Phylogeny And Biogeography Of Triplophysa(Nemacheilinae:Cypriniformes)of The Qilian Mountains Area

Triplophysa(Nemacheilinae,Cypriniformes)is an important group of fish fauna mainly distributed in the Tibetan Plateau and adjacent areas.At present,there are few studies focused on the phylogeny and biogeography of the Triplophysa.In this study,we collected seven species of Triplophysa as research objects,and its distribution includes five river systems around the Qilian Mountains areas,which located in the northeast edge of the Tibetan Plateau,including the Shiyang River,Heihe River and Shule River in the Hexi Corridor,Qaidam Basin river system and Yellow River system.We use cytochrome c oxidase subunit I(CO I)gene and cytochrome b(Cyt b)gene to construct the phylogenetic tree and estimate the divergence time of Triplophysa,and we also analyze the genetic diversity and population dynamics of Triplophysa.The relationship between the geological structure,climate turbulence caused by the uplift of the Tibetan Plateau and the phylogenetic structure,genetic differentiation of Triplophysa is also been discussed.In addition,we also preliminarily analyze the phylogenetic relationships and divergence time of 38 species of Triplophysa,which CO I and Cyt b mitochondrial DNA fragments can be obtained from Genebank.The main conclusions of this study are as follows:(1)The divergence time of seven species of Triplophysa is consisting with the time of the development of the river system and the uplift of the Qilian Mountains area since the Miocene.Therefore,the genetic differentiation of the seven species of Triplophysa is closely related to the evolution of the river system and the intermittent uprise of the Qilian Mountains caused by the uplift of the Tibetan Plateau.(2)There is a closely relationship between phylogenetic branches and geographic distribution of seven species of Triplophysa.The populations of the same species distribute in the same or adjacent river show closer phylogenetic relationships,and the haplotypes of different species can also show closer phylogenetic relationships because of their geographical proximity.In addition,five species of Triplophysa are not monophyletic except for the Triplophysa siluroides and Triplophysa hsutschouensis.(3)During the development process of the river systems,they have been connected with each other due to the uplift of the Tibetan Plateau,such as the Heihe River system and the Yellow River system,the Yellow River system and the Qaidam Basin river system.This can promote gene flow among different populations.The population dynamics of seven species of Triplophysa are closely related to the tectonic events caused by the uplift of the Tibetan Plateau and the repeated climatic changes caused by Quaternary glacial and interglacial cycles.(4)Triplophysa leptosoma has the highest haplotype diversity and nucleotide diversity.The haplotype of Triplophysa leptosoma mixed with other species,and the shared haplotypes has been generated with Triplophysa stoliczkae and Triplophysa microps.It indicated that this species has high genetic diversity,strong adaptability and wide distribution.(5)Genetic diversity and polymorphism in population of Triplophysa leptosoma show that,the nucleotide diversity(Pi)gradually decreased from east to west along the Qilian Mountains,it is caused by the geographical environmental of the river systems.(6)The phylogenetic branches of 38 species of Triplophysa also show that some species are not monophyletic.In addition,we suggest that Hedinichthys and Triplophysa should not be merged into one genus,based on phylogenetic branch of Triplophysa(Hedinichthys)yarkandensis.(7)The divergence time of 38 Triplophysa species consist with the uplift of the Tibetan Plateau in early Miocene.Therefore,we speculate that the strongly geological structure in early Miocene promoted the genetic differentiation of Triplophysa population,and spread to the adjacent areas of the Tibetan Plateau with the river development.Ultimately,the present species distribution pattern is formed.