The Floating Bladderwort


A carnivorous plant species that uses its radially arranged stolons like tiny pontoons to float at the waters surface may sound like something out of a science fiction novel. However, it is a very real strategy  adopted by one of the coolest carnivorous plants in North America. Utricularia inflata is one of the largest species of floating bladderwort on this continent and it is a species worth knowing.

Sometimes referred to as the swollen bladderwort, this species enjoys a native range that extends through much of the southeastern United States. For most of the year it exists in a state quite similar to other aquatic bladderworts. It has no true roots or leaves. Instead it produces a long, filiform stolon covered in tiny filaments that act as leaves with bladder traps situated at their tips. It sits in the water  column, gobbling up anything small and unfortunate enough to stumble into it.


When flowering time approaches, these aquatic carnivores begin producing a different kind of stolon. Arranged like spokes on a wheel, the plant puts out swollen, air-filled stolons that float at the waters surface. These structures support the inflorescence. Flowers are bright yellow and resemble those of many other bladderwort species. Entire bodies of water can literally erupt in a sea of yellow bladderwort flowers when the right conditions present themselves.


As mentioned, this species is carnivorous. It uses tiny bladder traps to suck in unsuspecting prey. Their diet is varied and includes pretty much anything that can fit into its bladder traps. One research paper reports both animal (rotifers, cladocerans, copepods, annelids, rhizopodeans, as well as small insects) and "plant" (Bacillariophyta, Chlorophyta, Cyanophyta, and Euglenophyta) prey.

Unfortunately these plants have been introduced far outside of their native range. In many areas they are becoming prevalent enough to be considered invasive. For instance, research done in the Adirondack Mountains of New York found that the presence of introduced populations of U. inflata caused significant changes in nutrient cycling, sediment chemistry, and overall net primary productivity.

This is a very neat species well worth a closer look. That being said, if you are a hobbyist such as myself, it is very important to remember that we should never release a species (no matter how cool it is) into areas where it isn't native.

Photo Credit:, Dr. Mark Whitten, [3] [4]

Further Reading: [1] [2]

Gooey Pitcher Fluids


There seems to be no end to the diversity of colors, shapes, and sizes exhibited by Nepenthes and their pitchers. These wonderful carnivorous plants grow these pitchers as a means of supplementing their nutritional needs as the habitats in which Nepenthes are found are lacking in vital nutrients like nitrogen. There are as many variations on the pitcher theme as there are Nepenthes but all function as traps in one form or another. How they trap insects is another topic entirely and some species have evolved incredible means of making sure prey does not escape. Some of my favorites belong to those species that employ sticky mucilage.

Arguably one of the most iconic of this type is Nepenthes inermis. This species is endemic to a small region of Sumatra and, to date, has only been found growing on a handful of mountain peaks in the western part of the country. The specific epithet ‘inermis’ is Latin for ‘unarmed’ as was given in reference to the bizarre upper pitchers of this plant. They look more like toilet bowls than anything carnivorous and indeed, they lack many of the features characteristic of other Nepenthes pitchers such as a peristome and a slippery, waxy coating on the inside of the pitcher walls.


These may seem like minor details but consider the role these features play in other Nepenthes. A peristome is essentially a brightly colored, slippery lip that lines the outer rim of the pitcher mouth. Not only does this serve in attracting insect prey, it also aids in their capture. As mentioned, the peristome can be extremely slippery (especially when wet) so that any insect stumbling around on the rim is much more likely to fall in. Once inside, a waxy coating on the inside of some pitchers aids in keeping insects down. They simply cannot get purchase on the waxy walls and therefore cannot climb back out. So, for N. inermis to lack both features is a bit strange.

Another interesting feature of N. inermis pitchers is the highly reduced pitcher lid. It hasn’t disappeared completely but compared with other Nepenthes, this pitcher lid barely registers as one. For most Nepenthes, pitcher lids serve multiple functions. For starters, they keep the rain out. Nepenthes are msot at home in humid, tropical climates where rain is a daily force to be reckoned with. For many Nepenthes, rain not only dilutes the valuable digestive soup brewing within each pitcher, it can also cause them to overflow and dump their nutritious contents. Pitcher lids can also help in attracting prey. Like the peristome, they are often brightly colored but many also secrete nectar, which insects find irresistible. Lured in by the promise of food, some insects inevitably fall down into the pitcher below.

Looking into the pitcher of  Nepenthes inermis .

Looking into the pitcher of Nepenthes inermis.

Considering the importance of such structures, it becomes a little bit confusing why some Nepenthes have evolved away from this anatomy. The question then remains, why would a species like N. inermis no longer produce pitchers with these features? Amazingly, the answer actually lies within the pitcher fluid itself.

Tip over the upper pitchers of N. inermis and you will soon discover that they are filled with an extremely viscous mucilage. It is so viscous that some have reported that when the pitchers are held upside down, the mucilage within can form an unbroken stream of considerable length. Its the viscosity of this fluid that is the real reason that N. inermis is able to capture prey so easily. Insects lured to the traps can catch a drink of the nectar on the tiny lid. In doing so, some inevitably fall down into the pitcher itself.

The upper pitcher of the closely related  Nepenthes dubia .

The upper pitcher of the closely related Nepenthes dubia.

Instead of slippery walls or downward pointing hairs keeping the insects in, the viscous pitcher fluid quickly engulfs the struggling prey. Some have even suggested that the nectar secreted by the tiny lid has narcotic effects on visiting insects, however, I have not seen any data demonstrating this. Once caught in the fluid, insects easily slide their way down into the depths of the pitcher where they can be digested. This is probably why the pitchers are shaped like tiny toilet bowls; their shape allows for a large sticky surface area for insects to get stuck while prey that has already been captured is funneled down to where digestion and absorption takes place. In a way, these types of pitchers behave surprisngly similar to the sticky traps utilized by other carnivorous plants like sundews (Drosera spp.).

The viscous fluid also comes in handy during the frequent rains that blanket these mountains. As mentioned above, rain would quickly dilute most pitcher fluids but not when the pitcher fluid itself is more dense. Water sits on top of the viscous mucilage and when the pitchers become too heavy, they tip over. The water readily pours out but little if any of the pitcher fluid is lost in the process. It seems that species like N. inermis no longer fight the elements but rather have adapted to meet them head on. As such, they no longer have a need for a large pitcher lid.

Nepenthes jamban  takes the toilet bowl shape to the extreme.

Nepenthes jamban takes the toilet bowl shape to the extreme.

Nepenthes inermis is not alone in having evolved pitchers like this. Viscous pitcher mucilage is a trait shared by its closest relatives - N. dubia, N. flava, N. jacquelineae, N. jamban, N. talangensis, and N. tenuis, as well as even more distantly related species such as N. rafflesiana. Because prey capture is so important for the fitness of individuals, it is no wonder that so many different forms have evolved within this genus. In fact, many experts believe that variations in the way in which prey is captured and utilized is one of the main reasons why Nepenthes have undergone such a dramatic adaptive radiation.

Sadly, the uniqueness in form and function of these pitchers has landed many of these species on the endangered species list. As if habitat destruction wasn’t already pushing some to the brink, species like N. inermis are being poached at alarmingly unsustainable rates. Due to their limited distributions, most populations simply cannot recover from even moderate levels of harvesting. The silver lining in all of this is that many Nepenthes are extremely easy to grow and propagate provided their basic needs are met. As more and more folks enter into the carnivorous plant hobby, hopefully more and more people will be sharing seeds, cuttings, and tissue cultured materials. In doing so, we can hopefully reduce some of the pressures placed on wild populations.

Photos via Wikimedia Commons

Further Reading: [1] [2] [3]

Crab Spiders and Pitcher Plants: A Dynamic Duo


Most pitcher plants in the genus Nepenthes seem pretty adept at catching prey. These plants specialize in nutrient-poor soils and their carnivorous habit evolved as a means of supplementing their nutritional needs. Despite the highly evolved nature of their pitfall traps (which are actually modified leaves), Nepenthes aren’t perfect killing machines. In fact, some get a helping hand from seemingly unlikely partners.

Spend enough time reading about Nepenthes in the wild and you will see countless mentions of arthropods hanging around their pitchers. Some of these inevitably become prey, however, there are others that appear to be taking advantage of the plant. Nepenthes don’t passively trap arthropods. Instead, they lure them in with bright colors and the promise of tasty treats like nectar. This is not lost on predators like spiders, who are frequent denizens of pitcher mouths.


Most notable to Nepenthes specialists are some of the crab spiders that frequently haunt Nepenthes traps. These wonderful arachnids sit at the mouth of the pitcher and ambush any insects that try to pay it a visit. Often times both predator and prey fall down into the pitcher, however, thanks to a strand of silk, the spiders easily climb back out with their meal. This may seem like bad news for the pitcher, however, recent research based out of the National University of Singapore has shown that this relationship is not entirely one sided.

By studying the interactions between spiders and pitcher plants both in the lab and in the field, ecologists discovered that at least one species of pitcher plant (Nepenthes gracilis) appears to benefit greatly from the presence of crab spiders. The key to understanding this relationship lies in the types of prey N. gracilis is able to capture when crab spiders are and are not present.

Not only did the presence of a resident crab spider increase the amount of prey in each Nepenthes pitcher, it also changed the types of insects that were being captured. Crab spiders are ambush predators that frequently attack prey much larger than themselves. It may seem as if this is a form of food robbery on the part of the crab spider but the spiders can’t eat everything. When they have eaten their fill, the spiders discard the carcass into the pitcher where the plant can make quick work digesting it for its own benefit.

Over time, simply having a spider hunting on the trap led to a marked increase in the number of insects in each pitcher compared to those without a spider. Even if these meals are already half eaten, the plant still gains nutrients. Additionally, the types of prey captured by pitchers with and without crab spiders changed. The spiders were able to capture and subdue insects like flesh flies, which normally aren’t captured by Nepenthes pitchers. As such, the resident crab spiders make available a larger suite of potential prey than would be available if they weren’t using the pitchers as hunting grounds.


The crab spiders may benefit the pitcher plant in other ways as well. Research on crab spiders has shown that their bodies are covered in pigments that register high in the UV spectrum. Insects can see UV light and often use it as a means of finding flowers as plants often produce UV-specific pigments in their floral tissues. The wide array of UV patterns on flowers are there to guide their pollinators into position. Researchers have documented that insects are actually more likely to visit flowers with crab spiders than those without, which has led to the idea that UV pigments in crab spiders actually act as insect attractants. Visiting insects simply cannot resist the UV stimulus and quickly fall victim to the resident crab spider.

Could it be that by taking up residence on a Nepenthes pitcher, the crab spiders are increasing the likelihood of insects visiting the traps? This remains to be seen as such questions did not fall under the scope of this investigation. That being said, it certainly offers tantalizing evidence that there is more to the Nepenthes-crab spider relationship. More work is needed to say for sure but the closer we look at such interactions, the more spectacular they become!

Photo Credits: [1] [2] [3] [4]

Further Reading: [1] [2] [3]

A Passionflower With a Taste for Insects?


For a plant to be considered carnivorous, it must possess one or more traits unequivocally adapted for attracting, capturing, and/or digesting prey. It also helps to demonstrate that the absorption of nutrients has a clear positive impact on growth or reproductive effort. For plants like the Venus fly trap or any of the various pitcher plants out there, this distinction is pretty straight forward. For many other species, the line between carnivorous or not can be a little blurry. Take, for instance, the case of the stinking passionflower (Passiflora foetida).

At first glance, P. foetida seems par for the course as far as passionflowers are concerned. It is a vining species native from the southwestern United States all the way down into South America. It enjoys edge habitats where it can scramble up and over neighboring vegetation. It produces large, showy flowers followed by edible fruits. When the foliage is damaged, it emits a strong odor, earning it the specific epithet “foetida.”

Not until you inspect the developing floral buds of this passionflower will the question of carnivory enter into your mind. Covering the developing flowers and eventually the fruit are a series of feathery bracts, which are covered in glandular hairs. The hairs themselves are quite sticky thanks to the secretion of fluids. As insects crawl across the hairs, they become hopelessly entangled and eventually die. So, does this make P. foetida a carnivore?


Many different plants produce sticky hairs or glands on their tissues. Often this is a form of defense. Herbivorous insects looking to take a bite out of such a plant either get stuck outright or have their mouth parts completely gummed up in the process. This form of defense seems to work quite well for such plant species so simply trapping insects doesn’t mean the plant is a carnivore. Worth noting, however, is the fact that it appears that many carnivorous plant traits have simply been retooled from defense traits.

The question remains as to what happens to the trapped insects after they are ensnared by P. foetida. Observations in the field suggest that there is more to these sticky hairs than simply defense. This led a team of researchers to look closer at the interactions between P. foetida and insects. What they found is rather fascinating.

It turns out that most of the insects captured by P. foetida bracts are herbivores that would have made an easy meal of the flowers and fruits. However, after getting stuck, the insect bodies quickly decay. Laboratory analyses revealed that indeed, the fluids secreted by the sticky hairs contained lots of digestive enzymes, mainly proteases and acid phosphatases. Still, this does not mean the plant is eating the insects. It makes sense from a defensive standpoint that a plant would not benefit from having lots of rotting corpses stuck to its buds. As such, digesting them removes the possibility of fungal or bacterial attack. To investigate whether P. foetida benefits from trapping insects beyond simply avoiding herbivory, the team needed to know if any nutritional benefit was being had.


The team took amino acids marked with a special carbon isotope and smeared it onto the bracts. Then they waited to see if any of the labelled amino acids showed up in the plant tissues. Indeed they did. The amino acids were absorbed by the bracts and translocated to the  calyx, corolla, anthers, and finally to the developing ovules. This is probably not too surprising  to those of us that spend time growing plants as numerous plant species can uptake at least some nutrients through their leaves. This is why foliar feeding can work as a means of fertilizing potted plants. Nonetheless, these results are enticing as it shows that P. foetida is not only capturing and dissolving insects, it also seems capable of absorbing at least some amino acids from its victims.

So, should we call P. foetida a carnivore? To be honest, I am not sure. Certainly all of the evidence suggests there is more going on than simply defense. However, does garnering the attention of hungry herbivores constitute prey attraction? Certainly other carnivores utilize food deception as a means of prey capture. Does simply being a palatable plant count as a lure? Does absorbing nutrients constitute carnivory? In some instances, yes, however, as mentioned, plenty of plant species can absorb nutrients from organs other than their roots.

I think the main question is whether P. foetida sees a marked increase in growth or reproduction due to the addition of the dead herbivores. What I think we can say is that the sticky bracts surrounding the flowers and fruits serve a dual purpose - defense against herbivores and potentially a nutrient boost as well. If anything, I think this should qualify as a form of protocarnivory.

Photo Credits: [1] [2] [3]

Further Reading: [1] [2]  

The Carnivorous Dewy Pine


The dewy pine is definitely not a pine, however, it is quite dewy. Known scientifically as Drosophyllum lusitanicum, this carnivore is odd in more ways than one. It is also growing more and more rare each year.

One of the strangest aspects of dewy pine ecology is its habitat preferences. Whereas most carnivorous plants enjoy growing in saturated soils or even floating in water, the dewy pine's preferred habitats dry up completely for a considerably portion of the year. Its entire distribution consists of scattered populations throughout the western Iberian Peninsula and northwest Morocco.


Its ability to thrive in such xeric conditions is a bit of a conundrum. Plants stay green throughout the year and produce copious amounts of sticky mucilage as a means of catching prey. During the summer months, both air and soil temperatures can skyrocket to well over 100°F (37 °C). Though they possess a rather robust rooting system, dewy pines don't appear to produce much in the way of fine roots. Because of this, any ground water presence deeper in the soil is out of their reach. How then do these plants manage to function throughout the driest parts of the year?

During the hottest months, the only regular supply of water comes in the form of dew. Throughout the night and into early morning, temperatures cool enough for water to condense out of air. Dew covers anything with enough surface area to promote condensation. Thanks to all of those sticky glands on its leaves, the dewy pine possesses plenty of surface area for dew to collect. It is believed that, coupled with the rather porous cuticle of the surface of its leaves, the dewy pine is able to obtain water and reduce evapotranspiration enough to keep itself going throughout the hottest months. 

Dewy pine leaves unfurl like fern fiddle heads as they grow.

Dewy pine leaves unfurl like fern fiddle heads as they grow.

As you have probably guessed at this point, those dewy leaves do more than photosynthesize and collect water. They also capture prey. Carnivory in this species evolved in response to the extremely poor conditions of their native soils. Nutrients and minerals are extremely low, thus selecting for species that can acquire these necessities via other means. Each dewy pine leaf is covered in two types of glands: stalked glands that produce sticky mucilage, and sessile glands that secrete digestive enzymes and absorb nutrients.

Their ability to capture insects far larger than one would expect is quite remarkable. The more an insect struggles, the more it becomes ensnared. The strength of the dewy pines mucilage likely stems from the fact that the leaves do not move like those of sundews (Drosera spp.). Once an insect is stuck, there is not much hope for its survival. Living in an environment as extreme as this, the dewy pine takes no chances.


The taxonomic affinity of the dewy pine has been a source of confusion as well. Because of its obvious similarity to the sundews, the dewy pine has long been considered a member of the family Droseraceae. However, although recent genetic work does suggest a distant relationship with Droseraceae and Nepenthaceae, experts now believe that the dewy pine is unique enough to warrant its own family. Thus, it is now the sole species of the family Drosophyllaceae.

Sadly, the dewy pine is losing ground fast. From industrialization and farming to fire suppression, dewy pines are running out of habitat. It is odd to think of a plant capable of living in such extreme conditions as being overly sensitive but that is the conundrum faced by more plants than just the dewy pine. Without regular levels of intermediate disturbance that clear the landscape of vegetation, plants like the dewy pine quickly get outcompeted by more aggressive plant species. Its the fact that dewy pine can live in such hostile environments that, historically, has kept its populations alive and well.


What's more, it appears that dewy pines have trouble getting their seeds into new habitats. Low seed dispersal ability means populations can be cut off from suitable habitats that are only modest distances away. Without a helping hand, small, localized populations can disappear alarmingly fast. The good news is, conservationists are working hard on identifying what must be done to ensure the dewy pine is around for future generations to enjoy.

Changes in land use practices, prescribed fires, wild land conservation, and incentives for cattle farmers to adopt more traditional rather than industrial grazing practices may turn the table on dewy pine extinction. Additionally, dewy pines have become a sort of horticultural oddity over the last decade or so. As dedicated growers perfect germination and growing techniques, ex situ conservation can help maintain stocks of genetic material around the globe.

Photo Credits: [1] [2] [3] [4] [5]

Further Reading: [1] [2] [3] [4]



The Parrot Pitcher Plant


Southeastern North America is the true home of the carnivorous plants belonging to the genus Sarracenia. Seven of the approximately eight species in this genus reside in North America's coastal plain forests and nowhere else. These evolutionary marvels are famous the world over for their carnivorous pitfall traps but not all members conform to this style of prey capture. The most aberrant of these carnivores is the so-called parrot pitcher plant (Sarracenia psittacina).

The parrot pitcher plant would be easy to pick out of a lineup, even with an untrained eye. Instead of tall, lanky, upright pitchers, it produces a rosette of smaller, entirely prostrate pitchers. Additionally, the leaf-like hood that covers the pitchers of its relatives appears to have grown into a dome-like structure speckled with translucent patches. Finally, the belly of each pitcher sports a leafy fin called an "ala" that runs the whole length of the tube. Indeed, with the exception of perhaps the purple pitcher plant (S. purpurea), the parrot is truly an oddball.

Its unique appearance is likely an adaptation to seasonal flooding and has changed the way in which this particular species captures prey. The pitchers of the parrot pitcher plant do not function as pitfall traps like those of its relatives. Instead, this species utilizes the "lobster trap" method of prey capture. Lured to its pitchers by their bright colors, insects gradually explore the traps. The fin-like ala directs these unsuspecting victims to the mouth of the pitcher. The translucent patches on the domed hood lure the insect into a false sense of security.

Once inside, the insects become disoriented and cannot easily find the proper escape rout. As they crawl farther into the pitcher, backward pointing hairs ensure that escape is impossible. Death is followed by digestion as the pitcher obtains yet another nutrient-rich meal. However, insects aren't the only game in town for the parrot pitcher plant.


Because of its prostrate habit, the parrot pitcher plant regularly finds itself underwater whenever its already wet habitat floods. This would be bad news for most other pitchers as their upright position would allow whatever was inside to float out and away. Such is not the case for the parrot pitcher. Underwater, the pitchers become even more like a lobster trap. Everything from aquatic insects to tadpoles and fish can and do fall victim to this plant. As such, not even seasonal flooding can put a damper on this unique pitcher plants meal ticket. It is a wonderful example species adaptation.


Like all members of the southeastern coastal plain community, the parrot pitcher plant is losing its habitat at an alarming rate. Habitat loss is an ever present threat, both in the form of outright destruction from logging and development as well as from sequestration of fire. Coastal plain communities are fire-adapted ecosystems and without it, the myriad species that call this region home are overgrown and choked out. Research has shown that the parrot pitcher plant, as well as other pitcher plants, greatly benefit from regular fires. Fire clears away competing vegetation and the plants respond with vigor.


Luckily, parrot pitcher plant numbers are stable at this point in time. Its low growth habit saves it from threats like mowing, which means that it can do well in places like roadside ditches that are less favorable for its taller relatives. I have said it before and I will say it again, if you value species like the parrot pitcher plant, please do everything you can to support land conservation efforts. Please check out what organizations such as The Longleaf Alliance, Partnership For Southern Forestland Conservation, The Nature Conservancy, and The National Wildlife Federation are doing to protect this amazing region. Simply click the name of the organization to find out more.

Photo Credits: [1] [2] [3] [4] [5]

Further Reading: [1] [2] [3]


The Bladderwort Microbiome Revealed


The bladderworts (Utricularia spp.) are among the most cosmopolitan groups of carnivorous plants on this planet. Despite their popularity, their carnivorous habits have been subject to some debate. Close observation reveals that prey capture rates are surprisingly low for most species. This has led some to suggest that the bladderworts may be benefiting from more passive forms of nutrient acquisition. To better understand how these plants utilize their traps, a team of researchers decided to take a closer look at the microbiome living within. 

The team analyzed the trap fluid of a handful of floating aquatic bladderwort species - U. vulgaris, U. australis, and U reflexa. In doing so, they uncovered a bewildering variety of microorganisms perfectly at home within the bladderwort traps. Thanks to sophisticated genetic tools, they were able to classify these microbes in order to investigate what exactly they might be doing inside the traps. 

Their findings were quite astonishing to say the least. The traps of these plants harbor extremely rich microbial communities, far richer than the microbial diversity of other carnivorous plant traps. In fact, the richness of these microbial communities were more akin to the richness seen in the rooting zone of terrestrial plants or the gut of a cow. In terms of the species present, the microbial communities of bladderwort traps most closely resembled that of the pitchers of Sarracenia species as well as the guts of herbivorous iguanas.

The similarities with herbivore guts is quite remarkable. Its not just coincidental either. The types of microbes they found weren't new to science but their function was a bit of a surprise. A large percentage of the bacteria living within the fluid are famously known for producing enzymes that digest complex plant tissues. Similarly, the team found related microbe groups that specialize on anaerobic fermentation. These types of microbes in particular are largely responsible for the breakdown of plant materials in the rumen of cattle.

As it turns out, the microbes living within the traps of these bladderworts are serving a very important purpose for the plant - they are breaking down plant and algae cells that find their way into the traps each time they open and close. In doing so, they give off valuable nutrients that the bladderworts can then absorb and utilize. Let me say that again, the bacteria living in bladderwort traps are digesting algae and other plant materials that these carnivorous plants can then absorb.

Now these bacteria are also responsible for producing a lot of methane in the process. Interestingly enough, the team was not able to detect measurable levels of methane leaving the traps. This would be odd if it wasn't for the community of methane-feeding microbes also discovered living within the traps. The team believes that these organisms metabolize all of the methane being produced before it can escape the traps. 

As remarkable as these findings are, I don't want to give the impression that these carnivorous plants have taken up a strict vegetarian lifestyle. The team also found myriad other microorganisms within the bladder traps, many of them being carnivores themselves. The team also found a rich protist community. A majority of these were euglenids and ciliates. 


These sorts of protists are important microbial predators and the numbers recorded within the traps suggest that they are a rather significant component of these trap communities. As they chase down and consume bacteria and other protists, they release valuable nutrients that the plants can absorb and utilize. Numbers of these predatory protists were much higher in older traps, which have had much more time to accumulate a diverse microbiome. Astonishingly, it is estimated that the protist communities can cycle the entire contents of the bladderwort traps upwards of 4 or 5 times in a 24 hour period. That is some serious turnover of nutrients!

The protists weren't the only predators found within the traps either. There are also a considerable amount of bacterial predators living there as well. These not only cycle nutrients in similar ways to the protist community, it is likely they also exhibit strong controls on the biodiversity within this miniature ecosystem. In other words, they are considered keystone predators of these microcosms.

Also present within the traps were large amounts of fungal DNA. None of the species they found are thought to actually live within the traps. Rather, it is thought that they are taken up as spores blown in from the surrounding environment. Exactly how these organisms find themselves living inside bladderwort traps is something worth considering. The plants themselves are known for being covered in biomfilms. It is likely that many of the organisms living within the traps were those found living on the plants originally. 

Taken together, the remarkable discovery of such complex microbial communities living on and within these carnivorous plants shows just how complex the ecology of such systems really are. Far from the active predators we like to think of them as, the bladderworts nonetheless rely on a mixture of symbiotic orgnaisms to provide them with the nutrients that they need. The fact that these plants are in large part digesting plant and algae materials is what I find most astonishing.

Essentially, one can almost think of bladderworts as plants adorned with tiny, complex cow stomachs, each utilizing their microbial community to gain as much nutrients as they can from their living environment. The bladderworts gain access to nutrients and the microbes get a place to live. The bladderworts really do seem to be cultivating a favorable habitat for these organisms as well. Analysis of the bladder fluid demonstrated that the plants actively regulate the pH of the fluid to maintain their living community of digestive assistants. In doing so, they are able to offset the relative rarity of prey capture. Keep in mind that this research was performed on only three species of bladderwort originating from similar habitats. Imagine what we will find in the traps of the multitude of other Utricularia species.

Photo Credits: [1] [2] [3] [4]

Further Reading: [1]


Evidence Of Carnivory In Teasel

As far as carnivorous plants are concerned, the common teasel (Dipsacus fullonum) seems like a strange fit. Observe this plant up close, however, and you might notice something interesting. Its leaves are perfoliate and form a cup-like depression where they attach to the main stem. Not only does this cup regularly fill with water, it also frequently traps small insects.

Many have speculated over the function of this anatomical trap. Much of this speculation has centered around the idea that it may serve as a form of protection for the flowers located above. Insect herbivores climbing up the stem in search of food instead find a moat of water. Some inevitably fall in and drown in the process. Other hypotheses have been put forward as well including the possibility of something approaching carnivory. 

The idea that common teasel could be, to some degree, carnivorous never really went away. For most of this time it has remained entirely theoretical. There simply was no empirical evidence available to say otherwise. All of that changed with a 2011 study published in PLOS. A research duo finally put this theory to the test in the first ever experiment to see if teasel gains any sort of nutrient benefit from its insect victims.


By systematically supplying teasel plants with insect prey, the team was able to look at how plants responded to the addition of a potential meal. They added various levels of insect larvae to some plants and removed them from others. For their study, evidence would come in the form of some sort of physiological response to the feeding treatments. If teasel really is obtaining nutrients from its insect victims, it stands to reason that those nutrients would be allocated to either growth or reproduction.

The resulting data offers the first evidence that teasel may in fact be benefiting from the insect carcasses. Although the team found no evidence that plants supplemented with insects were increasing in overall biomass, they did see a positive effect on not only the number of seeds produced but also their size. In other words, when fed a diet of insects, the plants weren't growing any larger but they were producing larger amounts of heavier seeds. This is a real boon for a plant with a biennial life cycle like teasel. The more healthy seeds they can produce, the better.

As exciting as these finds are, one must temper their expectations. As the authors themselves state in their paper, these findings must be replicated in order to say for certain that the effects they measured were due to the addition of insect prey. Second, no chemical analyses were made to determine if the plants are actively digesting these insects or even how available nutrients may be absorbed. Simply put, more work is needed. Perhaps teasel is a species that, evolutionary speaking, is on its way to becoming a true carnivore. We still can't say for sure. Nonetheless, they have given us the first evidence in support of a theory that went more than a century without testing. It is interesting to think that there is a strong possibility that if someone wants to see a carnivorous plant, they need go no further than a fallow field.

Photo Credits: [1] [2]

Further Reading: [1]

Not All Pitchers Are Equal: How Prey Capture Has Driven Speciation in the genus Nepenthes

Species of the genus Nepenthes are as bizarre as they are beautiful. Known the world around for their carnivorous lifestyle, these plants looks like something out of a macabre art exhibit. It is easy to get caught up in this beauty. I often find myself lost in thought while staring at full grown specimen. How did this genus come to be? Why are they so diverse? What is going on with the morphology of these plants?

Nepenthes hail from nutrient poor habitats, which has driven them to supplement their growth with nutrients gained via the breakdown of a variety of organisms. The business ends of a Nepenthes are their pitchers. We get so caught up in the bewildering diversity of shapes, colors, and sizes that we often overlook them as the anatomical marvels of evolution that they truly are. Whereas the main body of these plants often look quite similar among different species, it's the pitchers that really allow us to separate them out as distinct species. Pitcher morphology not only gives us a convenient means to identify these plants, research is now showing that the structure of these pitchers is likely to be the driving force in their evolution. 

Let's back up for a second. Before we get to the subject of adaptive radiation, we should take a closer look at the anatomy of these plants. To put it simply, the pitchers of Nepenthes are actually leaves, albeit highly modified versions. What we readily recognize as the photosynthetic leaves of a Nepenthes plant are actually modified leaf bases or petioles. Over evolutionary time, these bases have flattened to increase the amount of surface area available for photosynthesis.

From the tip of each of these "leaves" is produced a tendril. Gradually this tendril will elongate and the tip starts to swell. This tip will eventually become the pitcher. The pitchers themselves are highly modified leaves. They are some of the most specialized leaves in all of the plant kingdom. As the tip grows larger, it becomes clear that there is a distinctive lid apparatus. Once the pitcher is fully mature, this lid pops open revealing the death trap filled with digestive fluids.

As if producing pitchers wasn't cool enough, each species of Nepenthes produces two distinct forms - lower pitchers, which are produced by young plants as well as on mature plants near the ground, and upper pitchers, which are produced up on the climbing stems as they vine through the canopy. The upper and lower pitchers look radically different from one another to the point that one may easily confuse them for different species. The reason for such stark differences has to do with the type of prey captured. Lower pitchers are generally larger and can capture prey that crawls along the forest floor. Upper pitchers tend to be more slender and most often capture flying insects as well as other creepy crawlies hanging out in the forest canopy.

The key to the success of these traps seems pretty straight forward - insects attracted by bright colors and sweet nectar land on the traps and fall to their death. Certainly this holds true throughout the genus, however, there are at least two major variations on this theme and a handful of bizarre mishmashes. As the lid of a Nepenthes pitcher starts to open, a ring of tissue called the peristome unfurls. The shape and color varies wildly between species and this has to do with the methods in which they capture their prey. These variations are the key to the amazing diversity of Nepenthes we see throughout the range of this genus.

Nepenthes vogelii

Nepenthes vogelii

The first of the three strategies is referred to as the 'insect aquaplaning' strategy. Insects walking around on the peristome of the pitcher find it hard to get a foothold. These are species such as N. raja, N. ampullaria, and N. bicalcarata (just to name a few). The slipperiness of the peristome of these species is further enhanced when humidity is high. Considering how much it rains in these habitats, it is no wonder why capture efficiency is often as high as 80%. Although there is some variation on this theme, pitchers that utilize the insect aquaplaning strategy often lack waxy cells on the interior of the pitcher walls.

Slippery pitcher walls are the second strategy that Nepenthes have converged upon. These are species such as N. diatas, N. mirabilis, and N. alata (again, just to name a few) Insects attracted to the pitchers are often lured in by sweet nectar. Once they cross the lip of the pitcher, prey find it hard to hang on and inevitably fall inside. Once this happens, waxy cells lining the interior walls make it impossible for anything to climb back out. It should be mentioned that a slippery peristome and waxy pitcher walls are not mutually exclusive. That being said, there are clear trends among species that show a reduction in waxy cells as peristome size and slope increases.

This brings us to the oddballs. There are species like N. lowii, whose pitchers function as a toilet bowl for shrews, and N. aristolochioides, whose pitchers seemed to have abandonded both strategies and now function as light traps similar to what we see in Darlingtonia. Regardless of their strategy, the diversity in trapping mechanisms appear to be the driving force behind the bewildering diversity of Nepenthes

Nepenthes   aristolochioides

Nepenthes aristolochioides

All of the evidence taken together shows that prey capture is at the core of this radiation. There seems to be incredibly strong selective pressures that result in strong divergence in pitcher morphology. The disruptive selection that seems to be driving a wedge between the insect aquaplaning strategy and the waxy wall strategy may have its roots in reducing competition. Nutrients are low and competition for food is high. Different Nepenthes species could be evolving to capture different kinds of prey. Even closely related species such as N. ampullaria, N. rafflesiana, N. mirabilis, N. albomarginata, and N. gracilis all seem to occupy their own unique spot on the spectrum of prey capture strategy.

It could also be that Nepenthes are responding to the specific characteristics of the habitats in which they are found. Those inhabiting drier sites may favor the waxy wall strategy whereas those living in wetter habitats tend to favor the slippery peristome. More work needs to be done to investigate where and how these different strategies are maximized. Until then, I think it is safe to say that the diversity of this incredible genus has a lot to do with obtaining food. 

Photo Credits: [1] 

Further Reading:

[1] [2] [3]


Convergent Carnivores

A carnivorous lifestyle has evolved independently in numerous plant lineages. Despite the similarities between genera like Nepenthes, Sarracenia, and Cepholotus they are not closely related. Researchers have wondered how the highly modified leaves of various carnivorous plant species evolved into the insect trapping and digesting organs that we see today. Thanks to a recent article published in Nature, it has been revealed that the mechanisms responsible for carnivory in plants are a case of convergent evolution.

This research all started with the Australian pitcher plant Cepholotus follicularis. More closely related to wood sorrels (Oxalis spp.) than either of the other two pitcher plant families, this species offers a unique window into the genetic controls on pitcher development. Cepholotus produces two different kinds of leaves - normal, photosynthetic leaves and the deadly pitcher leaves that have made it famous the world over.

By observing which genes are activated during the development of these different types of leaves, the research team was able to identify which alleles have been modified. In doing so, they were able to identify genes involved in producing the nectar that attracts their insect prey as well as the genes involved in producing the slippery waxy coating that keeps trapped insects from escaping. But they also found something even more interesting.

Next, the team took a closer look at the digestive fluids produced by Cepholotus as well as many other unrelated carnivorous plant species from around the world. In doing so, the team made a startling discovery. They found that the genes involved in synthesizing the deadly digestive cocktails among these disparate lineages have a similar evolutionary origin.

Although they are unrelated, the ability to digest insects seems to have its origins in defending plants against fungi. You have probably heard someone say that fungi are more similar to animals than they are plants. Well, the polymer that makes up the cell walls of fungi is the same polymer that makes up the exoskeleton of insects - chitin. By comparing the carnivorous plant genes to those of the model plant Arabidopsis, the team found that similar genes became active when plants were exposed to fungal pathogens.

It appears that carnivorous plants around the world have all converged on a system in which genes used to defend themselves against fungal infection have been co-opted to digest insect bodies. Taken together, these results show that the path to carnivory in plants is surprisingly narrow. Evolution doesn't always require the appearance of new alleles but rather a retooling of genes that are already in place. 

Photo Credits: [1] [2]

Further Reading: [1]



A Poop-Eating Pitcher Plant

The aerial pitchers of Nepenthes hemsleyana ( are quite unique in that they are not intended to catch insects. Instead, they have evolved as specialized roosts for Hardwicke's woolly bats (Kerivoula hardwickii). This incredible mutualism is quite unique among these tropical carnivores. The bats get a safe place to roost and in return, they deposit nitrogen-rich feces. 

This mutualism is quite remarkable in that the upper pitchers of N. hemsleyana have pretty much forgone insect capture altogether. Despite the obvious benefits of this evolutionary relationship, no one had bothered to quantify the benefits gained by turning insect catching pitchers into bat roosts. That is, until now. 

A team of researchers based out of University of Greifswald in Germany utilized some cunning methods to demonstrate exactly how much N. hemsleyana relies on bat droppings. What they found what quite remarkable. Plants offered only insects not only had fewer leaves, they also exhibited slower growth, reduced photosynthetic capacity, and reduced survival. It would seem that this mutualism has evolved to the point of being obligate. 

It is estimated that around 95% of the nitrogen needs of this plant are met by bat feces alone. As it turns out, nitrogen bound up in insect tissues were mostly unavailable to the plant. This is not the case for nitrogen in bat poop. Nitrogen deposited by bats comes mostly in the form of urea, which degrades into ammonium and is readily absorbed by the pitchers. 

Essentially Nepenthes hemsleyana now relies on bats to capture prey for them. This "ecological outsourcing," as it has been termed, frees the plant from the rigors of having to capture and digest insects on its own, thus saving valuable energy reserves that can be allocated to structures such as leaves, stems, and flowers. Why this species has evolved this strategy is anyone's guess. Perhaps it has to do with the deep shaded forest understory in which it grows. 

Photo Credit: Merlin Tuttle (

Further Reading: [1]

A Digestive "On" Switch

A common thread throughout the world of carnivorous plants is that all hail from nutrient poor environments. That is why they evolved carnivory in the first place, as a way of supplementing their nitrogen and phosphorous needs. For as amazing as their various adaptations are, the evolutionary histories of the world's carnivorous plants are still largely shrouded in mystery. A recent paper published in the Annals of Botany takes a closer look at what goes on inside the pitchers of the tropical pitcher plant Nepenthes alata. What they found is quite amazing.

As it turns out, N. alata seems to be able to regulate the amount of digestive enzymes within its pitchers based on prey availability. This makes a lot of sense. Since these species live in nutrient poor conditions, it would be very wasteful to continuously produce digestive fluids. Instead, the research team found that the genes responsible for the productive of digestive enzymes turn on in response to certain cues. In this case, its the presence of insect tissues, specifically chitin. The addition of insect prey coincided with a 24 to 48 hour burst in digestive enzyme production followed by a gradual decrease as the insects were digested. As interesting as this is, these were not the only findings to come out of this research.

When the researchers looked closely at what kinds of enzymes N. alata were producing, they discovered evidence in support of a long-held hypothesis regarding the evolution of carnivory in plants. The genetic pathways induced by the addition of insect chitin are nearly identical to those seen in plant defense pathways. These pathways also induced the production of a series of proteins known to play a role in plant defense reactions against microbial pathogens. What's more, many of the enzymes N. alata were producing inside their pitchers are classified as defense-related proteins. Taken together, this is strong evidence in support of the hypothesis that carnivory in plants evolved from defense reactions already in place.

This finding comes in the wake of an earlier discovery that showed similar pathways in the traps of the Venus fly trap. This is yet more evidence for the fact that evolution does not always occur via novel pathways. Instead, systems that are already in place are retooled to fit a new set of challenges.

Photo Credit: [1]

Further Reading: [1]

On Lynx Spiders and Pitcher Plants

On the coastal plains of southeastern North America, there exists a wide variety of pitcher plant species in the genus Sarracenia. These plants are the objects of desire for photographers, botanists, ecologists, gardeners, and unfortunately poachers. Far from simply being beautiful, these carnivores are marvels of evolution, each with their own unique ecology.

Pitcher plants are most famous for capturing and digesting insect prey but their interactions with arthropods aren't always in their favor. Browse the internet long enough and you will inevitably find photographs like this one above in which a green lynx spider (Peucetia viridans) can be seen haunting the traps of a pitcher plant. Instead of becoming prey, this is a spider that uses the pitchers to hunt.

I should start by saying this is not an obligate relationship. Lynx spiders can be found hunting on a variety of plant species. Instead, they are more accurately opportunistic robbers, stealing potential meals from the pitcher plants they hunt upon. However, what this relationship lacks in specificity, it makes up for in being really interesting. Sarracenia are not passive hunters. They do not sit and wait for insects to blindly stumble into their traps. Instead, they utilize bright colors and tasty nectar to lure insects to their demise. This is exactly what the lynx spider is using to its benefit. 

The green lynx spider does not spin a web like an orb weaver. It is an ambush predator. They have keen eyesight and will quickly pounce on any insect unfortunate enough to get too close. The reason the spider itself does not become yet another meal for the pitcher plant is because they utilize their silk as an anchor. By attaching one end to the outside of the pitcher, the can safely hunt on the trap without the risk of become prey themselves. In fact, spiders hunting on traps even go as far as to retreat down into the trap if threatened.

Photo Credit: Zachary Ambrose - nccarnivores

Further Reading:

The Mountain Sweet Pitcher Plant


I am fascinated by pitcher plants. The myriad shapes, sizes, and colors make them quite a spectacle. Add to that their carnivorous habit and what is not to love? I am used to having to visit bogs or coastlines to see them in person so you can imagine my surprise to learn that a small handful of pitcher plants haunt the mountains of Southern Appalachia.


Sarracenia jonesii is a recent acquaintance of mine. I never knew this species existed until 2016. It is a slender pitcher plant whose traps grow taller and narrower than the purple pitcher plant (S. purpurea) but not nearly as tall and robust as species like S. leucophylla. Regardless of its size, this one interesting carnivore. One unique aspect of its ecology is the habitats in which it grows. What could be more strange than a pitcher plant clinging to sloping granite slabs?


Most mountainous areas don't hold water for very long. Aside from bowls and the occasional lake, gravity makes short work of standing water. In southern Appalachia, this often results in impressive cascades where sheets of water flow over granite outcrops and balds. Where water moves slow enough to not wash soil and moss away, cataract bogs can form. Soils are so thin in these areas that trees and shrubs can't take root, thus keeping competition to a minimum. Because granite is rather inert, nutrients are scarce. All of these factors combine to make prime carnivorous plant habitat.

A cataract bog clinging to the side of a waterfall.

A cataract bog clinging to the side of a waterfall.

Along the edges of these cataract bogs, anywhere sphagnum and other mosses grow is where S. jonesii finds a home. One would think that growing in such hard-to-reach places would protect this interesting and unique carnivore. Sadly, that is not the case. To start with, S. jonesii was never common to begin with. Native to a small region of North and South Carolina, it is now only found in about 10 locations. 

Habitat destruction both direct and indirect (alterations in hydrology) has taken its toll on its numbers in the wild. To add insult to injury, poaching has become a serious issue. In fact, an all green population of this species was completely wiped out by greedy collectors looking to add something rare to their collection. The good news is that there are dedicated folks working on conserving and reintroducing this plant into the wild. In 2007, conservationists at Meadowview Biological Research Station, with help from the National Fish and Wildlife Foundation Grant, successfully reintroduced a population of S. jonesii to its former range.

Although the future remains uncertain for this species, it nonetheless has captured hearts and minds alike. Hopefully the charismatic nature of this species is enough to save it from extinction. I only wish such dedicated conservation efforts were directed at more imperiled plant species, both charismatic and not. 

Further Reading: [1] [2] [3]

Genetic Origins of Carnivory in the Venus Fly Trap

Our fascination with the Venus fly trap (Dionaea muscipula) is undeniable. What's not to love about a plant that eats animals? Our obsession with this species has led to a long history of investigation (as well as deplorable practices like poaching). However, despite our familiarity with the Venus fly trap, we still have much to learn about its biology. For instance, little is known about the origins of the molecular machinery involved in its carnivorous lifestyle. Thanks to a 2016 paper published in Genome Research, we now have some insights.

As you can probably imagine, the Venus fly trap genome has been of interest to science for quite some time. After all, it is likely to harbor the keys to this carnivorous curiosity. However, despite looking, no carnivory-specific genes have ever been found. It's as if this wonder of evolution has no genetic basis. Of course, things are not that simple. A breakthrough was made when a team of researchers based out of Germany and Saudi Arabia decided to take a look at "transcription profiles." Essentially, these are chemical indicators of gene activity. When a gene is activated, it produces a chemical signal that can be easily traced. In doing so, researchers are able to get a clear picture of what is going on at a molecular level when an organism responds to its environment. 

What the team discovered is pretty amazing. Instead of a new family of carnivorous genes coming online, they found that the Venus fly trap has retooled a handful of genes that are used by many different plant species for defense. As it turns out, the Venus fly trap has coopted a set of genes that in most plants are activated when the plant becomes damaged. When the traps were stimulated by the insects stuck inside, transcripts for the production of chitinase, which is basically a insect digesting enzyme, became amplified. For non-carnivorous plants, chitinase is usually produced in response to insect attack or fungal infection and is believed to be a defense mechanism. This was not the only gene activity either. When an insect was trapped by the plant, transcripts for jasmonic acid saw an increase. Also, when digestive glands within the trap began to activate, the genes responsible for this were showing an expression pattern akin to that of nutrient transport in roots. 

It would seem that the evolution of carnivory in this species did not involve novel genes. Instead, the evolution of the Venus fly traps carnivorous lifestyle involved a reprogramming of sets of genes common to most plant species. In essence, the Venus fly trap has melted its shield to build a sword, only the sword is a trap of exquisite beauty and effectiveness. 

Photo Credit: Scott Schiller

Further Reading:

The Fanged Pitcher Plant of Borneo

As mammals, and even more so as apes, we tend to associate fangs with threats. The image of two dagger-like teeth can send chills up ones spine. Perhaps it is fitting then that a carnivorous plant from a southeast Asian island would sport a pair of ominous fangs. Friends, I present to you the bizarre fanged pitcher plant (Nepenthes bicalcarata).

This ominous-looking species is endemic to Borneo and gets its common name from the pair of "fangs" that grow from the lid, just above the mouth of the pitcher. Looks aren't the only unique feature of this species though. Indeed, the entire ecology of the fanged pitcher plant is fascinatingly complex.

Lets tackle the obvious question first. What is up with those fangs? There has been a lot of debate among botanists as to what function they might serve. Some have posited the idea that they may deter mammals from feeding on pitcher contents. Others see them as mere artifacts of development and attribute no function to them whatsoever.

In reality they are involved in capturing insects. The fangs bear disproportionately large nectaries that lure prey into a precarious position just above the mouth of the pitcher. Strangely enough, this may have evolved to compensate for the fact that the inside of the pitchers are not very slippery. Whereas other pitcher plant species rely on waxy walls to make sure prey can't escape, the fanged pitcher plant has relatively little waxy surface area within its pitchers. What's more, the pitchers are not very effective at capturing prey unless they have been wetted by rain. The fluid within the pitchers also differs from other Nepenthes in that it is not very acidic, contains few digestive enzymes, and isn't very viscous. Why?

Worker ants cleaning the pitcher (left) and an ant brood chamber inside of the pitcher tendril (right).

Worker ants cleaning the pitcher (left) and an ant brood chamber inside of the pitcher tendril (right).

The answer lies with a specific species of ant. The fanged pitcher plant is the sole host of a carpenter ant known scientifically as Camponotus schmitzi. The tendrils that hold the pitchers themselves are hollow and serve as nest sites for these ants. Ant colonies take up residence in the tendrils and will hunt along the insides of the pitchers. In fact, they literally go swimming in the pitcher fluid to find their meals!

This is why the pitcher fluid differs so drastically from other Nepenthes. The fanged pitcher plant actually does very little of its own digestion. Instead, it relies on the resident ant colony to subdue and breakdown large prey. As a payment for offering the ants room and board, the ants help the plant feed via the breakdown of captured insects (which are often disposed of in the pitchers) and the deposition of nitrogen-rich feces. Indeed, plants without a resident ant colony are found to be significantly smaller and produce fewer pitchers than those with ants. The ants also protect and clean the plant, removing fungi and hungry insect pests.

Sadly, like many other species of Nepenthes, over-harvesting for the horticultural trade as well as habitat destruction have caused a decline in numbers in the wild. With species like this it is so important to make sure you are buying nursery grown specimens. Never buy a wild collected plant! Also, if you are lucky enough to grow these plants, propagate them! Only by reducing the demand for wild specimens can we hope of curbing at least some of the poaching threats. Also, what better way to get your friends into gardening than by sharing with them amazing carnivores like the fanged pitcher plant.

Female flowers

Female flowers

Photo Credit: [1]
Further Reading: [1] [2] [3] [4] [5]

A Circumboreal Butterwort

The name "butterwort" may sound quite silly to most but those who have seen one in person can attest to the fact that there is nothing silly about the group of plants this name has been given to. Hailing from the genus Pinguicula, my favorite butterwort is Pinguicula vulgaris.

Referred to as the common butterwort, this species is sometimes hard to find if you live in North America. It has a circumboreal distribution and seems to be much more common in Europe and parts of Russia. Like all butterworts, P. vulgaris is a carnivore, though at first glance this may not be very obvious. The fleshy rosette of leaves are covered in mucilaginous glands that trap hapless insects. The leaves will sometimes roll in along the edge to pool the digestive juices around their prey.

Unlike more familiar carnivorous plants that can be found in acidic soils, P. vulgaris is a calciphile. It is most often encountered in fens, alvars, and other areas with limestone bedrock and alkaline waters. These types of habitats pose a different set of challenges for plants when it comes to obtaining nutrients. Phosphorus becomes bound to sediments in these alkaline conditions and research has shown that most butterworts respond best to supplemental phosphorus additions, though other nutrients like nitrogen are absorbed from prey as well.

If their carnivorous habits weren't interesting enough, the flowers of P. vulgaris (and all butterworts for that matter) are gorgeous. Sitting atop long stalks, the spurred blooms are a deep shade of violet. The nectar spur suggests that this species is pollinated by either long tongued bees or butterflies. Either way, they are presented well above the sticky leaves to reduce the chances of the plant eating the insects it needs for pollination.

Like all plants in the northern hemisphere, P. vulgaris needs to deal with winter. As temperatures and light levels begin to drop, P. vulgaris reverts to a cluster of buds called a hibernaculum. It has no roots and can easily blow around if exposed. This may serve to transport plants into new locations. Due to rampant habitat destruction, this plant is quite vulnerable in North America and threatened or endangered in many parts of its range.

Further Reading:

Sticky Friend

We have all had encounters with sticky plants. Outside of being an interesting sensory experience, the sticky nature of these floral entities would appear to have some evolutionary significance. Considering the cost of producing the glandular trichomes responsible for their stickiness, function is a reasonable question to ask about. For anyone who has taken the time to observe such plants, you will have undoubtedly noticed that insects tend to get stuck to them.

For carnivorous plants, the utility of these glands is readily obvious - trapped insects become food. Even non-carnivores like Roridula gain a nutrient benefit in the form of nutrient-rich feces deposited around the plant by specialized carnivorous bugs that consume trapped insects. However, there are many species of plants out there that fall under the category of "sticky" and a new paper explores this in a more general way.

The serpentine columbine (Aquilegia eximia) is endemic to the Coastal Range of California and it is indeed quite sticky. Its surfaces are covered in glandular hairs. Any given plant can be covered in insects unfortunate enough to come into contact with it. However, it is not a carnivore. As such, researchers wanted to see what benefits, if any, the columbine gained from producing these glands.

By manipulating the amount of insects that were stuck to each plant, researchers found that plants without "victims" actually received more insect damage. The key to this mystery were predators. Plants with lots of trapped victims had more predatory bugs hanging around. These predators, when present, reduced herbivory by deterring other insects that were too large to get stuck. What's more, most of the benefits were observed in the flower buds, which means predators increased the overall reproductive fitness of the serpentine columbine. If the columbine did not trap small insects, these predators would have no reason to hang around.

These predatory bugs were by no means specific to the columbine. In fact, observation of the surrounding plant community found that these predatory insects were present on other sticky genera such as Arctostaphylos, Hemizoni, Holocarpha, Calycidenia, Cordelanthus, Castilleja, Mimulus, Trichostema, and Grindelia. This suggests that the relationship between sticky plants and these generalist predators is more widespread than previously thought. It may also offer a unique window into one possible driver behind the evolution of carnivory in plants.

Photo Credit: David A. Hofmann (

Further Reading:

Carnivorous Bromeliads

Brocchinia reducta

Brocchinia reducta

I would like to introduce you to quite possibly the strangest members of the Bromeliad family - those of the genus Brocchinia. Aside from the odd appearance and habits of this particular group, researchers have learned quite a bit about the Bromeliad family as a whole from studying this group. From their origins to their impressive radiation, Brocchinia offers us a window into the history of this charismatic family.

Brocchinia are considered sister to all other bromeliads. They were the first genus to diverge some 70 million years ago. Their center of origin can be traced back to the Guayana Shield, a region in the northeast corner of what is now South America. The earliest members of this group were likely terrestrial plants growing in nutrient poor areas. Surprisingly, the epiphytic nature of many bromeliad species we know and love today evolved more recently.

Brocchinia reducta

Brocchinia reducta

Since this time, Brocchinia has undergone an impressive adaptive radiation. Because they have remained specialists on nutrient poor soils, much of this radiation has to do with the evolution of nutrient acquisiton. Like its cousins, Brocchinia utilize a "tank" formed by their tightly clasped leaves.

Interestingly, at least two species of Brocchinia, (B. reducta and B. hechtioides) have taken this to the extreme and have adopted a carnivorous lifestyle. Their tall, columnar growth form coupled with slick, waxy leaves means insects can't keep a foothold and fall down into the tank. The plants sweeten the deal by luring them in with sweet secretions.


Whether or not this was a case of true carnivory was highly debated until 2005 when a group of researchers analyzed the chemical makeup of the liquid inside the tank. They discovered that they plant was secreting an enzyme called phosphatase, which actively digest hapless insects that fall in. A true carnivore indeed!

Others have even more peculiar evolutionary adaptations for nutrient acquisition. B. tatei, for example, was discovered to house nitrogen-fixing cyanobacteria within its tank. Another species, B. acuminata, produces hallow chambers at the base of its leaves that house ant colonies. The ants pay rent via their nutrient-rich waste and voracious defense of their bromeliad home.

Brocchinnia acuminata

Brocchinnia acuminata

In total, this group is quite amazing. The amount of information we have been able to glean from studying Brocchinia has allowed us to shine a light on the whole bromeliad family. As we have also seen, the species within this group have quite the evolutionary history to tell in their own way. Brocchinia serves as a reminder to researchers blind to organismal study. We shouldn't have to study ecology at the expense of individual organisms. There is plenty to learn from both avenues of research.

Photo Credits: [1] [2] [3] [4]

Further Reading: [1] [2]