Analysis of a Genetic Isolate: The Case of Carloforte (Italy)

Abstract

We reviewed data collected during several studies concerning the genetic isolate of Carloforte (Sardinia, Italy) and analyzed new data on Y-chromosome markers.Carloforte is also a language island, where people still speaks Tabarchino, an archaic form of Ligurian dialect. Demographic data indicate that, in the early years of its history, Carloforte population was characterized by a high degree of endogamy and consanguinity rates that started to decrease around 1850, when marriages with Sardinian people began to occur more frequently. Cultural factors, mainly language, account for the high endogamy. Genetic data from classical markers, mtDNA and Ychromosome markers confirmed the strong isolation of Carloforte population, which appears significantly different from the neighboring population of Sardinia. Analysis of mtDNA emphasizes the crucial aspect of sampling strategy: two different samplings of the same population, one based on founder surnames, while the other based on grandparents' criterion, gave different results. Founder surnames sampling is not affected by recent events, and therefore better describes the ancestral population.Whereas, grandparents' criterion sampling gives a picture of the present population, shaped by more recent events, like migration and gene flow. This review further supports the notion that a comprehensive approach, including a detailed knowledge of the history of the population and the collection of different samplings, is essential in anthropology for reconstructing past and recent events that contributed to establish the present genetic structure of the population. Likewise, it is essential in medical genetics to identify genes involved in complex diseases. An ideal scenario is offered by a genetic isolate with a recent, and well documented, history, like Carloforte, which can be a paradigm for this type of investigations.Pre-print version. Visit

Overcoming the dichotomy between open and isolated populations using genomic data from a large European dataset

“…Carloforte is the most recent isolate of our dataset, with the founding event dating back to 1738 AD. The small time since isolation and the genetic introgression associated with migratory waves from Tunisia, Liguria and Campania have presumably limited the effect of inbreeding and drift on the genome 44 45 . The attenuation of isolation signatures for Sulcis Iglesiente compared to other Sardinian populations may be explained by the more exogamous behaviour of the villages in this area, a likely consequence of their location in coastal plains close to the Mediterranean Sea 46 .…”

Overcoming the dichotomy: new insights into the genomic diversity of open and isolated European populations

“…Carloforte is the most recent isolate of our dataset, with the founding event dating back to 1738 AD. The small time since isolation and the genetic introgression associated with migratory waves from Tunisia, Liguria and Campania have presumably limited the effect of inbreeding and drift on the genome 57,58 . The attenuation of isolation signatures for Sulcis Iglesiente compared to other Sardinian populations may be explained by the more exogamous behaviour of villages of this area, a likely consequence of their location in coastal plains close to the Mediterranean Sea 59 .…”

Y chromosome diversity in a linguistic isolate (Mirandese, NE Portugal)

“…If the historical circumstances can explain the presence in a border region of a language not used elsewhere in Portugal, the reasons that permitted its survival until now are largely due to the demographic and geographical context of Miranda. As in other linguistic isolates, in which low population size and geographic isolation have been identified as the cornerstone for language maintenance (Alonso et al, ; Babalini et al, ; Robledo et al, ), both factors account for the persistence of the Mirandese language.…”