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Understanding genetic diversity patterns of endangered species is an important premise for biodiversity conservation. The critically endangered salamander Andrias davidianus, endemic to central and southern mainland in China, has suffered from sharp range and population size declines over the past three decades. However, the levels and patterns of genetic diversity of A. davidianus populations in wild remain poorly understood. Herein, we explore the levels and phylogeographic patterns of genetic diversity of wild-caught A. davidianus using larvae and adult collection with the aid of sequence variation in (a) the mitochondrial DNA (mtDNA) fragments (n = 320 individuals; 33 localities), (b) 19 whole mtDNA genomes, and (c) nuclear recombinase activating gene 2 (RAG2; n = 88 individuals; 19 localities). Phylogenetic analyses based on mtDNA datasets uncovered seven divergent mitochondrial clades (A-G), which likely originated in association with the uplifting of mountains during the Late Miocene, specific habitat requirements, barriers including mountains and drainages and lower dispersal ability. The distributions of clades were geographic partitioned and confined in neighboring regions. Furthermore, we discovered some mountains, rivers, and provinces harbored more than one clades. RAG2 analyses revealed no obvious geographic patterns among the five alleles detected. Our study depicts a relatively intact distribution map of A. davidianus clades in natural species range and provides important knowledge that can be used to improve monitoring programs and develop a conservation strategy for this critically endangered organism.

The complete mitochondrial genome of Bangana decora was determined in this study. The gene composition, arrangement and transcriptional orientation in B. decora mitogenome were identical to most vertebrates. The complete mitogenome of B. decora was 16,607 bp in size with 13 protein-coding genes, 22 tRNA genes and a control region. Two start codon patterns and three stop codon patterns were found in protein-coding genes. Only the tRNA-Ser2 could not fold into a typical clover-leaf secondary structure due to the absence of the dihydrouridine arm. Sequence alignment results suggest that the complete mitogenome of B. decora is an efficient tool to study molecular phylogenetics, biogeography and adaptive evolution of this lineage.

The complete mitochondrial genome of Sinilabeo decorus tungting was determined in this study. The gene composition, arrangement and transcriptional orientation in S. decorus tungting mitogenome were identical to most vertebrates. Two start codon patterns (ATG and GTG) and three stop codon patterns (TAG, TAA and T) were found in protein-coding genes. Only the tRNA-Ser2 could not fold into a typical clover-leaf secondary structure for lacking the dihydrouridine arm. Sequences alignment results suggest that the complete mitogenome of S. decorus tungting is an efficient tool to check species identification by comparing different gene sequences.