Genetic history of Calabrian Greeks reveals ancient events and long term isolation in the Aspromonte area of Southern Italy

Stefania Sarno,Davide Gentilini,Elisabetta Cilli,Andrea De Giovanni,Alessio Boattini,Giovanni Romeo,Graziella Ciani,Paolo Abondio,Cristina Giuliani,Donata Luiselli,Marco Sazzini,Davide Pettener,Sara De Fanti,Rosalba Petrilli

doi:10.1038/s41598-021-82591-9

Abstract

Calabrian Greeks are an enigmatic population that have preserved and evolved a unique variety of language, Greco, survived in the isolated Aspromonte mountain area of Southern Italy. To understand their genetic ancestry and explore possible effects of geographic and cultural isolation, we genome-wide genotyped a large set of South Italian samples including both communities that still speak Greco nowadays and those that lost the use of this language earlier in time. Comparisons with modern and ancient populations highlighted ancient, long-lasting genetic links with Eastern Mediterranean and Caucasian/Near-Eastern groups as ancestral sources of Southern Italians. Our results suggest that the Aspromonte communities might be interpreted as genetically drifted remnants that departed from such ancient genetic background as a consequence of long-term isolation. Specific patterns of population structuring and higher levels of genetic drift were indeed observed in these populations, reflecting geographic isolation amplified by cultural differences in the groups that still conserve the Greco language. Isolation and drift also affected the current genetic differentiation at specific gene pathways, prompting for future genome-wide association studies aimed at exploring trait-related loci that have drifted up in frequency in these isolated groups.

Highlights

The Italian Peninsula represents a key area of investigation to explore population and demographic processes that characterized the peopling history of Europe and the Mediterranean, and to reconstruct patterns of genetic diversity at different geographical s cales[1]
In order to set the observed genetic variability into a wider context, a Principal Component Analysis (PCA) was firstly performed by comparing our newly analyzed Southern Italian populations to Mediterranean and European groups extracted from the Human Genome Diversity Project (HGDP)
The origins of the Greco-speaking communities today settled in the Aspromonte mountain area of Reggio Calabria (Southern Italy) have been largely debated from a linguistic point of view

Summary

Introduction

The Italian Peninsula represents a key area of investigation to explore population and demographic processes that characterized the peopling history of Europe and the Mediterranean, and to reconstruct patterns of genetic diversity at different geographical s cales[1]. The groups from the Aspromonte mountain area were compared with newly-collected samples coming from a similar, but less isolated geographical context, which encompasses four villages from the Calabrian province of Catanzaro (Girifalco, Jacurso, Pentone, Tiriolo), as well as with ‘open’ (i.e. not isolated) Southern Italian groups from Castrovillari (Northern Calabria, Southern Italy) and Benevento (Campania, Southern Italy) (Fig. 1a) In this context, the aim of this study is to investigate the past population events and the local demographic factors that significantly contributed to the current genetic differentiation of Calabrian Greeks. By comparing their allelic architecture to the more general Southern Italian population we looked for the effect of geographic and cultural isolation on the detected genetic structure

Objectives

Methods

Results

Conclusion