Mimicry in hoverflies (Diptera: Syrphidae): a field test of the competitive mimicry hypothesis

Although most studies on the evolution of mimicry and warning coloration in insects have considered predators as the major selective force, it is possible that competition for food resources could also facilitate selection for these conspicuous signals. For example, when warningly colored social wasps visit flowers, then they frequently behave aggressively toward heterospecifics, and they also attack and feed on other flying insects. Under these conditions, a resemblance to a wasp might provide a mimetic hoverfly with improved access to floral resources by reducing the frequency with which it is disturbed by other pollinators. We experimentally evaluated whether wasp-like colors and patterns were important in preventing other flower visitors from sharing the same flower resource, using pairwise presentations of both natural and artificial prey in the field. Flower visitors were more likely to visit unoccupied flowers compared with the flowers pinned with either natural or artificial specimens in 2 plant species with different inflorescences. However, flower visitors did not show a significantly reduced rate of visitation to flowers pinned with specimens bearing wasp-like colors and patterns compared with the flowers occupied by similar-sized specimens that were nonmimetic. Overall, we found no compelling evidence in this study to support the contention that wasp-like warning signals of hoverflies prevent other flower visitors from sharing flower resources, although insects showed a greater tendency to avoid visiting flowers pinned with a wasp compared with flowers pinned with a nonmimetic fly. Copyright 2007, Oxford University Press.