Demographic Histories, Isolation and Social Factors as Determinants of the Genetic Structure of Alpine Linguistic Groups

Great European mountain ranges have acted as barriers to gene flow for resident populations since prehistory and have offered a place for the settlement of small, and sometimes culturally diverse, communities. Therefore, the human groups that have settled in these areas are worth exploring as an important potential source of diversity in the genetic structure of European populations. In this study, we present new high resolution data concerning Y chromosomal variation in three distinct Alpine ethno-linguistic groups, Italian, Ladin and German. Combining unpublished and literature data on Y chromosome and mitochondrial variation, we were able to detect different genetic patterns. In fact, within and among population diversity values observed vary across linguistic groups, with German and Italian speakers at the two extremes, and seem to reflect their different demographic histories. Using simulations we inferred that the joint effect of continued genetic isolation and reduced founding group size may explain the apportionment of genetic diversity observed in all groups. Extending the analysis to other continental populations, we observed that the genetic differentiation of Ladins and German speakers from Europeans is comparable or even greater to that observed for well known outliers like Sardinian and Basques. Finally, we found that in south Tyroleans, the social practice of Geschlossener Hof, a hereditary norm which might have favored male dispersal, coincides with a significant intra-group diversity for mtDNA but not for Y chromosome, a genetic pattern which is opposite to those expected among patrilocal populations. Together with previous evidence regarding the possible effects of “local ethnicity” on the genetic structure of German speakers that have settled in the eastern Italian Alps, this finding suggests that taking socio-cultural factors into account together with geographical variables and linguistic diversity may help unveil some yet to be understood aspects of the genetic structure of European populations.

自史前时代以来，欧洲大型山脉一直对定居人群的基因流起到屏障作用，同时也为小型且有时文化多元的社群提供了定居之所。因此，定居于这些区域的人类群体，作为欧洲人群遗传结构多样性的重要潜在来源，值得深入探究。本研究中，我们发布了针对阿尔卑斯山区三类独特民族语群——意大利语族、拉登语族与德语族——的Y染色体（Y chromosome）变异的全新高分辨率数据。我们结合未发表数据与已发表文献中关于Y染色体和线粒体DNA（mitochondrial DNA）变异的资料，得以揭示不同的遗传模式。事实上，观测到的种群内与种群间多样性值因语群而异，德语使用者与意大利语使用者分别处于两个极端，这似乎反映了他们各自不同的人口史。通过模拟分析，我们推断持续的遗传隔离与奠基者群体规模缩减的共同作用，或许可以解释所有观测群体中遗传多样性的分布格局。将分析拓展至其他欧洲大陆人群后，我们发现拉登语使用者与德语使用者相对于欧洲主体人群的遗传分化程度，与撒丁岛人、巴斯克人这类知名遗传特殊群体的分化程度相当，甚至更高。最后，我们在南蒂罗尔人群中发现，名为封闭庄园制（Geschlossener Hof）的世袭习俗——该习俗或可推动男性迁徙——与线粒体DNA显著的群体内多样性相契合，但Y染色体却未呈现此特征；这一遗传模式与父居社会的预期模式恰好相反。结合此前关于“本地族群身份”对定居于意大利东部阿尔卑斯山区的德语使用者遗传结构可能产生影响的研究证据，本研究结果表明，将社会文化因素与地理变量、语言多样性一同纳入考量，或有助于揭示欧洲人群遗传结构中尚未被阐明的若干方面。