Molecular Phylogeny Of The East Asian Cyprinids (Pisces: Cypriniformes)

This study concerns the phylogenetic relationships among the East Asian cyprinids. Nucleotide sequences of the mitochondrial 16S rRNA gene, the recombination activation gene 2 and the S7 ribosomal protein gene were analyzed for use in phylogenetic reconstruction. Four representative species, belonging to the families Cobitidae, Homalopteridae, and Catostomidae respectively, were selected as outgroup. Phylogenetic trees were estimated with both maximum parsimony and maximum likelihood optimality criterion. The main conclusions and hypotheses of the present study were as follows. 1 Rasborins is the most basal cyprinid group, and the remaining cyprinids were clustered into two lineages, Barbine and Leuciscine. 2 Within Barbine, two clades could be identified. One clade comprises Cyprinins, Schizothoraxins, and Barbins that are closely related to each other, and the other Labeonins. 3 In Leuciscine, our molecular phylogeny led to the solid fact that the close relationships existed between North American phoxinins and Eurasian leuciscins, and that between East Asian Gobionins (including Gobiobotins) and European Gobio. The monophyly of the Acheilognathin fishes was supported by our molecular analyses. East Asian endemic cyprinid taxa, such as Squaliobarbins, Elopichthins, Hypophthalmichthins, Cultrins, Xenocyprinins, and the affiliated small group including Opsariichthys, Zacco, Aphyocypris, Hemigrammocypris, and Nicholsicypris, were closely related to one another and they could be recognized as a monophyly. The position of Tinca, which possibly belonged to the Leuciscine, was not well resolved. 4 The recent cyprinid fish fauna in East Asia probably originated in Early Miocene. Many similar fossil cyprinids from the Neogene deposits shared by eastern China and Japan indicated they formed a widespread cyprinid fish fauna. The recent cyprinid fauna of the East Asian mainland were established in Pliocene. After that, the Japanese Archipelago underwent the tectonic movements in Middle Pleistocene and the Japanese cyprinid fauna became different from the Chinese one. 5 The estimated rate of change for transversions in the mitochondrial 16S rRNA gene was 0.14% per million years (0.14%/MY) in cyprinids. The cladogenesis events in the extant East Asian endemic cyprinid taxa firstly began at onset of the East Asian Monsoon which was accompanied with uplift of the Qinghai-Tibetan Plateau. After that the East Asian monsoon was stably established, the major cladogenesis events in Squaliobarbins, Elopichthins, Hypophthalmichthins, Cultrins, and Xenocyprinins occurred. The alternation between glacial and interglacial period in the Quaternary contributed to the speciation, which accelerated the prosperity of Squaliobarbins, Elopichthins, Hypophthalmichthins, Cultrins, and Xenocyprinins in the East Asian mainland. 6 The main cause of the current distribution of Squaliobarbins, Elopichthins, Hypophthalmichthins, Cultrins, and Xenocyprinins that occurred in the East Asian mainland but not in the Japanese islands, was not only the vicariance events but also the considerable environmental changes, especially after the stable establishment of the East Asian monsoon. 7 Based on our molecular phylogeny of cyprinids, eight subfamilies, such as Rasborinae, Labeoninae, Cyprininae, Tincinae, Gobioninae, Leuciscinae, Acheilognathinae, and Xenocypridinae could be recognized within the family Cyprinidae. The monophyly of the subfamily Rasborinae was not supported bymolecular data. The relationships among these eight subfamilies were hypothesized to be the following: (Rasborinae, ((Labeoninae, Cyprininae), (Tincinae, Xenocypridinae, (Gobioninae, Leuciscinae, Acheilognathinae)))). 8 The Early Tertiary group was composed of Rasborinae, Labeoninae, and Cyprininae. The earliest Rasborinae and Cyprininae appeared in the Paleogene. The cyprinid fauna dominated by Rasborinae and Cyprininae continued probably from the Paleogene to the Miocene Epoch. 9 The northern cold-water group consists of Gobioninae, Leuciscinae, and Acheilognathinae. The extensive radiation of Leuciscinae began after the world-wide climatic cooling in the late Paleogene. The distribution of Leuciscine fishes in North American and Eurasia indicates their adaptation to higher-latitude freshwater habitats. 10 The East Asian group comprises Xenocypridinae. The cladogenesis events within the East Asian group were correlated with the origin and evolution of the East Asian monsoon affected by uplift of the Qinghai-Tibetan Plateau.