Genetic differentiation among populations of the migratory insect Spodoptera exigua

Author of the article:TENG Hai-Yuan；YUAN Yong-Da；ZHANG Tian-Shu；CHANG Xiao-Li WANG Dong-Sheng

Author's Workplace：Shanghai Key Laboratory of Protected Horticultural Technology, Institute of Eco-Environmentand Plant Protection, Shanghai Academy of Agricultural Sciences, Shanghai 201403, China；Shanghai Key Laboratory of Protected Horticultural Technology, Institute of Eco-Environmentand Plant Protection, Shanghai Academy of Agricultural Sciences, Shanghai 201403, China；Shanghai Key Laboratory of Protected Horticultural Technology, Institute of Eco-Environmentand Plant Protection, Shanghai Academy of Agricultural Sciences, Shanghai 201403, China；Shanghai Key Laboratory of Protected Horticultural Technology, Institute of Eco-Environmentand Plant Protection, Shanghai Academy of Agricultural Sciences, Shanghai 201403, China；Shanghai Key Laboratory of Protected Horticultural Technology, Institute of Eco-Environmentand Plant Protection, Shanghai Academy of Agricultural Sciences, Shanghai 201403, China

Key Words：Spodoptera exigua; mtDNA COⅠ; genetic diversity; genetic differentiation

Abstract：[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 subunit Ⅰ (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（H_d=0.172±0.041，P_i=0.000 77±0.000 2）in the total population was detected and genetic differentiation (F_ST=0.3182) and a high level of gene flow (N_m=1.0713) was apparent among different populations. The results of a Neutral test (Tajima’s D=-1.278，P＞0.10，Fu’s F_s=-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.