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[目的]明确双斑乙蠊Sigmella biguttata种群间遗传分化程度,并揭示该种地理分布格局成因.[方法]PCR扩增双斑乙蠊19个地理种群284头个体的线粒体基因COⅠ,COⅡ和ND1以及核基因ITS的序列;使用MEGA v.7.0,DnaSP v.5.0和Arlequin v.3.5软件分析双斑乙蠊地理种群的遗传多样性和遗传分化;采用中性检验和错配分布分析方法检测种群历史动态;采用最大似然法(maximum likelihood,ML)和贝叶斯法(Bayesian inference,BI)构建系统发育树,并利用中介邻接网络算法构建单倍型网络图;基于线粒体基因COI替换率推断双斑乙蠊各种群的分化时间.[结果]双斑乙蠊地理种群呈现出较高的遗传多样性(Hd=0.98835,π=0.02777).ML和BI系统发育树的拓扑结构一致且具有较高的支持率,显示双斑乙蠊所有地理种群分为3个支系8个组,表现出明显的谱系地理结构,这与SAMOVA得到的遗传结构分析结果一致.单倍型网络图显示不同地理种群间无共享单倍型.遗传分化和基因流(Nm)分析显示,种群间的Fst值大于0.25,最大Nm值小于1.种群历史动态检测结果表明,Group 2,Group 4,Group 6和Group 7经历了种群扩张,扩张时间均在末次间冰期,而Group 1,Group 3,Group 5和Group 8未发生种群扩张.双斑乙蠊各支系及各组的分化时间在中更新世期(0.5391-0.1544 Ma).[结论]双斑乙蠊不同种群间存在显著的遗传分化.温暖潮湿的气候环境有助于双斑乙蠊种群发生扩张,种群的遗传结构和地理分布格局受到地理屏障和第四纪更新世气候振荡的影响.“,”[Aim]This study aims to clarify the genetic differentiation among populations and to reveal the cause of the geographical distribution pattern of Sigmella biguttata.[Methods]The sequences of mitochondrial genes COⅠ,COⅡ and ND1 and nuclear gene ITS of 284 individuals from 19 geographic populations of S.biguttata were amplified by PCR.The genetic diversity and genetic differentiation of S.biguttata geographic populations were analyzed using MEGA v.7.0,DnaSP v.5.0 and Arlequin v.3.5,and the population historical dynamics was detected by neutrality test and mismatch distribution analysis.The phylogenetic trees were constructed using maximum likelihood(ML)and Bayesian inference(BI)methods and the haplotype network was constructed using median joining network algorithm.The divergence time of S.biguttata populations was inferred based on the substitution rate of mitochondrial gene COI.[Results]The overall genetic diversity of the geographic populations of S.biguttata was relatively high(Hd=0.98835,π=0.02777).The ML and BI trees yielded almost identical topologies with generally high support values,and all geographic populations of eight groups were clustered together to form three lineages and showed obvious phylogeographic structure,which was consistent with the result of SAMOVA analysis.There was no haplotype shared by different geographic populations according to the haplotype network.The genetic differentiation and gene flow(Nm)analysis showed that the Fst values among populations were more than 0.25 and the maximum Nm value was less than 1.The population historic dynamics analysis showed that Group 2,Group 4,Group 6 and Group 7 experienced population expansion,occurring in the last interglacial period,but Group 1,Group 3,Group 5 and Group 8 did not.The divergence time of lineages and groups was estimated in the Mid-Pleistocene(0.5391-0.1544 Ma).[Conclusion]There is significant genetic differentiation among populations of S.biguttata.A warm and humid climate contributes to the population expansion of S.biguttata,and the genetic structure and geographic distribution pattern of the populations are mainly affected by geographic barriers and climatic oscillation in the Quaternary Pleistocene.