Fig. 4

Geographic clines and hybrid zone depicting the transition between distinct lineages of Orthohantavirus hantanense (HTNV) in the Republic of Korea (ROK). This figure illustrates the geographic clines and hybrid zone, capturing the transition between different phylogenetic lineages of HTNV across the ROK between 1976 and 2023. The geographic clines reflect estimated shifts in the frequency of genetic traits along a transect extending from the westernmost location in Paju to the easternmost location in Yanggu. For the L segment, a genetic crossbreed area was observed extending from Yeoncheon to Hwacheon (45.3–89.4 km from Paju). The contact region was restricted to Hwacheon (64.3–89.4 km from Paju) in the M segment. The S segment displayed an inter-lineage hybridization zone spanning from Yeoncheon to Cheorwon (45.3–64.3 km from Paju). Symbol sizes represent the number of samples collected, whereas the colors indicate the genotype frequency at each location (red for lineage 1, orange for the hybrid zone, and green for lineage 2). The grey-shaded areas represent regions of 95% credible clines, with dotted lines indicating the boundaries of the hybrid zone.