Bayesian mimicry in the non-rewarding saprophytic orchid Danxiaorchis yangii

Bayesian mimicry, a type of deceptive pollination, is a complicated
strategy used by non-rewarding plants to attract pollinators, but some
hypotheses concerning this phenomenon have not been systematically
verified. In order to show in detail a case of Bayesian mimicry on
saprophytic orchid Danxiaorchis yangii in this study, we compared
floral characteristics of Danxiaorchis yangii and Lysimachia alfredi as
well as the pollination behavior of the insect Dufourea
sp. towards the two species. Lysimachia alfredi can
provide a reward to Dufourea sp., whereas Danxiaorchis yangii
cannot. The flowering phenology and geographical distribution of these two
plants are highly overlapping. Statistical analysis of quadrat and L.
alfredi transplanting test data revealed that the fruit set rate
of Danxiaorchis yangii was significantly positively correlated with the
number of nearby L. alfredi individuals. In a glass cylinder experiment,
Danxiaorchis yangii and L. alfredi attracted Dufourea sp. through visual
signals, but the insect could not distinguish between flowers of the two
plants before landing on flowers. We observed that the ultraviolet
reflection spectra of Danxiaorchis yangii and L. alfredi are highly
similar. In addition, we found that the hexagonal color models of the two
plants are consistent with the bee’s visual characteristics, thus
indicating that the visual signals of the flowers of the two plants are
greatly similar. All of these results provide evidence that Danxiaorchis
yangii simulates the visual signals of L. alfredi through
Batesian mimicry, thereby deceivingly attracting Dufourea sp.