Phylogenetic relationships and genetic differentiation of two Salamandrella species as revealed via COI gene from Northeastern China

Due to traditional classification methods' limitations, some cryptic species remain undiscovered. To better explore the existence of the Schrenck salamander (Salamandrella tridactyla, a cryptic species of Siberian salamander S. keyserlingii) in China, we conducted a molecular phylogenetic analysis to confirm the taxonomic relationship among Salamandrella species and investigate genetic variation. We used complete sequences of the mitochondrial COI gene from 65 specimens collected across a wide range in Northeastern China. Thirty-five haplotypes were obtained from six populations. They showed medium-high haplotype diversity (Hd) and low nucleotide polymorphism (π). The phylogenetic tree and haplotype network analysis revealed that populations from Greater Khingan Ridge (Huma: HM) and Lesser Khingan Ridge (Tieli: TL) belong to S. keyserlingii, while populations from Changbai Mountain (Shangzhi-zhuziying: SZ, Shangzhi-cuijia: SC, Hailin: HL, and Baishan: BS) belong to S. tridactyla. This indicates the monophyly of Salamandrella and each of the two species. There was a substantial level of genetic differentiation between different species and within populations of the same species. This differentiation was significantly related to geographical distance. At last, the mismatch distribution and neutrality analyses indicated that the TL populations have undergone expansion of history. The study supplements the distributional range of Schrenck salamander. And it provides a theoretical basis for species conservation of Salamandrella species.