Population Genetics Of Jinshaia Sinensis And J.abbreviata In The Upper Yangtze River

The upper reaches of the Yangtze River are abundant in fish species,with high proportion of endemic species.Large hydropower stations such as Xiangjiaba and Xiluodu dams have been built in the river section,which destroyed the fish habitat and exacerbated ecological vulnerability.Jinshaia sinensis and J.abbreviate,which belongs to order Cypriniformes,family Balitoridae,are the only two species of Jinshaia and both endemic in the upper reaches of the Yangtze River.The two fishes have many similar biological characteristics,such as producing drifting eggs,benthic living,omnivorous food and overlapped geographical distributions.However,there are also significant differneces between them,such as the number of fins,scales on the body surface and population size,which are good mode for the adaptive evolution of species.Therefore,the study of population genetic diversity is helpful for the conservation of Jinshaia’s resources in the upper reaches of the Yangtze River.In this study,a total of 136 J.sinensis and 90 J.abreviata were collected in the upper Yangtze River from 2016 to 2018.We used mitochondrial DNA(Cyt b and D-loop)and microsatellite DNA(SSR)markers to evaluate the genetic diversity of J.sinensis and J.abreviata.The main results are as follows:1. We evaluated the genetic diversity of J.sinensis population from Banan,Jiangjin,Hejiang,Yibin,Qianwei,Qiaijia,Heishuihe,and Panzhihua in the upper reaches of the Yangtze River.Using mitochondrial DNA D-loop and Cyt b.The genetic diversity of J.sinensis was high with haplotype diversity(H_d)being 0.999 and 0.947,and nucleotide diversity(P_i)being 0.0182 and 0.0046,respectively.Microsatellite analysis showed that J.sinensis also has high genetic diversity,with the average expected heterozygosity rang offing from 0.709 to 0.861 and observed heterozygosity from 0.867 to 0.909.Analysis of molecular variance(AMOVA)did not show significant geographically structure.However,haplotype phylogenic tree and network based on the mitochondrial DNA revealed shallow three lineages within J.sinensis populations.AMOVA,Bayes Classification and principal coordinates analysis based on microsatellite also showed that there was no significant genetic differentiation among populations.However three supgroups could be distinguished,indicating a lack of long-term isolation of subpopulations and a high level of gene flow.The neutral test,mismatch distribution and Bayesian skyline plot(BSP)showed that the J.sinensis had experienced historical population expansion in the fourth interglacial of Pleistocene.2. We evaluated the genetic diversity of J.abbreviate population from Banan,Hejiang and Qianwei in the upper reaches of the Yangtze River.Based on the mitochondrial DNA(cytb and D-loop)sequence,the haplotype diversity(H_d)was 0.411 and 0.278,and nucleotide diversity(P_i)was 0.0005 and 0.0004,indicating low level of genetic diversity.Microsatellite analysis showed that J.abbreviate has high genetic diversity,with the average expected heterozygosity range offing from 0.637 to 0.692 and the observed heterozygosity from 0.856 to 0.890.AMOVA analysis did not show significant differentiation,and mt DNA haplotype phylogenic tree and network did not reveal any geographical cluster.The results of Bayes Classification and principal coordinates analysis were identical using microsatellite marker and mt DNA sequence.The K2P genetic distance between the two species of mt DNA haplotypes was low,and did not appear species gap,indicating recent speciation.Population dynamics analysis showed that J.abbreviate had experienced historical population expansion in the fourth interglacial of Pleistocene.With the development of ladder hydropower in the Yangtze River,we suggest that the monitoring of resources and genetic diversity should be focused in the future.