Population genetics of wild boars across South Korea shows broad-scale distance-driven structure and a region-specific riverine barrier

In South Korea, expanding wild boar populations have increased concerns regarding human-wildlife conflict and the spread of African swine fever (ASF). Yet their population genetic structure and connectivity remain poorly understood, limiting effective wildlife and disease management. We present the most comprehensive population-genetic analysis of wild boars ( Sus scrofa ) in South Korea, using 13 polymorphic microsatellite loci and1,813 individuals collected nationwide between 2019 and 2023. Overall, wild boars exhibited high genetic diversity across the peninsula with moderate regional variation. Gangwon region showed the highest diversity (N A = 7.3, H O = 0.70), whereas Jeolla region exhibited the lowest (N A = 6.6, H O = 0.61). Mild heterozygote deficits and non-random allelic associations suggested fine-scale population structuring, particularly in Chungcheong region. Pairwise F ST values indicated low but statistically significant genetic differentiation, with Gyeonggi and Gangwon forming a largely continuous genetic unit, while Jeolla was the most differentiated. The comparatively high differentiation between Chungcheong and Jeolla, despite their geographic proximity, suggests that the Geum River and associated landscape features reduce connectivity beyond that expected from geographic distance alone. Bayesian clustering analyses revealed two primary genetic clusters with additional hierarchical subdivision, while discriminant analysis of principal components indicated gradual geographic differentiation among predefined regional groups and extensive overlap among neighbouring populations. Significant isolation by distance and AMOVA further demonstrated that most genetic variation is maintained within individuals despite detectable regional genetic structure. These findings demonstrate that South Korean wild boars maintain high genetic diversity alongside stable regional genetic structure, shaped by habitat configuration, riverine barriers, and historical dispersal processes. This genetic framework provides a basis for regionally coordinated ASF surveillance and spatially informed wildlife management in South Korea.