How carnivorous Venus flytrap plants feed

This video says about itself:

Best Venus Flytrap Trapping Compilation 2018

Footage from the last 12 months, featuring everything from small flies to snails and mealworms getting trapped.

From the University of Freiburg in Germany:

Venus flytrap snapping mechanisms virtually captured

Biomechanical analyses and computer simulations reveal the Venus flytrap snapping mechanisms

June 23, 2020

Summary: The Venus flytrap (Dionaea muscipula) takes only 100 milliseconds to trap its prey. Once their leaves, which have been transformed into snap traps, have closed, insects can no longer escape. Using biomechanical experiments and virtual Venus flytraps a team has analyzed in detail how the lobes of the trap move.

Freiburg biologists Dr. Anna Westermeier, Max Mylo, Prof. Dr. Thomas Speck and Dr. Simon Poppinga and Stuttgart structural engineer Renate Sachse and Prof. Dr. Manfred Bischoff show that the trap of the carnivorous plant is under mechanical prestress. In addition, its three tissue layers of each lobe have to deform according to a special pattern. The team has published its results in the journal Proceedings of the National Academy of Sciences, USA.

The diet of the Venus flytrap consists mainly of crawling insects. When the animals touch the sensory hairs inside the trap twice within about 20 seconds it snaps shut. Aspects such as how the trap perceives its prey and how it differentiates potential prey from a raindrop falling into the trap were already well known to scientists. However, the precise morphing process of the halves of the trap remained largely unknown.

In order to gain a better understanding of these processes, the researchers have analyzed the interior and exterior surfaces of the trap using digital 3D image correlation methods. Scientists typically use these methods for the examination of technical materials. Using the results the team then constructed several virtual traps in a finite element simulation that differ in their tissue layer setups and in the mechanical behavior of the layers.

Only the digital traps that were under prestress displayed the typical snapping. The team confirmed this observation with dehydration tests on real plants: only well-watered traps are able to snap shut quickly and correctly by releasing this prestress. Watering the plant changed the pressure in the cells and with it the behavior of the tissue. In order to close correctly, the traps also had to consist of three layers of tissue: an inner which constricts, an outer which expands, and a neutral middle layer.

Speck and Mylo are members of the Living, Adaptive and Energy-autonomous Materials Systems (livMatS) cluster of excellence of the University of Freiburg. The Venus flytrap serves there as a model for a biomimetic demonstrator made of artificial materials being developed by researchers at the cluster. The scientists use it to test the potential uses of materials systems that have life-like characteristics: the systems adapt to changes in the environment and harvest the necessary energy from this environment.

Venus flytraps catch spiders and insects by snapping their trap leaves. This mechanism is activated when unsuspecting prey touch highly sensitive trigger hairs twice within 30 seconds. A study led by researchers at the University of Zurich has now shown that a single slow touch also triggers trap closure — probably to catch slow-moving larvae and snails: here.

Carnivorous plants, lecture

This 20 May 2020 video from the Natural History Museum in London, England says about itself:

Plants that bite back | Live talk with NHM scientist

Don’t be fooled by their calm exterior, plants have a dark side.

Join us as we look at the different ways carnivorous plants catch their food and discover the ones you can see growing wild in Britain.

Carnivorous plant genomes, new research

This 2018 video is called True Facts: Carnivorous Plants.

From the University of Würzburg in Germany:

The carnivorous plant lifestyle is gene costly

May 14, 2020

Summary: The genomes of three carnivorous plants — the Venus flytrap, spoon-leaved sundew and the waterwheel plant — have been decoded. The result has caused some surprises.

Plants can produce energy-rich biomass with the help of light, water and carbon dioxide. This is why they are at the beginning of the food chains. But the carnivorous plants have turned the tables and hunt animals. Insects are their main food source.

A publication in the journal Current Biology now sheds light on the secret life of the green carnivores. The plant scientist Rainer Hedrich and the evolutionary bioinformatician Jörg Schultz, both from Julius-Maximilians-Universität (JMU) Würzburg in Bavaria, Germany, and their colleague Mitsujasu Hasebe from the University of Okazaki (Japan) have deciphered and analysed the genomes of three carnivorous plant species.

They studied the Venus flytrap Dionaea muscipula, which originates from North America, the globally occurring waterwheel plant Aldrovanda vesiculosa and the spoon-leaved sundew Drosera spatulata, which is widely distributed in Asia.

All three belong to the sundew family. Nevertheless, they have each conquered different habitats and developed their own trapping mechanisms. In Dionaea and Aldrovanda, the ends of the leaves are transformed into folding traps. The sundew, on the other hand, attaches its prey to the leaf surface with sticky tentacles.

Basic genes for carnivory

The first thing the international research team found out was that, despite their different lifestyles and trapping mechanisms, Venus flytrap, sundew and waterwheel have a common “basic set” of genes that are essential for the carnivorous lifestyle.

“The function of these genes is related to the ability to sense and digest prey animals and to utilise their nutrients,” explains Rainer Hedrich.

“We were able to trace the origin of the carnivory genes back to a duplication event that occurred many millions of years ago in the genome of the last common ancestor of the three carnivorous species,” says Jörg Schultz. The duplication of the entire genome has provided evolution with an ideal playing ground for developing new functions.

Genetic poverty despite a special way of life

To their surprise, the researchers discovered that the plants do not need a particularly large number of genes for carnivory. Instead, the three species studied are actually among the most gene-poor plants known. Drosera has 18,111, Dionaea 21,135 and Aldrovanda 25,123 genes. In contrast, most plants have between 30,000 and 40,000 genes.

How can this be reconciled with the fact that a wealth of new genes is usually needed to develop new ways of life? “This can only mean that the specialization in animal food was accompanied by an increase in the number of genes, but also a massive loss of genes,” concludes developmental biologist Hasebe.

Root genes are active in the trapping organs

Most of the genes required for the insect traps are also found in slightly modified form in normal plants. “In carnivorous plants, several genes are active in the trapping organs, which in other plants have their effect in the root. In the trapping organs, these genes are only switched on when the prey is secure,” explains Hedrich. This finding is consistent with the fact that the roots are considerably reduced in Venus flytrap and sundew. In the waterwheel they are completely absent.

Further research into the trapping function

The researchers now have an insight into the evolution of carnivory in plants and hold three blueprints for this particular way of life in their hands. Their next goal is to gain an even better understanding of the molecular basis of the trapping function.

“We have found that the Venus flytrap counts the electrical stimuli triggered by the prey, can remember this number for a certain time and finally makes a decision that corresponds to the number,” says Hedrich. Now it is important to understand the biophysical-biochemical principle according to which carnivorous plants count.

Fossil carnivorous plants, animals discoveries in amber

This November 2019 video says about itself:

6 of the Coolest Things We’ve Found in Amber

Amber is amazing stuff! It can preserve organisms whole, and essentially freeze them in time, and the specimens we’ve found in it so far range from amazing to downright bizarre. Here are six of the coolest things we’ve found trapped in amber.

Hosted by: Hank Green.

How Venus flytraps catch insects, spiders

This 27 September 2019 video says about itself:

Venus flytraps rarely catch flies, despite their name — instead, spiders and ants make up most of their diet. When a victim walks by and brushes against a trigger hair on the inside of the trap’s modified leaves, it sets off an electrical signal. If the bug doesn’t escape within 20 to 30 seconds, the trap slams shut faster than you can blink!

How carnivorous plants survive

This 2009 video is called Life – Venus Flytraps: Jaws of Death – BBC One.

From the University of Würzburg in Germany:

Venus flytraps: No escape for mosquitoes

July 8, 2019

Summary: Venus flytraps are capable of detecting the movements of even the smallest insects. This mechanism protects the plant against starving from hyperactivity.

Physically bound to a specific location, plants have to devise special ways to secure their supply of vital nutrients. Most plants have developed a root system to the nutrients they need in order to survive out of the soil. But what if nutrient-poor soils fail to provide the necessities of life? Carnivorous plants such as the Venus flytrap have found a way out of this dilemma.

The Venus flytrap is native to the wetlands of North and South Carolina on the East Coast of the USA. Instead of taking in nutrients through its roots alone, the carnivorous plant traps prey within its leaves that can snap shut within a fraction of a second. The plant is capable of sensing prey through delicate trigger hairs on the inside of its flat leaves. Since prey insects come in different sizes and the Venus flytrap cannot afford to be fussy, the plant grows traps across a variety of sizes.

Now researchers from the universities of Würzburg and Cambridge have discovered that the tactile sensors in these traps already respond to minute pressure stimuli, converting them to electrical signals that cause the trap to close. They have published their results in the current issue of Nature Plants.

Trigger hair converts touch into electricity

“Each trap lobe features three to four multicellular hairs which are torsion-resistant except for a notch at the base. When an insect, lured by the smell, colour or nectar of the trap, touches the trigger hair, the hair will yield in the area of the non-reinforced base. This causes the sensory cells in this area to be stretched on one side and compressed on the other side,” says Professor Rainer Hedrich, explaining the operating principle of the Venus flytrap. The biophysicist and plant researcher, who holds the Chair of Botany I at the University of Würzburg, has been studying the carnivorous plant species for some time.

When the sensory cells are deformed in this way, the tactile sensors respond by converting mechanical energy into electrical signals, triggering an action potential, which rapidly propagates from the base of the trigger hair throughout the entire trap. When a trigger hair is touched a second time within a short time period, the process is restarted — and only then does the trap close.

But how much does an insect deflect the trigger hair? What is the minimum size and weight that an insect must have in order to be detected by the Venus flytrap? Professor Hedrich had these questions in mind when conducting his latest study. “It was clear from the beginning that we would not easily get the answers using flying insects,” Professor Hedrich explains. So when looking for a suitable insect prey to use in their experiments, Professor Hedrich and his team opted for ants. Professor Walter Federle, a biomechanics expert and ant specialist at the University of Cambridge, provided the necessary expertise and support for the experiments of the Würzburg plant scientists.

Minimal deflection triggers electrical stimulation

How can ants be made to touch a trigger hair on command? To solve this problem, ant specialist Federle chose leaf-cutting ants. This ant species regularly commutes between the foraging site and the nest. For the experiment, Federle mounted single-trap lobes within the foraging trail of a leaf-cutting ant colony. He then monitored the ant traffic on the flytrap trail using a high-speed camera that recorded all contacts. The result: Federle’s analysis yielded a minimum and maximum trigger hair deflection of 3.5 and 7.5 degrees, respectively.

Now in order to determine the angle and force necessary to trigger an action potential in the Venus flytrap, the scientists replaced the ants with computer-controlled micro-manipulators equipped with special force transducers. After the micro-manipulators had been deposited on the trigger hairs, the deflection angle was varied progressively. “We were surprised to find that our voltage detectors already recorded an action potential at a deflection of around 2.9 degrees,” says Dr Sönke Scherzer, lead author of the study and a scientist in Professor Hedrich’s department. This means that the Venus flytrap already detects the weakest contact with a leaf-cutting ant.

A trap for each fly size

An ant or housefly creates a force when walking which is approximately equivalent to its body weight. So a fly weighing ten milligrams is capable of generating 100 micronewtons, a force that is easily sufficient to excite a large trap. However, if a mosquito weighing just three milligrams ends up in such a large trap, the trigger hairs will not be deflected.

But since a mosquito, too, can be an important source of nutrients, the Venus flytrap has also developed smaller traps during the course of evolution. These mini-traps also respond to the smaller forces generated by the lightweight mosquito. “This trap-size-based sensitivity of the trigger hairs is crucial for the economic efficiency of the traps,” Professor Hedrich explains. After all, it costs the plant much more energy to reopen a large trap than a small one. “If underweight, low-nutrient prey insects were able to trigger large traps, the cost-benefit ratio would turn out negative and the Venus flytrap would slowly starve in the worst case,” Professor Hedrich explains.

When trigger hairs get weary

Once the trap has closed, the insect prey usually does not just accept its fate. Instead it struggles and tries to escape. In its panic, it constantly touches the tactile hairs, triggering up to 100 action potentials in two hours. According to Professor Hedrich, the Venus flytrap takes into account these electrical signals and initiates a corresponding response that ranges from the production and excretion of digestive enzymes to taking up the nutrients from the decomposed prey.

The scientists conducted another experiment to determine how often a single trigger hair can be stimulated within one hour. The result: “From a frequency of a tenth of a hertz, that is one stimulation every ten seconds, the trigger hair starts to exhibit signs of fatigue,” says Sönke Scherzer. At higher frequencies, an action potential was no longer triggered each time a tactile hair is stimulated and eventually the electrical events did not take place at all. When the scientists interrupted the repeated stimulation sequence for a minute, the hair fully regained its mechano-electrical properties.

Sensory cells under the microscope

To build on this research, the researchers aim to find out how the flytrap counts and why the tactile hair stops responding when stimulated at high frequency. For this purpose, they will isolate the trigger hairs and sensory cells and determine a number of properties such as the fatigue and recovery of the ion channels that convert the tactile stimulus to an electrical event.

Carnivorous plant study captures universal rules of leaf making: here.

Canadian carnivorous plants eat young salamanders

This 10 June 2019 video says about itself:

Botanical carnivory: Hungry plants and their salamander prey

Botanical carnivory: New research published by Algonquin Wildlife Research Station student Patrick Moldowan (University of Toronto, Canada), Alex Smith (University of Guelph, Canada), Njal Rollinson (University of Toronto), and colleagues (Teskey Baldwin, Tim Bartley, Hannah Wynen, University of Guelph) demonstrate a sinister side of the plant world. This video shows two young Spotted Salamanders (Ambystoma maculatum) trapped in the pitcher of a Northern Pitcher Plant (Sarracenia purpurea), a carnivorous plant that lives in nutrient-poor bogs. Salamanders for supper? Yes!

Video by: Patrick D. Moldowan.

From the University of Guelph in Canada:

Bug-eating pitcher plants found to consume young salamanders, too

June 7, 2019

Summary: Pitcher plants growing in wetlands across Canada have long been known to eat creatures — mostly insects and spiders — that fall into their bell-shaped leaves and decompose in rainwater collected there. But researchers have discovered that vertebrates — specifically, salamanders — are also part of their diet.

Call it the “Little Bog of Horrors.” In what is believed to be a first for North America, biologists at the University of Guelph have discovered that meat-eating pitcher plants in Ontario’s Algonquin Park wetlands consume not just bugs but also young salamanders.

In a paper published this week in the journal Ecology, the research team reports what integrative biologist Alex Smith calls the “unexpected and fascinating case of plants eating vertebrates in our backyard, in Algonquin Park.”

Pitcher plants growing in wetlands across Canada have long been known to eat creatures — mostly insects and spiders — that fall into their bell-shaped leaves and decompose in rainwater collected there.

But until now, no one had reported this salamander species caught by a pitcher plant in North America, including Canada’s oldest provincial park, a popular destination where the plants have been observed for hundreds of years.

Noting how long the park has held its secret — despite generations of visiting naturalists, its proximity to major cities and a highway running through its southern end — Smith said, “Algonquin Park is so important to so many people in Canada. Yet within the Highway 60 corridor, we’ve just had a first.”

In summer 2017, then undergraduate student Teskey Baldwin found a salamander trapped inside a pitcher plant during a U of G field ecology course in the provincial park.

He’s a co-author on the new paper along with other researchers at U of G and the University of Toronto.

Monitoring pitcher plants around a single pond in the park in fall 2018, the team found almost one in five contained the juvenile amphibians, each about as long as a human finger. Several plants contained more than one captured salamander.

Those observations coincided with “pulses” of young salamanders crawling onto land after changing from their larval state in the pond. Smith said these bog ponds lack fish, making salamanders a key predator and prey species in food webs.

He said some of the animals may have fallen into the plants, perhaps attracted by insect prey. Others may have entered the plants to escape predators.

Some trapped salamanders died within three days, while others lived for up to 19 days.

Prey caught inside the plant’s specialized leaves is broken down by plant digestive enzymes and other organisms in the water held inside the leaf. Smith said other factors may kill salamanders in pitcher plants, including heat, starvation or infection by pathogens.

He said pitcher plants may have become carnivorous to gain nutrients, especially nitrogen, that are lacking in nutrient-poor bog soil.

Other flesh-eating plants grow in nutrient-poor environments around the world. They include sundews, which use their sticky leaves to catch insects, and the Venus flytrap, whose carnivory partly inspired the Seymour plant in the sci-fi musical Little Shop of Horrors.

Meat-eating pitcher plants have been known since the eighteenth century. One species discovered a decade ago in Asia consumes mostly insects and spiders but also captures small birds and mice.

Smith said the Algonquin Park discovery opens new questions for biologists. Are salamanders an important prey source for pitcher plants? Are the plants important “predators” of the amphibians? Might the salamanders compete with plants for insect prey — and even “choke” the plant?

Tongue-in-cheek, he added that the find may also prompt park officials to rewrite interpretive materials. “I hope and imagine that one day the bog’s interpretive pamphlet for the general public will say, ‘Stay on the boardwalk and watch your children. Here be plants that eat vertebrates.'”

Venus flytrap research, from Darwin till now

This 2009 video says about itself:

Attenborough: Venus Fly Trap | BBC Earth

David Attenborough looks at how this well known carnivorous plant captures its prey.

From the University of Chicago Press Journals in the USA:

Venus flytrap ‘teeth’ form a ‘horrid prison’ for medium-sized prey

March 26, 2019

In “Testing Darwin‘s Hypothesis about the Wonderful Venus Flytrap: Marginal Spikes Form a ‘Horrid Prison’ for Moderate-Sized Insect Prey”, Alexander L. Davis investigates the importance of marginal spikes, the “teeth” lining the outer edge of the plant’s snap traps, in successfully capturing prey. He found that Venus flytraps experience a 90 percent decrease in moderate-sized cricket prey capture success when marginal spikes are removed. This effect disappears, however, for larger prey, suggesting that the spikes may provide a foothold for large prey to escape.

The study combined field observations, laboratory experiments and semi-natural experiments, and was the first to test the adaptive benefit of marginal spikes, one of Darwin’s original hypotheses about the Venus flytrap. “We provide the first direct test of how prey capture performance is affected by the presence of marginal spikes, trichomes that provide a novel function in Venus flytraps by forming what Darwin described as a ‘horrid prison'”, Davis writes.

Botanical carnivory is a novel feeding strategy that has arisen at least nine different times in evolutionary history of plants. Pitfall traps evolved independently at least six times and sticky traps five. The snap traps characteristic of the Venus flytrap, however, have most likely evolved only once in the ancestral lineage. Darwin was the first to document evidence for carnivory in flytraps, and proposed that the cage-like structure enhances prey capture success.

For the laboratory portion, Davis and his coauthors assembled “prey capture arenas”, wherein 34 Venus flytraps were set up in planters with “on ramps” for crickets. The number of individual traps open and closed, along with whether or not the closed traps contained prey, were recorded initially, after three days, and again after a week. Davis then removed the marginal spikes from half of the plants. He allowed a week of recovery so the traps could reopen, and conducted a second trial. Cricket mass, the length of the plants’ traps, and the prey capture success rate of the traps on each plant were recorded and analyzed using logistic regression models.

Davis and coauthors then moved to a semi-natural experiment in the North Carolina Botanical Garden. Davis placed 22 plants in the North Carolina Botanical Garden, with half of the traps on each plant with intact marginal spikes and the other half with the spikes removed. Plants were kept on the group in a forested, open area of the gardens, and with ramps that allowed terrestrial arthropod access for a period of 4 weeks. For all prey catches, trap length, as well as prey mass and — digestion permitting — prey type, were recorded. Results were calculated using a generalized linear mixed effects model, then combined with results from the laboratory experiments using Fisher’s method.

Davis found that marginal spikes are adaptive for prey capture of small and medium-sized insects, but not larger insects. In the controlled laboratory prey capture trials, 16.5% of trap closures resulted in successful prey capture, whereas only 5.8% of trap closures were successful when marginal spikes were removed. Similarly, plants in the botanical garden had a prey capture success rate of 13.3% with marginal spikes intact and 9.2% with spikes removed.

The benefits of the marginal spikes were most dramatic for medium-size traps, which experienced the most rapid decline in capture rate for medium-size prey and gained the most from having the marginal spikes intact. Surprisingly, this effect disappeared for larger prey, which Davis speculated could be due to larger insects using the spikes as leverage for prying themselves free.

These findings offer clues for explaining the evolution of one of the most unique plant traits. “Characterizing the role of adaptive traits aids our understanding of selective forces underlying the diversity of trap types and the rarity of snap traps, offering insights into the origins of one of the most wonderful evolutionary innovations among all plants,” Davis writes.

Waterwheel carnivorous plants, new study

This 2015 video is called Closure of a trap of Aldrovanda vesiculosa (waterwheel plant), a carnivorous plant.

From the University of Freiburg in Germany:

A varied menu for the carnivorous waterwheel plant

March 25, 2019

The Freiburg biologists Dr. Simon Poppinga, Anna Westermeier and Prof. Dr. Thomas Speck, working in cooperation with researchers from the Ruhr University Bochum and the Institute of Botany of the Czech Academy of Sciences in Třeboň (Czech Republic), have for the first time reconstructed in detail the “menu” of the carnivorous waterwheel plant (Aldrovanda vesiculosa). This shows that the plant is not at all fussy about what it eats, and catches anything and everything that fits into its trap and triggers the snap mechanism. The team has published its results in the open-access journal Integrative Organismal Biology.

Using its snap traps, which are only a few millimeters in size, the waterwheel plant catches prey animals that live underwater. The traps snap shut within about 20 milliseconds of mechanical stimulation. The basic trapping principle of the waterwheel plant is the same as the terrestrial Venus flytrap (Dionaea muscipula). However, the two types differ not only with regard to the mediums in which they live, that is water and air respectively, but also in the size, rapidity and movement mechanics of their traps. The researchers believe it is important to establish whether the plants have adapted to catching special types of prey, in order to better understand their ecology and evolution. This knowledge is also key to possible conservation measures, because increasing loss of suitable habitat is threatening the waterwheel plant with extinction.

The scientists undertook comparative analyses of the prey composition of a total of eight different populations of the waterwheel plant in Germany and the Czech Republic. This showed that the prey’s mode of locomotion is irrelevant to Aldrovanda, because besides fast swimming prey, the researchers also often found slow crawling animals such as snails in the traps. The 43 prey taxa identified ranged from tiny water mites to comparatively large mosquito larvae and back swimmers that barely fit into the traps. Likewise, the trap size does not act as a morphological filter for certain prey sizes, as large traps also contained small prey animals (and vice versa). Since the waterwheel plant occurs in highly fragmented habitats, which may be very different in terms of the composition of their animal inhabitants, the diverse diet of Aldrovanda could be an advantage over a stricter prey specialization, the researchers speculate.

The Plant Biomechanics Group at the Botanical Garden of the University of Freiburg has a research focus into the investigation of plant movement principles, especially the fast traps of carnivorous plants. The team has already investigated the Aldrovanda traps in respect to their biomechanics and functional morphology as part of an international research cooperation and have transferred their deformation principle into a biomimetic facade shading, the Flectofold.

Asian pitcher plants, American pitcher plants and mosquitoes

This January 2017 video says about itself:

While the carnivorous cravings of most flesh-eating plants are limited to small insects, one exception is the pitcher plant. It can consume anything that fits in its mouth–including a mouse!

From the University of Wisconsin-Madison in the USA:

An ocean apart, carnivorous pitcher plants create similar communities

August 29, 2018

After a six-hour ride over increasingly treacherous roads, it took a full day’s hike up almost 3,000 feet for Leonora Bittleston to reach Nepenthes Camp in the Maliau Basin, an elevated conservation area in Malaysian Borneo with a rich, isolated rainforest ecosystem.

After waiting three years for collecting permits, Bittleston, then a graduate student at Harvard University, entered the basin in search of one thing: pitcher plants. These carnivorous plants have evolved traps to lure, drown and digest animal prey to supplement nutrient-poor soils.

Bittleston needed samples of the liquid inside the pitchers to compare to pitcher plants from much closer to home in Massachusetts and along the Gulf Coast. Though unrelated, both plant families had converged on similar adaptations for trapping prey, and Bittleston wanted to know if the communities of microbes and small animals housed in each liquid-filled pitcher were as similar as the traps themselves.

In new research published Aug. 28 in the journal eLife, Bittleston, University of Wisconsin-Madison botany and bacteriology professor Anne Pringle, and others, reveal that the communities created inside pitcher plants converge just as the shape and function of the plants themselves do. Despite being separated by continents and oceans, pitchers tend to house living communities more similar to one another than they are to their surrounding environments.

Asian pitchers transplanted to Massachusetts bogs can even mimic the natives so well that the pitcher plant mosquito — a specialized insect that evolved to complete its life cycle exclusively in North American pitchers — lays eggs in the impostors.

The researchers say this work provides a much richer picture of how convergence can extend well beyond relatively simple functional roles, like plant carnivory, to include a network of interactions among different species that evolve under related conditions. Bittleston and Pringle collaborated with Naomi Pierce at Harvard, as well as researchers at the Universiti Malaysia Sabah, University of Malaya and Jiangsu University.

Pitcher plants are classic examples of convergent evolution, where unrelated organisms nonetheless home in on similar adaptations to their environment. Along with Venus fly traps and other carnivorous plants, pitcher plants also capture the imagination by turning the tables on animals as they devour them.

But despite that gruesome image, pitcher plants serve as more than just death traps — they are also ecosystems unto their own. Each liquid-filled pitcher houses diverse microbial life and even living complex organisms and insects that escape digestion. It’s those communities that attracted the attention of Pringle and Bittleston.

“We spent hours talking about what a convergent ecosystem would look like”, says Pringle, who began the research while she was at Harvard. “We discussed the idea that similar interactions between species could evolve over and over again.”

Pitcher plants were a natural model to test these ideas. The traps are essentially sterile before they open. Yet during the lifespan of an individual pitcher, they seemed to curate predictable communities of microbes and small invertebrates. This suggested to Pringle and Bittleston that the pitchers created consistent conditions that repeatedly selected for similar communities. Since the Southeast Asian and North American pitchers were so outwardly similar, the researchers wondered if their miniature ecosystems would be as well.

It was a taxing research project that required collecting samples in dense, often inaccessible bogs. Bittleston traveled to state protected areas around the Gulf Coast and to bogs in the Harvard Forest to gather samples from the North American species. And in addition to the trek to the Maliau Basin, she collected fluid from pitchers in Singapore’s protected parks, a comparatively easy, but memorable, venture.

“There were times I was on this very clean Singaporean subway in my field clothes, super sweaty, with these big bags full of tubes with pitcher plant samples,” says Bittleston, who is now a postdoctoral researcher at the Massachusetts Institute of Technology. “So it was a funny scene.”

With more than 330 samples from 14 species in hand, the researchers used advanced gene sequencing technology to get a snapshot of the various species making a home inside the pitchers, as well as the species found in nearby soil and water samples. When analyzed for the number and type of species and similarities in community structure, some clear patterns emerged.

While environmental samples contained a large number of different species, the liquid in both groups of pitcher plants had a greatly reduced diversity, indicating a more specialized environment. And the species that pitchers housed tended to come from the same families. Both Southeast Asian and North American pitchers greatly enriched for bacterial organisms like the Actinomycetales or Enterobacteriaceae as well as insects in the fly order and microscopic, filter-feeding animals called rotifers.

The researchers also set up a field experiment, transporting potted Southeast Asian pitchers to bogs in the Harvard Forest and looking at how the pitcher communities developed.

“And in fact, the Southeast Asian species assembled communities that looked like the North American communities”, says Pringle. “That’s cool.”

One clear example of this similarity was the presence of pitcher plant mosquito larvae, normally found exclusively in North American pitchers, in the non-native Asian pitcher plants. Only the most acidic Asian pitchers were inhospitable to this specialized insect.

Alongside the pitcher plants, Bittleston set out test tubes that mimicked the cylindrical shape of the pitchers. Like the pitchers, these test tubes collected rain water and began to develop miniature ecosystems. But the biological communities in the test tubes assembled were off a bit from the natural pitchers, and the tubes never fooled the mosquitoes, which steered away from them.

“It’s not enough to be a passive receptacle that captures rain water and some drowned insects,” says Bittleston. “There really is something that’s different about being this convergently evolved organism that creates a particular environment that curates a particular community.”

The work lends support to ideas Bittleston and Pringle developed in previous work: that the interactions between different species can converge during evolution just as the forms and functions of individual species can.

“These pitchers are independently evolved, two very different families of plants, but they interact with the microbial communities that they’re assembling within them in some similar manner,” says Pringle. “And we’re finding that those interactions are predictable in some way.”