Large-scale spatial dynamics of Drosophila suzukii in Trentino, Italy

Drosophila suzukii (Diptera: Drosophilidae) is an invasive alien species devastating soft fruit crops in newly invaded territories. Little is known about the importance and potential of long-distance dispersal at a regional scale. The goal of this work is to investigate D. suzukii dispersal ability during different times of the season, and along an elevational gradient in a mountain valley in Trentino Province, Italy. We employed a mark–release–recapture strategy using protein markers. Flies were recaptured using fruit-baited traps. The protein-marked flies were positively identified using ELISA procedure. Additional microsatellite analyses were performed on D. suzukii collected during autumn at different elevations to characterize the population structure. Results suggest that a portion of the local D. suzukii population moves from low to high elevations during spring and summer and travels back to low elevations in autumn. Genetic analysis further revealed that samples collected during autumn at different elevations belong to the same population. These results show that D. suzukii are able to fly up to about 9000 m away from the marking point and that seasonal breezes likely facilitate long-distance movement. We suggest that these migrations have multiple functions for D. suzukii, including conferring the ability to exploit gradual changes of temperature, food, and ovipositional resources in spring and autumn, as well as to assist in the search for suitable overwintering sites in late autumn. Our findings help to unveil the complex ecology of D. suzukii in Italian mountainous regions and provide important clues for improving the efficacy of integrated pest management control techniques to combat this pest.