Fig. 3 a) Ancestry coefficients for a) two clusters (K=2), b) three clusters (K=3), and c) four clusters (K=4).
Four geographically distinct groupings with sharp species boundaries can be distinguished and assigned to the given regions from Western to Eastern Eurasia. When two clusters were set (K=2), cluster 1 (Western Siberia) was genetically distinct from cluster 2 (Eastern Siberia) (Fig. 3 a). Cluster 1 spreads out from Northern to Southern Siberia over the entire zone of the West Siberian Plain. Cluster 2 runs from across the Taymyr Peninsula in the northern part of Siberia through Yakutia to Bolshoi Toko in Southern Yakutia. Between cluster 1 and cluster 2, the Yenisey River and the Central Siberian Plateau form a clear boundary. Under three clusters (K=3), the former Eastern Siberian cluster divides into two distinct clusters (Fig. 3 b): cluster 2 (Yakutia) and further east in the region of Chukotka cluster 3 (Chukotka). Under four clusters (K=4), the Yakutian cluster is divided into a western and an eastern cluster (Fig. 3 c). Between cluster 3 (Western Yakutia) and cluster 4 (Eastern Yakutia), the Lena River is visible, which is located parallel to the Verkhoyansk Range.
Many individuals (63%) can be assigned with 75–100% confidence to a definite cluster (Fig. 5). When comparing the admixture plots with the spatial distribution of the clusters (Fig. 3 c), it becomes apparent that the individuals in the core area of the clusters have a clear affiliation to exclusively one cluster and the individuals at the edge of the clusters have a fragmented affiliation to different clusters. This is also apparent in the pie charts on a map provided in Appendix S5.