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Orchids found to be sexual deceivers
This unusual work is being carried out by Dr Florian Schiestl, based at the Australian National University, who is interested in whether Australian orchids, which manipulate male wasps into trying to mate with them, do so by mimicking the sex pheromones of female wasps. Only a few orchids throughout the world use this system to attract pollinators - and Australia is home to most of them. "It's a form of 'sexual deception'," said Schiestel, a Postdoctoral fellow ANU's Division of Botany and Zoology. "The pollinators don't really benefit from the arrangement. The time they spend being sexually deceived by the orchids, they could be spending mating with females."  Last year, Schiestl was part of a team which discovered that the European orchid, Ophryus sphegodes, attracted its bee pollinator because the flowers produced exactly the same compounds, and in similar relative proportions as those in the sex pheromone of the female bee.He has been using a process known as gas chromatography-electroantennographic detection, that involves exposing the antennae of the male pollinator insect to different chemicals. If the receptor cell in the antennae 'smells' a compound, a measurable current is produced. Alas, mere humans cannot smell the varying bouquets presented for the delight of pollinators as they are only picked by antennae. The 14 compounds found so far involved in the chemical mimicry are common straight-chain saturated and unsaturated hydrocarbons which are also part of the plant surface wax, where their primary role is to prevent the loss of water. Each plant, just like each individual female insect, has a particular combination of these chemicals to give an individual smell. Observations related to the chemicals used by the European orchids have revealed that because of these individual variations in the pheremones, the bees eventually get to know individual orchids that deceive them and will only end up trying to mate with each flower once. "This is advantageous to the flower because it prevents self pollination." Dr Schiestl and his co-workers propose that in an ancestor of Ophyrus, an occasional mutant produced a combination that happened to resemble that of the sex pheromone of the pollinator species, and natural selection would have favoured further plant mutants with a hydrocarbon pattern with an even closer resemblance. Anna Salleh - ABC Science Online More Info?
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