Abstract
The gyspy moth Lymantria dispar Linnaeus, a widely distributed leaf-eating pest, is considered geographically isolated in the world, with two Asian gypsy moth subspecies, Lymantria dispar asiatica and Lymantria dispar japonica. In China, only one subspecies, L. d. asiatica, has been observed. In this study, we characterized gypsy moth diversity and divergence using 427 samples covering a wide range of the species distribution, with a focus on sampling along a latitudinal gradient in China. We combine the quantitative analysis of male genitalia and the genetic diversity analysis of nine microsatellite loci of nuclear genes nuclear genes to study the structure of gypsy moth individuals in 23 locations in the world and the male genitalia of gypsy moths in some areas. In mixed ancestry model-based clustering analyses based on nuclear simple sequence repeats, gypsy moths were divided into three well-known subspecies, a unique North American cluster, and a southern Chinese cluster with differentiation between the Asian gypsy moth and European gypsy moth. We also found individuals identified as European gypsy moths in two distant regions in China. The results of a quantitative analysis of male genitalia characteristics were consistent with an analysis of genetic structure and revealed the differentiation of gypsy moths in southern China and of hybrids suspected to be associated with L. d. japonica in the Russian Far East. Admixture in gypsy moths can be explained by many factors such as human transport. In China, we detected European gypsy moths, and found unexpectedly high genetic diversity within populations across a wide range of latitudes.
Highlights
Genetic lineages within species often exhibit striking geographic patterns, and the genetic structure of populations is shaped by various processes [1,2,3]
L. dispar was divided into three typical subspecies by morphological characteristics, female flight ability, and geographical region [20]: L. dispar dispar in Europe and North America, known as the European gypsy moth (EGM); and L. dispar asiatica and L. dispar japonica, collectively referred to as the Asian gypsy moth (AGM)
Gypsy moth individuals were grouped by the K-value calculated using STRUCTURE v.2.3, and genetic variance between populations, individuals, and groups was evaluated by analysis of molecular variance (AMOVA) implemented in ARLEQUIN v.3.5 [60]
Summary
Genetic lineages within species often exhibit striking geographic patterns, and the genetic structure of populations is shaped by various processes [1,2,3]. L. dispar was divided into three typical subspecies by morphological characteristics, female flight ability, and geographical region [20]: L. dispar dispar in Europe and North America, known as the European gypsy moth (EGM); and L. dispar asiatica and L. dispar japonica, collectively referred to as the Asian gypsy moth (AGM). An analysis of mitochondrial and nuclear genes of worldwide gypsy moths divided gypsy moths into three groups: North America, Europe/Siberia, and Asia. The discordance between nuclear and mitochondrial gene analyses should be resolved in future studies, due to the different evolution rate [33]. In these studies, gypsy moths in China are classified as the typical AGM (L. dispar asiatica) based on single sampling locations, mostly in northern China. To better probe genetic differentiation in gypsy moths in China, we used more comprehensive sample collection, including collection of subspecies found in other regions (L. d. dispar and L. d. japonica), combined with nuclear genetic analyses and morphological evaluations of male genitalia, to explore gypsy moth diversity
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