It’s a stark demonstration of nature at its most devious: researchers have discovered a plant that attracts pollinating flies by mimicking the odour of half-eaten ants.
The species of dogbane is the first plant known to boost its chances of reproducing by copying the scent that ants release as an alarm call to their nestmates when they come under attack by spiders and other predators.
“This is the first evidence of ant mimicry in plants,” said Ko Mochizuki, a botanist at the University of Tokyo. “Without this specific scent, the plant would not be able to achieve reproductive success.” The species of dogbane, Vincetoxicum nakaianum, is native to Japan and was named only last year.
The first hint of its deceptive tactics came when Mochizuki spotted fruit flies gathering around the plant’s flowers in the nursery at Tokyo’s Koishikawabotanical gardens.
The flies move from plant to plant searching for injured ants and carcasses left behind after spiders have attacked them. But in the process, the flies do the plant a major favour by helping to pollinating them.
Intrigued as to what attracted the flies, Mochizuki analysed chemicals released by the plant and found a cocktail of volatile compounds including nonane, undecane and other substances known as 8Ac, 10Ac and 6-MMS.
He then analysed pheromones released by ants in a jar when they were attacked by a jumping spider. These substantially overlapped with the odours released by the dogbane, according to the report in Current Biology.
“When attacked, ants release alarm pheromones to alert their nestmates to danger,” Mochizuki said. “Spiders that specialise in preying on ants digest their internal tissues and usually leave behind the exoskeleton.”
In further experiments, Mochizuki used a Y-shaped maze to see which odours most appealed to the fruit flies. The insects were not attracted to crushed ants, but did head for ants that had been attacked by spiders. The flies feed on the body fluids of injured insects.
While some insects are known to mimic ant pheromones so they can gain access to ant nests and feed on their larvae, the dogbane is the first plant known to pull off a similar trick. And it is extremely effective, Mochizuki said.
“The odour of injured ants emitted by Vincetoxicum nakaianum flowers has a striking effect in attracting pollinators,” he said.