On Alien Worlds, Some of the Plants Might Want to Eat You (If You’re a Bug)
Especially in environments where there’s not much else to eat.
In a recent article published in the Proceedings of the National Academy of Sciences, Qianshi Lin from the University of British Columbia in Canada and colleagues report finding a new lineage of carnivorous plants in North America. The plant, Triantha occidentalis, secretes its own enzymes to digest small insects captured in sticky traps adjacent to its flowers, which still leaves large bees and butterflies free to pollinate the flowers. It’s the first time this particular strategy has been seen in carnivorous plants—all the more surprising, since Triantha is found close to urban centers on the Pacific Coast, and apparently nobody noticed them before.
There are about 650 known species of carnivorous plants, out of a total of 300,000 or so vascular plants. Most of the 650 are found in bogs. About 50 species are aquatic, but some are even found on the edges of deserts or growing on limestone.
Might we expect to find this type of plant on an alien world that hosts complex life? Probably yes. Charles Darwin was fascinated by carnivorous plants and thought of them as an example of convergent evolution. His assumption was validated much later by genomic studies showing that carnivory evolved independently in flowering plants at least eleven times. It seems to occur as a response to a scarcity of nutrients, especially a lack of nitrogen. Such plants were around as far back as the Cretaceous era more than 65 million years ago, and they’ve demonstrated amazing creativity in trapping bugs, not only with sticky “glue” such as Triantha occidentalis uses, but with rapid leaf movements—like the Venus flytrap—or by creating an internal vacuum to suck in unfortunate critters.
Carnivorous plants have also inspired science fiction writers. In the 1951 novel (and later movie) The Day of the Triffids, giant mobile plants start killing off survivors in a post-apocalyptic world. In the 1960 film The Little Shop of Horrors, a plant feeds on human blood, and in an early Star Trek episode, the Enterprise comes across a world where plants have won a war for dominance over animals (Captain Kirk and crew only find the remains of extinct creatures).
Back to Earth. No carnivorous plant is known to capture prey larger than a beetle. And even on an alien planet, they would be unlikely to eat larger animals (legends about man-eating trees notwithstanding). But they’re yet another example of the diversity of life on our own world, and the likelihood that even stranger things are out there, waiting to be discovered.