Flower mimics the scent of dead beetles to draw in helpful flies
Although we've already heard about plants that mimic the smell of rotten meat or feces in order to attract pollen-spreading scavengers, botanists have now discovered that a certain plant really focuses that concept – it mimics the smell of dead beetles, to draw in a specific type of fly.
Named Aristolochia microstoma, the plant has so far only been found in Greece. And while other members of its family are known for their big, colorful flowers, A. microstoma's flowers are drab in appearance, and they lie close to the ground where they often get covered with fallen leaves or other debris.
Scientists already knew that those flowers emit a foul odor, to attract scavenging animals that help A. microstoma to reproduce by transferring pollen between individual plants. Recently, however, researchers from Austria and Germany discovered that one of the molecules that makes up the flowers' unique "bouquet" is produced by very few other flowering plants.
Known as 2,5-dimethylpyrazine, the compound has a musty scent. It's not found in vertebrate carcasses or feces, but it is emitted by the decomposing carapaces of dead beetles. Flies of the genus Megaselia – commonly called coffin flies – would likely be attracted to such an odor, as they mate above dead beetles' bodies then lay their eggs within them.
Indeed, when the scientists collected arthropods from 1,457 wild A. microstoma plants, coffin flies were found to be the only species that was carrying pollen within the flowers.
Those flowers draw the flies in with their scent, using downwards-facing hairs to temporarily trap them in a lower chamber that contains the flower's reproductive organs. Once the flies have had a chance to deposit any pollen they might already be carrying – and to get coated with fresh pollen from the flower's stamen – the hairs wither away so that the flies can escape and visit other A. microstoma plants.
"We conclude that A. microstoma likely uses a strategy that has never been reported before: its flowers mimic the smell of invertebrate carrion to attract and imprison pollinators," says Prof. Stefan Wanke, from the Dresden University of Technology. "The peculiar orientation of the flowers close to the ground may also help, as pollinating coffin flies search for breeding sites or food close to the ground, in leaf litter or between rocks."
A paper on the research, which also involved scientists from the Paris-Lodron University of Salzburg, was recently published in the journal Frontiers in Ecology and Evolution.