Geographical location and elevation of the Nakdong River Basin in Korea (base map data source: https://gadm.org/).

(A) The location of the Korean Peninsula in Northeast Asia. (B) Digital elevation model (DEM) of the Nakdong River Basin and its rivers and mainstreams, with occurrence sites (n = 321) and genetic data locations (n = 8) of nutrias indicated as open black circles and closed red squares, respectively. The shuttle radar topography mission (SRTM) DEM with 30-m resolution was provided by the USGS Earth Explorer platform (https://earthexplorer.usgs.gov/). The genetic data location coordinates were obtained from the study by Kim et al. [28]. River and stream data were derived from the OpenStreetMap database (http://www.openstreetmap.org).