Botanists at the University of Wisconsin-Madison and the University of British Columbia have discovered a new carnivorous plant in western North America. The plant called Triantha occidentalis lives in wetlands and marshes from Alaska to California and from the mainland to Montana. In summer, it grows into tall, flowering stems covered with sticky hairs that trap small insects such as midges. Scientists have found that the plant gets more than half of its nitrogen from these captured insects, a welcome boost in its nutrient-poor habitat.
It is the 12th known independent evolution of predation in the plant kingdom and was first discovered in the order Alismatales, a group of predominantly aquatic flowering plants. It is also only the fourth reported predation of monocots, one of the main groups of flowering plants.
“What’s especially unique about this carnivorous plant is that it catches insects near its insect-pollinated flowers,” said lead author Qianshi Lin. “At first glance, it looks like a conflict between carnivorousness and pollination, because you do not want to kill the insects that help you reproduce,” the researcher commented phys.org.
However, the plant seems to be capable of separating a friend from food.
“We believe Triantha occidentalis is capable of this because its glandular hairs are not very sticky and can only trap gnats and other small insects, so much larger and stronger bees and butterflies, which act as its pollinators, are not caught.” says Tom Givenish, professor of botany at Madison State University and co-author of the report.
The discovery was led by Lin and Sean Graham of UBC, who partnered with Givenish and Cecile Anet, professor of botany and statistics at Washington State University at Madison. The researchers reported their findings on Monday, August 9, in the Proceedings of the National Academy of Sciences.
Graham had previously performed genome analysis on Alismatales when his team noticed that Triantha had lost a gene that is often missing in predatory plants.
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The Trianta’s environment also seemed favorable to predation. The carnivorous lifestyle is so energy intensive for plants that it seems that a lot of water and light are needed for their development.
“Only in habitats where nutrients alone are limited can you expect predation to be an advantage,” says Givnish, who previously studied conditions that cause predation and discovered other carnivorous plants not associated with Trianta. Insects can be an excellent source of nutrients that are lacking in soil, especially nitrogen and phosphorus.
In field experiments, Lin fed Triantha fruit flies labeled with the stable nitrogen-15 isotope, which allowed him to track nutrient intake into the plant. Anya helped Lin analyze the results of the experiments.
Using models developed by Givnish, the researchers calculated that the plant got up to 64% of its nitrogen from insects, which is similar to known carnivorous plants and far exceeds the level accidentally absorbed by non-predatory plants.
Lin also discovered that Triantha belongs to a group of carnivorous plants that can directly digest their prey. It produces an enzyme called phosphatase that can break down phosphorus-containing nutrients in its prey. Some carnivorous plants instead rely on microbes to digest prey in puddles of water instead, before the plant can absorb the debris.
In the future, researchers plan to study more species to see how widespread predation is among members of the Triantha genus.
“It looks like there are other members of this group who will turn out to be carnivores,” Givnish says.
The fact that the Trianta’s carnivorous lifestyle has eluded attention for so long, despite the abundance of plant and its growth near major cities, suggests that more carnivorous plants are waiting to be discovered in the wilderness.
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