The Spider Orchid Caladenia crebra Produces Sulfurous Pheromone Mimics to Attract its Male Wasp Pollinator

Abstract

One of the most intriguing natural observations is the pollination of orchids by sexual deception. Chemicals underpin this interaction between the orchid and its sexually attracted male insect pollinator, with the signaling compounds involved, called semiochemicals, predicted to mimic the chemical composition of the sex pheromone. We identified floral semiochemicals from Caladenia (spider orchids) for the first time. We further demonstrate that C. crebra attracts its single pollinator species with a unique system of (methylthio)phenols, three of which are new natural products. Furthermore, as predicted, the same compounds constitute the sex pheromone of the pollinator, the thynnine wasp Campylothynnus flavopictus, representing the first occurrence of sulfurous sex pheromones in Hymenoptera.