Mitochondrial genomic characterization of two endemic Chinese freshwater crabs of the genus Sinopotamon (Brachyura: Potamidae) and implications for biogeography analysis of Potamidae

As an endemic freshwater crab group in China, the phylogenetic relationships within Sinopotamon are still controversial because of the limited taxon samples. In this study, the complete mitogenomes of Sinopotamon chishuiense with 17,311 bp and the nearly complete mitogenomes of S. wushanense with 16,785 bp were firstly sequenced and analyzed. Compared with other reported mitogenomes of Potamidae, some novel patterns of gene rearrangement were detected in these two Sinopotamon mitogenomes, which could be illuminated by the mechanisms of tandem duplication‐random loss, recombination, and translocation. Phylogenetic analyses showed the nonmonophyly of the Sinopotamon and a sister group relationship with Tenuilapotamon. These crabs from the eastern and southern of the Yangtze River basin were more closely related while other crabs form the plateau areas formed a separate clade. Divergence time indicated that the Sinopotamon and its sister group Tenuilapotamon diverged from other potamiscine freshwater crabs approximately 42.65 Mya, which belongs to the recent main uplifts period of the Tibetan Plateau in the Late Miocene. Combined with the similar evolutionary rates and relatively stable habitat altitude of these Sinopotamon species, these results implied that the ecological environment may be relatively stable during the speciation. Overall, our study yielded worthy perceptions for the evolutionary and taxonomic relationship of Sinopotamon and will help to better clarify the gene rearrangement events of the invertebrate mitogenome and lay the foundation for further phylogenetic study of Sinopotamon. Overall, our study yielded valuable insights into the evolutionary history and taxonomic relationship of Sinopotamon and these results will help to better explain the gene rearrangement events of the invertebrate mitogenome and lay the foundation for further phylogenetic study of Sinopotamon.