Spread and population genetics of biocontrol agent Torymus sinensis in Croatia, Slovenia and Hungary

Torymus sinensis (Hymenoptera: Torymidae), a classical biocontrol agent of chestnut gall wasp Dryocosmus kuriphilus (Hymenoptera: Cynipidae), was released in Croatia, Slovenia and Hungary in 2015. Following the introduction, the research of parasitism rates and population genetic indices on 40 different sites was performed in order to monitor and evaluate the success of establishment. T. sinensis established viable and genetically diverse populations and successfully spread naturally from Italy across Slovenia to Croatia and Hungary. T. sinensis populations from release and non-release sites share common gen pool, adding to the hypothesis that the spread occurred naturally from Italy, even before official releases in Slovenia, Croatia and Hungary were done. Population genetic indices showed that populations of T. sinensis did not suffer from bottleneck-induced founder effect phenomenon. This rapid dispersal of T. sinensis was aided by high concentration of the host, as well as the lack of competition of native parasitoids.