November/December – 2007
Author: Anne Gaskett
During National Science Week, ANNE GASKETT reported compelling evidence that native Australian orchids use their colour, shape and fragrance to seduce male insects. Her ground-breaking research has important implications for the control of agricultural pests.
Australian orchids are engaged in an arms race, using sensory overload to seduce male insects. Macquarie University PhD student Anne Gaskett has discovered just how they do it. Her work is important to the conservation of orchids and the control of economically important agricultural pests.
Gaskett has been analysing the smells, colours and shapes of flowers from an insect’s perspective. She has found that orchids mimic female insects so well that male insects cannot resist mating with them and accidentally ferrying pollen from plant to plant.
“I have accumulated the first compelling evidence of an ongoing and escalating arms race between orchids and their unwitting insect pollinators,” Gaskett explains.
“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.”
The Australian bush is rife with such sexual deception, Gaskett says, as native orchids lure pollinators with false promises of romance.
Gaskett has been studying the hardworking orchid dupe wasp (Lissopimpla excelsa), which is fooled into copulating with not just one, but five native tongue orchid species (Cryptostylis) in urban and regional Australia. All the tongue orchid species mimic the female dupe wasp, but to the human eye they look quite different.
By using modern technology to study the physics of the colours of the orchids and the female insects, Gaskett has revealed that they are identical when viewed by male insects. The flowers are also shaped to mimic female insect bodies.
To the human eyes the female wasp looks orange and black and the orchids are pink, maroon and orange-red. However, receptors in human and wasp eyes are very different. Unlike humans, wasps see ultraviolet light. When Gaskett used a spectrometer to study the wavelengths of light reflected from orchids and female wasps, she was amazed to find they were virtually identical.
“The smell is the most important thing for attracting the insect,” she said. “But the colours say this is the source of that alluring fragrance.”
Gaskett is now looking at the impact of the chemical components of orchid perfumes directly on wasp antennae, to understand what makes these fragrances irresistible.
“The key to the orchids’ success is bombarding young male wasps with an extremely compelling sensory overload of irresistible sex signals,” Gaskett explains.
Studying these intimate interactions addresses big questions about nature and evolution and highlights the millions of other unknown interactions crucial for a sustainable and healthy environment.
“These insects might be fools for love, but their role as orchid pollinators makes them indispensable.”
Gaskett’s next step will be to analyse the seductive orchid bouquets to discover which elements mimic the female wasp pheromones.
So what led Anne Gasket down this research path?
“I’ve always enjoyed getting out and investigating nature,” said Gaskett. “In the past, I’ve focused on animals, studying projects such as Antarctic fish diet around Macquarie Island, and spider mating and sex pheromones.
“When I was designing my PhD research I wanted to expand into botany and learn lab techniques useful for applied research in the future. I wanted a topic that would involve local community groups and enthusiasts plus travel and fieldwork opportunities, and avoid nocturnal animals – I didn’t want to be up all night!
“Studying orchids suited all these requirements and since Australia has most of the world’s sexually deceptive orchids, I thought I was well placed to use local native plants to discover interesting results with some global impact,” she said.
To study the orchids’ scents, Gaskett borrowed techniques from agricultural studies for identifying pest insects, usually very specific sex pheromones.
“If you can identify and make synthetic versions of the pheromones, you can use it as bait to trap male insects so they can’t reproduce or get into the crops,” she said.
The identification procedure is called gas chromatography – electro-antennography. It involves sampling the scent of an orchid, or a female of a pest species, and using gas chromatography to break the scent down into its separate components.
“You attach an antenna from the orchid-visiting insect or pest species so that as the scent is separated, it also blows across the antenna. You can detect when the antenna’s chemoreceptors fire and, therefore, which components are attractive to the insect,” Gaskett explains.
“I’ve used this project as an opportunity to promote and improve my skills with these techniques so the future might see me working in a much more applied capacity.”
Gaskett was one of 16 early-career scientists presenting their research to the public for the first time thanks to Fresh Science, a national program sponsored by the Federal and Victorian Governments. Her work has been funded for three years by a 2005 American Orchid Society Fellowship.
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About Fresh Science
Fresh Science is a national competition that identifies new and interesting research being done by early-career scientists around the country. Their stories are released to the media before, during and after National Science Week, which was held in August.
Sixteen scientists were selected from more than 80 nominations. They were flown to Melbourne for a day of media training after which they presented their work to the media, school students, the general public, scientists, government and industry over the course of three days.
Described by some as a boot camp in science communication, previous Fresh Scientists have attracted national and international interest resulting in hundreds of media stories, including national television news. Details of previous winners, their press releases and media coverage can be seen on the Fresh Science website.
Now in its 10th year, Fresh Science is a national event, which brings together scientists, the media and the public. It is designed to:
– Enhance reporting of Australian science
– Highlight and encourage debate on the role of science in Australian society
– Provide role models for the next generation of Australian scientists.
If you are a scientist who was awarded a PhD less than five years ago, have a significant peer-reviewed scientific achievement and think you can tell an interesting story in everyday language, then check out the selection criteria on the Fresh Science website www.scienceinpublic.com for the 2008 Fresh Science competition.