Population Genetic Strueture And Historical Demography Of Mongoloniscus Sinensis (Dollflls,1901)(Crustacea: Isopoda) Based On Mitochondrial Cytochrome Oxidase I

Oniscidea is a particular significant taxon in the terrestrializationprocesses of animals. In this study, we choose Chinese Palaearctic endemicMongoloniscus sinensis (Dollflls,1901) as the research material, andmitochondrial cytochrome oxidase I (mtCoI), which was maternally inheritedgenes, was employed as molecular markers to reveal the populationsstrueture and historical demography. All the specimen of26populations werecollected from26counties in15cities in Shanxi, Henan, Hebei, Beijing andShandong4provinces. Total genome DNA extraction from193samples with4periopods and mtCoI gene were amplified by PCR. Then the PCR productswere sequenced and the results cut down to a DNA fragment of600bp afteralignment. The frequancy of all the haplotypes nucleotide basic group shows,the average content of T (39.7%), C (15.1%), A (27.8%), G (17.5%) and A+T(67.5%) was significantly higher than that of C+G (32.6%).87haplotypesfrom193mtCoI gene sequences were identified, with357conserved sites and243variable sites, among which185parsimony informative sites and58single mutation sites.36.00variable sites exist ttransversion and20.00sitesexist transversion phenomenon. So the average conversion ratio Ti/Tv is1.80.We analysised all sequences of all populations about haplotypedistribution and sequence variation.87haplotypes existed, the haplotype diversity (Hd) was higher and the average haplotype diversity was0.796349.Nucleotide polymorphism value Piis0.08170,6haplotypes shared in allpopulations. Phylogenetic relationship between haplotypes and haplotypenetwork diagram shows that: between the87Mongoloniscus sinensis(Dollflls,1901) haplotypes based on maximum parsimony, maximum likelihoodanalysis and the posterior probabilities of the BI analysis preliminaryclustered into6well supported clades (C1-C6). According to the order of theclades and geographic events, suggesting that the possible evolution line ofthis species is from north to south. While the most likely orign of this genus isin the northeastern plains of China.Population genetic structure and phylogeographic analysis shows: theaverage genetic distance between populations is0.05787, the average FST(p<0.01) value is0.525, the average GST(p>0.05) value is0.26154, indicatingthat genetic differentiation exists both within populations and among thegroups and populations, and the degree of differentiation is high. Also,indicating that Mongoloniscus sinensis populations present a high potential ingenetics and evolution. AMOVA analysis showed that the species variationoccurs within populations and among populations contribution are quitesimilar.Gene flow analysis results: Nmvalue of1.83, indicating that gene flowoccurred to some extent among these populations, and sufficient tocounteract the influence of genetic drift, but there are still some populationsNmvalue of less than1or close to1, indicating that these gene flow betweenpopulations is relatively weak, not enough to resist the influence of geneticdrift, which leads to genetic differentiation. Mismatch distribution exhibits amultimodal distribution curve, indicating that Mongoloniscus sinensis did notexpand population in close historical period of time.Neutrality test resultsshows that Tajima’s D was-1.33511and Fu’s Fs value-2.45405(p<0.01), bothof them are negative. Neutral test results combined with the mismatchdistribution results show that Mongoloniscus sinensis experienced populationexpansion, but is relatively flat growth and rapid expansion did not occur in the near future.