How Did Carnivorous Plants Evolve to Eat Meat?

Most plants might seem harmless, but some have developed a taste for meat. Carnivorous plants aren’t big enough to eat humans, but insects and small animals aren’t so lucky. Find out more about why some plants are meat-eaters and how they evolved to be that way.

There are a total of 600 different carnivorous plant species. While they might have evolved separately, these plants shared a common issue: The environments where they were growing lacked sufficient nitrogen and phosphorus in the soil. In order to compensate, these plants evolved to catch and digest prey.

For centuries, people have been enamored with carnivorous plants. After all, plants aren’t meant to be predators, but that doesn’t change the fact that plants all over the world have adapted to become meat eaters. In fact, you can find them on every continent except Antarctica.

While many of them have different adaptations and appearances, they all share three common attributes:

They capture and kill prey
They have a mechanism to facilitate the digestion of the prey
They derive significant benefit from the nutrients they digest

When compared to your typical plant, it might be difficult to see the similarities since carnivorous plants have such specialized parts. So how did they actually come into being?

Carnivorous Plant Beginning

Seventy million years ago, a genetic anomaly turned your regular plant into a carnivore. While in many cases this genetic mutation might have died out, in the case of carnivorous plants it helped them survive and propagate. The early ancestors of carnivorous plants likely lived in the same environment you’ll find today’s meat-eating plants — waterlogged areas such as swamps, bogs, marshlands, and so on. These areas tend to be acidic and low in oxygen, making it difficult for soil to maintain a rich supply of nitrogen — a key nutrient for plants.

Not all waterways are good for carnivorous plants. While they might get their nutrients from animals, they still need the sun for photosynthesis. The trap leaves might be effective at capturing prey, but they’re not great for photosynthesis. In order to balance this out, carnivorous plants tend only to grow in sunny wetlands where there aren’t any large tree canopies or tall grass blocking sunlight. So if you’re looking for a carnivorous plant, focus on wet areas that get a lot of sunlight.

Why wetlands? The same reason why the plants need to have a lot of direct sunlight. The plant’s root system evolved to absorb nutrients from the prey they capture. While most carnivorous plants still have a root system, it’s poorly developed and inefficient. Similar to the leaf tradeoff, the root tradeoff means these plants can only grow in areas with plentiful water since they don’t have a system capable of storing or transporting water efficiently.Why wetlands? The same reason why the plants need to have a lot of direct sunlight. The plant’s root system evolved to absorb nutrients from the prey they capture. While most carnivorous plants still have a root system, it’s poorly developed and inefficient. Similar to the leaf tradeoff, the root tradeoff means these plants can only grow in areas with plentiful water since they don’t have a system capable of storing or transporting water efficiently.

Of course, not all plants that live in the same conditions as carnivorous ones develop a taste for meat. In fact, the most successful wetland plants are from the Typha genus, more commonly known as cattails. These plants are so successful in wetland conditions that they often outcompete other plants thanks to their spongy stems and extensive root system that sucks up whatever nutrients are in the soil.

It’s perhaps because of this very competition that some plants had to find other ways to get nutrients. Not only does the surrounding soil have pitiful amounts of nitrogen and phosphorus, but other plants were just better adapted at absorbing them. In nature, it’s evolve or die, and luckily a mutation made it possible for carnivorous plants to be competitive in this challenging environment.

Steps to Become a Carnivorous Plant

It didn’t happen overnight. In fact, it probably took tens of millions of years for carnivorous plants to perfect this system to obtain as many nutrients from their prey as possible. Scientists recently studied different carnivorous plants (Venus flytrap, pitcher plants, and sundews) and were able to figure out some common steps that needed to happen in order to for these plants to become carnivorous:

Generate a second copy of its DNA. By doing so, the plants were able to still produce regular leaves and roots, but the second pair of genes for these parts were able to serve other functions. Some leaf genes developed into genes for traps while some root genes specialized in finding new ways to absorb nutrients
Start receiving new nutrients from the prey that would fall into the traps. At this point, traditional roots and leaves were no longer necessary and many genes that were not directly tied to carnivorous nutrition disappeared. Most aquatic carnivorous species have a weakly developed root system only meant to keep them anchored to the ground.
The final transformation comes when the plants undergo evolutionary changes to match their environment. The roots and leaves are now trap-specific. What was once the root system now creates enzymes needed to digest and absorb nutrients from prey. Leaves became traps to ensnare the prey. Some plants took a more passive approach and turned their leaves into enticing and slippery landscapes like the pitcher plant. Others, like the Venus flytrap, use modified leaves with sensitive hairs that snap shut on prey when their hairs are triggered multiple times.

Types of Carnivorous Plants

Since plants are not capable of chasing down their prey, they have to come up with elaborate traps to lure their prey. There are five varieties of trapping devices:

Snap – As the name suggests, this trap will close around the prey when it triggers motion sensitive hairs on the leaves of the plant. The most recognizable example of this is the Venus flytrap.

Pitfalls – The leaves of these plants form a long and deep vessel filled with digestive enzymes where the prey falls. The opening of the trap is enticing, but also slippery, ensuring the prey will fall while the sticky enzymes at the bottom prevent the prey from escaping. Pitcher plants are the perfect example of these types of traps.
Flypaper – Similar to actual flypaper that you use, these plants emit a sticky glue (and digestive juices) on their leaves to catch their prey. Some plants, like sundews, can even move to envelop their prey further. Sound familiar? Recent genetic research has shown the Venus flytrap evolved from sundew-like ancestors.
Bladder – this underwater trap is used only by bladderworts. The plant uses a bladder to pump out water, which creates a vacuum within. When a potential meal triggers the bristles on the surface of the bladder, a trap door opens, sucking everything inside before closing again.
Lobster pot – Only found in the carnivorous corkscrew plants, these traps use a technique many fishermen use: Create a trap with an easy entrance, but no visible exit. When small microfauna enter the hollow stalk of the plant, it quickly turns into a trap as the stalk splits and spirals into a confusing maze. The spirals forming the lower portions are also lined with inward-facing hair so whatever is trapped inside cannot reverse direction and go out the same way they came in.

Carnivorous plants might seem like a mystery to many, but their adaptations occurred because they would not have survived otherwise. Many of these plants continue to change and adapt to fit the environment around them.

Not all carnivorous plants absorb creatures directly. In fact, some have evolved to attract creatures in the hopes of collecting their excrement. An example of this is the giant montane pitcher plant. It entices mountain tree shrews with its sweet nectar. While snacking, the shrew often defecates inside the pitcher plant to mark its territory. The feces collects at the bottom of the plant and when it rains, the nutrients (nitrogen and phosphorus) get flushed into the plant.

More Carnivorous Plants in the Future?

Will carnivorous plants continue to grow and evolve? While humans today might not be around to see it, chances are in another 10 million years or so these carnivorous plants might evolve further. Who knows. Maybe one day they will start chasing down their prey!