Illuminating the Past: Coral Reefs Facilitate Diversification of Biofluorescence in Ray-finned Fishes

Biofluorescence, the absorption of high-energy light and its reemission at lower energy wavelengths, is widespread across vertebrate and invertebrate lineages, especially fishes. New observations over the past decade have significantly increased our understanding of the diversity and multifunctionality of fluorescence in fish lineages. Herein, we present a comprehensive account of all known biofluorescent ray-finned fishes and infer a dated maximum likelihood phylogeny of Actinopterygii to estimate the age and number of times biofluorescence evolved across this massive assemblage. We show that biofluorescence evolved at least 35 times in ray-finned fishes and is estimated to date back ~184 mya in Aulopiformes (lizardfishes). In Acanthomorpha, we find most biofluorescent families are reef-associated and their number increased considerably throughout the Cenozoic, paralleling the rapid increases in modern reef-associated fish families and coral diversity during this period. Our results suggest that biofluorescence could be a key innovation driving the diversification of reef fishes.