Fake figs, fooled fig wasps and rewarded phorid flies: brood-site mimicry and mutualism in Heterostemma ficoides (Apocynaceae).

About 900 specific fig-fig wasp interactions are distributed throughout tropical ecosystems. Despite this ubiquity, floral mimicry of figs (inflorescences of Ficus spp.; Moraceae) has never been observed. Recently, we found a bizarre Apocynaceae, Heterostemma ficoides, bearing globose closed flowers that look similar to figs and are visited by a Kradibia wasp, the pollinator of Ficus heterophylla. Does the flower of H. ficoides mimic the fig to achieve its pollination success? We investigated floral visitors and their activities on H. ficoides flowers, compared chemical and physical cues between these flowers and F. heterophylla figs, then tested the attraction of the Kradibia wasps to floral volatiles of H. ficoides. Heterostemma ficoides flowers were visited by a community of Diptera and Hymenoptera, some of which breed in F. heterophylla figs. Pollination was mainly achieved by a Megaselia fly and secondarily by the Kradibia wasp. Floral volatiles of H. ficoides resembled those of F. heterophylla figs and attracted the Kradibia wasp. While the fly completed its cycle on H. ficoides flowers, the fig wasp could not. This system represents an unprecedented combination of two pollination modes and constitutes the first example in which a brood-site mutualism operates simultaneously with brood-site deception.