Map showing the study sites in western Japan.

Abbreviations for the river names correspond to those given in S1 Table. Circles and squares represent localities where fish specimens were collected for this study and localities where sequences are cited from the DDBJ, respectively. These shaded-relief maps are made by ourselves base on maps provided under CC BY 4.0 by the Geospatial Information Authority of Japan (https://maps.gsi.go.jp).