Mate choice errors in an invasive longhorn beetle

Tetropium fuscum is a European longhorn beetle, native to Western Europe and Northern Eurasia, that was introduced to Halifax, Nova Scotia, Canada circa 1990. In the roughly 25-30 years since its introduction into North America, T. fuscum has spread less than 150 km from its point of introduction. Many other introduced insects have spread much more rapidly, such as Agrilus planipennis, however T. fuscum is unusual in that it coexists with a native congener in its invasive range. We propose that the slow North American spread of T. fuscum is at least partially due to interactions with the native congener Tetropium cinnamopterum. Tetropium fuscum and T. cinnamopterum are morphologically and ecologically similar, sharing closely timed emergence in the spring, overlapping flight periods, as well as similar host plant choices and mating behaviours. Notably, the male-produced mating pheromone blends in both species share the molecule S-fuscumol as the main attractive component. These similarities led us to ask whether mate-choice errors could be a contributing factor in the slow North American spread of T. fuscum. We used mating experiments to determine if mate-choice errors take place between these two species, as well as next-generation sequencing (NGS) techniques to look for introgression between invasive and native populations of Tetropium in New Brunswick and Nova Scotia. This research will allow us to better predict future growth rates of this pest species to aid in mitigation efforts.