Corallorhiza striata is the first example of a pseudocopulatory orchid in North America and an instance of "double deception" in fully mycoheterotrophic plants.

Abstract

<h4>Premise</h4>Orchids have many pollination strategies, from highly species-specific mutualisms with insects to deceit pollination, including sexual deception. The family also has the most leafless, parasitic species (mycoheterotrophs) of any plant family. The occurrence of two types of deception simultaneously in individuals of a single species previously has been suggested to be highly improbable.<h4>Methods</h4>We studied Corallorhiza striata in the field, documenting the behavior of pollinators on the plants. We compared structural features of C. striata flowers to those of other species in the genus and tested for the presence of nectar. We also examined over 6000 iNaturalist photo records of C. striata to expand our pollinator search.<h4>Results</h4>The only pollinators for which we found clear evidence were males of the ichneumonid wasp Pimpla pedalis, which visited the nectarless flowers and exhibited mating-type behavior. The floral structure of C. striata, especially with respect to the labellum, is distinct from that of bee- and fly-pollinated species of Corallorhiza. We demonstrated that wasps were attracted to flowers in the absence of visual cues.<h4>Conclusions</h4>Corallorhiza striata is the first example of a pseudocopulatory orchid from North America, and Corallorhiza is only the second genus known to deceive an ichneumonid. It is trophically and reproductively deceptive in the same life stage. Four other fully mycoheterotrophic species and three partial mycoheterotrophs also are known to engage in both deceptions indicating that, although rare, simultaneous deception can be a successful strategy. Such parasitic plants provide opportunities to study unusual evolutionary and ecological phenomena.