Study On The Genetic Structure Of Three Labeoninae Fishes In The Nujiang River

The Placocheilus cryptonemus,Epalzeorhynchus bicornis and Garra orientalis belong to Cyprindae,Labeoninae,and they are three species of small freshwater fishes. The former two species is only distributed in the Nujiang River.The P.cryptonemus mainly inhabits the middle and lower reaches of the Nujiang River,and the E.bicornis, Gorientalis mainly the lower reaches.The stock declined drastically in recent years due to over-fishing and habitat destruction.The P.cryptonemus and E.bicornis have been included in China Red Data Book of Endangered Animals.Nujiang River’s hydropower project in the future will be greater impact to their survival.Therefore,we must strengthen the research of their protection.However,little knowledge is available about its population genetic structure and genetic diversity.Here,the mitochondrial DNA（mtDNA） cytochrome b genes were amplified by means of polymerase chain reaction（PCR） and sequenced,to test the population genetic structure and genetic diversity.Total 138 individuals of P.cryptonemus were collected from five sites（populations） in Nujiang River,including Gongshan（GS,n=26）,Fugong（FG,n=22）,Lushui（LS,n=28）, Daojie（DJ,n=27）,Longzhenqiao（LZ,n=35）.The results showed that 21 variable sites were detected in the aligned sequences of 1140 bp,and 21 haplotypes were recoverd among the specimens,only one haplotype shared among all populations.The haplotype diversity（h） and nucleotide diversity（π） were 0.826 and 0.00215,respectively.The genetic diversity is low.Within populations,LS gained the highest values of genetic diversity,which were 0.804 and 0.00264 for h andπrespectively,and DJ the lowest, which were 0.214 and 0.00032 for h andπrespectively.The pairwise Kimura 2-paramter genetic distances between populations were calculated,and the distance between FG and LZ displayed the highest,up to 0.0346,while that between LS and DJ was the lowest to 0.00093.The neutral test of Fu’s Fs showed a significant negative value（-7.664） and the pairwise nucleotide differences distribution showed a singlet,indicating population expansion in history.The fixation indices(F_st) of analysis of molecular variance （AMOVA） among populations was 0.3051（P＜0.05）,which signaled strong population structure.Total 70 individuals of E.bicornis were collected from four sites in the Nujiang River, including Lushui（LS,n=13）,Daojie（DJ,n=21）,Sanjiangkou（SJ,n=18）,Mucheng（MC, n=18）.The results showed that 13 variable sites were detected in the aligned sequences of 1140 bp,and 16 haplotypes were recoverd among the specimens,but only five haplotypes shared among all populations.The h andπwere 0.579 and 0.00070,respectively.Within populations,MC gained the highest values of genetic diversity,which were 0.797 and 0.090 for h andπrespectively,and LS the lowest,which were 0.423 and 0.164 for h andπrespectively.The pairwise Kimura 2-paramter genetic distances between populations were calculated,and the distance between LS and MC displayed the highest,up to 0.00080, while that between LS and DJ was the lowest to 0.00059.The neutral test of Fu’s Fs showed a significant negative value（-16.520） and the pairwise nucleotide differences distribution showed a obviously single peak,indicating population expansion in history. The F_st of AMOVA among populations was 0.0049（P＞0.05）,which showed no significant population structure and suggested that there existed strong gene flow.Total 28 individuals of Gorientalis were collected from three sites in the Nujiang River,including Daojie（DJ,n=10）,Sanjiangkou（SJ,n=9）,Mucheng（MC,n=9）.The results showed that 6 variable sites were detected in the aligned sequences of 1140 bp, and 7 haplotypes were recoverd among the specimens,but only one haplotypes shared among all populations.The h andπwere 0.442 and 0.00043,respectively.The genetic diversity is low.The pairwise genetic distances between populations were calculated,and the distance between SJ and MC displayed the highest,up to 0.00058,while that between SJ and MC was the lowest to 0.00058.The F_st of AMOVA among populations was 0.0175 （P＞0.05）,which showed no significant population structure and suggested that there existed strong gene flow.The datas here should be important and useful for making scientific strategy for the natural resource protection of the three fishes during the development of the Nujiang River.Future research should focus on using nuclear and more polymorphic markers such as AFLP or microsatellite DNA to obtain the detail information of the three species of fishes.