Research focuses on orchids mimicking female wasps

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Friday, August 24, 2007

Anne Gaskett, a PhD student from Macquarie University in Sydney, has been conducting new research into the nature of the relationship between five species of native Australian tongue orchids and the orchid dupe wasp (Lissopimpla excelsa).

The research builds on an original discovery in the 1920s that the orchids convince male wasps that the flowers are actually females of the same species. The wasps then attempt to mate with the flowers, before moving on, often to another orchid, thus pollinating them. The discovery received worldwide attention at the time.

"I wanted to know what it was about the five orchids that could persuade the male that they were all a female [wasp]," she says, adding that the flowers all look very different to the human eye, and that usually only one species of insect pollinates one species of plant.

"I have accumulated the first compelling evidence of an ongoing and escalating arms race between orchids and their unwitting insect pollinators," Gaskett, says, "Over generations the insects learn to avoid having sex with orchids, and this means only the most persuasive orchids reproduce, which drives the acceleration of orchid subterfuge."

Gaskett has discovered that the wasp, however, quickly learns to avoid the orchid, meaning that "...only the most persuasive orchids will continue to reproduce," she says. She has also discovered that the flowers have various structures that feel like parts of a female wasp to a male, including mimic 'love handles', which the male would normally hold on to during mating. Gaskett says of this particular discovery that the flowers have "curves in all the right places".

Gasket has also used a spectrometer to analyse the colours of four of the orchids and a female wasp, and found that, although they look very different to humans, they actually match almost exactly.

Gasket's research is important to the conservation of the orchids, and to developing sensitive control methods for use against agricultural pests. She says of the wasps "these insects might be fools for love, but their role as orchid pollinators makes them indispensable."

Gasket has currently turned her attentions to the role of scent in the process, and is testing the effect of the perfumes of the orchids on the antennae of the male wasps.

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