Chemistry of Sexual Deception in an Orchid-Wasp Pollination System
Pollination by sexual deception of male pollinators is known only in orchids from Australia and Europe. These orchid flowers mimic the odour and appearance of female insects and pollination is achieved during mating attempts by the male. This pollination is sometimes known as "pseudocopulation" meaning false mating, although attempted mating is not necessary for pollination in all species, hence we use the more general term of "sexual deception". In Australia at least 100 species (perhaps has many as 300) in at least 9 orchid genera, are involved. Not only are male wasps of several kinds exploited, but also ants and sawflys. Although some orchids look remarkably like female wasps (see photos below) we have known for a long time that the floral odor (although not detectable to human noses), rather than appearance is most important. The exciting breakthrough we have described in our Science paper (Schiestl et al. 2003) is that a single compound, identical in the female and the orchid Chiloglottis trapeziformis , is sufficient to attract the male wasps. This single compound is unique, representing a new class of compounds previously unknown to science. This is also the first known case in orchids (and probably plants generally) where the orchids have evolved and copied an identical compound to that used by their pollinator as a sex pheromone.
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Australian National University Media Release