中国甜菜夜蛾地理种群的遗传分化与基因流

【目的】为了明确我国甜菜夜蛾Spodoptera exigua地理种群间的遗传分化及基因流，阐明该种害虫在我国的种群历史动态。【方法】本研究对采自我国20个地理种群的529头甜菜夜蛾样品进行线粒体COI基因序列测定与分析，利用DnaSP 5.0和Arlequin 3.11软件分析种群间遗传多样性、遗传分化、基因流水平及分子变异，构建了单倍型系统发育树与单倍型网络图。【结果】在所分析的所有529个序列样本中，共检测出10个单倍型，其中Hap_1为所有种群所共享。总群体遗传多样性较低（Hd=0.257±0.025，Pi=0.0007±0.0001，Kxy=0.323），群体间遗传分化较小（F_ST=0.211），基因流水平较高（N_m=1.870）。AMOVA分析表明，甜菜夜蛾遗传变异主要来自种群内，种群间变异水平较低。各种群间遗传分化程度与地理距离无显著相关性（R²=0.005，P>0.05）。各单倍型相互散布在不同种群中，未形成明显系统地理结构。中性检验（Tajima’s D=-2.177, P<0.05; Fu’s F_S=-8.629, P<0.05)与错配分布分析表明，我国甜菜夜蛾种群曾经历种群近期扩张。【结论】研究结果揭示，甜菜夜蛾各种群间的基因交流并未受到地理距离的影响，验证了甜菜夜蛾具有高度的迁飞能力。

Genetic differentiation and gene flow among geographic populations of Spodoptera exigua (Lepidoptera: Noctuidae) in China

【Aim】 This study aims to identify the genetic differentiation and gene flow among geographic populations of Spodoptera exigua in China and clarify its population demographic history. 【Methods】 In the present study, the genetic diversity, genetic differentiation, gene flow and molecular variance were analyzed using DnaSP 5.0 and Arlequin 3.11 based on the partial sequences of mtDNA COI gene in 20 geographic populations of S. exigua in China. Phylogenetic trees and the haplotype network of COI haplotypes were also constructed. 【Results】 The results showed that a total of 10 haplotypes were defined among 529 sequences, including Hap_1 shared by all populations. Low level of genetic diversity (Hd=0.257±0.025, Pi=0.0007±0.0001, Kxy=0.323) in the total populations was detected. There was little genetic differentiation (F_ST=0.211) and a high level of gene flow (N_m=1.870) among different geographic populations. The analysis of molecular variance (AMOVA) showed that the percentage of variation within a population was greater than that among populations. There was no significant correlation between the pairwise genetic distances for mtDNA COI sequences and the natural logarithm of geographical distance. The phylogenetic trees and haplotype network showed that haplotypes were distributed in different clades and had no obvious geographical structure. Finally, the neutral test (Tajima’s D=-2.177, P<0.05; Fu’s F_S=-8.629, P<0.05) and unimodal mismatch distribution indicated that S. exigua experienced recent population expansion in China. 【Conclusion】 The results suggest that the gene flow among S. exigua populations is not affected by the geographical distance, further confirming that the moth has a high ability of migration.