基于线粒体COI基因的桔小实蝇种群遗传分化研究

【目的】推测桔小实蝇Bactrocera dorsalis在中国的扩散路径和新发生地区的入侵来源。【方法】本研究测序获得来自中国、泰国、日本、老挝、孟加拉国和美国等地31个种群的192头桔小实蝇个体的COI序列（1 496 bp，占COI基因全长97.3%），并以软件DnaSP 5.0， MEGA 6.0和Arlequin 3.5等完成各种群的遗传多样性、种群间的遗传分化以及单倍型分析。【结果】所测31个桔小实蝇种群总体表现出较高水平的核苷酸多样性（0.00663）和高水平的单倍型多样性（0.98069）。以F-统计法度量种群间遗传分化程度, 结果显示中国桔小实蝇地理种群间遗传分化较弱, 中国种群与泰国、日本、老挝、孟加拉国、美国种群间的遗传分化程度不同, 中国种群与美国种群及日本种群的遗传分化最大。而Mantel检验发现，中国、泰国、日本、老挝、孟加拉国和美国种群间的遗传分化与空间距离有关（R=0.670, P<0.0001）, 中国种群间的遗传分化不是地理隔离所造成的（R=0.038, P=0.534）。中国种群与泰国、日本、老挝、孟加拉国和美国种群间不存在共享单倍型。根据种群系统发育树，可将中国原发生地区种群划分为西南、东南两大分支。中性检验和错配分析结果均表明桔小实蝇曾存在大规模的扩张。【结论】桔小实蝇以东南地区和西南地区为源头向中国内陆扩散，其中广东、福建、广西和贵州种群为中国内陆种群较为有影响力的源头。根据遗传多样性、遗传分化、单倍型分析，推测新发生地区桔小实蝇的来源, 例如安徽合肥桔小实蝇种群主要来源于福建长乐、广东珠海和上海。

Population genetic differentiation analysis of the oriental fruit fly,Bactrocera dorsalis (Diptera: Tephritidae) based on mtDNA COI gene

【Aim】 This study aims to infer the invasion routes of the oriental fruit fly, Bactrocera dorsalis Hendel in China and the invasion source of its recent introduction region. 【Methods】 mtDNA COI (1 496 bp, 97.3% of full length) of 192 individuals of 31 populations from China, Thailand, Japan, Laos, Bangladesh and USA was sequenced. The genetic diversity of each population and genetic differentiation between populations were analyzed by DnaSP 5.0, MEGA 6.0 and Arlequin 3.5, as well as haloptype analysis. 【Results】 High nucleotide diversity (0.00663) and haplotype diversity (0.98069) were detected overall from the 31 populations of B. dorsalis. Genetic differentiation between populations analyzed using F-statistics method revealed that lower genetic differentiation were detected between populations of China, different levels of genetic differentiation were detected between populations from China and populations from Thailand, Japan, Laos, Bangladesh and USA, and the highest genetic differentiation was detected between populations from China and populations from USA and Japan. Mantel test showed that genetic differentiation among 31 populations from China, Thailand, Japan, Laos, Bangladesh and USA bore a relation to spatial distance (R=0.670, P<0.0001), but spatial distance was not responsible for genetic differentiation among populations from China (R=0.038, P=0.534). There was no shared haloptype among populations from China, Thailand, Japan, Laos, Bangladesh and USA. The phylogenetic tree showed that original populations from China clustered into two groups, i.e., the southwest group and the southeast group. Neutrality test and mismatch distribution analysis revealed that B. dorsalis populations had experienced a large-scale expansion. 【Conclusion】 It is inferred that there are two main invasion routes to inland China, one is from Southeast China and the other from Southwest China, and Guangdong, Fujian, Guangxi and Guizhou are the influential invasion sources. Based on the results of genetic diversity, genetic differentiation and haplotype network, it is inferred that the main sources of B. dorsalis introduced to Anhui (Hefei) are from Fujian (Changle), Guangdong (Zhuhai) and Shanghai.