Genetic variation, phylogeographic structure of Spodoptera exigua in the welsh onion‐producing areas of North China

Abstract

The beet armyworm, Spodoptera exigua (Lepidiptera: Noctuidae), is an important agricultural pest in China, causing serious economic losses in the main welsh onion-producing areas of North China. In order to effectively monitor and manage this pest, it is necessary to investigate its genetic variation and intraspecific phylogeographic structure in North China. In this study, we used a DNA fragment of cytochrome oxidase subunit I (COI) consisting of 518 bps to investigate its genetic diversity. A total of 500 individuals of this species were collected from 20 geographic locations, and 8 haplotypes were identified. Low levels of genetic diversity (h = 0.256 AE 0.025, p = 0.00058 AE 0.00008) for the total populations in these study regions were obtained. Phylogenetic and median-joining network analyses indicated that there was no distinct geographic distribution pattern among haplotypes. The results also indicated that the mean pairwise sequence difference between the populations was 0.1%, ranged from zero to 0.2%. The genetic differentiation (F st ) between the populations varied from À0.198 to 0.656, and there was a significant differentiation between the population of Kunshan (KUNS), Shenyang (SY), Lucheng (LUC), Binzhou (BZ) and the remaining populations, respectively. The analysis of molecular variance (AMOVA) showed that the percentage of variation within a population (69.05%) was greater than that between the populations (30.95%), and the level of population differentiation (F ST = 0.310, P < 0.001) was highly significant after 1000 random permutations. Finally, unimodal mismatch distribution combined with negative, Tajima's D (D = À1.956, P < 0.05) and Fu's Fs (Fs = À5.875, P > 0.05) indicated that S. exigua experienced recent population expansion in North China.

Mitochondrial DNA phylogeography of Spodoptera exigua across a broad geographic area in China

“…() and Wang et al. (); the evidence to date strongly suggests low genetic divergence among most members of this species, potentially the result of either recent or rapid population expansion after a population bottleneck or selection acting on some portion of the mitochondrial genome. What is more, due to mountain isolation, such as Yanshan Mountain and Taihang Mountain, there was a significant differentiation between Shenyang (SY), Lucheng (LC), Baoding (BD) and the remaining populations.…”

“…; Wang et al. ; Wang and Zhou ). However, they provided insufficient information regarding the genetic diversity of this species and the relationships between geographic variables and genetic diversity.…”

“…; Wang et al. ; Wang and Zhou ). Previous studies have shown low genetic variation, little genetic differentiation and no significant population genetic structure among the different geographic populations detected for this species.…”

“…However, these studies covered a relatively small geographic area or used a limited number of molecular markers (Wang et al. ; Wang and Zhou ). Thus, these results provided insufficient information for a clear understanding of the genetic diversity and population structure of this species across a broad geographic area in China.…”

“…It is evident that a good estimation of the level of genetic diversity and genetic structure of an organism can aid in the understanding of its biology and ultimate control in an integrated pest management system (Roderick and Navajas 2003;Timm et al 2005). However, information regarding the genetic variability and phylogeographic structure of S. exigua at large temporal and spatial scales in China is lacking and to date, few molecular studies have been conducted on this destructive pest (Niu et al 2006;Wang et al 2014;Wang and Zhou 2016). Previous studies have shown low genetic variation, little genetic differentiation and no significant population genetic structure among the different geographic populations detected for this species.…”