Stop and smell the dying bees. The scent of a South African plant mimics the chemicals honeybees release when they鈥檙e under attack.
Scavenging flies on the lookout for a meal are then tricked into pollinating the plant鈥檚 flowers.
Many plants attract insect pollinators by exuding substances meant to mimic the sexy smell of potential mates or the alluring aroma of rotting flesh.
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But we don鈥檛 know the details of how most of the deceptive flora hoodwink their visitors, says at the University of Salzburg, Austria.
D枚tterl and his colleagues focused on solving the mystery for , a South African plant that produces 鈥減itfall flowers鈥�, umbrella-shaped blossoms that keep pollinators trapped within their petals for about a day, before releasing them, now packed with pollen.
To identify the plant鈥檚 pollinators, the team gathered the insects they found imprisoned within its flowers. The most common was a type of small fly that dines on the drippings left by spiders as they kill and consume honeybees.
The team wondered if the plant could be exploiting the fly鈥檚 culinary preferences to bait the insect.
鈥淲hat does a honeybee eaten by a spider and this flower have in common?鈥� D枚tterl asks.
Fake attack
To find out, the scientists simulated an attack by squeezing the honeybees with their fingers or poking them with a narrow glass cylinder, then collecting the defensive compounds the bees released. The team also extracted the chemicals given off by the plant, and found several compounds in common.
Flies can perceive about half of those compounds, as subsequent experiments showed.
When the researchers left vials containing a blend of four of the overlapping substances outside, they lured in about half a dozen flies each in under an hour, while similar control vials of acetone were left alone.
鈥淭hey really look for a combination of compounds,鈥� D枚tterl says, referring to the scavenging flies. That makes sense because the individual chemicals are common in nature 鈥� many plants emit one or two of them 鈥� but the mixture is unique. 鈥淲e found no other organism, other than the honeybee and this flower, which releases all four compounds together,鈥� D枚tterl adds.
Cheating plants
The team鈥檚 use of multiple methods provides convincing evidence for how the flowers attract the flies, says at the University of Ulm in Germany.
鈥淚t鈥檚 a new fascinating example of chemical mimicry in plants that try to attract pollinators, and try to cheat them,鈥� Ayasse says.
It鈥檚 also a good example of an intricate pollination system, says at Western University in London, Ontario.
鈥淚t goes to show that there are many ways to get a pollinator,鈥� McNeil says. 鈥淭he more we look, I think we鈥檙e going to discover more and more.鈥�
Journal reference:
Read more: Orchid鈥檚 sexual deception triggers ejaculation; Plant tricks dung beetles by making its seeds look like dung
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