Sex-biased patterns shaped the genetic history of Roma

Abstract

The Roma population is a European ethnic minority characterized by recent and multiple dispersals and founder effects. After their origin in South Asia around 1,500 years ago, they migrated West. In Europe, they diverged into ethnolinguistically distinct migrant groups that spread across the continent. Previous genetic studies based on genome-wide data and uniparental markers detected Roma founder events and West-Eurasian gene flow. However, to the best of our knowledge, it has not been assessed whether these demographic processes have equally affected both sexes in the population. The present study uses the largest and most comprehensive dataset of complete mitochondrial and Y chromosome Roma sequences to unravel the sex-biased patterns that have shaped their genetic history. The results show that the Roma maternal genetic pool carries a higher lineage diversity from South Asia, as opposed to a single paternal South Asian lineage. Nonetheless, the European gene flow events mainly occurred through the maternal lineages; however, a signal of this gene flow is also traceable in the paternal lineages. We also detect a higher female migration rate among European Roma groups. Altogether, these results suggest that sociocultural factors influenced the emergence of sex-biased genetic patterns at global and local scales in the Roma population through time.

Figure 1

Number of samples of each origin for mtDNA and MSY lineages. West Eurasian lineages are further subdivided into European (EUR), West Asian (WA), and unassigned (UN).

Figure 2

Spatial distributions of φst distances between Roma (only samples with a South Asian lineage origin) and South Asian populations in mtDNA (a) and MSY (b).

Figure 3

Reduced median joining networks for mtDNA coding region (a) and MSY (b) Roma samples, colored by haplogroup with main lineage labels.

Figure 4

Haplogroup distribution for each Roma group colored by origin (i.e. red colors for South Asian, blues and greens for West Eurasian). mtDNA lineages in the upper charts and MSY in the lower. Haplogroups are colored as in Fig. 3. SP-NW: Spain North-West; MKD-B: Macedonia Balkan; ROM-V: Romania Vlax; UKR-R: Ukraine Romungro; HUN-V: Hungary Vlax; HUN-R: Hungary Romungro; LT-NW: Lithuania North-West.