MtDNA ND2 Sequence Diversity Of Culter Alburnus From 6 Major Lakes In Eastern China

Being one of "four most famous freshwater fishes in China",Culter alburnus is very important in freshwater fishing,and it is of high economic value.Being top predator in water ecosystem,it can inhibit overbreeding of small-sized fishies,and it is regarded as the key species to keep river healthy.Due to increasingly environmental pollution and overfishing in recent years,wild resources of Culter alburnus has been damaged,and average size and longevity is decreasing rapidly,so the fish is in great need of protection.Genetic diversity is the material basis for conservation biology and germplast improvement.With recent collapse of wild resourse and progress in artificial breeding of Culter alburnus,demanding of more high quality of germplasm in artifical breeding and exchange of large quantity of fish fry of in aquaculture is increasing,it is necessary and urgent to study genetic variation of wild populations of Culter alburnus in species' range.In this study,mtDNA ND2 sequences of 91 individuals of Culter alburnus from 6 large lakes were analyzed to survey genetic dierisity in eastern China.The result is as follows:1.Sequences of MtDNA ND2 gene of Culter alburnus were 1047bp long,and genetic distance (0.00191～0.00369) among 6 geographical populations were much less than the differentiation level of subspecies,they should be regarded as one single species.Average genetic distance,nucleotide diversity(Pi) and the number of nucleotide differences(K) within 6 populations were 0.00264,0.00260 and 2.75236 respectively,suggesting poor genetic diversity in Culter alburnus.Of which,genetic diversity of Hongzehu population were the highest and Xingkai population were the poorest. 2.Genetic differentiation index(Fst),gene flow(Nm) analysis among 6 populations showed that:Xiakaihu populations were distinct from the other populations(Fst＞0.52770,p＜0.01), and Weishanhu populations were also well differentiated(Fst＞0.25698,p＜0.01) from other populations.Hongzehu population were obviously differented from Chaohu and Taihu (0.05＜Fst＜0.15,p＜0.01),Taihu populations were also differented from Chaohu and Dongtinghu,Dongtinghu populations was just weakly differentiated from Hongzehu and Chaohu populations(0＜Fst＜0.05,p＜0.01).3.Tajima's D and Fu's neutrality test results revealed that Culter alburnus as a whole had experienced a population expansion,and the fact that Culter alburnus had a high haplotype diversity(Hd) 0.91502,but low nucleotide diversity(Pi) 0.00260,also suggested the species were derived from ancester with small effective population size.Nested clade analysis revealed that the richest haplotype Hap4,Hap8(16.5%and 9.9%respectively) were nested in the middle of most parsimony haplotype network,suggested that they might be ancestral haplotypes.4.Culter alburnus in 6 lake populations might be protected as 4 management Unit:Xikaihu population,Weishanhu population,Hongzehu population,and Dongtinghu-Chaohu- Taihu populaltions.Protection emphasis should be on Xingkaihu population,Weishanghu population,Hongzehu Population and Taihu population.The study will provide scientific data in conservation of genetic resource,protection and utilization of natural resources,and germplast improvement.