By the late 1800s, garish stories about killer plants were popping up everywhere. Terrible, tentacle-wielding trees snapped and swallowed unwary travelers in distant lands. Mad professors grew monstrous sundew and pitcher plants on raw steak until their gluttonous creations turned and ate them too.
Young Arthur Conan Doyle stayed closer to science in a yarn involving the ever-popular carnivore, the Venus flytrap. Using brand new botanical knowledge, he accurately described the bilobed traps, the way they caught insects, and how thoroughly they digested their prey. But even his flytraps were impossibly large, large enough to bury and consume a human. Carnivorous, man-eating plants had a moment, and you can thank Charles Darwin for that.
Until Darwin’s day, most people refused to believe that plants eat animals. It was against the natural order of things. mobile animals ate; Plants were food and couldn’t move – if they killed, it had to be in self-defense or by accident. Darwin spent 16 years conducting meticulous experiments that proved otherwise. He showed that the leaves of some plants had been transformed into elaborate structures that not only trap insects and other small creatures, but also digest them and absorb the nutrients released from their corpses.
In 1875 Darwin published insectivorous plants, in which he listed everything he had discovered. In 1880 he published another myth-busting book, The power of movement in plants. The realization that plants can both move and kill inspired not only a hugely popular horror story genre, but also generations of biologists striving to understand plants with such unlikely habits.
Today, carnivorous plants are witnessing another big moment, as researchers begin to find answers to one of botany’s great unsolved mysteries: How did normally docile flowering plants evolve into murderous carnivores?
Since Darwin’s discoveries, botanists, ecologists, entomologists, physiologists, and molecular biologists have studied every aspect of these plants, drowning prey in liquid-filled jugs, immobilizing them with sticky “flypaper” sheets, or imprisoning them in snap traps and underwater suction traps. They detailed what the plants catch and how — and something about the benefits and costs of their whimsical lifestyle.
More recently, advances in molecular science have helped researchers understand the key mechanisms underlying the carnivorous lifestyle: how fast a flytrap snaps shut, for example, and how it transforms into an insect-juicing “stomach” and then into an “intestine” to absorb the remains of its prey. But the big question remained: How did evolution equip these dietary misfits with the means to eat meat?
Fossils have provided almost no evidence. There are very few, and fossils cannot show any molecular details that could point to an explanation, says the biophysicist Rainer Hedrich of the University of Würzburg in Germany, who researches the origins of the carnivore in 2021 Annual review of plant biology. Innovations in DNA sequencing technology now mean researchers can approach the question in a different way, by looking for genes associated with carnivores, pinpointing when and where those genes are turned on, and tracing back their origins.
There’s no evidence that carnivorous plants acquired any of their animal habits by hijacking genes from their animal victims, says Hedrich, although genes are sometimes transferred from one type of organism to another. Instead, a number of recent findings point to the hijacking and repurposing of existing genes that have ancient functions ubiquitous among flowering plants.
“Evolution is sneaky and flexible. It leverages the tools you already have,” he says Victor Albert, a plant genome biologist at the University at Buffalo. “In evolution, it is easier to reuse than to create something new.”
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