Linguistic, geographic and genetic isolation: a collaborative study of Italian populations

Summary - The animal and plant biodiversity of the Italian territory is known to be one of therichest in the Mediterranean basin and Europe as a whole, but does the genetic diversity of extant humanpopulations show a comparable pattern? According to a number of studies, the genetic structure of Italianpopulations retains the signatures of complex peopling processes which took place from the Paleolithic tomodern era. Although the observed patterns highlight a remarkable degree of genetic heterogeneity, they donot, however, take into account an important source of variation. In fact, Italy is home to numerous ethnolinguisticminorities which have yet to be studied systematically. Due to their difference in geographicalorigin and demographic history, such groups not only signal the cultural and social diversity of our country,but they are also potential contributors to its bio-anthropological heterogeneity. To fill this gap, researchgroups from four Italian Universities (Bologna, Cagliari, Pisa and Roma Sapienza) started a collaborativestudy in 2007, which was funded by the Italian Ministry of Education, University and Research andreceived partial support by the Istituto Italiano di Antropologia. In this paper, we present an account ofthe results obtained in the course of this initiative. Four case-studies relative to linguistic minorities fromthe Eastern Alps, Sardinia, Apennines and Southern Italy are first described and discussed, focusing ontheir micro-evolutionary and anthropological implications. Thereafter, we present the results of a systematicanalysis of the relations between linguistic, geographic and genetic isolation. Integrating the data obtainedin the course of the long-term study with literature and unpublished results on Italian populations, weshow that a combination of linguistic and geographic factors is probably responsible for the presence of themost robust signatures of genetic isolation. Finally, we evaluate the magnitude of the diversity of Italianpopulations in the European context. The human genetic diversity of our country was found to be greaterthan observed throughout the continent at short (0-200 km) and intermediate (700-800km) distances, andaccounted for most of the highest values of genetic distances observed at all geographic ranges. Interestingly,an important contribution to this pattern comes from the “linguistic islands” (e.g. German speaking groupsof Sappada and Luserna from the Eastern Italian Alps), further proof of the importance of considering socialand cultural factors when studying human genetic variation.