Abstract: 【Aim】 In order to speculate the dispersal path of Bactrocera dorsalis to the north and the source of transmission in the northern regions in China. 【Methods】 In this study, the mtDNA COⅠ sequences of 144 samples from 15 geographical populations of B. dorsalis were determined. According to the mtDNA COⅠ sequence, the genetic diversity and genetic differentiation of different geographical populations of B. dorsalis were analyzed by using relevant software.【Results】 Among the mtDNA COⅠ sequences of 144 samples of B. dorsalis, 75 haplotypes were obtained, and the haplotype H_7 was shared by seven geographical populations. There were shared haplotypes between northern geographical populations and populations in the original region, and most of them were population exclusive haplotypes. The 15 geographical populations of B. dorsalis showed high levels of nucleotide diversity (Pi=0.02076) and haplotype diversity (Hd=0.99413), and the genetic differentiation among different geographical populations of B. dorsalis was large. The phylogenetic tree showed that the haplotype distribution pattern of each geographical population of B. dorsalis was mixed, and no obvious phylogeographic structure was formed. The phylogenetic tree was divided into two branches, the geographical populations from Wuhan, Hubei (HUBWH), Beibei, Chongqing (CQBB), Fuzhou, Fujian (FJFZ), Hengyang, Hunan (HUNHY), Nanjing, Jiangsu (JSNJ), Haikou, Hainan (HANHK), Baoding, Hebei (HBBD), Zhengzhou, Henan (HENZZ), and Guangzhou, Guangdong (GDGZ) converged into one branch, the geographical populations from Sanya, Hainan (HANSY), Nanning, Guangxi (GXNN), Lijiang, Yunnan (YNLJ), Shaoyang, Hunan (HUNSY), Tai′an, Shandong (SDTA) and Linyi, Shandong (SDLY) converged into one branch, and new geographical populations in the north were distributed in both branches. The results of the overall mismatch analysis showed a single peak, indicating that B. dorsalis has experienced large-scale population expansion. 【Conclusion】 With Hainan, Guangxi and Guangdong as the geographical source, B. dorsalis may spread to the central region, and then spread to the northern region from Hunan, Jiangsu and other places. According to genetic diversity, genetic differentiation and haplotype analysis, it is speculated that Guangxi, Guangdong and Hunan are the more influential geographical sources of the northern geographical populations of B. dorsalis. Haikou of Hainan has frequent fruit trade with the northern regions, resulting in the spread of B. dorsalis to the northern region with transportation.

Key words:  Bactrocera dorsalis, genetic diversity, genetic differentiation, invasion, population diffusion