Genetic Diversity Analysis Of Jinshaia Sinensis And Glyptothorax Sinense In The Upper Reaches Of Yangtze River Based On Mitochondrial DNA D-loop Region

The upper reaches of the Yangtze River are rich in hydropower resources and biodiversity.In recent years,the construction of cascade projects has blocked the river,which destroyed the natural continuity of the river,and had a great impact on the ecological environment and biodiversity of biological resources.The small benthic omnivorous fishes living in the middle and upper reaches of the Yangtze River.They are highly dependent on habitat and widely distributed.These fishes forming different ecological groups in various landforms,which are very suitable as experimental materials for studying genetic diversity.In this study,according to the distribution characteristics of Glyptothorax sinense and Jinshaia sinensis,232 and 224 samples were sampled in GLP,HJ,HSH,NLJ,QJ,YB and so on which are located in the middle and upper reaches of the Yangtze River in 2017.Further analysis of whether the construction of hydropower station has an impact on their life.Formulate policies to ensure that biological resources are not destroyed while developing clean energy.The main results are as follows:The mitochondrial reference genomes of G.sinense and J.sinensis were found in the Genome database of NCBI,and compared with the PCR product sequencing results to determine the start and end sites of the control region(D-loop).The length of G.sinense D-loop region is between 876-880 bp,the length variation is small.While the length of J.sinensis D-loop region is between 888-918 bp,and the length variation is slightly larger than G.sinense.135 variation sites were found in the population of G.sinense and 219 were found in J.sinensis.The ETAS(extend terminal associated sequences),and a battery of conserved DNA sequences such as CSB-F and CSB-1 of G.sinense and J.sinensis were identified.The sequence characteristics of D-loop region and its terminal associated sequences,central domain and conserved sequence block were analyzed.The core sequence ACTA of the TAS and its reverse complementary sequence TGTA were found,the characteristic sequence GACATA of CSB-1 as well.The genetic diversity parameters and genetic differentiation of the two species of fish in each region were analyzed.The populations of J.sinensis in almost all locations and the populations of G.sinense in half of the locations showed rich haplotype diversity(Hd > 0.5)and rich nucleotide diversity(Pi > 0.005).The average Hd and Pi were 0.94114 and 0.01869 respectively in J.sinensis,and 0.75675 and0.00596 in G.sinense.In terms of genetic diversity,the performances of J.sinensis in different regions are relatively similar,and in general,it is higher than G.sinense.The haplotypes of the two fish were identified and analyzed,the haplotype network diagram and haplotype evolutionary tree were made,and AMOVA analysis was carried out.The haplotype network of G.sinense has obvious branches.In addition,the region-specific haplotypes are clustered as stellate distribution,and the dominant haplotypes are at the center.The haplotype network of J.sinensis has no obvious branches.Furthermore,the region-specific haplotypes are scattered,and there are few dominant haplotypes.This shows that the G.sinense genetic differentiation of various regions is relatively obvious,but the J.sinensis is not obvious.The haplotype evolution tree and AMOVA analysis both confirmed this conclusion at the same time.In the AMOVA analysis,the molecular variation of G.sinense mainly among populations in different regions,more than 61.26%.In contrast,the molecular variation of J.sinensis mainly within populations,only 40.47%.Neutrality tests were carried out for the two fish,and nucleic acid mismatch distribution curves were plotted.The Tajima’s D and Fu’s values of Yibin and Dawen river Suijiang populations of the G.sinense are-1.91068,-11.67323 and-1.65616,-12.58743 respectively,which are significantly negative,.However,only the Heishuihe,Niulanjiang and Hejiang populations showed a unimodal trend in the distribution curve of nucleic acid mismatches.It indicates that these groups may have experienced rapid expansion or continuous growth in the past.There is no significant negative value in the neutral test of J.sinensis populations.Nucleic acid mismatch curves are not unimodal,too.It shows that the probability of J.sinensis experienced rapid expansion or sustained growth in the past is very small.