Floral yeasts driving pollinator recruitment in a Neotropical orchid

Background/Question/Methods

The Neotropical cloud forest inhabiting orchid Dracula felix has long been postulated to be a fungal mimic due to the form of its lower labellum and attraction to it by drosophilid flies that are often found feeding on fungal fruiting bodies in the surrounding area.  The low number of co-occurring flowers in the area, combined with the high number of fruiting fungi appears to have driven the evolution of the orchid genus Dracula to mimic these co-occurring fungi so that pollinators may be recruited.  Over several years of working with these orchids we have noticed a particular lapping behavior by the pollinating flies on the labella and sepals of the Dracula flowers.  In this study we have investigated the role of floral yeasts as being the driving olfactory cue to attracting pollinators and offering a food reward to retain them for pollination purposes.  

Under sterile conditions yeasts were cultured from wild D. felix flowers at our field site in northwestern Ecuador and placed on surgical silicone flower replicas.  The models were situated near active populations of real flowers and observed for visitation and time spent on the models; pollinator visitation of neighboring real flowers was recorded as well. 

 

 

 

Results/Conclusions

Data was analyzed by ANOVA of the log transformed hourly visitation rate. Visits to the yeast treated models did not differ from visits to the real flowers (F_1,44 =0.0154, p=0.9016).  This suggests a strong link between the yeasts and recruitment of pollinators to the orchid flowers. In a separate experiment the same models did not attract pollinators on their own due to visual cues only.