A pretty little white flower that grows near urban centers of the Pacific Northwest turns out to be a killer.
The bog-dwelling western false asphodel, Triantha occidentalis, was first described in the scientific literature in 1879. But until now, no one realized this sweet-looking plant used its sticky stem to catch and digest insects, according to researchers who note in their study published Monday it's the first new carnivorous plant to be discovered in about 20 years.
"We had no idea it was carnivorous," says Sean Graham, a botanist with the University of British Columbia. "This was not found in some exotic tropical location, but really right on our doorstep in Vancouver. You could literally walk out from Vancouver to this field site."
Fewer than 1,000 plant species are carnivorous, and these plants tend to live in places with abundant sun and water but nutrient-poor soil.
Graham's team was doing an unrelated project on plant genetics and noticed that the western false asphodel had a genetic deletion that's sometimes seen in carnivorous plants. The researchers started to think about the fact that this flower grew in the kind of environment that's home to various other insect-eating plants.
"And then they have these sticky stems," Graham says. "So, you know, it was kind of like, hmm, I wonder if this could be a sign that this might be carnivorous."
To see if the plants could actually take in nutrients from insects, researcher Qianshi Lin, now at the University of Toronto, Mississauga, fed fruit flies nitrogen-15 isotopes, so that this nitrogen could be used as a tracker. He then stuck these flies to stems of this plant.
Later, an analysis showed that nitrogen from the dead insects was indeed getting into the plants. In fact, Triantha was getting more than half of its nitrogen from prey. In the Proceedings of the National Academy of Sciences published online Monday, Lin and his colleagues say that this is comparable to what's seen in other carnivorous plants.
What's more, the researchers showed that the sticky hairs on the flower stalk produce a digestive enzyme that's known to be used by many carnivorous plants.
And when the research team looked at specimens of this plant preserved in herbariums, they found small dead insects stuck to the stems.
Aaron Ellison, a botanist with Harvard University who was not part of the research team, says the discovery was the result of "a really nice chain of scientific thinking."
All the other known carnivorous plants capture prey with the help of modified leaves, he notes.
"Nobody would be looking at a flower stalk as the primary mode of carnivory," Ellison says. "That is quite a surprise."
Usually carnivorous plants keep their deadly traps far away from their flowers, so there's no danger of accidentally killing off pollinators. But in this case, it looks like the stem is only able to ensnare tiny insects such as midges, not the larger bees or butterflies involved in pollination. The plant doesn't just grow in Canada; the researchers note in their study that the flower is found near "several major urban centers on the Pacific coast."
The whole experience has Graham wondering what else is out there secretly eating insects. After all, it's not that uncommon for plants to have sticky stems, which are thought to be used as a defense mechanism to keep insects from eating the plant.
"I suspect," Graham says, "that there might be more carnivorous plants out there than we think."
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