The deceptive pollination of Anacamptis morio: generalized food deception or an initial step towards adaptive mimicry?

Background: To attract their pollinators non-rewarding orchids rely on various deception strategies that range from generalised food deception to floral mimicry of a specific model (Batesian mimicry). Aims: We evaluated whether the deceptive orchid Anacamptis morio may represent an initial step in the evolutionary trajectory from generalised food deception to Batesian mimicry by resembling the rewarding Polygala nicaeensis, a species with purple flowers very similar to those of A. morio. Methods: We assessed the pollination success of A. morio in relation to co-flowering rewarding species. Then, we estimated male and female reproductive success of A. morio depending on the presence of and similarity to the putative model P. nicaeensis. Results: The pollination success of A. morio covaried with that of P. nicaeensis and its pollination efficiency was higher when the two species co-occurred. However, we did not find supporting evidence that A. morio mimicked its potential rewarding model. We also found that the orchids with stronger colour reflectance exhibited greater pollination success, according to a scenario of ecological facilitation rather than adaptive mimicry. Conclusion: Co-flowering rewarding species with a colour similar to the orchid may enhance the specific pollinator abundance and condition their foraging preference, hence producing a positive effect on the reproductive success of A. morio.