New genetic evidence supports isolation and drift in the Ladin communities of the South Tyrolean Alps but not an ancient origin in the Middle East

Abstract

The Alps are one of the most significant geographical barriers in Europe and several isolated Swiss and Italian valleys retain the distinctive Ladin and Romansch languages, alongside the modern majority of Italian and German languages. Linguistically, Ladin belongs to the Romance languages, but some studies on mitochondrial DNA (mtDNA) variation have suggested a major Middle Eastern component to their genealogical origin. Furthermore, an observed high degree of within-population diversity has been interpreted as reflecting long-standing differentiation from other European populations and the absence of a major bottleneck in Ladin population history. To explore these issues further, we examined Y chromosome and mtDNA variation in two samples of Ladin speakers, two samples of German speakers and one sample of metropolitan Italian speakers. Our results (1) indicate reduced diversity in the Ladinspeaking and isolated German-speaking populations when compared to a sample of metropolitan Italian speakers, (2) fail to identify haplotypes that are rare in other European populations that other researchers have identified, and (3) indicate different Middle Eastern components to Ladin ancestry in different localities. These new results, in combination with Bayesian estimation of demographic parameters of interest (population size, population growth rate, and Palaeolithic/Neolithic admixture proportions) and phylogeographic analysis, suggest that the Ladin groups under study are small genetically isolated populations (subject to strong genetic drift), having a predominantly European ancestry, and in one locality, may have a greater Palaeolithic component to that ancestry than their neighbours.

Evidence of high genetic variation among linguistically diverse populations on a micro-geographic scale: a case study of the Italian Alps

“…Furthermore, the number of haplotypes shared by Ladins from Fassa valleys and those from other alpine areas is relatively low (four with LadB, four with LadG and zero with LadV) and only one haplotype is shared simultaneously among all Ladin groups. This is consistent with the high diversity among Dolomitic Ladin communities reported by Thomas et al 6 On the whole, the data accumulated so far suggest that the genetic heterogeneity among Ladins could be due to the combined effect of a scarce reciprocal genetic exchange, probably due to geographic isolation, and genetic drift.…”

“…The remaining Trentino populations are scattered in the central group showing a certain degree of genetic heterogeneity (14/28; average Fst, from 0.013 to 0.018). It is interesting to note that the Ladins from the Fassa valley analyzed in this study are genetically separated from the other Ladin groups studied by Thomas et al 6 and Vernesi et al, 40 with all the pairwise genetic distances among these groups of Ladins being statistically significant. Our data set was also compared with a subset of 25 European populations, six of which, in previous studies, had been reported to be isolated (Aromuns from Albany and Macedonia, 41 the Csango from Hungary, 42 the Sardi from Urzulei 43 and the Ladin from the Badia and Gardena valleys in south Tyrol; 6 Supplementary Figure S3 and Supplementary Table S3).…”

“…In fact, they are separated from the neighbor population from Fiemme valley by their lowest pairwise Fst genetic distance (0.006), and share the highest number of haplotypes (9). Unfortunately, groups that are geographically close to Ladins have not been sampled in previous studies, 6,40 which hampers any comparison with the results obtained in the course of the present investigation. However, the genetic distance between Ladins from Fassa valley and those previously studied is relatively high [(from 0.02 (with Ladins from Badia valley, LadB) to 0.08 (with Ladins from Veneto, LadV), see Supplementary Figure S2)].…”

“…[1][2][3] The considerable data accumulated so far has allowed researchers to reconstruct the phylogeography of principal lineages and make inferences concerning key events in the prehistory of European populations. 4 However, mtDNA variation has been little studied at micro-geographic level through dense sampling [5][6][7] despite the fact that exploring how genetic diversity is distributed in geographically close populations, we may complement studies which aim to identify patterns of variation on a larger scale (macro-regional, continental or global), identifying local areas of genetic discontinuity and populations with peculiar gene pools.…”

Dissecting the genetic make-up of North-East Sardinia using a large set of haploid and autosomal markers

“…We confirmed that Sardinians are genetically differentiated, because of genetic drift and past founder effects, as revealed by the high prevalence of the M26 mutation on the Y chromosome, the low frequency of a derived mutation of the Sardinian-specific Y chromosome haplogroup, as well as the moderate frequency of the UB53a mitochondrial haplogroup. The large number of founder lineages and the high haplotype diversity suggests either a large founding population size, 40 or some degree of genetic admixture. …”