How carnivorous plants developed their taste for prey

A close-up of the pitchers of Cephalotus follicularis, the Australian pitcher plant. A soup of digestive fluids sits at the bottom of these waxy pitchers, breaking down the flesh and exoskeletons of insects that fall in. The plant was photographed in Western Australia, the only place in the world where the species is known to naturally occur.

Source: Mitsuyasu Hasebe

A new study sheds a bit more light on the unusual, and a bit bizarre, species of carnivorous plants that trap and kill food, instead of drawing their nutrition from sunlight and soil.

A large team of researchers from several institutions in Asia, Australia, Europe and North America have found that carnivorous plant species on different continents all became meat eaters through similar sets of genetic changes.

Like most carnivorous plants, pitcher plants tend to live in nutrient-poor environments, the authors noted in their study. So they catch and digest arthropods (such as insects, spiders, centipedes or similar creatures), or even small animals such as amphibians.

Pitcher plants take their name from the "pitchers" or cups of fluid that line their limbs. The pitchers have slippery inner walls with a pool of digestive fluids sitting at the bottom of the cup. The secreted juices and scents lure the plants' prey, which they trap and slowly dissolve.

The team compared genetic information from three different species of carnivorous pitcher plant: one from Asia, one from Austrialia and a third from the Americas.

The similarities they found were striking. Through a series of genetic changes, all three species converted certain common plant enzymes, typically meant for self-defense or immunity, into ones that can aid digestion.

One such enzyme is chitinase, used to disintegrate the "chitin" that makes up the exoskeletons of insects. Another enzyme aids with grabbing the nutrients from broken down material.

This is a notable example of "convergent evolution," where species that arise independently at great distances from each other end up looking and behaving similarly by responding to similar challenges in their environments, the researchers said in their study, which was published Monday in the journal Nature Ecology & Evolution.

That they evolved independently may suggest these changes were particulary valuable or useful, but it also suggests there may be a limited number of ways a plant can become a carnivore.

"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," said study co-author Victor A. Albert, a biologist at the University at Buffalo, in a news release. "And in the end, they all come up with the same solution."

There are other examples of convergent evolution in nature. For example, Albert and his colleagues have previously shown that the development of caffeine in coffee is distinct from the way caffeine developed in tea and chocolate.