Artificial light at night induces stress and affects evolutionary change in bats

Artificial light at night (ALAN), a pervasive component of urbanization, is rapidly transforming nocturnal environments and imposing novel selection pressures on wildlife. While behavioral responses to ALAN are increasingly well documented, physiological and evolutionary consequences are not well understood, limiting species conservation management. We used a multi-omics framework to investigate the ecological and evolutionary consequences of ALAN on a light sensitive species, the lesser horseshoe bat (Rhinolophus hipposideros), combining experiments with transcriptomics, population genomics and landscape ecology. Experimental light exposure resulted in 252 differentially expressed genes, enriched for functions in DNA damage repair, apoptosis regulation and oxidative stress mitigation. Whole genome sequencing identified genetic variation associated with ALAN and urbanization, including variants in genes linked to visual and neural function. Landscape analysis revealed that ALAN and distance to broadleaf woodland best explained patterns of population connectivity. These findings demonstrate the possible drivers behind behavioral responses, showing that ALAN can act both as an acute molecular stressor and contribute to evolutionary change, with possible consequences for movement ecology and local adaptation. Given the accelerating expansion of urbanization, understanding species-specific responses to ALAN across molecular, demographic and evolutionary timescales is critical for predicting outcomes for biodiversity and informing urban planning.