Cyprininae phylogeny revealed independent origins of the Tibetan Plateau endemic polyploid cyprinids and their diversifications related to the Neogene uplift of the plateau

Origin and diversification of the Tibetan polyploid cyprinids(schizothoracins) may help us to explore relationships between diversification of the cyprinids and the Tibetan Plateau uplift. Cyprininae phylogeny was analyzed using mitochondrial and nuclear DNA sequences to trace origins of polyploidy and diversifications of schizothoracins. Ancestral states reconstruction for ploidy levels indicated that the Cyprininae was diploid origin and the schizothoracin clades tetraploid origins. There were two diversification rate shifts along with diversification of the cyprinine fishes in response to the Tibetan uplift. The unusual diversification shifts were located to branches subtending the clades of Tibetan polyploid cyprinids. Our analyses suggested that(i) phylogeny of Cyprininae recovered two independent origins of the Tibetan polyploidy schizothoracins;(ii) diversifications of the schizothoracins were closely related to the Neogene uplift of the Tibetan plateau in the following ways: the relatively ancient Late Oligocene-Middle Miocene adaptive radiation may be associated with the uplift of the southern Tibet and Himalaya; the Middle Miocene-Early Pleistocene lineage-specific diversification broadly coincident with major phase of the Neogene Tibetan uplift; and the most recent Pleistocene diversification shift in Schizothorax closely coincident with the successive Kunlun-Huanghe and Gonghe movements of the Tibetan uplift and the glaciation-induced climate oscillations on the plateau.

Effect of total dissolved gas supersaturated water on early life of David's schizothoracin (Schizothorax davidi)

The effect of total dissolved gas （TDG） supersaturation on fish living downstream of dams is one of the main ecological risks of high dam construction. A strategy for mitigating the negative effects is needed urgently since many high dams are under construction in the upper reaches of the Yangtze River in China. Experiments on the hatching process of David＇s schizothoracin were carried out and the results show that the hatching rate decreased with increasing TDG levels, and that most eggs hatched within a very short time in the higher TDG saturation groups. By using a stereomicroscope, damages to the head, yolk sac, body, anus, etc. were found in larvae which hatched in TDG supersaturated water. Results show that the lesion rate increased with increasing TDG levels. Furthermore, 7-d-old David＇s schizothoracin were exposed to TDG supersaturated water levels of 100%, 105%, 110%, 115%, 120%, 125%, 130%, 135%, and 140% for testing their tolerance to TDG supersaturation. We found that the median lethal concentrations （LC50） for 13, 14, 20, 35, 52, 73, and 96 h exposure were 138%, 138%, 134%, 130%, 129%, 128%, and 126%, respectively. The median lethal times （LTs0） were 7.49, 11.04, 19.25, and 35.38 h for exposure to water with TDG levels of 145%, 140%, 135%, and 130%, respectively.

Signatures of functional constraint at Fgfr1a Genes in schizothoracine fishes (Pisces: Cypriniformes): The dermal skeleton variation adapted to high-altitude environments

Fishes harbor a huge resource of phenotypic diversity and are useful for understanding the genetic basis of mor­phological variation.However,it is difficult to transfer classical genetic mapping to most non-model species.In this study,we performed a comparative sequence analysis of Fgfr1a to first interpret the evolution of this candi­date scale-loss gene in 15 schizothoracine fishes with various scale phenotypes.While considerable amino acid(AA)substitutions were observed,molecular evolution analysis indicates that the overall coding regions were subject to functional constraint.We also identified extra copies of Fgfr1a in 4 scale-loss fishes and detected ac­celerated evolution in one AA substitution specific to these duplicates.We speculate that Fgfr1a had accumulat­ed mutations in the ancestral lineage of scale-loss schizothoracine fishes before experiencing duplication events,which was further followed by the diversification of species.In silico mutation analysis predicted deleterious ef­fects of the mutations while no disruptive molecular mechanism was detected.Collectively,our results highlight the important role of Fgfr1a gene in the adaptive evolution of schizothoracine fishes during their radiation in the Qinghai-Tibetan Plateau.