I. Study areas
Genetic data were collected from 292 B. gargarizans individuals from four countries (China, North Korea, South Korea, and Russia). Among them, 165 Chinese samples were from GenBank (Zhan & Fu, 2011), while the remaining 127 were newly sequenced in this study. Of these new samples, 87 individuals were from South Korea, 3 from North Korea, 3 from Russia, and 34 from China (Fig. 1 ; Table S1 ). Following Zhan and Fu (2011), we categorized samples a prioribased on geography (W, C, SE, NE). Tissue samples (toe tips, muscle, or tadpole tails) of new specimens were collected from the field and preserved in 95% ethanol.