Multiple Maternal Lineages of <i>Strauchbufo raddei</i> (Strauch, 1876) in Mongolia Revealed by Mitochondrial DNA

The Mongolian toad Strauchbufo raddei (Strauch, 1876) is one of widely distributed and dominated amphibian species in eastern Asian, including Mongolia. In this study, we amplified and sequenced a total of 50 samples of S. raddei, from three main regions in its Mongolian distribution range namely, Northern, Eastern, and Gobi regions. Our phylogenetic trees (Bayesian inference; BI and time-calibrated) and network analysis clearly support presence of multiple maternal mitochondrial DNA lineages for S. raddei in Mongolia. As expected, samples from these three regions were clustered separately in BI tree (Bayesian posterior probability (BPP 0.52). In addition, the population specific haplotypes, estimated genetic distances (e.g. uncorrelated p distance; ranged from 1% to 25%) and hierarchical AMOVA suggested relatively strong population genetic structure of S. raddei across Mongolia. Time-calibrated tree and ancestral range analysis showed that the first colonization of S. raddei may have occurred in Northern part of Mongolia approximately 9.63 mya, then dispersed over other parts of the country. Estimated approximate time for crossing event of S. raddei over dry steppe and semi-desert regions in Mongolia was 5.02 – 2.50 mya. Finally, high level of genetic diversity (overall; haplotype diversity, Hd = 0.93; nucleotide diversity, π = 0.011) of S. raddei were observed in Mongolia. Importantly, through this study, we contributed to closing sampling gaps in distribution range of S. raddei in Eastern Asia, which is key to better understanding species history, as well as describing cryptic lineages.