Phylogeny and speciation time estimation of two Koreocobitis species (Teleostei; Cypriniformes; Cobitidae) endemic to Korea inferred from their complete mitogenomic sequences

The genus Koreocobitis (Teleostei; Cypriniformes; Cobitidae) is endemic to Korea and consists of two species. Koreocobitis naktongensis was recently separated from Koreocobitis rotundicaudata and erected as a novel species based on distinct morphological differences. Additionally, they show disjunctive separation in biogeography; K. rotundicaudata inhabits only the Han River drainage of the East Korea Subdistrict, and K. naktongensis is found only in the Nakdong River drainage of the South Korea Subdistrict. We determined the complete mitogenomic sequences of these two species to evaluate their phylogenetic position and to estimate the speciation time inferred from the partitioned nucleotide matrix of concatenated mitochondrial genes. The phylogenetic analysis revealed that the two Koreocobitis species consistently branched out together and formed a monophyly with Misgurnus species, with high statistical support within the cobitid lineage. The speciation time between the two Koreocobitis species was estimated to be 18.8 ± 3.7 million years ago (Mya), which is quite younger than that between two subdistrict populations of Coreoleuciscus splendidus showing the identical biogeographical separation pattern (ca. 31.2 Mya). These results indicate that the Noryeong/Sobaek Mountain Ranges functioned as an apparent vicariant barrier that not only allowed speciation of the Koreocobitis species but also contributed to the high genetic differentiation of C. splendidus populations for such a long period of time.