Population genomic and phenotype diversity of invasive Drosophila suzukii in Hawai‘i

In the context of evolutionary theory, invasion biology provides a fantastic enigma: how does a species with limited standing genetic variation survive and adapt to a novel environment? Reduced genetic diversity is typically associated with low fitness and evolutionary potential, yet some introduced species have proven to be successful invaders despite undergoing a genetic bottleneck during the early stages of colonization. Our goal in this study was to characterize population genomic and phenotype diversity of invasive Drosophila suzukii (Diptera: Drosophilidae) since colonizing the Hawaiian archipelago as early as the 1980s. Wing phenotype analysis revealed that high altitude populations possessed significantly larger wings than low altitude populations, supporting the hypothesis that insects cope with high altitude environments by developing larger wings. While we discovered low genetic diversity and differentiation in all Hawai‘i populations, three unique genetic clusters were detected with a model-free, multivariate statistical approach. We identified 23 candidate loci under selection using two complementary analyses to detect F_ST outliers across the genome. For 12 of these loci, predicted proteins are associated with Drosophila spp. chemosensation, amino acid and sodium ion transport, a Ras effector pathway, and cytidine deamination. Despite a genetic bottleneck, adventive D. suzukii populations are beginning to differentiate across the Hawaiian archipelago and selection for key behavioral and cellular processes are likely ongoing.