Origin of non-nativeXylosandrus germanus, an invasive pest ambrosia beetle in Europe and North America

Xyleborine ambrosia beetles (Coleoptera: Scolytinae: Xyleborini) are among the most important and destructive pests in forests, tree nurseries and plantations worldwide. Their cryptic lifestyle, fungal mutualism, inbreeding and broad host range have predisposed them to become remarkably successful invaders and colonize novel habitats across the world. The black timber bark beetle,Xylosandrus germanus(Blandford), is native to East Asia, but now established in North America and Europe. It is an economically significant invasive pest in North American nurseries and orchards, and European forests. Managing and preventing the spread of exotic species such asX. germanusrequires an understanding of invasion pathways and mechanisms associated with their source populations. In this study, we sequenced the mitochondrial gene COI and nuclear gene ArgK from six native and 24 non-nativeX. germanuspopulations to identify their origins. The genetic structure ofX. germanusin non-native habitats is highly uniform and points to introductions from Honshu and/or Hokkaido, Japan. However, different haplotypes of the inferred Japanese source lineage, which dominate in North America and Europe today, together with temporal incidence of records ofX. germanusindicate that these continents were invaded independently. While European populations were probably introduced only once prior to 1951, the genetic pattern of North American populations suggests thatX. germanuswas introduced several times.

Automated summary

Xyleborine ambrosia beetles are highly destructive pests in forests, nurseries, and plantations worldwide, mainly due to their cryptic lifestyle, fungal mutualism, and broad host range. The black timber bark beetle Xylosandrus germanus, originally from East Asia, has become a significant invasive pest in North America and Europe. Genetic analysis suggests that non-native populations of X. germanus in North America and Europe likely originated from Japan, with multiple introductions into North America but likely only one introduction into Europe.