How Did Carnivorous Plants Evolve Their Taste For Meat?

The Cephalotus follicularis pitcher plant, native to Australia. Mitsuyasu Hasebe

Josh Davis 07 Feb 2017, 22:22

With their taste for meat, carnivorous plants have long captured people’s fascination. Whether they're feasting on insects, rats, or even tree shrew poop, how the plants turned the tables on what would usually be their predator is an intriguing question. Now, researchers think they have figured out how distantly related pitcher plants have all come up with the same solution.

Pitcher plants, those carnivorous plants that catch their prey in modified leaves filled with digestive enzymes, are found right around the world, including Australia, Asia, and the Americas. But the interesting thing is that they all evolved independently on different branches of the evolutionary tree. This gave the researchers a brilliant opportunity to see if there were any common factors linking them, apart from their superficial resemblance.

After sequencing the genome of one species native to Australia, Cephalotus follicularis, the researchers were able to figure out how they developed the digestive enzymes necessary to break down captured prey. They found that the plant had co-opted the genes usually used to produce proteins in response to environmental stress, such as from herbivores munching on their leaves, and tweaked them to produce the deadly enzymes.

But after comparing these genetic alterations to other distantly related pitcher plants from other parts of the world, they found somewhat of a surprise. Rather than simply looking like each other, it seems that the different carnivorous plants have also made strikingly similar genetic alterations. All three pitcher plants analyzed had taken the genes normally reserved for self-defense and used them to produce enzymes such as chitinase instead. Chitinase allows the plants to break down and digest the tough exoskeleton of insects.

“It suggests that there are only limited pathways for becoming a carnivorous plant,” explains University at Buffalo’s Victor A. Albert, co-author of the study published in Nature Ecology and Evolution, in a statement. “These plants have a genetic tool kit, and they're trying to come up with an answer to the problem of how to become carnivorous. And in the end, they all come up with the same solution.”

This is an impressive example of what biologists term convergent evolution. This is when two completely unrelated animals that are either living in a similar environment or niche evolve similar adaptations, such as numbats and anteaters, or ichthyosaurs and dolphins. “Such parallel development often points to a particularly valuable adaptation,” says Mitsuyasu Hasebe, who led the investigation.

The likely reason for the plants all coming up with the same solution is that they live in similar environments. Living in nutrient-poor ecosystems, the ability to trap insects in order to gain nutrients would be a vital adaptation to survive.

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