The critical impact of sub- and supra-optimal temperatures on male fertility potential of an invasive fruit fly

This study investigates the impact of temperature on male fertility in the invasive pest Drosophila suzukii, focusing on both developmental and post-emergence temperature effects. We exposed flies to 11 temperatures (10-30°C) over varying durations, revealing asymmetrical thermal performance curves. Developmental temperatures between 9.8–29°C and adult temperatures between 10.05–34.8°C defined fertility limits (TFmin and TFmax). Males exposed to sub- or supra-optimal temperatures were sterile at emergence, with sterility persisting across life stages. Supra-optimal temperatures in adults induced sterility within days, while sub-optimal temperatures at adulthood prevented fertility. Cold-acclimated males, in reproductive quiescence, progressively regained fertility when transferred to 20°C, showing anatomical recovery but reduced mating attractiveness. This study defines male sterility thermal limits and highlights the partial fertility recovery in cold-acclimated males, providing insights into D. suzukii population dynamics after winter.

Methods
Here investigated the impact of temperature on male fertility in the invasive pest, Drosophila suzukii. We assessed both developmental and post-emergence temperatures, using a range of 11 temperatures from 10 to 30°C and varying chronic exposure durations.To assess the reproductive capacity of overwintering D. suzukii males, we also reared and acclimated males at low temperature and evaluated their fertility and its recovery, mating competitiveness, and size of reproductive organs at various time points.