Fatal bogus invitations to romance might just be the newest trick discovered among some pulpit wildflowers.
The fatal part is not the surprise. Jack-in-the-octopuses (arisema) are the only known plants that routinely kill their own pollinating insects, says evolutionary ecologist Kenji Suetsugu of Kobe University in Japan. The new twist, if confirmed, would be using sexual deception to lure pollinators into death traps.
So far, biologists have found only three plant families with any species that claim to offer insects sex, Suetsugu says online March 28 at Plants, People, Planet. But unlike the deception in the pulpits, those other attractions are not fatal, just false.
The the orchid family has turned out to be multiple trapsSome so seductive that a male insect leaves wasted sperm and pollen on a flower. However, he does not even take a sip of nectar (Serial Number: 5/3/08; Serial number: 03/27/08). Similar scams have appeared among daisies: some dark bumps that a human in dim light might mistake for an insect can driving male flies into frenzies in yellow, orange or red gorge petals. However, enthusiasm fades with repeated disappointment (Serial number: 01/29/14). And among the lilies, one species hangs velvety purple petals where deceived insects wallow.
Two species of jack-in-the-pulpit in Japan have now raised suspicions that their family, the arums, should be added to the list of sexual traps. For visually oriented humans, the 180 or so arisema species seem like just a cheery reminder of the infinite weirdness of evolution. A kind of flapping canopy, sometimes striped, leans over a small hollowed-out “pulpit” with a stump at the tip of the little finger or a lump of vegetable flesh fungus peeking over the edge. Below the rim, bands of flowers open in succession (male flowers surmounted by flowers with female parts) as the plant grows from skinny young cat to big mama.
These strange flowers rely primarily on pollinators that deserve a much larger fan base: fungus gnats. Small as punctuation marks and difficult to identify, these midges are true flies. But don’t hold that against them. They don’t lurk on picnic tables or bang on windows. Pollinating mosquitoes “are very fragile,” Suetsugu says, and their wings don’t make any noise that a human can hear.
Nor can a human being always smell what attracts fungus gnats. It’s clear, though, that the assorted canopied pulpits can have strong happy hour appeal for those pollinators looking to meet the right mosquito. This will go terribly wrong.
A small escape hatch deep in the trap remains open during the male phase of bloom, but that two-millimeter hole disappears during the big mom stage. A mosquito cannot get past the slippery, flaky wax on the inner wall of the plant to get out. So any mosquito fooled twice is doomed.
Biologists had assumed that pulpit-seeking fungus gnats were perfuming the air with fungal scents, a pleasant place to have children. Lots of guys seem to do it, but home smells don’t explain a strange observation by Suetsugu and his colleagues. Of the important pollinator species for two Japanese jack-in-the-pulpits (A. angustatum Y A. peninsulae), almost all the specks found in the traps were males.
A male-targeted scent lure could mimic the scent of female mosquitoes, the researchers propose. That is a total fraud. Even if the hopeful males find a mate in the waxy green dungeon, they and their young would starve. They are stuck on a plant with no fungus to eat. Whatever that ruinous smell is, a human nose can barely detect it, Suetsugu reports.
The notion that biologists have so far missed a scent important to other animals seems “more than possible” to Kelsey JRP Byers of the John Innes Center in Norwich, England. Byers’ work overturned a common assumption that monkey flowers (mimulus) had no odor despite the fact that hawk moths, which fly at night and are known to track odors, visit flowers.
“We are such visual creatures,” says Byers, who studies floral scents. We can laugh at how insects mistake a patch of discolored plant tissue for a fabulous female, but we’re missing the scents. Fungus gnats, however, even look like citizens of a stinkier world, with giant man-style antennae “like an ostrich feather on a hat.”
At least now, modern analytical laboratory techniques and equipment are opening up the vast sensory world of communication that floats around us. To see if even familiar plants like jack-in-the-pulpits are up to something strange, scientists need to identify the lure itself. Then maybe we understand the irresistible Valentine scent of a female fungus gnat.