Carnivorous Plants Turning Vegetarian
June 15, 2012

Carnivorous Sundew Turning Vegetarian

It´s a bad sign when even carnivorous plants decide to embrace a vegetarian lifestyle.

A newly published study in New Phytologist journal has revealed the common Sundew plant is becoming so full from snacking on nitrogen deposits in Swedish bogs, that they´re eating fewer bugs. These bogs are normally scant in the way of nitrogen, therefore the plants have taken to snacking on insects to supplement their diet. However, as human activities (such as industrialization and other burning of fossil fuels) have increased the level of pollution in the air and nitrogen in the soil, these plants don´t have the need to eat these insects anymore, and are therefore are letting them live.

"They're more full-up. If you've got enough food in the fridge, you don't go to the shops to buy some more,” says Jonathan Millet, plant ecologist at Loughborough University in the U.K., speaking with National Geographic.

As often happens, this one little change is having some major implications on the entire ecosystem.

According to Dr. Millet and his team, Sundew plants which live in lightly polluted areas got 57% of their nitrogen from their prey. Plants in more heavily polluted areas, on the other hand, received only 20% and 30% of their nitrogen through prey. While this may sound like a good thing for the Sundew, Dr. Millet says the long-term effects could be dire.

"Basically, it's like adding more fertilizer," said Dr. Millett.

"For an individual sundew it looks like it´s better. They're bigger and they'll probably be fitter and do better, but the problem is that they have to divert resources into being carnivorous."

Carnivorous plants actually thrive in environments with very little nitrogen, as it reduces the competition between plants.

As such, the plants in these areas have evolved to survive by powering their complicated trapping systems. If more plants move into the neighborhood in search of nitrogen-rich soil, these systems could end up hurting the Sundew more than helping them.

"When there's more nitrogen available... the non-carnivorous plants can 'out-compete' them," says Dr. Millett.

"So it's quite likely we'll see less abundance and perhaps local extinctions from carnivorous species. The individual plants get bigger and fitter, but the species as a whole is less well adapted to high-nitrogen environments and will lose out over time."

This study confirmed it´s not just the increased amounts of nitrogen being absorbed that´s harmful to the carnivorous plants. While the amount of prey being consumed by these plants falls, these plants are presumably trying to save their energy buy catching fewer bugs. Therefore, as other plants move in, they´ll be able to easily take over the weakened Sundews.

Dr. Millet thinks other plants, including heather and other grasses, will start to move into the neighborhood and shade these plants. Sundew plants don´t like the shade and therefore could suffer under such cover.

"The carnivorous plants do tend to do better on an individual basis when there is more nitrogen, but this ... isn't enough to keep up with these more competitive plants."

As it stands, there is a large population of Sundew and is not yet feared to become extinct. However, Dr. Millet´s study suggests other plants like it could soon be in trouble.

"I would be surprised if nitrogen [pollution] doesn't have an impact on carnivorous plants" as a group, he said.