Better Resolution for Cytochrome than Cytochrome Oxidase Subunit I to Identify Species (Teleostei: Cyprinidae) from the Tibetan Plateau and Its Adjacent Area.

The genus is one of the most diverse groups of schizothoracine fish. Many species within this genus possess highly similar morphological characters and are very difficult to be identified accurately only based on morphology. The present study aims to test the effectiveness of mitochondrial cytochrome oxidase subunit I () gene and cytochrome () gene for discriminating the fish. A total of 185 individuals of 11 species for gene and 264 individuals of 23 species for gene were used for analyzing, respectively. According to the genetic distances, only one species based on gene and five species based on gene had "barcoding gaps," respectively. The tree-based analysis displayed that four species based on gene and six species based on gene clustered monophyletic group with strong support, respectively. The optimal threshold value of is 0.005 based on gene and 0.008 based on gene. The results of genetic similarity tests performed through online BLAST showed that 108 of 185 similarity searches succeeded in identifying conspecific sequences based on gene and 199 of 264 succeeded in identifying conspecific sequences based on gene. Considering greater interspecific genetic distance in Kimura 2-parameter (K2P) analysis and many clades with higher supporting values in tree-based analysis, we suggest that gene has better resolution in discrimination of species than gene. However, there are still many confused clustering relationships based on molecular data currently available. Incomplete lineage sorting, the existence of possible cryptic species and problematic morphological identification, etc. might have greatly weakened the resolution of gene in discrimination of species.