Urban–rural diversification in response to nighttime dim light stress in <i>Drosophila suzukii</i>

Abstract Human disturbance in cities leads to environmental changes, such as habitat fragmentation, raised ambient temperature, night lighting, and noise. Here, we examine the plastic response to artificial light at night (ALAN) of morphological and reproductive traits in isofemale strains derived from four rural and four urban populations of Drosophila suzukii. The individuals from urban and rural populations were reared under 12 h daylight, followed by either 12 h darkness (control) or dim light (treatment). Adult morphology changed with ALAN exposure regardless of fly origin, but the impact on morphological traits was more pronounced in rural populations. The level of male courtship activities was decreased by ALAN exposure, although the response varied between the rural and urban populations. Egg size and shape were slightly affected by ALAN for both rural and urban populations. The number of eggs laid increased more under ALAN stress in rural populations compared with urban populations. Our results suggest that exposure to ALAN induces a plastic response in these traits and that individuals in urban populations have evolved to mitigate the impacts of ALAN stress. These findings highlight the potential for urban populations to adapt to human-induced environmental stressors, with important implications for predicting species responses to urbanization.