A Venus flytrap requires a pollinator to make seeds and reproduce. But who those pollinators are have long remained a mystery. One reason: Scientists and gardeners tend to focus on the carnivorous plant’s clever traps. Now researchers have finally looked at which species visit the plant’s delicate white flowers. And they’ve found little overlap with species that serve as the plant’s meals.
There are hundreds of species of carnivorous plants found across the planet. Few, however, attract quite as much fascination as the Venus flytrap. The plants are native to just a small section of North Carolina and South Carolina. But these tiny plants can now be found around the world. They’re a favorite among gardeners, who grow them in homes and greenhouses.
Although scientists have extensively studied the famous trap, they’ve largely ignored the flower that blooms atop a stalk 15 to 35 centimeters (9 to 14 inches) high. That means they’ve also largely missed seeing what pollinates that flower.
“The rest of the plant is so incredibly cool that most folks don’t get past looking at the active trap leaves,” says Clyde Sorenson. He’s an entomologist, or insect biologist, at North Carolina State University in Raleigh.
Because flytraps grow in such a small area of the Carolinas, field studies can be difficult, adds Elsa Youngsteadt. She’s an insect ecologist, also at NCSU. And there’s another problem when studying flytrap pollination. Most people who raise these plants cut off their flowers. Why? It helps the plant put more of its energy into making traps.
Sorenson and Youngsteadt realized that the answer to what pollinates these flytraps was sitting almost literally in their backyard. So they started sleuthing.
Tallying pollinators and prey
Their team collected flytrap flower visitors and prey on four days in May and June 2016. All came from three sites in Pender County, N.C.
“This is one of the prettiest places where you could work,” Youngsteadt says. Venus flytraps are habitat specialists. They’re found only in certain spots of longleaf pine savannas in the Carolinas.
“They need plenty of sunlight but like their feet to be wet,” notes Sorenson. In May and June, the spots where the flytraps grow are “just delightful,” he says. Other carnivorous plants show up there, too. These include pitcher plants and sundews.
The researchers brought their finds back to the lab for identification. They also catalogued what kind of pollen the blooms’ visitors picked up — and how much.
Arthropods include a range of invertebrate animals, including insects, spiders and centipedes. Nearly 100 different arthropod species visited the flowers, the team reports February 5 in American Naturalist. “The diversity of visitors,” says Youngsteadt, “was surprising.” However, only three species — a sweat bee and two beetles — appeared especially important. They were either the most frequent visitors or had carried the most pollen.
Only 13 species were found both in a trap and on a flower. And of nine potential pollinators in that group, none was trapped in high numbers. For a carnivorous plant, “you don’t want to eat your pollinators,” Sorenson says. His team’s data now suggests flytraps do a good job of sparing their helpers.
Keeping pollinator and prey separate
There are three ways that a plant can keep pollinators and prey separate, the researchers note.
Flowers and traps could exist at different times of the year. However, that’s not the case with Venus flytraps. Traps develop earlier but stick around and are active during plant flowering.
The traps and blooms could also be spaced far apart. Pollinators tend to be fliers while prey were more often crawlers, such as spiders and ants. This matches up with the high flowers and low traps. But the researchers would like to do some experiments that manipulate the heights of the structures, Youngsteadt says. That would let them see just how much that separation matters.
The third option is that different scents or colors might lure different species to the flowers and traps. That’s another area for future study, Youngsteadt says. While scent and color are known attractants for the traps, little is known about whether those factors lure in pollinators.
Venus flytraps are considered vulnerable to extinction, Sorenson notes. The plant’s habitat is being destroyed as housing and other developments expand into their areas. What is left of that habitat is being degraded as fires are suppressed. (Fires help clear vegetation and keep sunlight shining on the flytraps.) Finally, people steal flytraps from the wild by the thousands.
While research into flytrap pollinators won’t hold off any of those threats, it could aid in future conservation efforts. “Anything we can do to better understand how this plant reproduces will be of use down the road,” Sorenson says.
But what really excites the scientists is that they discovered something new so close to home. “One of the most thrilling parts of all this,” Sorenson says, “is that this plant has been known to science for [so long], everyone knows it, but there’s still a whole lot of things to discover.”
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arthropod Any of numerous invertebrate animals of the phylum Arthropoda, including the insects, crustaceans, arachnids and myriapods, that are characterized by an exoskeleton made of a hard material called chitin and a segmented body to which jointed appendages are attached in pairs.
beetle An order of insects known as Coleoptera, containing at least 350,000 different species. Adults tend to have hard and/or horn-like “forewings” which covers the wings used for flight.
carnivorous plant A plant that trap animals, usually insects, as food.
conservation The act of preserving or protecting something. The focus of this work can range from art objects to endangered species and other aspects of the natural environment.
diversity A broad spectrum of similar items, ideas or people. In a social context, it may refer to a diversity of experiences and cultural backgrounds. (in biology) A range of different life forms.
ecology A branch of biology that deals with the relations of organisms to one another and to their physical surroundings. A scientist who works in this field is called an ecologist.
entomology The scientific study of insects. One who does this is an entomologist. A paleoentomologist studies ancient insects, mainly through their fossils.
extinction The permanent loss of a species, family or larger group of organisms.
generation A group of individuals (in any species) born at about the same time or that are regarded as a single group. Your parents belong to one generation of your family, for example, and your grandparents to another. Similarly, you and everyone within a few years of your age across the planet are referred to as belonging to a particular generation of humans.
greenhouse A light-filled structure, often with windows serving as walls and ceiling materials, in which plants are grown. It provides a controlled environment in which set amounts of water, humidity and nutrients can be applied — and pests can be prevented entry.
habitat The area or natural environment in which an animal or plant normally lives, such as a desert, coral reef or freshwater lake. A habitat can be home to thousands of different species.
insect A type of arthropod that as an adult will have six segmented legs and three body parts: a head, thorax and abdomen. There are hundreds of thousands of insects, which include bees, beetles, flies and moths.
native Associated with a particular location; native plants and animals have been found in a particular location since recorded history began. These species also tend to have developed within a region, occurring there naturally (not because they were planted or moved there by people). Most are particularly well adapted to their environment.
naturalist A biologist who works in the field (such as in forests, swamps or tundra) and studies the interconnections between wildlife that make up local ecosystems.
pitcher plant A carnivorous plant that traps bugs in traps filled with fluid and shaped like pitchers.
pollen Powdery grains released by the male parts of flowers that can fertilize the female tissue in other flowers. Pollinating insects, such as bees, often pick up pollen that will later be eaten.
pollinate To transport male reproductive cells — pollen — to female parts of a flower. This allows fertilization, the first step in plant reproduction.
pollinator Something that carries pollen, a plant’s male reproductive cells, to the female parts of a flower, allowing fertilization. Many pollinators are insects such as bees.
population (in biology) A group of individuals from the same species that lives in the same area.
prey (n.) Animal species eaten by others. (v.) To attack and eat another species.
savanna A grassland sometimes also populated with trees. Most are fairly dry for part or much of the year.
species A group of similar organisms capable of producing offspring that can survive and reproduce.
threatened (in conservation biology) A designation given to species that are at high risk of going extinct. These species are not as imperiled however, as those considered “endangered.”
vegetation Leafy, green plants. The term refers to the collective community of plants in some area. Typically these do not include tall trees, but instead plants that are shrub height or shorter.