Phylogeography of a Holarctic defoliator, the gypsy moth (Lymantria dispar, Lepidoptera: Erebidae), inferred from microsatellite data

The gypsy moth (Lymantria dispar Linnaeus) is among the most destructive defoliating pest insects in the world. Its current distribution encompasses forests throughout the entire temperate region of the northern hemisphere. Lymantria dispar is native to Europe and Asia and was introduced to North America from Western Europe 145 years ago. Given its economic importance, we examined the population structure and evolutionary history of L. dispar and considered how geographic factors have shaped patterns of genetic variation in this species. With an extensive sampling of 1738 moths throughout the Holarctic and using microsatellite allele frequencies, we identified four genetic clusters representing four distinct geographic areas. Surprisingly, introduced North American populations represent a unique cluster and harbor private microsatellite alleles. The Ural Mountains are thought to be the phylogeographic break between L. d. dispar and L. d. asiatica. But we found that specimens identified as L. d. asiatica from east of the Urals cluster with L. d. dispar. In East Asia, the subspecies L. d. asiatica and L. d. japonica overlap and form an extensive hybrid zone in northeastern China, the Russian Far East, and the Korean Peninsula. We found evidence of multiple cross-strait dispersal events in this region.