The Research On Genetic Diversity And Genetic Structure Of Niviventer Confucianus Population In Land Bridge Islands Of Qiandao Lake

Qiandao Lake is located in Chun'an County in the west of Zhejiang province, which is an artificial lake due to built the Xin'an river hydropower dams,because of more than 1078 islands above 2500m² in the lake,so people named it.The island was separated by the water,and then the flora and the fauna had no gene exchange between their species,so it supplies natural fragmentation sites of flora and fauna to researchers.Considering this advantages,we applied Microsatellite molecular markers to study the formation of large lakes to the impact of genetic diversity in Niviventer confucianus,and then explored the maintaining mechanism of biological diversity in land bridge islands environment,put forward corresponding protection countermeasure.The main results as follows:1,70 Microsatellite primer pairs originated from rat and mouse were tested in Niviventer confucianus,of which,40pairs could amplified effective bands to some extent,but after PCR reaction system improved,only 21 loci amplified stable bands, finally screened 13 pairs showed high polymorphism and the ratio was 18.57%, homologic rate of cross-species amplification reached 30%.The lowest and highest value of polymorphic information content(PIC) of the 13 most polymorphic loci was 0.576 and 0.911 respectively,of which,there were 10 loci,the value of polymorphic information content exceeded 0.8,which was much higher than 0.5.It indicated that Microsatellite loci screened by cross-species included abundant genetic information, which suitable for population genetics research of Niviventer confucianus. 2,For the Niviventer confucianus population of Qiaodao Lake,a total of 134 distinct alleles were observed in 13 loci over the complete data set,of which 1 was private allele and 133were common alleles.The average number of observed alleles(Na) was 10.31 and the average number of effective alleles(Ne) was 8.60,the values of expected heterozygosity(He) ranged from 0.645 to 0.919 with an average of 0.859, the value of polymorphic information content(PIC) was from 0.576 to 0.911 with an average of 0.839,the genetic diversity was relatively high in species level;there was only one loci of the 13microsatellite loci,which F_IS was above zero,the rest was below zero and the average was -0.176,it showed that hybrid was dominant in Niviventer confucianus population.AMOVA indicated that genetic variation mainly appeared within populations(95.28%),between populations,the genetic variation was 4.72%,which coincide with the isolation conditions.Hardy-Weinberg test indicated that terrestrial species didn't appear deviation and large island populations were relatively fewer compared with small islands,so,we can confer that species were affected by habitat fragments more obviously in small islands,so it's difficult for the species to maintain a balance.3,The values of expected and observed heterozygosity ranged from 0.778 to 0.855 and 0.888 to 0.956 respectively,the values of PIC ranged from 0.717 to 0.796,the number of effective alleles(Ne) ranged from 4.90 to 6.97 of the 15 different populations.Through Pearson correlation analysis between sampled areas and every index of genetic diversity,for example Na,Ne,He,Ho and PIC,we found that there was a positive correlation between Na and areas,other index and areas had no distinct correlation,by this token,habitat fragmentation arise from island isolation haven't brought significant change of genetic diversity in Niviventer confucianus population, but the max of each index of genetic diversity all appeared in relatively large islands, which reflected that genetic diversity was higher in large islands than in small islands.4,The coefficient of genetic differentiation(Fst) ranged from 0.0013 to 0.1152 in 15 different populations between each other,of which,49.52%had no differentiation and 50.48%appeared moderate degree of differentiation;The level of gene flow(Nm) in seasonally connected island species was higher than connectionless.The Nm between each other of the 15 populations ranged from 1.9201 to 192.06 with an average of 7.9488,the frequency gene exchange induced low genetic differentiation between populations.Gene flow is bound to the decreasing trend in different Niviventer confucianus population over time.5,Dendrogram based Nei's Genetic distance was analyzed with NJ and UPGMA cluster analysis to the 15 different populations,the 15 populations were divided into three subkinds,clustering results showed the characteristics of regional distribution; The results of main coordinate analysis and cluster analysis was consistent.6,Mantel correlation test was carried out between different species in natural of geographical distance and genetic distance(DS) and the coefficient of genetic differentiation F_ST/(1-F_ST).Results showed that there was no significant correlation (P＞0.05) between the different species of the geographical distance and genetic distance(r=0.1977,P=0.085) as well as the differentiation coefficient(r=0.1566, P=0.111).Taking into account the genetic variation and other factors,we removed the isolated species and re-Mantel test,and then found that there was a significant positive correlation between geographic distance and genetic distance(r=0.4512, P=0.011),the differentiation coefficient also had significant correlation(r=0.3866, P=0.011) with them,which consistent with the distance of the divisive model (Isolation by distance,IBD).It indicated that the formation of island lake habitats had an obvious affection to confucianus population;they were facing a relatively strong interference and the species was unstable,prone to appear genetic drift and inbreeding depression.Therefore,this paper argues that,the genetic differentiation between species in Qiandao Lake maybe arise from isolated island under a variety of factors, which are probably the intrinsic mechanism of differentiation in confucianus population under the island lake environment.7,The original habitat of confucianus was submerged by the storage reservoir,in response to adverse environmental factors,species were forced to transfer high-altitude areas,so,the stability of the original species were broken.15 species experienced a bottleneck effect in the near future. 8,According to the gene flow of seasonally linked island of confucianus between species,the corridor for the mutual isolated species plays an important role in gene exchange,therefore,on the process of the protection of endangered species,we should divide the management unit appropriately,to determine the survived area and set up corresponding corridor to ensure gene exchange and increase their progenitive ability.