An Ancient Mediterranean Melting Pot: Investigating the Uniparental Genetic Structure and Population History of Sicily and Southern Italy

Abstract

Due to their strategic geographic location between three different continents, Sicily and Southern Italy have long represented a major Mediterranean crossroad where different peoples and cultures came together over time. However, its multi-layered history of migration pathways and cultural exchanges, has made the reconstruction of its genetic history and population structure extremely controversial and widely debated. To address this debate, we surveyed the genetic variability of 326 accurately selected individuals from 8 different provinces of Sicily and Southern Italy, through a comprehensive evaluation of both Y-chromosome and mtDNA genomes. The main goal was to investigate the structuring of maternal and paternal genetic pools within Sicily and Southern Italy, and to examine their degrees of interaction with other Mediterranean populations. Our findings show high levels of within-population variability, coupled with the lack of significant genetic sub-structures both within Sicily, as well as between Sicily and Southern Italy. When Sicilian and Southern Italian populations were contextualized within the Euro-Mediterranean genetic space, we observed different historical dynamics for maternal and paternal inheritances. Y-chromosome results highlight a significant genetic differentiation between the North-Western and South-Eastern part of the Mediterranean, the Italian Peninsula occupying an intermediate position therein. In particular, Sicily and Southern Italy reveal a shared paternal genetic background with the Balkan Peninsula and the time estimates of main Y-chromosome lineages signal paternal genetic traces of Neolithic and post-Neolithic migration events. On the contrary, despite showing some correspondence with its paternal counterpart, mtDNA reveals a substantially homogeneous genetic landscape, which may reflect older population events or different demographic dynamics between males and females. Overall, both uniparental genetic structures and TMRCA estimates confirm the role of Sicily and Southern Italy as an ancient Mediterranean melting pot for genes and cultures.

Complex interplay between neutral and adaptive evolution shaped differential genomic background and disease susceptibility along the Italian peninsula

“…Distributions of these two ancestry fractions suggest that they plausibly reflect the combined impact of multiple population movements stratified along a wide time interval, but broadly following coastline migratory routes towards Southern Italy. The Middle Eastern-like ancestry could be the complex result of events spanning from earlier arrival of Neolithic farmers in Southern Italy than in Northern Italy78, in line with emerging genetic evidence supporting early Neolithic colonization routes following northern Mediterranean coastlines103031, to more recent historical processes12143233. Results from ALDER analysis actually suggest that gene flow from the Middle East interested C_ITA until more recent times, pointing to an admixture signature plausibly ascribable to events occurred during recurrent expansions and contractions of the Byzantine Empire (1.7–0.5 kya)28 (Supplementary Table S2).…”

The Italian genome reflects the history of Europe and the Mediterranean basin

“…Previous studies, analysing uniparental markers, found Y-chromosome genetic discontinuity across Italy. This contrasts with a general lack of structure for mitochondrial DNA, 2,4 and with a higher homogeneity for maternal than paternal genetic contributions, suggesting different demographic and historical dynamics for females and males in Italy.…”

“…Due to its crucial position at the centre of the Mediterranean basin, the Italian peninsula has experienced a complex history of colonization and migration and the genetic signatures of these human origins are still present in contemporary Italians. [2][3][4] Deeper insight into the history of the Italian population is also critical for understanding the peopling of Europe.…”

Traces of medieval migrations in a socially stratified population from Northern Italy. Evidence from uniparental markers and deep-rooted pedigrees

“…Reference data include 32 populations from: North-Western Italy, South-Eastern Italy and Sicily (21, Boattini et al, 2013;Sarno et al, 2014), French Basques (3, Martínez-Cruz et al, 2012, Germany (3, Ręba"a et al, 2013), Poland and Slovakia (4, Ręba"a et al, 2013), Balkans (1, Regueiro et al, 2012). A full list is available in Supplementary Table S1 and their geographic position is represented in Supplementary Figure S1.…”

“…Single Base Extension products were analysed with capillary electrophoresis on an ABI Prism 310 Genetic Analyser. Two additional SNPs (E-M81, E-M123) were finally tested with RFLP analysis, by using HpyCH4IV and DdeI enzymes, respectively, as in Sarno et al (2014).…”