Ant diversity and foraging across the diel cycle is unaltered by experimental exposure to artificial light at night

Abstract

The foraging of resources by ants supports diverse ecosystem functions across Earth's terrestrial sphere. However, not only is there limited knowledge on how foraging patterns of ant communities change from day to night, but it is unknown how such activity may be affected by artificial light at night (ALAN) – a burgeoning threat to nocturnal organisms worldwide. We investigated the composition and foraging patterns of diurnal and nocturnal woodland ant communities, and their responses to an experimental exposure to ALAN over 15 days. We detected a high turnover in community composition between diel periods, with nocturnal communities comprising fewer species, removing 73 % less insect biomass, but displaying stronger recruitment to protein resources than diurnal communities. Relative to unlit controls, no significant effect of ALAN was detected on any aspect of ant community structure and foraging. Our results demonstrate that the partitioning of diel time and resource type is an important coexistence mechanism maintaining ant biodiversity, and suggest that a brief exposure to ALAN does not significantly impact the foraging activities of ecologically dominant generalist ant species. While further research is needed to ascertain the long-term effects of ALAN exposure on ant biodiversity, the limited impacts in the short-term may be explained by nocturnal ant species' reliance on chemical cues and other non-visual navigational strategies, in contrast to flying insects for which strong impacts of ALAN have been documented.