Molecular Identification of Acrossocheilus jishouensis (Teleostei: Cyprinidae) and Its Complete Mitochondrial Genome

Molecular identification, such as DNA barcoding, is a useful tool that is widely applied in distinguishing species. To identify the cyprinid Acrossocheilus jishouensis, which was previously known to be restricted to only its type locality, we conducted molecular identification of this species based on 23 samples in five localities. Molecular identification based on the mitochondrial COI gene sequence showed that the morphologically similar samples from the five populations were all A. jishouensis, as the mean genetic distances between populations were very small (0.1-1.6%); thus, the distribution of this species was substantially expanded. The whole mitochondrial genome of one sample was also assembled, which was 16,594 bp in length and consisted of 13 protein-coding genes (PCGs), two rRNA genes, 22 tRNA genes, and one control region. All PCGs began with ATG except the COI gene, which started with GTG; seven PCGs used the complete stop codon TAA, while four terminated in T(AA) and two ended with TAG. The overall base composition reflected a higher proportion of A+T than G+C and a positive AT-skew and negative GC-skew pattern except for the opposite in ND6. Phylogenetic relationships inferred using BI and ML methods revealed that both Acrossocheilus and Onychostoma were nonmonophyletic, which indicated that the traditional diagnoses between these two genera need to be assessed further. The results of this study not only expanded the known distribution ranges of A. jishouensis, but also provided a valuable data resource for future molecular and evolutionary studies of Acrossocheilus and other cyprinids in Barbinae.