Mitochondrial genome characterization and phylogeny of Hynobius notialis, a Korean endemic salamander

Hynobius notialis is a recently described salamander species endemic to the southern Korean Peninsula, with a restricted distribution and vulnerable conservation status. Despite its evolutionary and conservation significance, the complete mitochondrial genome of this species has not yet been characterized. In this study, we sequenced and analyzed the entire mitogenome of H. notialis (16,408 bp), comprising 13 protein-coding genes, 22 tRNAs, two rRNAs, and a single control region. Most genes are encoded on the heavy (H) strand, whereas ND6 and several tRNAs are located on the light (L) strand, consistent with the typical organization observed in other vertebrates. Comparative analyses revealed that the nucleotide composition of H. notialis is highly conserved relative to other Hynobius species and Onychodacytuls fischeri, reflecting family-level evolutionary constraints on mitochondrial genome evolution. Phylogenetic reconstruction using complete mitogenomes showed that H. notialis is most closely related to H. unisacculus, forming a monophyletic clade with H. unisacculus and H. quelpaertensis, which together with H. yangi and H. leechii constitute a broader monophyletic group of Korean Hynobius species. These results not only clarify the phylogenetic position of H. notialis but also provide a valuable molecular resource for future studies on evolutionary history, biogeography, and conservation of Korean endemic salamanders.