基于ITS-1基因的菜粉蝶地理种群遗传分化研究

为了探讨我国不同地区菜粉蝶种群之间的遗传分化情况, 本研究运用克隆测序法, 对我国16个地区79只菜粉蝶Pieris rapae rDNA的ITS-1基因序列进行测定并分析; 同时, 以东方菜粉蝶Pieris canidia为外群, 重建了它们的系统发生树, 初步探讨了它们的生物地理学分化格局。序列分析结果显示: 所测菜粉蝶的ITS-1序列长度介于337~458 bp之间。经序列比对后, 在347个位点中共有281个保守位点, 63个变异位点, 16个简约信息位点和47个单突变位点; AMOVA软件分析其核苷酸多态性指数(nucleotide diversity) Pi为0.014, 每位点Theta (per site) Eta为0.041, 遗传分化指数(F_ST)为0.351 (P<0.05); DnaSP软件共检测出48个单倍型(haplotype)序列, 单倍型多样性(haplotype diversity)的频率为0.989。系统发生分析结果表明: 现存的菜粉蝶各地理种群与其地理分布没有直接的对应关系根据系统发生树结果推测, 该蝶种在我国的最早建群可能发生于辽宁、内蒙古及北京一带, 其后, 通过幼虫寄主植物的水陆运输以及成虫的迁飞向我国的不同地区扩散。

Analysis of genetic variation in different geographical populations of Pieris rapae Linnaeus(Lepidoptera:Pieridae)based on rDNA ITS-1 sequence evidence

In order to investigate the genetic variations of different geographical populations of Pieris rapae Linnaeus in China, the ribosomal DNA gene interval transcribed spacer 1 (ITS-1) sequences of 79 indididuals from 16 areas were determined and analyzed. Upon these gene sequence data and using Pieris canidia as the outgroup, we reconstructed phylogenetic trees by means of neighbor-joining and minimum evolution analyses, aiming to clarify their biogeographical divergence pattern. The results of the sequence variation analyses showed that the sizes of the ITS-1 of Pieris rapae range from 337 to 458 nucleotides in length. Aligned with the ClustalW software, the total 347 sites, which contain 281 conserved, 63 variable and 16 parsimonious informative, were obtained. Meanwhile, for the whole population of this study, the nucleotide diversity Pi and the Theta (per site) Eta were calculated to be 0. 014 and 0.041, respectively. Moreover, total 48 haplotypes were identified and the haplotype diversity 0.989 was obtained by the software DnaSP. Additionally, the fixation index (F_ST) 0.351 (P<0.05) was calculated by the analysis of molecular variance (AMOVA) software. The result of phylogenetic analysis indicated no pronounced correlation between their haplotypes and the geographical regions. Based on the phylogenetic trees, it is inferred that the Pieris rapae in China probably colonized first in the Liaoning, Inner Mongolia and Beijing, and then spread to other areas by transportation of their host plants and migration of their adults.