The genetic relationship between Moldavians and Romanians deserves special attention, since these two groups speak practically the same language and share many cultural features. It is reasonable to assume that Moldavians and Romanians inherited genetic lineages, shared with other Balkan populations, from Vlachs who, in turn, received them from Paleo-Balkan tribes. However, Moldavians and Romanians do not form a cluster that would have separated them from the neighboring populations. Indeed, in the space of multi-dimensional scaling based on the RST distances between STR haplotypes, Romanian populations appeared scattered among the Balkan populations and did not cluster with the Moldavians (Figure 3). According to the AMOVA analysis, the degree of within-group differentiation among Moldavian and Romanian populations was significantly greater than genetic differences between either Romanians or Moldavians and the group comprised of the Balkan populations (Table 3). Moldavians and Romanians also appear dissimilar on the diagram of binary lineages (PC plot, Figure 2). Thus, sharing nearly the same language is not accompanied by specific genetic similarity between Moldavians and Romanians. Furthermore, Italian populations that share the Romance/Latin language with Moldavians and Romanians, show little genetic similarity with them. These results agree with previous genetic studies suggesting that the genetic landscape of southeast Europe had been formed long before the modern linguistic/ethnic landscape was shaped [16], [48].
In contrast to Romanians and most other Balkan populations, Moldavians show a clear genetic similarity to western and eastern Slavs. This is strongly implied by haplogroup R-M17, which dominates the paternal lineages of the Slavs and is broadly represented in Moldavians. Stefan et al. [18] have already noticed the increased presence of R-M17 chromosomes in Moldavians and explained it as a trait inherited from ancient (prehistoric) population of the North Pontic Steppe. However, genetic continuity in this scenario is not supported by archaeological and historical records, which suggest repeated dramatic demographic changes in Moldova’s population during the 4th –14th centuries AD. Recent admixture with Slavic neighbors appears to be a more parsimonious explanation for the elevated R-M17 frequency in Moldavians. The noteworthy domination of R-M17 chromosomes in Moldavians compared to Romanians is due to the R-M458 subclade. Haplogroup R-M458 likely has its roots in western/northern Poland, where it has its greatest modern concentration and microsatellite diversity [49]. Given the geographical proximity of Moldova to the Polish and other Slavic population groups and historically attested interactions between Moldavians and Slavs [10], [12], [13], [14], it is reasonable to assume that an influx of Slavs helped elevate the frequency of R-M17 chromosomes among Moldavians to underscore the Moldavian-Romanian differentiation. Furthermore, Romanians and Moldavians also display differences in the structure of R-M17* STR haplotypes. Although our network analysis (Figure 4) primarily shows homogeneity of the diversity of R-M17 haplotypes, Moldavian R-M17 chromosomes align closer with Ukrainian (Slavic) chromosomes than with Romanian ones, further supporting the contribution from Slavic neighbors to the Moldavian paternal gene pool.
Despite repeated invasions by nomads from Asian heartlands, only two (N-P43 and Q-M242) out of 125 Moldavian Y chromosomes studied here belonged to haplogroups of apparently northern/central Asian origins. These results are in good agreement with earlier studies on Y-chromosome variation in eastern and central Europe, asserting a minimal impact of gene flow from Siberia/central Asia [25], [41], [50], [51].
In conclusion, the results presented in this report allow to hypothesize that an admixture of autochthonous populations of the Balkan-Carpathian zone with neighboring Slavic populations was likely the main factor that contributed to the diversity of the Y-chromosomal genetic pool of present-day Moldavians and, in particular, to the differences in the Y chromosomal lineage composition between Moldavian and Romanian populations. Analyses of mitochondrial DNA and genome-wide assessments of haplotype sharing between Moldavians and neighboring populations would be essential to produce a comprehensive picture of phylogeographic origins of Moldavian genetic lineages.