Gene flow and genetic structure in the Galician population (NW Spain) according to Alu insertions

Abstract

Background: The most recent Alu insertions reveal different degrees of polymorphism in human populations, and a series of characteristics that make them particularly suitable genetic markers for Human Biology studies. This has led these polymorphisms to be used to analyse the origin and phylogenetic relationships between contemporary human groups. This study analyses twelve Alu sequences in a sample of 216 individuals from the autochthonous population of Galicia (NW Spain), with the aim of studying their genetic structure and phylogenetic position with respect to the populations of Western and Central Europe and North Africa, research that is of special interest in revealing European population dynamics, given the peculiarities of the Galician population due to its geographical situation in western Europe, and its historical vicissitudes. Results: The insertion frequencies of eleven of the Alu elements analysed were within the variability range of European populations, while Yb8NBC125 proved to be the lowest so far recorded to date in Europe. Taking the twelve polymorphisms into account, the GD value for the Galician population was 0.268. The comparative analyses carried out using the MDS, NJ and AMOVA methods reveal the existence of spatial heterogeneity, and identify three population groups that correspond to the geographic areas of WesternCentral Europe, Eastern Mediterranean Europe and North Africa. Galicia is shown to be included in the Western-Central European cluster, together with other Spanish populations. When only considering populations from Mediterranean Europe, the Galician population revealed a degree of genetic flow similar to that of the majority of the populations from this geographic area. Conclusion: The results of this study reveal that the Galician population, despite its geographic situation in the western edge of the European continent, occupies an intermediate position in relation to other European populations in general, and Iberian populations in particular. This confirms the important role that migratory movements have had in the European gene pool, at least since Neolithic times. In turn, the MDS and NJ analyses place Galicia within the group comprised of Western-Central European populations, which is justified by the influence of Germanic peoples on the Galician population during the Middle Ages. However, it should also be noted that some of the markers analysed have a certain degree of differentiation, possibly due to the region's position as a 'cul-de-sac' in terms of Iberian population dynamics.