Mitochondrial DNA Profiles of Individuals from a 12th Century Necropolis in Feldioara (Transylvania)

Abstract

The genetic signature of modern Europeans is the cumulated result of millennia of discrete small-scale exchanges between multiple distinct population groups that performed a repeated cycle of movement, settlement, and interactions with each other. In this study we aimed to highlight one such minute genetic cycle in a sea of genetic interactions by reconstructing part of the genetic story of the migration, settlement, interaction, and legacy of what is today the Transylvanian Saxon. The analysis of the mitochondrial DNA control region of 13 medieval individuals from Feldioara necropolis (Transylvania region, Romania) reveals a genetically heterogeneous group where all identified haplotypes are different. Most of the perceived maternal lineages are of Western Eurasian origin, except for the Central Asiatic haplogroup C seen in only one sample. Comparisons with historical and modern populations describe the contribution of the investigated Saxon settlers to the genetic history of this part of Europe.

Keywords: Transylvania; medieval individuals; mitochondrial DNA; population genetics.

Figure 1

Geographic and genetic relationships between two medieval populations from the current territory of Romania: the population from Feldioara (labeled in red), located in the historical region of Transylvania, was investigated in this study, while the population from Capidava (labeled in grey, and labeled as seROU_med in further graphs and text), located in the province of Dobruja, was analyzed in previous studies [20,42]. Pie charts represent the frequencies of the major haplogroups in these populations. The size of the charts is proportional to the number of samples from each necropolis.

Figure 2

Haplogroup-based analyses of 21 historical populations. (a) PCA plot of the first two principal components; (b) Ward type hierarchical clustering (AU p-values in percent are given as red numbers on the dendogram). The investigated population from Feldioara (cROU_med) is clustered with early medieval individuals from Bavaria (DEU_med), Longobards from Hungary (HUN_Long), Vikings from Norway (NOR_Vik), and Early medieval Icelanders (ISL_med). This cluster is distinct from the one formed by mid-Byzantine population from southwestern Anatolia (TUR_Byz) and a medieval population from southeastern Romania (seROU_med). Abbreviations and mtDNA haplogroup frequencies are reported in Table S4.

Figure 3

Levelplot of the linearized Slatkin population differentiation (Fst) values and significant p-values. Lower left corner: significant p-values (<0.05) are indicated in red. Upper right corner: larger Slatkin Fst values indicating greater genetic distances are marked by dark blue shades. The exact Fst and p-values are given in Table S5.

Figure 4

PCA plot of the investigated population (cROU_med) and modern Eurasian populations, based on mtDNA frequencies. MtDNA data for modern Eurasian populations were retrieved from previously published data in Rusu et al. 2018 [20] and references therein.

Figure 5

MDS plot of the investigated population (cROU_med) and modern Eurasian populations. The MDS plot was performed using linearized Slatkin Fst values, detailed in Table S6. Stress value is 0.1085145.