Hairs of new carnivorous plant trap gnats, but allow bees to pollinate flowers

Triantha occidentalis produces flowering stems with sticky hairs that trap small gnats and midges, and isotopic analysis has confirmed that the plant can successfully digest the trapped insects. Photo by Danilo Lima

Aug. 9 (UPI) -- Botanists have identified a new carnivorous plant in western North America. The species, Triantha occidentalis, represents the 12th independent origin of plant carnivory.

Found in bogs and wetlands from California to Alaska, and as far inland as Montana, Triantha occidentalis sprouts tall flowering stems with small, sticky hairs that trap gnats and midges

According to a new paper, published online Monday in the journal PNAS, more than half the plant's nitrogen is sourced from the small insects ensnared by its hairs.

The insect-eating plant is a member of the Alismatales order, a large group of mostly aquatic flowering plants belonging to the Monocotyledons clade. Monocots include thousands of grass and grass-like flowering plants

"What's particularly unique about this carnivorous plant is that it traps insects near its insect-pollinated flowers," lead study author Qianshi Lin said in a press release.

"On the surface, this seems like a conflict between carnivory and pollination because you don't want to kill the insects that are helping you reproduce," said Lin, who was a doctoral student at UBC at the time of the study.

However, scientists determined that the plant species' insect-trapping hairs aren't all that sticky. The hairs possess just enough adhesiveness to ensnare small species, gnats and midges, while allowing bees and butterflies to come and go undeterred

While surveying the genome of Triantha occidentalis, scientists noticed the plant was missing a gene frequently absent in carnivorous species. Given its close proximity to other known carnivorous plants, researchers estimated the species might also be digesting insects.

Carnivorous plants are most common in habitats where nutrients are scarce but water and sunlight ware abundant.

In the field, Lin fed the plants fruit flies tagged with stable isotope nitrogen-15. After tracking the path of the nitrogen isotope, researchers confirmed that the species acquires some 65% of its nitrogen from digested insects.

RELATEDFlower attracts pollinating flies by mimicking smell of attacked bee

Triantha occidentalis uses the enzyme phosphatase to break down phosphorous-bearing nutrients in the gnats and midges trapped by its hairs.

Though Triantha occidentalis is fairly common and found near many large cities, the plant's carnivory eluded scientists for decades.

Researchers now plan to take a closer look at other members of the Triantha genus to see if other carnivorous plants are hiding in plain sight.

"It seems likely that there are other members of this group that will turn out to be carnivorous," said co-author Tom Givnish, professor of botany at the University of Wisconsin.