A plant frequenting bogs and wetlands from Alaska to California has been harboring a deadly secret. To tolerate nutrient-poor conditions, it has evolved to trap insects in sticky hairs that coat its flowering stems, lapping up their corpses for nitrogen.
Triantha occidentalis, as it’s known to botanical folk, is the 12th known independent evolution of a carnivorous diet among plants. This discovery, published in PNAS, makes it the only member of the Alismatales order to obtain nutrients this way. The order is largely made up of aquatic flowering plants living in habitats that, while rich in moisture, are lacking in nutrients.
What makes this plant stand out among its fellow bloodthirsty comrades is that it has placed its murder weapon rather close to its junk, if you catch our drift, so a balance has to be struck between feeding and… mating. However, it seems T. occidentalis found a way to satisfy both hungers by being selective with its victims.
“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 co-author Tom Givnish, a University of Wisconsin-Madison professor of botany, in a statement.
Suspicion regarding T occidentalis’s diet arose after genomic studies revealed it was missing a gene that’s often missing in carnivorous plants. That, plus the fact that it was known for trapping insects and the poor conditions of its favored hangouts, led researchers to believe it could be the next botanical carnivore.
“Only in habitats in which nutrients and nutrients alone are limiting would you expect carnivory to be an advantage,” said Givnish.
To confirm their suspicions, the team fed T. occidentalis fruit flies laced with the isotope nitrogen-15. Analysis showed that the plants were indeed ingesting the flies, and with the help of models researchers calculated that the plant likely acquires around 64% of its nitrogen from carnivory.
So, we know the plant is eating insects, but how is it eating them? After an insect becomes trapped in its sticky hairs, T. occidentalis releases an enzyme called phosphatase that directly breaks down the prey. This frees up delicious phosphorous-bearing nutrients for the plant to feast upon, without the need for microbes that other carnivorous plants rely on to liquefy their meals.