Adaptation to Nighttime Light via Gene Expression Regulation in .

Urbanization causes environmental changes like habitat loss, fragmentation, and pollution, which reduce biodiversity. Urban organisms face stressors, such as heat islands, air and water pollution, and anthropogenic noise, all of which can disrupt their development, behavior, and physiology. While some species adapt to urban environments, their responses and the role of evolution in urbanization are limited, as most studies focus on phenotypic traits. Artificial light at night (ALAN), a common urban stressor, disrupts behaviors and physiological processes, including circadian rhythms, sleep, and reproduction. The present study examined the effect of ALAN on body size, survival, activity rhythms, and gene expression in urban and rural strains of in common garden experiments. ALAN reduced wing and thorax sizes regardless of sex and origin, decreased survival in rural populations, and increased it in urban populations. ALAN elevated overall activity, especially in the early night, while urban females displayed reduced sensitivity regarding activity and sleep. The circadian rhythm length was disrupted in rural populations but not in urban populations. Transcriptomic analysis revealed ALAN-induced gene expression changes, particularly in urban females, with photoreceptor- and circadian rhythm-related genes responding differently between urban and rural populations. These results indicate that urban populations have evolved adaptive mechanisms to counter ALAN's effects, likely mediated through gene regulation. This study highlights ALAN's impact on diverse traits and its potential for adaptive evolution in urban environments. Evolutionary adaptations in traits related to urban stress responses may enhance the ecological success of in urban habitats.