Artificial light changes visual perception by pollinators in a hawkmoth-plant interaction system

Abstract

Night-flying pollinators, such as hawkmoths, are particularly vulnerable to the global spread of urban artificial lighting which is changing nighttime environments worldwide, impacting organisms and their interactions. Incident light quality can alter flower and leaf color perception by insects, depending on the emission spectra of light sources and the spectral sensitivity of insects. We asked, using Manduca sexta visual models, whether color contrast against natural backgrounds is altered by artificial lights for flowers and leaves of 16 plant species with an estimated long history of coevolution with hawkmoth pollinators. Specifically, we compared the perception of flowers and leaves by hawkmoths under artificial lights, including light-emitting diodes (5000 K LED), mercury vapor (MV), and high-pressure sodium (HPS) artificial lights, with the perception under natural illuminations. The models we implemented estimate that LED and HPS lighting change hawkmoth perception of flowers and leaves, with color loci appearing nearer to each other in hawkmoths perceptual space than they would be under natural nighttime conditions. Receptor Noise Limited models show that under the different lighting conditions hawkmoths would still discriminate flowers from their leaves in most but not all species. Consequently, artificial lights likely alter perception by hawkmoths of floral and leaf signals possibly affecting interactions and fitness of plants and pollinators. Our results emphasize the intricate and insidious ways in which human-made environments impact species interactions. Further studies should confirm whether light pollution represents a novel selective force to nocturnal interacting partners as emerging evidence suggests. Addressing the effects of artificial lighting is crucial for designing infrastructure development strategies that minimize these far-reaching effects on ecosystem functioning.