Urban ecology of Drosophila suzukii

Urban environments are vulnerable to the introduction of non-native species and sometimes contribute to their invasion success. Knowing how urban landscape features affect the population dynamics of exotic species is therefore essential to understand and manage these species. The spotted-wing drosophila, Drosophila suzukii, is a highly polyphagous fruit fly that has become a very problematic invasive species over the last decade. Because of its important damage on fruit production, D. suzukii populations have mainly been studied in agricultural areas, while their dynamics in urban landscape remain poorly explored. The objective of this study was to investigate the role of urban environment in the invasion success of D. suzukii by identifying local and landscape factors driving the abundance of the fly along seasons and urbanization gradients. To achieve this, 526 insect traps were randomly set in four different habitats (urban forest, park, riverside and town centre) along an urbanization gradient in the city of Amiens (France), between September 2018 and August 2019. The influence of landscape and local environmental variables on Drosophilidae species diversity and composition was examined using GLM and multivariate analyses. We found that Drosophilidae species richness and abundance were negatively impacted by urbanization. The Drosophilidae community was dominated by D. subobscura and D. suzukii, but their relative abundance varied with seasons. Drosophila suzukii used urban forest during winter and also during heat waves in summer. The fly was still active in this habitat in winter when the ground was covered with snow. The cover of brambles, shrubs, soil litter and dead wood debris were identified as valuable ecological indicators of the presence of D. suzukii. We highlight the role of the different components of urban environment in the ecology of D. suzukii, particularly with regard to its winter survival. These results could serve for designing management strategies in urban habitats in order to reduce the invasion success of D. suzukii.