Pollinators can prefer rewarding models to mimics: consequences for the assumptions of Batesian floral mimicry

Abstract

Many members of the Orchidaceae offer no rewards to pollinators and attract them through deception. One common approach is to mimic the specific floral signals of co-flowering species that are rewarding (Batesian floral mimicry) to exploit their pollinators. We investigated two putative Batesian floral mimics, Disa gladioliflora subsp. capricornis and Disa ferruginea, within a single community to determine whether their pollinators are able to discriminate them from their models. Despite mimics being indistinguishable from models in terms of floral colour as perceived by pollinators, strong preference for model flowers was observed in both systems. We nevertheless recorded frequent pollen transfer in D. gladioliflora subsp. capricornis, suggesting pollination still occurs in the face of pollinator discrimination. Although the inability of pollinators to discriminate between models and mimics is often cited as a requirement for Batesian floral mimicry, we suggest that this need not be the case. Pollination by discriminating visitors may still lead to fruit set, with the most accurate mimics expected to have the highest fitness. Batesian floral mimicry may thus be best indicated when mimic fitness is positively correlated with its resemblance to model flowers.