Study On Genetic Variation Of Rattus Losea Populations In Zhoushan Archipelago

Island is often as a natural laboratory for ecologists and evolutionary biologists.Rattus losea belongs to Rodentia,Muridae,Rattus.The genetic variation of Rattus losea were studied by microsatellite(SSR)and mitochondrial DNA(mtDNA D-loop).Rattus Losea was sampled in eight islands including Liuheng Island,Xiaozhairuo Mountain,Dazhairuo Mountain,Cishan Island,Damao Island,Xiaomao Island,Taohua Island and Xiaopanzhi Island.The main results and conclusions as following:1.Based on the conservatism of microsatellite flanking sequences,cross-species amplication of micro satellite loci is an effective method.In this study,sixty-three microsatellite markers of Rat(Rattus norvegicus)and Mouse(Mus musculus)were screened for Ratus losea.The results showed seventeen microsatellite loci could be amplified stably and eight of them were highly polymorphic,and the polymorphism information content(PIC)was more than 0.5.These microsatellite loci can be used for population genetics of Rattus Losea.2.Based on the size of alleles,a total of 114 alleles were detected and genetic diversity parameters as following:average number of alleles was 8.5 ± 0.4881,average number of effective alleles was 5.2981 ± 0.3576(4.8001?5.9017),average observed heterozygosity was 0.9546 ± 0.0154(0.9286?0.9769),average expected heterozygosity was 0.8088 ± 0.0165(0.7877?0.8333)and average polymorphic information content 0.7708 ± 0.0225(0.7398?0.8055),which reflected high genetic diversity within the species.Among these islands,the genetic diversity of Cishan Island and Liuheng Island is highest and the genetic diversity of Xiaozhairuo Mountain and Xiaomao Island is lowest.The overall genetic differentiation among populations of micro satellite amplification was at a moderate differentiation level,the Fst value was 0.0510.Pairwise Fst was low,ranging from 0.0219(CS-DM)to 0.1087(XM-XZRS).Analysis of microsatellite molecular variance showed the variation among populations accounted for 5.10%and variation within populations accounted for 94.90%.The variation of nuclear gene of Rattus losea mainly exists within the populations.3.The content of A,T,C,G of mtDNA D-loop sequences respectively was 32.9%,29.0%,25.1%and 13.0%.The content of A+T was more than G+C,which indicated that the nucleotide composition prefer to G+C in a degree.Fourteen variable sites were recorded,including 7 transitions and 3 transversions and 4 Indels.The number of polymorphic sites ranged from 0 to 11,the number of haplotypes ranged from 1 to 6,haplotype diversity ranged from 0 to 0.6411,nucleotide diversity ranged from 0 to 0.0024.Among these populations,the genetic diversity of the population XM and XZRS was lowest,which had no polymorphic sites.The population CS or DM had one or two InDel sites,so genetic diversity at a middle level.Compared to other populations,the population DZRS and TH had higher genetic diversity.The overall genetic differentiation of mtDNA D-loop sequences among populations was at a higher differentiation level,the Fst value was 0.7450.Pairwise Fst ranged from 0.1389 to 1.0000.Only the population Xiaozhairuo Mountain and XPZ Island were at a moderate differentiation level.Analysis of molecular variance of D-Loop sequences revealed the major component of variation contributed to interpopulation(74.50%),while within populations accounted for 25.50%.The variation of mitochondrial gene of Rattus losea mainly existed among the populations.Phylogenetic reconstructions performed using neighbour-joining was strong consistent with the network analysis of mtDNA D-loop haplotypes,which indicated that the 8 populations had two matrilinear origin.The Rattus Losea populations of Xiaozhairuo Mountain,Dazhairuo Mountain,Cishan Island,Damao Island,Xiaomao Island,and Xiaopanzhi Island origined from the same matriline and the Rattus Losea populations of Liuheng Island and Taohua Island belonged to another matriline.4.Combined with the bottleneck analysis and D-loop sequences variation,in addition to populations of Dazhairuo Mountain and Xiaopanzhi Island,the other six Rattus Losea populations all had experienced bottleneck in different degree.