Population structure of Drosophila suzukii and signals of multiple invasions to the continental U.S.

Drosophila suzukii, or spotted wing drosophila, is now an established keystone pest in many parts of the world, causing serious agricultural damage to the fruit crop industry. Native to East Asia, D. suzukii infestations have appeared on both East and West Coasts of the United States, occupying a wide range of climates. To efficiently control this pest, knowledge of past migration events, population structure, and genetic diversity is needed. To improve on previous studies examining genetic structure of D. suzukii, we sequenced whole genomes of individual flies collected across the continental U.S., as well as several representative sites in Europe, Brazil, and Asia, to identify hundreds of thousands of genetic markers for analysis. We analyzed these markers to detect population structure, migration events, and estimate genetic diversity and differentiation within and between continents. We observe strong population structure between West and East Coast populations of the U.S., but no evidence of any population structure North to South, suggesting there is no broad-scale adaptations occurring in response to the large differences in regional winter temperatures. We also find evidence of repeated migration events from Asia into North America have provided increased levels of genetic diversity, which does not appear to be the case for Brazil or Europe. This large genomic dataset will spur future research in genomic adaptations underlying D. suzukii pest activity and development of novel control methods for this agricultural pest.