Dissecting pollinator responses to a ubiquitous ultraviolet floral pattern in the wild

1. Color patterns on flowers can increase pollinator visitation and enhance foraging behavior. Flowers uniform in color to humans, however, can appear patterned to insects due to spatial variation in UV-reflectance on petals. A UV ‘bullseye’ pattern that is common among angiosperms—UV-absorbing petal bases and reflective apices—purportedly functions as a nectar guide, enhancing pollinator orientation, and experimental evidence suggests that UV reflectance increases apparency to pollinators. 2. We test the pollinator-attracting and -orienting functions of floral UV pattern and UV reflectance under natural conditions. Specifically, we address whether UV reflection alone, or UV pattern influences small bee and syrphid fly attraction rates (approaching, landing, and foraging visits), foraging rates, and likelihood of foraging and orienting to the center of flowers, using Argentina anserina, a species whose flowers exhibit variability in the size of the UV bullseye. We manipulated UV propert...