Promise of sex may save orchid

University of Western Australia, Science Alert 29 Oct 09;

A team of researchers from The University of Western Australia, Kings Park and Botanic Garden (KPBG) and the Australian National University is racing the clock to save an orchid unique to Western Australia’s south-west.

One of the nine species of Drakaea orchid is already extinct and others are endangered – and scientists are battling to save it, along with its specially adapted pollinator, the Zaspilothynnus wasp.

In a bizarre interaction, Drakaea orchids have evolved to look and smell more like female insects than plants. By offering male wasps the false promise of sex, the orchid is pollinated without having to produce ‘costly’ food as a lure for pollinators, as most plants do.

Each of the orchid species, which are different sizes, has its own amorous wasp species. Each orchid also has its own chemical brew with which to attract the corresponding wasp. And the difference between specific sexual pheromones, which comprise compounds new to science, can be as little as two hydrogen atoms.

The UWA team includes, from the School of Chemistry, Professor Emilio Ghisalberti and Dr Gavin Flematti, who identified karrikins, a family of compounds that stimulates seed germination in many plants.

ANU Professor Rod Peakall, a UWA Botany graduate, explained the orchids have everything to gain from the wasps’ misguided attempts at love-making and the wasps nothing.

By identifying the compounds involved in ensuring the orchids’ pollination – and knowing how to attract the vital pollinators – the team hopes to preserve the remaining Drakaea species.

UWA’s Professor Kingsley Dixon, also the Director, Science, KPBG, said a lack of knowledge about the importance of pollination in restoring native ecosystems was threatening the successful restoration of global biodiversity hotspots, one of which is the orchids’ habitat.