Molecular Phylogenetics And Phylogeography Of Schizothoracinae (Teleostei: Cyprinidae) In Lake Qinghai And Adjacent Drainages

Lake Qinghai and adjacent Yellow River and Qaidam drainage include 7 unique species and 1 subspecies of Schizothoracinae. Molecular phylogenetics of them have recently received much attention. Among them, 4 species (G. przewalskii, G. eckloni, G. scolistomus and Schizopygopsis pylzovi) of Gymnocypris and Schizopygopsis are widely distributed in those areas, and these fishes dwelling in the isolated river habitats provide an ideal model for phylogeographical studies. In this study, the complete mtDNA cytochrome b gene(1141bp)and D-loop control region (594 bp) sequences were sequenced for analysesing the genetic structure and phylogenetic relationships of G. przewalskii, G. eckloni, G. scolistomus, Schizopygopsis pylzovi and Platypharodon extremus from Lake Qinghai, Yellow River and Basin Qaidam, respectively. we aimed to provide a diversification of the mtDNA lineages hypothesis for the schizothoracine fishes in this area, and combining the geological data clarified the relation of origin between G. przewalskii and G. eckloni, and the effect of the uplift of Qinghai-Tibet Plateau on speciation, this will also provide biological evidence for the forming of the Lake Qinghai and the history of headward erosion for Yellow River. 1. Congruent phylogenies were obtained indicating that the samples collected from the same species did not form monophyletic groups, but they grouped three highly divergent lineages (A, B and C). Among them, lineage A contained all G. przewalskii, G. scolistomus and a part of G. eckloni from Yellow River, lineage B was only composed of other G. eckloni from Yellow River, and lineage C formed a monophyly by G. eckloni from Basin Qaidam. Analysis of molecular variance (AMOVA) indicated that most of the genetic variation was detected among the three mtDNA lineages. and suggesting there were three diversiform lingeages for Gymnocypris in this region. 2. Our mtDNA data did not support that G. przewalskii was a polytypic species, and neither G. scolistomus was an independent species nor a subspecies of G. eckloni. The G. eckloni from Basin Qaidam was a monophyletic group (lineage C) with high bootstrap value, and long-term interruption of gene flow was evidenced by high Fst values, suggesting thepopulation of G. eckloni from Basin Qaidam might have be a different species. 3. The divergent mtDNA lineages of G. eckloni from Yellow River suggested a part of the gene flow among the populations was restricted by several gorges on the upper reaches of Yellow River. The lineage B of G. eckloni might relate to its history of headward erosion of Yellow River. 4. The result of network analysis showed the G. eckloni from Yellow River had multiple maternal origins, they might be the genetic character of the ancestor from the endemic schizothoracinae fishes, which incorporated in the course of the headward erosion by Yellow River reach. 5. In network structure analysis, a founder haplotype of unique to Yellow River linked all specimens form G. przewalskii suggesting that G. przewalskii might originate from one lineages of G.eckloni of Yellow River. The G. przewalskii ganzihonensis coming from G. przewalskii was supported, but genetic divergence between them has been not largely formed. 6. The test of selective neutrality showed that lineages diversification of G. przewalskii took place about 0.14MaBP years ago, it was near the times that the "Gonghe Movement"event of Qinghai-Tibetan Plateau to cause the separation of Lake Qinghai from the upper reaches of Yellow River. So that "Gonghe Movement"event in the late Pleistocene might well explain to shape the evolutionary pattern of G. przewalskii and G. eckloni. A local expansion of the G. eckloni from Yellow River about 0.072MaBP might happen in the course of headward erosion of Yellow River. The population expansion was tested also within G. eckloni from Basin Qaidam about 0.036MaBP, it might be related to the very dry during late Pleistocene in Basin Qaidam. This result was also supported by the mismatch analysis. 7. All Gymnocypris populations exhibited a low nucleotide diversity, especially the Gymnocypris populations from Basin Qaidam showed a very low nucleotide diversity suggesting that they might have experienced a very severe bottleneck. This result is congruent with a fact that the global climate became extremely worsen to cause extinction of some species in the later Pleistocene. Our result suggested a high priority in conservation programs for Gymnocypris population of Basin Qaidam. 8. Correlation test between the rakers variety of the population of Gymnocypris and genetic distances showed a non-significant correlation, and suggested that the rakers and oblique mouth cleft might have little significance in the phylogeny of the Gymnocypris fishes. 9. The Schizopygopsis from Lake Tuosuo of Basin Qaidam did not form monophyleticgroup. Our results supported the morphological classification that merged the Schizopygopsis kessleri into Schizopygopsis pylzovi. The divergent time of the Schizopygopsis Pylzovi of Yellow River and Lake Tuosuo was about 0.07MaBP ago in the late Pleistocene.