The taxonomy and phylogeny of the cyprinid genus Opsariichthys Bleeker (Teleostei: Cyprinidae) from Taiwan, with description of a new species

The morphological and mitochondrial genetic differentiation in the cyprinid genus, Opsariichthys Bleeker (Nederlandsch Tijdschrift voor de Dierkunde 1:187-218, 1863) have been surveyed in Taiwan. Among them, there are three valid species can be recognized in Taiwan including Opsariichthys pachycephalus Gunther (1868) distributed in northern and western Taiwan, Opsariichthys evolans (Jordan and Evermann Proc US Nat Mus 25:315-368, 1902) in northern Taiwan and an unnamed species from southern Taiwan described herein as Opsariichthys kaopingensis Chen and Wu, new species which can be well distinguished from the related O. pachycaphalus by their body proportions, scale counts, and specific coloration patterns. We utilized mitochondrial complete D-loop sequence data to infer phylogenetic relationships within a subset of related genera of opsariichthines, and to examine evidence for genetic differentiation in these two sibling species formerly assigned to "Zacco" pachycephalus and their genetic relationship with other congeneric species around nearby regions. The clade of O. pachycephalus and O. kaopingensis in genetically were recovered as more closely related to Opsariichthys uncirostris (Temminck and Schlegel 1846) species complex including both O. uncirostris and O. bidens Gunther (1868) from Japan and mainland China than to typical Zacco from Japan. This molecular phylogenetic insight strongly supports the assignment for both so-called "Zacco" pachycephalus and this new species described herein as the typical monophyletic members of Opsariichthys and the type species of Zacco as Zacco platypus (Temminck and Schlegel 1846) from Japan is sister clade for all species groups in Opsariichthys. Opsariichthys pachycephalus and O. kaopingensis were strongly differentiated by large mitogenetic distances and phylogenetic support from distance and discrete method and Bayesian inference based on complete mtDNA D-loop sequences, with an average mitogenetic divergence of 3.3%, which may suggest that the separation of the two species happened much earlier than the last glacial period. Opsariichthys evolans seems to share the close genetic relationship with O. acutipinnis (Bleeker Nederlandsch Tijdschrift voor de Dierkunde 1:187-218, 1863) from the Yangtsi River basin.