This Flower Hides a Secret: It’s Truly a Carnivore
This wildflower looks innocent. Found in wetlands not far from major cities in the Pacific Northwest, it attracts pollinators with white flowers on a long, sticky stem. You can even buy Western False Asphodel seeds from garden stores.
But, according to a new study published Monday in the Proceedings of the National Academy of Sciences, botanists have overlooked one characteristic trait of the perennial: it is the newest and most unexpected carnivorous plant in the world.
There are 13 known families of carnivorous plants, from insectivorous sundew and Venus flytrap to pitcher plants large enough to drown and devour a mouse. Most live in sunny, moist habitats where vital nutrients are scarce – peat bogs, acid bogs, jungle roofs – and have to get their food from living prey.
“Carnivorous plants usually have a strong signal that they are carnivores,” said Qianshi Lin, a botanist at the University of British Columbia and author of the study. “They usually grow with other carnivorous plants in nutrient-poor environments. And they usually have a structure that can trap insects. “
While the western false asphodel is found in environments where other carnivorous plants appear, Dr. Lin that no one suspected that he could also be carnivorous. “This plant has long been ignored because it is of no use and people just don’t know much about it.”
During the summer bloom, western false asphodels produce leafless flower stalks up to 31 inches in height covered with sticky hairs. While herbarium specimens often have small flies or beetles on these hairs, it was widely believed that the hairs were part of the plant’s defense strategy, killing insects that could attack the leaves and flowers, said Dr. Lin.
The first indication that the plant had an appetite for insects came when T. Gregory Ross, also of the University of British Columbia, noticed markers in plant genetics that are sometimes associated with carnivorous plants. That was enough for Dr. Lin and her colleagues to check again.
In order to prove that a plant is carnivorous, one has to show that nutrients migrate from animal to plant. To test this, Dr. Lin and her colleagues laced fruit flies with nitrogen-15 isotopes and placed them on the stems of the false aphodel as well as on the carnivorous sundew and the more harmless migratory herb.
When they checked the nitrogen levels on all three plants, Dr. Lin, they found that the sundew and the false asphodel had ingested roughly the same amount of nitrogen isotopes. And to hold it in place, the hair on the stem of the false asphod secreted a phosphatase, a digestive enzyme that many carnivorous plant species use to pull phosphorus from insects. The western false asphod actually digested prey.
“We found that the nutrients got into the flowers and fruits first,” said Dr. Lin and indicated that the supplementary feeding of the insects helped the plant with reproduction. And while more study is needed, it is possible that the plant is storing excess insect nutrients in its roots to support next year’s flowering period.
Among the predatory plants, the western false asphod is so far unique: No other species only uses flower stalks to catch prey. “Most will avoid having their traps around their reproductive parts because that would trap or kill their pollinators, which is obviously bad for them,” said Dr. Lin. “That’s pretty unusual.”
To get around this problem, Dr. Lin, the plant’s hair and secretions appear to be adapted only to very small prey – mosquitoes and tiny flies – and are most likely too weak to accidentally catch a butterfly or a bee.
Western false asphodeles could be a new example of how certain plants adapt previously existing structures to carnivores. Plants such as the sticky purple geranium and tomato also have adhesive hairs on their surface, which are generally regarded as a defense mechanism. But as soon as you already catch insects, Dr. Lin, it could be a relatively short evolutionary step for plants growing in impoverished environments to digest.
But does that count as a fully-fledged carnivore? Andreas Fleischmann, curator for vascular plants at the Bavarian Natural History Collections, said that, in his opinion, the main criterion for carnivorous plants is not whether the plant digests insects, but whether it attracts them.
It has not yet been shown that the false asphodel actively attracts the insects it eats, he said. The vast majority of carnivorous plants deliberately lure their prey to special leaf traps with enticing scents and eye-catching colors. The wrong asphodel can represent a different evolutionary strategy: don’t waste the insects you defensively kill, said Dr. Fleischmann.
However, the study raises the intriguing possibility that there are other plant species – perhaps even known ones – whose insect digestion has not yet been noticed. The western false asphodel has three sister species that have yet to be tested and that may also be carnivores.
“It’s a good reminder that even in familiar environments we still don’t know much about the ecology of many individual plant species,” said Dr. Lin.