Science

New Lineage of Carnivorous Plants Discovered

The newly-identified lineage of carnivorous plants is represented by the western false asphodel (Triantha occidentalis), a species of flowering plant from North America; its trap is unique among carnivorous plants and, unexpected based on theory, in placing all of its prey-capture sites next to its insect-pollinated flowers.

Flower of the western false asphodel (Triantha occidentalis) at Cypress Provincial Park, British Columbia, Canada. Image credit: Danilo Lima.

Flower of the western false asphodel (Triantha occidentalis) at Cypress Provincial Park, British Columbia, Canada. Image credit: Danilo Lima.

“Carnivorous plants have fascinated people since the Victorian era because they turn the usual order of things on its head: this is a plant eating animals,” said Professor Sean Graham, a researcher in the Department of Botany and the Botanical Garden at the University of British Columbia.

“We’re thrilled to have identified one growing right here in our own backyard on the west coast.”

Triantha occidentalis can be found in the wetlands and bogs from Alaska to California and inland to Montana.

In the summer, it shoots up tall flowering stems coated with sticky hairs that trap small insects like gnats and midges.

“What’s particularly unique about this carnivorous plant is that it traps insects near its insect-pollinated flowers,” said Qianshi Lin, a doctoral student in the Department of Botany and the Botanical Garden at the University of British Columbia.

“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.”

“However, the plant appears to be capable of sorting out friend from food.”

“We believe that Triantha occidentalis is able to do this because its glandular hairs are not very sticky, and can only entrap midges and other small insects, so that the much larger and stronger bees and butterflies that act as its pollinators are not captured,” said Professor Tom Givnish, a researcher in the Department of Botany at the University of Wisconsin-Madison.

In their study, the reseachers discovered that Triantha occidentalis acquires more than half of its nitrogen (N) by digesting these ensnared insects, a welcome treat in its nutrient-poor habitat.

“We tested the hypothesis that Triantha occidentalis is carnivorous by doing a field experiment with 15N-labeled insects to demonstrate nutrient uptake,” they said.

“We demonstrated significant N transfer from prey to Triantha, with an estimated 64% of leaf N obtained from prey capture in previous years, comparable to levels inferred for the cooccurring round-leaved sundew, a recognized carnivore.”

“N obtained via carnivory is exported from the inflorescence and developing fruits and may ultimately be transferred to next year’s leaves.”

“Glandular hairs on flowering stems secrete phosphatase, as seen in all carnivorous plants that directly digest prey.”

This is the 12th known independent evolution of carnivory in the plant kingdom.

It is the first time the trait has been discovered in the Alismatales order, a group of largely aquatic flowering plants.

It is also just the fourth established instance of carnivory in the monocots, one of the major groups of flowering plants.

Some other species in the Triantha genus also have sticky hairs that trap insects. The authors plan to study these species to see how widespread carnivory might be in the genus.

“It seems likely that there are other members of this group that will turn out to be carnivorous,” Professor Givnish said.

“The fact that Triantha’s carnivorous lifestyle escaped notice for so long despite the plant’s abundance and its growth near large cities suggests that more carnivorous plants are waiting to be discovered off the beaten path.”

The team’s paper was published in the Proceedings of the National Academy of Sciences.

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Qianshi Lin et al. 2021. A new carnivorous plant lineage (Triantha) with a unique sticky-inflorescence trap. PNAS 118 (33): e2022724118; doi: 10.1073/pnas.2022724118

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