Nondescript on the forest floor, the flowering plant Aristolochia microstoma has developed an arresting means of self-preservation: It smells like dead bugs, which attracts the living bugs that act as the plant’s pollinators.
Research describing the plant’s strategy was published this month in the journal Frontiers in Ecology and Evolution. Like the more famous and attractive stinking corpse lily of Indonesia, A. microstoma of Greece uses its stench as a means of survival. But unlike most other plants that work this sort of deception with captivating flowers, A. microstoma does it with an ugly crop of small brown knobs as it lies mostly inert on the forest floor. The plant’s chemical cocktail gives it a unique eau-de-decaying-insect that intrigued the researchers.
“We show that the flowers of A. microstoma emit an unusual mix of volatiles that includes alkylpyrazines, which are otherwise rarely produced by flowering plants,” said study co-author Stefan Dötterl, a plant ecologist at Paris-Lodron University in Salzburg, Austria, in a press release. “Our results suggest that this is the first known case of a flower that tricks pollinators by smelling like dead and rotting insects rather than vertebrate carrion.” How divine.
The plant’s specific trap is as follows: It lures pollinators—namely Megaselia, or coffin flies, known for dining on and spawning in carrion—into the depths of its brown flowers using its alluring death scent. When the flies arrive at a chamber containing the plant’s sexual organs, they are trapped from leaving again by hairs that line the inside of the flower. The flies carry in pollen to the plant’s female organs, and while they’re stuck in the inner chamber, the plant’s male organs release pollen back onto the insects. Only then do the hairs lining the flower retreat, allowing the insects back out of the flower.
You may say that you don’t know the smell of decaying insects by memory, and that’s not unreasonable. The researchers identified 16 chemical compounds in the plant’s scent using gas chromatography with mass spectrometry. Oligosulfides were some of the ingredients, which often exude smells like decomposing meat. But another scent in the mix was one associated with cooked rice or roasted peanuts (it also naturally occurs in rodent urine and the carcasses of some decomposing beetles).
The researchers believe that the uncommon chemical mixture released by A. microstoma is meant specifically for the coffin flies; otherwise, the plant could’ve opted for a simpler cocktail to attract one of the many insects that inhabit the leaf litter where the plant resides. Perhaps not coincidentally, that’s also where the flies look for breeding sites. In their search for dead tissue in which to procreate, some flies find themselves trapped, temporarily, in a dreadful flower that needs their help to carry out its own reproduction. Evolution is weird.