During a long walk in the summer of 1860, Charles Darwin noticed for the first time a peculiar phenomenon among plants that puzzles scientists to this day.
On the English heath there was an ordinary sundew (Drosera rotundifolia) with a whole bunch of bugs glued to its leaves.
And that chance meeting brought Darwin to one for 16 years trying to prove that some plants can eat animals, dissolve their proteins with enzymes and absorb the nutrients for growth.
At first, even his wife had trouble believing him.
“He is currently undergoing treatment Drosera like a living creature, and I suppose he’s hoping to prove it’s an animal,’ she said wrote to a friend at the time.
Today, naturalists no longer dispute the existence of carnivorous plants, but that doesn’t mean we fully understand how these curious life forms evolved to attract, capture, hold and digest animal prey, especially large prey like amphibians and small mammals.
Carnivorous plants today come in a wide variety of shapes and sizes, including corkscrew traps and traps. Some, like Droserause simple sticky traps to catch insects, while others, such as the infamous Venus Fly Trap, have developed more complex ‘snap-trap’ prisons for their prey.
Recent genetic research initially suggests snap traps evolved of ‘flypaper’ fall in at least three or four clades independently.
In 2018, a study found evidence that carnivorous plants evolved independently within flowering plants at least 10 times. Time and time again unrelated plants seem to do that reuse similar herbivore genes to better suit a predatory lifestyle.
“These plants have a genetic toolbox and they’re trying to find an answer to the problem of how to become a carnivore,” explained University of Buffalo biologist Victor Albert in 2017.
“And in the end they all come up with the same solution.”
Carnivorous plants usually grow in nutrient-poor areas, such as swamps and wetlandsand a single decent-sized insect can supply a Venusian flytrap with enough phosphorus and nitrogen to last for weeks.
So we have their motivation for creating such complex and energy-intensive traps, and new genetic studies have also begun to unravel the how.
It turns out they co-opted part of a universal plant defense system that uses jasmonate chemicals. Most plants use these to warn each other of danger, but as we found out in 2019, they use fly traps to recruit the enzymes that break down their prey and to engage nutrient transporters.
But this method is only seen in one group of these vegetative predators. Butterworts don’t use the same system, and many other strains’ strategies remain secret.
Until scientists better understand the trade-offs of botanical carnivore, the reason for the evolution of so many animal-hungry plants around the world will likely remain elusive.
And there is no time to waste on future research. In 2020, researchers estimate that a quarter of all known carnivorous plants are threatened with extinction.
If we don’t investigate their mysteries now, we may never get the chance.