中国橘小实蝇不同地理种群遗传多样性分析

Genetic diversity of different geographical populations of the citrus fruit fly,Bactrocera dorsalis(Diptera:Tephritidae)in China

【目的】为推测中国橘小实蝇Bactrocera dorsalis向北方扩散的路径和北方地区的传播来源。【方法】本研究对橘小实蝇15个地理种群的144个样本的mtDNA COⅠ序列进行测定;依据mtDNA COⅠ序列利用相关软件对橘小实蝇不同地理种群的遗传多样性、遗传分化等进行分析。【结果】在橘小实蝇144个样本的mtDNA COⅠ序列中获得了75个单倍型,其中单倍型H_7为7个地理种群所共享,北方地理种群与原发生地区种群间存在共享单倍型,绝大部分为种群独享单倍型。15个橘小实蝇地理种群总体表现出高水平的核苷酸多样性(Pi=0.02076)和单倍型多样性(Hd=0.99413),不同橘小实蝇地理种群间遗传分化较大。系统进化树显示,橘小实蝇各地理种群中的单倍型分布格局较为混杂,未形成明显的系统地理结构;系统进化树分为2支,湖北武汉、重庆北碚、福建福州、湖南衡阳、江苏南京、海南海口、河北保定、河南郑州、广东广州的地理种群聚为一支,海南三亚、广西南宁、云南丽江、湖南邵阳、山东泰安、山东临沂的地理种群聚为一支,北方新发生地理种群在两个分支中均有分布。橘小实蝇整体错配分析结果显示为单峰,表明橘小实蝇有过大规模的种群扩张。【结论】橘小实蝇可能以海南、广西和广东为地理源头向中部地区扩散,再从湖南、江苏等地向北方地区扩散。根据遗传多样性、遗传分化和单倍型分析,推测广西、广东和湖南为橘小实蝇北方地理种群较为有影响力的地理源头,海南海口地区与北方地区有着频繁的果品贸易往来,从而导致橘小实蝇随着运输扩散至北方地区。

【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 COⅠsequences of 144 samples from 15 geographical populations of B.dorsalis were determined.According to the mtDNA COⅠsequence,the genetic diversity and genetic differentiation of different geographical populations of B.dorsalis were analyzed by using relevant software.【Results】Among the mtDNA COⅠsequences 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.