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

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). 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. 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. 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. 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.