Ultraviolet reflectance in fruits, ambient light composition and fruit removal in a tropical forest

Ultraviolet (UV) reflectance patterns in fruits and UV perception ability i n frugivores were linked through a fruit survey and with a field experiment that examined fruit removal under varying light conditions. The reflectanc e spectra were measured for fruits from 57 tropical plant species on Barro Colorado Island, Panama. Relationships among UV reflectance in fruits, colo ur vision of the dispersal agents, light regime and fruit ripening were exa mined using both non-phylogenetic tests and the concentrated changes test t o analyse the phylogenetic distributions of these traits. Ultraviolet-refle cting fruits occurred in both open and closed light habitats and were stron gly associated with dispersal by birds and rodents, both of which perceive UV radiation. In addition, only mature fruits reflected UV. Natural rates o f fruit removal were studied experimentally over 3 months in the understore y shrub Psychotria emetica (Rubiaceae). Ambient light was manipulated by pl acing a UV-absorbing filter over fruiting plants, with control treatments o f plants under clear filters (UV-transmitting) and plants without filters. Fewer fruits were removed when ambient UV was filtered out, establishing th at ultraviolet reflectance can be an important attractant for some fruit di spersers. The results indicate a prominent role for UV reflectance in plant -frugivore relations and demonstrate a link between the perceptual abilitie s of animals and the colour of the fruits they consume.