迁飞性昆虫甜菜夜蛾遗传分化研究

Genetic differentiation among populations of the migratory insect Spodoptera exigua

【目的】甜菜夜蛾Spodoptera exigua逐渐成为世界性重要害虫,为明确甜菜夜蛾不同地理种群的遗传分化及遗传多样性,本研究探讨其在中国的种群遗传变异。【方法】测定了采自15个地理种群154个甜菜夜蛾的线粒体COⅠ基因的547 bp序列,利用DnaSP 5.0、Arlequin 3.5.1.2等软件对甜菜夜蛾不同种群间的遗传多样性、遗传分化及分子变异进行分析,并建立单倍型系统进化树。【结果】在所分析的154个COⅠ序列中,共检测出5个单倍型,其中H1为各种群所共享种群内遗传多样性较低(Hd=0.172±0.041,Pi=0.00077±0.0002),种群内遗传分化相对较大(FST=0.3182),基因流水平较高(Nm=1.071)。中性检验结果不显著(Tajima’s D=-1.278,P>0.10,Fu’s Fs=-1.660,P>0.10),说明中国地区甜菜夜蛾在较近的历史时期内没有出现种群扩张现象。分子变异分析(AMOVA)结果表明,甜菜夜蛾遗传变异主要来自种群内部(68.18%),而种群间未发生明显的遗传分化。根据各地理种群的单倍型建立的系统发育树表明,各单倍型散布在不同的地理种群中,无明显的地理分布格局。【结论】甜菜夜蛾不同种群的遗传距离与地理距离间无显著线性相关性,不同种群间的基因交流不受地理距离的影响。这些数据表明,除了遗传因素之外,不同因素的组合,例如地理距离、环境条件和生理行为,可能在甜菜夜蛾种群内和之间形成变异中起重要作用。

[Objectives]To investigate genetic variation among different populations of the beet armyworm,Spodoptera exigua,in China.[Methods]The genetic diversity,genetic differentiation,and molecular variance of 154 individual S.exigua from 15 populations were analyzed using DnaSP 5.0,Arlequin 3.5.1.2 based on variation in 547 bp segments of the mitochondrial cytochrome coxidase subunitⅠ(COⅠ)gene.Phylogenetic trees of COⅠhaplotypes were constructed from the resultant data.[Results]A total of 5 haplotypes were identified;haplotype No.1(H1)was shared by all populations.A low level of genetic diversity(Hd=0.172±0.041,Pi=0.00077±0.0002)in the total population was detected and genetic differentiation(FST=0.3182)and a high level of gene flow(Nm=1.0713)was apparent among different populations.The results of a Neutral test(Tajima’s D=-1.278,P>0.10,Fu’s Fs=-1.660,P>0.10)were not significant,indicating that there is no evidence of recent population expansion.An analysis of molecular variance(AMOVA)found no obvious genetic differentiation among populations with a high proportion of the total genetic variance attributable to variation within populations(68.18%).A phylogenetic tree based on haplotypes of the different geographic populations indicates no obvious geographical structure in different clades.[Conclusion]Genetic diversity among different populations of S.exigua is low,and there is no significant linear correlation between geographic distance and genetic differentiation.Gene flow between different populations is therefore not affected by geographic distance.These data suggest that a combination of different factors,such as geographic distance,temperature,and physiological behavior,in addition to genetic factors,could play an important role in forming variation within and between S.exigua populations.