Climate-associated genetic variation in Eustenopus villosus, a biological control agent for yellow starthistle

The prevalence and influence of contemporary evolution in biological control systems is understudied considering the number of biological agents exposed to novel environmental conditions. Using a ddRADseq dataset, we tested for genetic adaptation to climate in populations of Eustenopus villosus (Boheman) (Coleoptera: Curculionidae), locally known as the hairy weevil, which is used in classical biological control programs for yellow starthistle (Centaurea solstitialis L.) in the western United States. We identified candidate single nucleotide polymorphisms (SNPs) associated with climate for both the native (Eurasia) and introduced ranges (western United States) and explored the extent to which founder events in the introductions have affected levels of variation at candidate SNPs. We hypothesized that human-mediated redistribution of insects, which resulted in both long-distance ‘jump’ dispersal and serial dispersal, have reduced adaptive genomic variation associated with climate in the introductions. Next, we tested whether candidate SNPs associated with climate in the native range exhibit similar associations in the introductions, or if new associations have evolved. We identified several candidate SNPs in introduced populations despite a loss of genomic variation, which suggests that adaptive evolution occurred despite serial introductions, and founding events did not prevent climatic adaptation. Candidate SNPs differed between native and introduced populations, which may indicate that local adaptation has occurred in different regions of the genome.