How The Australian Pitcher Plant Became A Flesh-Eater

Researchers have sequenced the full genome of a carnivorous Aussie plant.

A new study investigating the evolution of carnivorous plants has found how the Aussie pitcher plants came to appreciate the taste of flesh.

Pitcher plants capture insects by luring them into a simple trap—a cupped leaf that’s so slippery on the inside, the bugs have trouble climbing out. At the bottom of this pitcher-shaped trap the plants house digestive fluids that help break down the flesh and exoskeletons of the captured prey.

Such plants are found in Australia, the Americas, and Asia, but it was determined back in 1992 that the pitcher plants from different continents are not actually related; surprisingly, they evolved their flesh-eating habits independently from each other.

Curious about how such a trait could evolve several times and yet appear so similar, an international team of researchers recently sequenced the genome of the Australian pitcher plant (Cephalotus follicularis), and compared its digestive juices to two other carnivorous pitcher plants. The study was published last week in Nature Ecology & Evolution.

The Australian pitcher plant (C. follicularis) evolved independently from pitcher plants elsewhere.

Turns out the three species took remarkably similar routes to becoming carnivores. According to genetic analysis, all three plants started using the same ancient proteins as enzymes for digesting prey. Originally, they used these proteins as protection against disease and other threats.

Lead author Mitsuyasu Hasebe from Japan’s Institute for Basic Biology says that the pitcher plants are a true example of a process known as ‘convergent evolution’—when unrelated species develop similar traits.

“Such parallel development often points to a particularly valuable adaptation,” he says.

According to co-author Kenji Fukushima, the plants probably evolved this skill in order to avoid starving to death.

“Carnivorous plants often live in nutrient-poor environments, so the ability to trap and digest animals can be indispensable given the dearth of other sources of nourishment.”

There are hundreds of pitcher plant species around the world. Our Australian version is relatively small—the pitchers are usually between 2-4 centimetres in height, although when the plant flowers it grows a tall stem that can often exceed 60 centimetres.

The biggest carnivorous plant in the world is also a pitcher plant, Nepenthes rajah in Borneo. Its traps can sometimes reach 40 centimetres in height, holding several litres of digestive fluid. This “king of pitcher plants” is so big it’s known to sometimes trap and digest small vertebrates.

Header image: The Australian pitcher plant is quite a small member of the carnivorous trap plant group. PHOTO BY NATALIE MCNEAR, FLICKR/CC BY-NC 2.0

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