trihybrid origin, as proved through genetics. The aim of this study was to investigate the structure of the Uruguayan population, resulting from population movements and surname drift in the country. The distribution of the surnames of 2,501,774 people on the electoral register was studied in the nineteen departments of Uruguay. Multivariate approaches were used to estimate isonymic parameters. Isolation by Distance was measured by correlating isonymic and geographic distances. In the study sample, the most frequent surnames were consistently Spanish, reflecting the fact that the first immigration waves occurred before Uruguayan independence. Only a few surnames of Native origin were recorded. The effective surname number (α) for the entire country was 302, and the average for departments was 235.8 ± 19. Inbreeding estimates were lower in the south-west of the country and in the densely populated Montevideo area. Isonymic distances between departments were significantly correlated with linear geographic distance (p < 0.001) indicating continuously increasing surname distances up to 400 km. Surnames form clusters related to geographic regions affected by different historical processes. The isonymic structure of Uruguay shows a radiation towards the east and north, with short-range migration playing a major role, while the contribution of drift, considering the small variance of α, appears to be minor.

The peopling of South America and the trans-Andean gene flow of the first settlers

Genetic and archaeological data indicate that the initial Paleoindian settlers of South America followed two entry routes separated by the Andes and the Amazon rainforest. The interactions between these paths and their impact on the peopling of South America remain unclear. Analysis of genetic variation in the Peruvian Andes and regions located south of the Amazon River might provide clues on this issue. We analyzed mitochondrial DNA variation at different Andean locations and >360,000 autosomal SNPs from 28 Native American ethnic groups to evaluate different trans-Andean demographic scenarios. Our data reveal that the Peruvian Altiplano was an important enclave for early Paleoindian expansions and point to a genetic continuity in the Andes until recent times, which was only marginally affected by gene flow from the Amazonian lowlands. Genomic variation shows a good fit with the archaeological evidence, indicating that the genetic interactions between the descendants of the settlers that followed the Pacific and Atlantic routes were extremely limited.