Fruit-Penetrating Ability is Associated With the Number of Modified Lateral Bristles in the Ovipositor of Drosophila suzukii

In some insects, the evolution of herbivory was facilitated by the acquisition of specialized structures that confer adaptive advantages, allowing access to new ecological niches. A notable evolutionary innovation in Drosophila suzukii is the ovipositor, characterized by an arrangement of heavily sclerotized bristles aligned along the distal margins of the plates. This structure allows flies to pierce the skin of fruits, facilitating oviposition inside the fruit and consequently annulling the agricultural value of the fruit. However, the specific features of the ovipositor that underlie the ability to penetrate the fruit remain poorly understood. To address this gap, we investigated variation in the number of modified lateral bristles (MLBs) and assessed whether this trait may affect the ability to penetrate the fruit skin during oviposition. Our study revealed remarkable intrapopulation variation, with a substantial proportion of the genetic variance being additive. We also performed selection experiments and were able to both increase and decrease the number of MLBs. Finally, oviposition assays showed that females with more MLBs produce more perforations in the skin of blueberries. Overall, these results suggest that MLBs may contribute to fruit-piercing ability during oviposition, and the substantial amount of additive genetic variance indicates that the number of MLBs can evolve. We highlight the importance of further studies to shed light on the subtleties of the genetic architecture of the trait.