| Loaches of the genera Cobitis Linnaeus, 1758, Niwaella Nalbant, 1963 and Bibarba gen. nov. are of the subfamily Cobitinae, Family Cobitidae, Order Cypriniformes. Cobitis are a small benthic freshwater fish with a wide distribution area covering large parts of Eurasia, Sunda Islands and one additional species in north-west Africa. The genus Cobitis presents a difficult taxonomic problem, because the species are morphologically little differentiated. For a long time, most spined loaches were considered to belong to the genus Cobitis and named as C. sinensis. The taxonomic status of some forms of Cobitis and its related genera present problematic. The phylogenetic relationships of the genus Cobitis remain unsolved.In present study, the taxonomic revision on the genera Cobitis, Niwaella and its related genera from China were revised. Both methods morphology and molecular systematics were combined to study.1. Taxonomic revisionOn the basis of the specimens of the genus Cobitis and its related genera, kept in the Freshwater Fishes Museum (FFM) of the Institute of Hydrobiology (IHB) at the Chinese Academy of Sciences (CAS) in Wuhan (Hubei Province), the variation pattern of all major macromorphological characters were analyzed. The results show that sexual dimorphism (present or no) and the secondary sexual characters (e.g., lamina circularis or the scale of Canestrini), pigmentation pattern, the number and the pattern of the pairs of barbles arranged around the mouth, the shape of suborbital spine were considered as good characters for the delimitation of the Cobitis and its related genera; the pigmentation pattern, shape of lamina circularis in males, body scales, suborbital spine and mental lobes were generally features of species identification in spined loaches.Cobitis and Bibarba show the sexual dimorphism, which are males smaller than females, in males, the second pectoral fin ray thickened and elongated, while Niwaella do not show the sexual dimorphism. A lamina circularis present at the base of the second pectoral ray in males of Cobitis, and in the third pectoral ray of Bibarba, while no lamina circularis present in Niwaella.Three pairs of barbels (one rostral pair, one maxillary pair, and one maxillo-mandibular pair) are present in both Cobitis and Niwaella, while two pairs of barbels (one rostral pair and one maxillo-mandibular pair) in Bibarba.Some species of Cobitis are similar to Bibarba in the pigmentation pattern, having five longitudinal lines of dark speckles on the dorsolateral sides of the body (Gambetta's pigmentation pattern). And some species of Cobitis are similar to Niwaella by having no the Gambetta's pigmentation pattern, by scattered small dark speckles or large dark blotches on the dorsolateral surface, and a dark stripe or rounded black spots along the lateral midline, or some blotches below the lateral midline. Cobitis and Niwaella have a black stripe extends from the occiput through the eye to the insertion of the rostral barbel, while Bibarba have a black stripe extending from the operculum through the eye to the insertion of the rostral barbell. At the level of the base of the caudal fins, one dark spots is present in Cobitis and Niwaella, while two dark spots in Bibarba.The suborbital spine of Cobitis are thick and straight or slightly curved, without medio-lateral process, in Niwaella which relatively thick and curved, without medio-lateral process, while in Bibarba the suborbital spine relatively thick and stout suborbital spine with a strong medio-lateral process.Based on examination of specimens, 22 species and 2 incertitude species of Cobitis were confirmed to be Chinese, 8 old species (C. dolichorhynchus Nichols, 1918, C. melanoleuca Nichols, 1925 and C. rarus Chen, 1981 were considered to be valid) and 14 new species. Based on these characters, the species C. laterimaculata Yan and Zheng, 1984, was transferred from Cobitis to Niwaella. And two new species, N. xinjiangensis sp. nov. and N. longibarba sp. nov., were described. A new genus Bibarba gen. nov., and a new species, B. bibarba sp. nov., were described for the Chengjiang River, a tributary of the Hongshuihe River in Guangxi Province of southern China.2. Molecular evolutionWe determined 54 complete mitochondrial cyt b gene sequences, which contain 52 individuals representing 18 species of Cobitis as well as 2 individuals presenting one species of Bibarba. And we retrieved 2 species of Cobitis as well as one species of Lepidocephalus, one species of Sabanejewia from the Genbank. Totally 61 sequences were used to infer the phylogenetic relationships of the Cobitis, with B. bibarba, L. octocirrhus, and S. balcanica as outgroups. Phylogenetic trees were estimated with maximum parsimony, neighbor joining and Bayesian optimality criteria. Our results show that the molecular data analysis evidences the morphological diagnosable species of the genus Cobitis from China. In the phylogenetic trees, species of the genus can be mainly grouped into five clades: (1) C. arenae represents the basal sister species of the genus Cobitis, supporting a southern China origin of the Cobitis; (2) four species distributed in the southern drainage, and C. sp (Pingjiang), C. granoei distributed in the middle and northern drainage; (3) C. leptosoma sp. nov. distributed in Beijiang River; (4) C. sinensis and C. latifasciata sp. nov. distributed in the Yangtse River and the population of C. latifasciata sp. nov. distributed in the Lijiang River; (5) nine species distributed in southern, middle and northern drainages. Based on the molecular estimate and using dispersal-vicariance, we estimate divergent times of the Cobitis fishes and test the vicariance and dispersal biogeographical hypotheses of Chinese Cobitis. The results indicated that the Cobitis most possibly originated in middle Miocene. The species divergence mostly concentrated in Quaternary. And several rapid speciation events were happened in a relatively short time. The distribution pattern of the Chinese Cobitis may be explain by both vicariance and dispersal theory.
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