Genetic variation reveals complex population structuring of Tomicus piniperda L. (Coleoptera, Scolytidae) in the UK: Implications for management of this important pest

1. Tomicus piniperda is a common pest of pine trees responsible for significant economic damage. Although the impact of T. piniperda on forestry is likely to increase in the future due to climate change, little is known about its dispersal within the United Kingdom (UK) or between continental Europe and the UK.

2. This study addressed these knowledge gaps using mitochondrial and microsatellite DNA markers.

3. Mitochondrial DNA revealed high levels of genetic diversity as previously reported for this species across Europe. Nuclear DNA diversity revealed two geographically incoherent groups (Scotland, Wales, Belgium and the Netherlands vs. England and Switzerland). These genetic patterns likely reflect a combination of historical gene flow, anthropogenic introduction and restricted contemporary gene flow between the UK and Europe.

4. Significant structure was found among UK samples suggesting T. piniperda might not disperse extensively between pine stands. This differs from widespread gene flow across continental Europe and may be due to the low percentage of land covered by forests in the UK in addition to the high fragmentation of its forest cover.

5. Genetic variation was higher among the Scottish samples compared to those from more southern clines, suggesting the potential proximity of Scotland to a Pleistocene glacial refuge for T. piniperda.