Quantcast
Animals
Amy M Jasperson / Flickr

Friend or Food? Why Venus Flytraps Don’t Eat Their Pollinators

By Clyde Sorenson, Elsa Youngsteadt and Rebecca Irwin

The Venus flytrap, Dionaea muscipula, lives in a tough neighborhood. It only grows in 12 counties in coastal North and South Carolina, in soils that are very nutrient-poor and often waterlogged. To augment these starvation resources, it captures and digests insects and other animal prey.


Of the roughly 600 known species of carnivorous plants worldwide, the Venus flytrap is by far the most famous; it fascinated Charles Darwin and many other naturalists since his time. Scientists have spent an extraordinary amount of time and effort trying to understand how its unique active snap-trap leaves close so quickly. But, for the Venus flytrap, no one has ever paid much attention to the critical service that animals provide for most flowering plants: pollination.

With colleagues at North Carolina State University, the North Carolina Botanical Garden and the U.S. Fish and Wildlife Service, we recently set out to discover who pollinates the Venus flytrap. We wanted to know whether the plant preyed on the same insects that pollinate it—and if it did not, to begin to understand why.

The Predator's Dilemma

The last thing a carnivorous plant "wants" to do is consume an insect that has pollen on it from another plant of its species—especially if insects that transport the pollen efficiently are uncommon. Eating one's pollinators wastes the energy used to make that pollen, and it could reduce the number of potential seeds a plant can make.

Scientists have proposed three mechanisms that can help explain how carnivorous plants avoid making this evolutionary mistake. First, the plant's flowers and traps can open at different times of the growing season, as occurs in some pitcher plants. Second, the flowers and traps can use different attractants, such as scents or colors, as is true of some sundews. Third, its flowers can be located away from its traps.

Venus flytraps in bloomClyde Sorenson, CC BY-ND

We know that the Venus flytrap's flowers and traps are both open at the same time, so separation in time does not explain how the plant avoids eating its allies. The plant's flowers typically are located 6 to 10 inches above its traps on a long, bare stalk. The traps, which can snap shut in less than a second when anything touches their sensitive trigger hairs, are usually very close to the ground.

The plant's architecture thus suggests that maybe separation in space helps to protect pollinators. To understand whether or not Venus flytraps successfully avoid eating their pollinators through another mechanism, we first had to compare the insects found on the flowers to those found in the traps.

Identifying Flytrap Pollinators and Prey

We spent a total of almost 30 person-hours collecting all the arthropod visitors we could find in Venus flytrap stands in coastal North Carolina. Most of the insects and spiders we caught were captured straight into small plastic vials, but we used nets for particularly agile individuals.

We put the creatures we captured on dry ice, which quickly killed them, took them back to our lab, and swabbed them with dyed gelatin to remove any pollen. The dye stained the pollen so we could identify and count it. Then we identified the arthropods and the different kinds of pollen they carried, if any. In total we collected, swabbed and identified 409 insects and spiders.

We also carefully removed captured prey from plants' closed traps and popped these specimens into small vials of alcohol for identification in the lab. Some were still kicking when we extracted them, while others had been reduced to empty husks by the digestive enzymes that flytraps secrete from their leaves when they catch prey. However, we were able to successfully identify 212 individuals.

Longhorned beetle on a Venus flytrap flowerClyde Sorenson, CC BY-ND

Pollinators: Bees and Beetles

The Venus flytrap has beautiful, saucer-shaped white flowers about three-quarters of an inch wide. This kind of flower frequently attracts a wide range of insects. We captured almost a hundred different species from flytrap flowers.

Most of the specimens carrying flytrap pollen—which has huge, distinctive grains—were either bees or beetles. A small green sweat bee, a checkered beetle and a flower longhorn beetle appear to be the three most important pollen transporters, measured by their abundance in the flowers and the amount of pollen they carried.

Three-quarters of the insects we retrieved with flytrap pollen on them also carried pollen from other plants blooming at the same time in the vicinity. This told us that most of these insects were not focusing solely on flytraps. Pollinators that carry flytrap pollen and visit other flowers may "waste" the flytrap pollen by depositing it on those flowers. And pollen from other species carried to flytrap flowers by "unfaithful" pollinators can interfere with flytrap pollen, if it finds its way to the flower's stigma.

Prey: Spiders and Ants

The prey items we removed from the traps were also diverse, but two-thirds were either spiders or ants. We did not find any of the 10 most frequent flower visitors in the traps, except for one crab spider. Most of the small proportion of species we found in both traps and flowers did not turn out to be carrying pollen when we retrieved them from flytrap flowers.

These findings indicate that there is very little overlap between prey species and pollinator species. Most of the insects that visit flytrap flowers are capable of flight and use that ability to get to the flowers. In contrast, most of the prey animals find their way into the traps by walking into them. (A better name for the plant might be "Venus spidertrap.")

Our findings suggest that physical separation between the Venus flytrap's flowers and traps helps prevent the plant from consuming its pollinators. But we can't yet rule out other mechanisms that may also help keep the plant from eating its allies.

Venus flytrap habitatJennifer Koches, USFWS

Prized Plants

The Venus flytrap is threatened, and its numbers are declining. North and South Carolina's human populations are growing, and the flytrap's coastal habitat is highly desirable for development. The plant requires frequent low-intensity fires to maintain its exposure to the sun; in many places, humans have suppressed these fires.

More perniciously, poachers collect the plants illegally for sale to unsuspecting plant lovers. Poaching wild flytraps is now a felony in North Carolina. And a group of scientists has petitioned the U.S. Fish and Wildlife Service to list the Venus flytrap as an endangered species. Going forward, understanding the Venus flytrap's reproductive ecology will be critical for conserving this remarkable plant.

Reposted with permission from our media associate The Conversation.

Show Comments ()

EcoWatch Daily Newsletter

Sponsored
Politics
Scott Pruitt speaking at meeting at the USDA headquarters in Washington, DC, on Jan. 17. Lance Cheung / USDA

Breaking: Sierra Club Demands Pruitt’s Emails After Only 1 Disclosed by EPA

As part of ongoing litigation, the Sierra Club has demanded that the U.S. Environmental Protection Agency (EPA) search Scott Pruitt's personal email accounts for work-related emails, or certify clearly and definitively that the administrator has never used personal email for work purposes. The demand comes on the heels of a successfully litigated Freedom of Information Act (FOIA) request for all of EPA Administrator Scott Pruitt's email and other communications with all persons and parties outside the executive branch. These facts were first reported in Politico early this morning.

Keep reading... Show less
Animals

Iceland Flouts Global Ban to Slaughter First Protected Fin Whale of New Hunting Season

Iceland's multi-millionaire rogue whaler Kristján Loftsson and his company Hvalur hf have resumed their slaughter of endangered fin whales in blunt defiance of the international ban on commercial whaling.

The hunt is Iceland's first in three years and marks the start of a whaling season that could see as many as 239 of these majestic creatures killed.

Keep reading... Show less
Food
Life- Trac / CC BY-SA 3.0

Farm Bill With Huge Giveaways to Pesticide Industry Passes House

A farm bill that opponents say would harm endangered species, land conservation efforts, small-scale farmers and food-stamp recipients passed the U.S. House of Representatives 213 to 211, with every House Democrat and 20 Republicans voting against it, The Center for Biological Diversity reported.

Keep reading... Show less
Energy
First gas from the Oselvar module burns on the flare of the BP Ula oil platform in the North Sea. Varodrig / CC BY-SA 3.0

Oil and Gas Operations Release 60 Percent More Methane than EPA Thought, Study Finds

A study published Thursday found that U.S. oil and natural gas operations release 60 percent more methane than currently estimated by the U.S. Environmental Protection Agency (EPA), according to a press release from the Cooperative Institute for Research in Environmental Sciences (CIRES) at University of Colorado, Boulder.

Keep reading... Show less
Sponsored
Health
Pexels

Natural Remedies: 8 Plants That Promote Wellness

It may seem like natural remedies are having a moment, but the trend is nothing new. Herbalism—the use of plants for their medicinal properties—has been around long before modern-day pharmacies, and certain sprigs and leaves are still touted for their healing powers. Whether you're planning your next natural shopping trip or want to try growing some helpful herbs at home, this overview can help you get started.

Keep reading... Show less
Food
Vegetables in Whole Foods Market. Masahiro Ihara / CC BY 2.0

Food's Environmental Impact Varies Greatly Between Producers

By Jason Daley

There's no way around it—everything in the grocery store, from nuts and kale to beef and apples, has an environmental impact. Fertilizer causes water pollution, farm fields can encroach on habitat, and a lot of carbon gets released when food is transported from one place to another. But it turns out not every stalk of broccoli or pound of Gouda has the same ecological footprint. A new study of food systems in the journal Science shows the same items sitting next to each other on the shelf can have radically different impacts.

Keep reading... Show less
Sponsored
Politics
U.S. Senator Ted Cruz of Texas. Gage Skidmore / Flickr / CC BY-SA 2.0

GOP Senators Demand Probe of Federal Grants on Climate Change

A group of Republican senators are calling for an investigation of the National Science Foundation (NSF) over a program that "[turns] television meteorologists into climate change evangelists," according to a Wednesday press release from the office of Sen. Ted Cruz (Texas).

Keep reading... Show less
Popular
pxhere

World's Plastic Waste Problem Now Predicted to Reach 111 Million Metric Tonnes by 2030

Mountains of plastic waste are building up around the globe after China implemented a ban on other countries' trash.

By 2030, an estimated 111 million metric tons of single-use drink bottles, food containers and other plastic junk will be displaced because of China's new policy, according to a new paper from University of Georgia researchers, who cited UN global trade data for their study.

Keep reading... Show less
Sponsored

mail-copy

The best of EcoWatch, right in your inbox. Sign up for our email newsletter!