Cultural, geographic and genetic isolation in Italian ethno-linguistic minorities

The identification of isolation signatures is fundamental to better understand the genetic structure of human populations and to test the relations between cultural factors and genetic variation. In contrast to the methodological advancements achieved in the study of isolation in natural populations, current approaches in human population genetics are based on the evaluation of within and among-group diversity, but it remains difficult to distinguish between the effects of reduced sample size, purifying selection and differential admixture and the consequences of long-term isolation. To overcome these limitations, we have integrated the analysis of classical genetic diversity measures with a Bayesian method to estimate gene flow and have carried out simulations based on the coalescent with the aim to test whether a short history of cultural and geographical isolation may have left detectable genetic signatures in some Italian populations. The investigation has been primarily conducted using mitochondrial and Y chromosome polymorphisms, that continue to represent today important tools to study human isolates. The research has been conducted in Italy due to the fact that its history of migrations has determined a degree of ethno-cultural heterogeneity of the most complex in the European continent. However, all these migration events explain at least part of the genetic structure of extant Italian populations, the understanding of which needs to take into account the important component of the historic ethno-linguistic minorities, most of them are concentrated within the Alpine environment. This study has been first focused on the analysis of the genetic structure of four linguistic islands of the Eastern Italian Alps (Lessinia, Sappada, Sauris and Timau) integrated with the estimation of incoming and outgoing gene flow under an isolation with migration model using mitochondrial DNA data between the populations that show robust signatures of isolation and a neighbor or a Central Western European population. The study has been extended by the investigation of high resolution data on Y chromosomal variation in three distinct Alpine ethno-linguistic groups (Italian, Ladin and German), in order to understand how their genetic diversity is patterned. Combining unilinear polymorphisms, we used coalescent simulation to test the role of effective size and gene flow in determining their genetic diversity. We extended the dataset with numerous Italian populations in order to evaluate the association of linguistic and geographic factors with genetic isolation. Furthermore, a comparison of the extent of genetic diversity observed in Italy and Europe were performed taking into account both open populations and geographically and/or linguistically isolated groups. Finally, we tested the usefulness of a panel of 15 autosomal microsatellite loci usually used in forensic genetics to understand the effects of physical barriers and linguistic diversity on the genetic structure of Alpine populations. The comparison between mitochondrial, Y chromosomal and autosomal patterns of variation observed suggests that not only geographic factors and linguistic diversity, but also socially aspects (e.g. residence rules, marital behaviours, inheritance and succession systems) should be taken into account when studying the genetic structure of Alpine populations. From an anthropological point of view, this research highlights the important contribution of the so called “linguistic islands” (e.g. German speaking groups of Sappada and Luserna from the Eastern Italian Alps) to the genetic diversity of Italy. Notably, the aims of this project have not been limited to scientific outputs, having also included the development of a community-based participatory research protocol, which also takes into account the importance of the return of scientific results to the involved communities.