Abstract
Many anthropological, linguistic, genetic and genomic analyses have been carried out to evaluate the potential impact that evolutionary forces had in shaping the present-day Sardinian gene pool, the main outlier in the genetic landscape of Europe. However, due to the homogenizing effect of internal movements, which have intensified over the past fifty years, only partial information has been obtained about the main demographic events. To overcome this limitation, we analyzed the male-specific region of the Y chromosome in three population samples obtained by reallocating a large number of Sardinian subjects to the place of origin of their monophyletic surnames, which are paternally transmitted through generations in most of the populations, much like the Y chromosome. Three Y-chromosome founding lineages, G2-L91, I2-M26 and R1b-V88, were identified as strongly contributing to the definition of the outlying position of Sardinians in the European genetic context and marking a significant differentiation within the island. The present distribution of these lineages does not always mirror that detected in ancient DNAs. Our results show that the analysis of the Y-chromosome gene pool coupled with a sampling method based on the origin of the family name, is an efficient approach to unravelling past heterogeneity, often hidden by recent movements, in the gene pool of modern populations. Furthermore, the reconstruction and comparison of past genetic isolates represent a starting point to better assess the genetic information deriving from the increasing number of available ancient DNA samples.
Highlights
Sardinians, albeit clearly Europeans, represent the main outlying gene pool in the European genetic landscape [1,2,3,4,5]
In order to evaluate the position of Sardinians in a wider European and Mediterranean population context and visualize the relationships between Sardinians and other Italian populations, a Principal Component (PC) analysis was carried out on haplogroup frequencies, exploiting available literature data normalized to the highest possible level of phylogenetic resolution (Table S2)
Genetic drift and long isolation can explain the presence of haplogroups that are very rare in other European populations such as R1b-V88 and G2-L91 as well as the increase of frequency of haplogroup I2-M26
Summary
Sardinians, albeit clearly Europeans, represent the main outlying gene pool in the European genetic landscape [1,2,3,4,5]. The central-eastern zone is the asylum land of the ancient Sardinian population during invasions and is a domain of pastoral culture This zone includes the more conservative or “archaic” area, defined by archaeological, linguistic [32], geo-linguistic and genetic factors [8] (for a more detailed subdivision of Sardinia on the basis of genes, languages and surnames, see [14]). This study exploited a sampling strategy based on the origin of the family name [19] and a detailed Sardinian Y-chromosome phylogeny [22,43] to reconstruct ancient genetic isolates of the Sardinian male component and to address the following questions: can we detect the ancient heterogeneity in the actual Sardinian gene pool? Our results provide new clues for understanding the fine genetic structure of the Sardinian population, an essential piece of information in an evolutionary context, and for reducing confounding effects caused by population structure in association studies
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