Population structure of Sicily within Mediterranean genetic landscapes: a paternal perspective

Sicily, due to its strategic geographical position, located in the heart of Mediterranean Basin, has received the passage of various human groups both in pre-historical and historical times, acting as a bridge in different major migratory events. In addition to the Upper Paleolithic and Mesolithic cultures, several migrations have affected the genetic composition of the island after the Neolithic transition (Greeks, Phoenicians, Romans, Arabs and Normans), thus contributing to complicate the genetic landscape of the largest Mediterranean island. Made up of different superimposed historical genetic layers, Sicily offers a unique opportunity to test hypotheses connected with the peopling of Mediterranean shores. Both the presence (Romano et al. 2003, Di Gaetano et al. 2008) and absence (Rickards et al. 1998) of an internal genetic differentiation along the east-west axis has been previously described in Sicily, and several hypotheses, connected with the aforementioned dynamics of peopling, have been proposed to explain the heterogeneity observed. Nevertheless the extent of each independent historical contributions to the current genetic composition of Sicilian population is still highly debated. The present study aims to contribute to this debate using new samples and deeper analyzing the Y chromosome genetic markers. More precisely, a total of 24 Y-SNPs and 17 Y-STRs have been typed in more than 300 individuals from 8 different provinces, 5 in Sicily (Agrigento, Catania, Ragusa-Siracusa, Enna, Trapani) and 3 in Southern Italy (Matera, Lecce, Cosenza). Y-chromosome preliminary results reveal a substantial lack of genetic structure within the island, coupled with high levels of within-population genetic variability. These findings well agree with Sicily's historic role as major migration crossroads. Comparing our results with other Mediterranean populations (Southern Europe, Northern Africa and the Levant) we observe a marked geography-related global structure within the Mediterranean Basin. Two well separated clusters have been identified, suggesting a shared genetic background between north-western Mediterranean populations (Iberian Peninsula and Northern Italy) on one side, and south-eastern ones (Sicily and Southern Italy, Balkan Peninsula, North Africa and Levant) on the other side. The completion of Y-chromosome analysis, as well as the future study of mtDNA variation, will consent to explore more in detail specific issues related to the peopling of Sicily and to clarify its role in Mediterranean genetic context