Spotted-wing drosophila, Drosophila suzukii (Diptera: Drosophilidae), exhibits large-scale spatial genetic structure across Canada but not fruit host-associated genetic structure

Spotted-wing drosophila, Drosophila suzukii, is a global pest of soft fruits that is capable of reproducing on a wide range of cultivated and wild plant species. In Canada, D. suzukii was first reported in British Columbia (BC) in 2009 and is now widespread across the country. Understanding the genetic structure of D. suzukii populations could be important for pest management if there are phenotypic differences between genetically distinct populations. For example, insect pest populations could respond differently to directional selection imposed by insecticides, differ in their host plant preferences, and vary in their susceptibility to biological control agents. Here, we used double digest restriction-site associated DNA sequencing (ddRADseq) to examine large and fine-scale patterns of genetic structure of D. suzukii reared from fruit hosts in Canada. We found that this species has large-scale spatial genetic structure; flies from western and eastern Canada each formed a distinct genetic cluster. At the local scale, D. suzukii populations showed no evidence of host-associated structuring in BC, suggesting that pest management tactics may be best applied at the landscape level. Our results highlight the need for to investigate ion of phenotypic differences between western and eastern D. suzukii populations in Canada.