A Passionflower With a Taste for Insects?

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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?

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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.

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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

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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.

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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.

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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.

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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

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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.

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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.

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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.

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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 Carnivorous Waterwheel

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Bladderworts (Utricularia spp.) aren't the only carnivorous plants stalking prey below the water surface. Meet the waterwheel (Aldrovanda vesiculosa). At first glance it looks rather unassuming but closer inspection will reveal that this carnivore is well equipped for capturing unsuspecting prey. 

The waterwheel never bothers with roots. Instead, it lives out its life as a free floating sprig, its stem it covered in whorls of filamentous leaves, each tipped with a tiny trap. The trapping mechanism is a bit different from its bladderwort neighbors. Instead of bladders, the waterwheel produces snap traps that closely resemble those of the Venus fly trap (Dionaea muscipula). These traps function in a similar way. When zooplankton or even a small fish trigger the bristles along the rim, the trap snaps shut and begins the digestion process.

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This similarity to the Venus fly trap is more than superficial. DNA analysis reveals that they are in fact close cousins. Together with the sundews, these plants make up the family Droseraceae. The evolutionary history of this clade is a bit confusing thanks to a limited fossil record. Today, the waterwheel is the only extant member of the genus Aldrovanda but fossilized seeds and pollen reveal that this group was once a bit more diverse during the Eocene. Whenever these genera diverged, it happened a long time ago and little evidence of it remains.

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At one point in time, the waterwheel could be found growing in wetland habitats throughout Africa, Europe, Asia, and even Australia. Today it is considered at risk of extinction. Its numbers have been severely reduced thanks to wetland degradation and destruction. Of the 379 known historical populations, only about 50 remain in tact today and many of these are in rough shape. Agricultural and industrial runoff are exacting a significant toll on its long term survival. To make matters worse, sexual reproduction in the waterwheel is a rare event. Most often this plant reproduces vegetatively, reducing genetic diversity. What's more, natural dispersal into new habitats is extremely limited. 

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Oddly enough, populations of this plant have popped up in a few locations in eastern North America. These introductions were not a mistake either. Carnivorous plant enthusiasts concerned with the plight of this species in its native habitat began introducing it into water ways in New Jersey, New York, and Virginia where it is now established. Oddly enough, these introductions have performed far better than any of the reintroduction attempts made in its native range in Europe. Of course, this is always cause for concern. Endangered or not, the introduction of a species into new habitat is always risky. Still, there is hope yet for this species. Its popularity among plant growers has led to an increase in numbers in cultivation. At least folks have learned how to cultivate it until more comprehensive and effective conservation measures can be put into place. 

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

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

The Bladderwort Microbiome Revealed

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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. 

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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.

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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.

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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

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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 Primer on Trigger Plants

I would like to introduce you to another group of plants capable of abrupt movements. Whereas many species have evolved moving parts as a means of capturing prey or deterring herbivores, the following genus moves as means of achieving pollination. Meet the genus Stylidium a.k.a. the trigger plants.

Native to parts of Asia and Australia, these beautiful little herbs are quite diverse, making generalizations difficult. Still, there is one thing they all share, a fused set of reproductive organs that lash out at unsuspecting pollinators. When a visiting insects of sufficient size lands on a flower, its weight causes a rapid change in turgor pressure within the column's tissues.

  Stylidium debile     [SOURCE]

Stylidium debile  [SOURCE]

The rapid change in pressure sends the column flying. The position of this reproductive hammer varies from species to species. Some bash their pollinators on the back whereas others strike them under the abdomen. When the flowers first mature, only the male portions are ripe. Thus, the initial visit dusts the insect with pollen. Once the pollen is gone, the column resets itself and the female portions start to mature. The next time an insect visits the bloom, the stigma will do the bashing. With any luck, the visiting insect will have already been dusted with pollen from a previous plant. In this way, the plant avoids self pollination.

Another morphological aspect shared among member of this genus are the production of glandular trichomes. These minute hairs cover the body of the plant and produce sticky mucilage that ensnares tiny insects. It was originally thought that this was a merely a defense mechanism that may represent a form of proto-carnivory.

However, analysis of the mucilage revealed that plant is also producing digestive enzymes capable of breaking down insects unfortunate enough to have been caught. It remains to see whether or not the plants absorb nutrients in the same way as sundews but the fact that these plants share the same nutrient-poor habitats as many other Australian carnivores lends some credibility to asking that question.

Photo Credit: http://bit.ly/2hJjMyc and Francis Nge

Further Reading: [1] [2]

Bacteria Help the Cobra Lily Subdue Prey

The aptly named cobra lily (Darlingtonia californica) is one of North America's most stunning pitcher plants. Native to a small region between northern California and southwestern Oregon, this bizarrely beautiful carnivore lives out its life in nutrient poor, cold water bogs and seeps. Although it resides in the same family as our other North American pitcher plants, Sarraceniaceae, the cobra lily has a unique taxonomic position as the only member of its genus.

It doesn't take much familiarity with this plant to guess that it is carnivorous. Its highly modified leaves function has superb insect traps. Lured in by the brightly colored, tongue-like protrusions near the front tip of the hood, insects find a sweet surprise. These tongue-like structures secrete nectar. As insects gradually make their way up the tongue, they inevitably find themselves within the downward pointing mouth of the pitcher. This is where those translucent spots on the top of the hood come in.

These translucent spots trick the insects into flying upwards into the light. Instead of a clean getaway, insects crash into the inside of the hood and fall down within the trap. The slippery walls of the pitchers interior make escape nearly impossible but that isn't the only thing keeping insects inside. Research has shown that the cobra lily gets a helping hand from bacteria living within the pitcher fluid.

Unlike other pitcher plants, the cobra lily does not fill its traps with rain water. The downward pointing mouth prevents that from happening. Instead, the pitchers secrete their own fluid by pumping water up from the roots. Although there is evidence that the cobra lily does produce at least some of its own digestive enzymes, it is largely believed that this species relies heavily on a robust microbial community living within its pitchers to do most of the digesting for it. This mutualistic community of microbes save the plant a lot of energy while also providing it with essential nutrients like nitrogen in return for a safe place to live.

That isn't all the bacteria are doing for this pitcher plant either. As it turns out, the pitchers' microbial community may also be helping the plant capture and subdue its prey. A recent study based out of UC Berkeley demonstrated that the presence of these microbes helps lower the surface tension of the water, effectively drowning any insect almost immediately.

The microbes release certain compounds called biosurfactants. Through an interesting chemical/physical process that I won't go into here, this keeps insects from using the surface tension of the water's surface to keep them afloat, not unlike a water strider on a pond. Instead, as soon as insects hit the bacteria infested waters, they break the surface tension and sink down to the bottom of the pitcher where they quickly drown. There is little chance of escape for a hapless insect unlucky enough to fall into a cobra lily trap.

Although plant-microbe interactions are nothing new to science, this example is the first of its kind. Although this prey capture role is very likely a secondary benefit of the microbial community within the pitchers, it very likely makes a big difference for these carnivores living in such nutrient poor conditions.

Photo Credit: Wikimedia Commons

Further Reading: [1]

The Termite-Eating Nepenthes

Plants and eusocial insects have some interesting ecological relationships with one another. A vast majority of these relationships are between a plant a members of the order Hymenoptera (ants, bees, and wasps), but what about those other eusocial insects, the termites?

Despite the social similarities they share with many ants, bees, and wasps, termites are actually distant relatives of the cockroaches. As many already know, termites also have a relationship with plants. Thanks to symbiotic bacteria residing in their gut, termites are able to make a living eating wood and building massive colonies, sometimes in undesirable locations like in the framework of your house. However, there is at least one species of plant out there that has evolved a different kind of relationship with termites.

Meet Nepenthes albomarginata. Native to Borneo, Malaysia, and Sumatra, this tropical carnivore seems to have a taste for termites. However, unlike flies or ants that are attracted to sweet nectar, termites have a different palate. Feeding on plant materials, termites don't necessarily seem like the kind of insect a plant would want to attract. N. albomarginata has seemingly found a way to attract tasty termites without becoming a meal itself.

As the specific epithet suggests, there is a white ring located around the margin of the pitchers' mouths. The ring is made up of a dense coat of hairs called trichomes. It was discovered that sometimes this white ring would disappear overnight. The pitchers without the white ring were also chock-full of partially digested termites. Just how the termites find these pitchers isn't quite certain. Researchers have not yet been able to isolate a scent compound.

Either way, the termites swarm the ring. While many termites make off with a free meal, plenty more of them slip and fall into the trap. It has been found that N. albomarginata obtains upwards of 50% of its nitrogen needs from termites in this way. What's more, all of this happens in a span of a single evening. Once the ring is picked clean, the pitchers are no longer attractive to the termites. They go their way and the plant has its meal. Because of the social structure of these peculiar insects, the loss of these individuals is never high enough to represent a serious selective pressure.

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:

http://bit.ly/2cyXlvS

http://bit.ly/2cyWTxT

The Mountain Sweet Pitcher Plant

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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.

DSCN9284.JPG

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?

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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]

Zoophagous Liverworts?

Mention the word "liverwort" to most folks and you are going to get some funny looks. However, mention it to the right person and you will inevitably be drawn into a world of deep appreciation for this overlooked branch of the plant kingdom. The world of liverworts is best appreciated with a hand lens or microscope.

A complete lack of vascular tissue means this ancient lineage is often consigned to humid nooks and crannies. Look closely, however, and you are in for lots of surprises. For instance, did you know that there are liverworts that may be utilizing animal traps?

Right out of the gates I need to say that the most current research does not have this labelled as carnivorous behavior. Nonetheless, the presence of such derived morphological features in liverworts is quite sensational. These "traps" have been identified in at least two species of liverwort, Colura zoophaga, which is native to the highlands of Africa, and Pleurozia purpurea, which has a much wider distribution throughout the peatlands of the world.

The traps are incredibly small and likely derived from water storage organs. What is different about these traps is that they have a moveable lid that only opens inward. In the wild it is not uncommon to find these traps full of protozoans as well as other small microfauna. Researchers aimed to find out whether or not this is due to chance or if there is some active capture going on.

Using feeding experiments it was found that some protozoans are actually attracted to these plants. What's more these traps do indeed function in a similar way to the bladders of the known carnivorous genus Utricularia. Despite these observations, no digestive enzymes have been detected to date. For now researchers are suggesting that this is a form of "zoophagy" in which animals lured inside the traps die and are broken down by bacterial communities. In this way, these liverworts may be indirectly benefiting from the work of the bacteria.

This is not unheard of in the plant world. In fact, there are many species of pitcher plants that utilize similar methods of obtaining valuable nutrients. Certainly the lack of nutrients in the preferred habitats of these liverworts mean any supplement would be beneficial.

Photo Credits: Matt von Konrat Ph.D - Biblioteca Digital Mundial (eol.org), HESS ET AL. 2005 (http://www.bioone.org/doi/abs/10.1639/6), and Sebastian Hess (http://virtuelle.gefil.de/s-hess/forsch.html)

Further Reading:
http://www.bioone.org/doi/abs/10.1639/6

A Plant With Lobster-Pots

Pitfall, pitcher, urn, snap, bladder, sticky - all of these words have been used to describe the various means by which carnivorous plants capture their prey. But what about "lobster pot?" Believe it or not, there is a genus of plants that has evolved a strategy for catching prey that would make lobster fishers proud.

That genus is Genlisea. It comprises roughly 30 species of what are common called "corkscrew plants." They are native to both Central and South America as well as Africa. These plants are small and can be found growing in saturated, nutrient-poor soils, conditions that select for any trait that can supplement what the plant can't get from its soil environment. Unlike more charismatic carnivorous plants, the meat-eating habit of this group would not be readily discernible to the casual observer.

Above ground they resemble their cousins the bladderworts (Utricularia). The flowers are quite showy and most species present them in either yellow or purple. At ground level sits a dense rosette of leaves. These are only part of the foliar picture. The corkscrew plants produce an entirely different set of leaves that take care of their nutrient needs. To find these, however, one must look underground.

Genlisea have no roots. Instead, they are anchored into the soil by truly bizarre, highly modified leaves. These leaves produce no chlorophyll and look absolutely nothing like what we expect leaves to look like. Instead, they form a hollow cylinder that corkscrews down into the permanently saturated soils in which it lives. This is where its carnivorous habits take place.

Along the length of each corkscrewed leaf runs a slit-like opening. Lining the mouth and inside of the chamber are backwards pointing hairs. Like a lobster pot trap, animals can enter these slits with ease. Getting back out, however, is nearly impossible. The only option trapped critters have is to continue onward to their doom. Towards the end of the traps sits a chamber where most of the digestion takes place. A quick caveat here: to say animals is a bit misleading. Most of what these plants are feeding on are small, soil-dwelling protozoans.

Regardless, the traps are quite efficient. It was only recently discovered that this was a true form of carnivory. Darwin himself had suggested it after careful examination but it wasn't until the 1990's that any digestive enzymes were detected. Still, it is a bit of a mystery exactly how or even if these plants actually attract their prey. Some researchers have found substances within the cylinders that are hypothesized to act as chemical attractants, however, more work needs to be done on this.

The traps don't spell certain death for all life. In an interesting study, researchers identified 29 different kinds of algae living inside the traps. Since dissolved oxygen is quite low inside, most of these algae are specialized for anoxic environments. The nature of the relationship between the algae and the corkscrew plants is not certain at this point. Some think it might be commensal whereas others feel that the algae may compete with the plant for phosphorus. Again, more work is needed.

The carnivorous nature of this genus isn't the only interesting aspect of their evolutionary history either. Some member of this genus, specifically Genlisea aurea, exhibit some of the smallest genomes of any flowering plant. This is not an ancestral state for this group meaning that at one time, the common ancestor had a much larger genomes but subsequent pruning has gotten rid of most of the "non-coding" sequences. Though there is plenty of speculation as to why this has happened, it is still anyone's guess at this point.

Photo Credits: NoahElhardt (assumed-Wikimedia Commons), Scott Zona (http://bit.ly/1ZHACAk), and B Mlry (http://bit.ly/1ZHAEbw)

Further Reading:
http://www.tandfonline.com/doi/pdf/10.1080/12538078.2005.10515466

http://aob.oxfordjournals.org/content/114/8/1651

http://aob.oxfordjournals.org/content/100/4/849.short

http://aob.oxfordjournals.org/content/100/2/195.short

http://bmcgenomics.biomedcentral.com/articles/10.1186/1471-2164-14-476

bit.ly/1WurdqE

Going Veg With Nepenthes ampullaria

Carnivory in the plant kingdom is an interesting evolutionary adaptation to living in nutrient poor environments. It has arisen in only a handful of different plant families and indeed, the genera that exhibit it are considered highly derived. There is something to be said about a sessile organism that can take down mobile prey at the rate that most carnivorous plants do.

Perhaps part of our fascination with these botanical wonders stems from their move towards dietary habits not unlike our own. The reason for their predatory behavior is to acquire nutrients like nitrogen and phosphorus. Without these essential nutrients, life as we know it would not exist. It is no wonder then that carnivorous plants have evolved some very interesting ways of getting them into their tissues and to me, there is nothing more peculiar than the way in which Nepenthes ampullaria gets its much needed nitrogen fix.

A rather widespread species, N. ampullaria is at home in the understory of the rain forests of the southeast Asian islands. It differs from its carnivorous cousins in a multitude of ways. For starters, the pitchers of N. ampullaria are oddly shaped. Resembling an urn, they sit in dense clusters all over the jungle floor, below the rest of the plant. Unlike other Nepenthes, the pitchers have only a small, vestigial lid with no nectar glands. Finally, the slippery, waxy surface that normally coats the inside of most Nepenthes pitchers is absent in the pitchers of N. ampullaria. All of these traits are clues to the unique way in which this species has evolved to acquire nitrogen.

N. ampullaria doesn't lure and digest insects. Instead, it relies on leaf litter from the forest canopy above for its nutritional needs. The urn-like shape, lack of a hood, and clustered growth enable the pitchers to accumulate considerable amounts of leaf litter in the pitchers. Because the pitchers are relatively long lived for a Nepenthes, lasting upwards of 6 months, they offer up a nice microhabitat for a multitude of insect and even frog larvae. The collective group of organisms living within the pitchers are referred to as an inquiline community.

 Photo by: Benjamin Tapley http://www.inaturalist.org/photos/44997

Photo by: Benjamin Tapley http://www.inaturalist.org/photos/44997

Over time, an inquiline community develops in each of the pitchers. This is the key to the success of N. ampullaria. As the inquiline organisms breakdown the leaf litter, they release copious amounts of nitrogen-rich waste. The pitchers can then absorb this waste and begin to utilize it. At least one study found that an individual plant can obtain 35.7% of its foliar nitrogen in this manner. It has also been demonstrated that the pitchers actively manipulate the pumping of hydrogen ions into the fluid within to keep it less acidic than that of other Nepenthes.

I don't know if I would consider this a case of herbivory as the nitrogen is still coming from an animal source but it is nonetheless an interesting adaptation. Instead of using valuable resources on actively digesting its own prey, N. ampullaria is getting other organisms to do the work for it. Not too shabby.

Photo Credit: Jonathan A. Moran, Charles M. Clarke, and Barbara J. Hawkins

Further Reading:

http://bit.ly/1IRbYG9

http://jxb.oxfordjournals.org/content/61/5/1365

http://link.springer.com/article/10.1007/s004420050390

http://bit.ly/1S10oej

The Fanged Pitcher Plant of Borneo

As mammals, and even more so as apes, we tend to associate fangs with threat. 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. Ladies and gentlemen, I present to you the bizarre fanged pitcher plant (Nepenthes bicalcarata).

This peculiar 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 the fangs? There has been a lot of debate amongst botanists as to what purpose 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 very 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?

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 of the plant are hollow and serve as nest sites for these ants. They take up residence in the tendrils and will hunt along the insides of the pitchers. They literally go swimming in the pitcher fluid for their meals!

This is why the fluid differs so drastically from other Nepenthes. The fanged pitcher plant actually does very little of its own digestion. Instead, it relies on the ants 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 and the deposition of nitrogen-rich feces. Indeed, plants without a resident ant colony are 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!

Further Reading:
http://www.gtoe.de/public_html/publications/pdf/5-1/Merbach%20et%20al.%201999,%20Ecotropica%205_45-50.pdf

http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2435.2011.01937.x/abstract;jsessionid=894F843898B727CD6E7BF16E109A70F2.f01t01

http://discovermagazine.com/2001/oct/featplants

http://www.iucnredlist.org/details/39624/0

http://www.scientificamerican.com/article/it-seems-that-in-almost-a/

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:
http://plants.usda.gov/core/profile?symbol=PIVU

http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.1984.tb04105.x/abstract

http://mnfi.anr.msu.edu/abstracts/botany/Pinguicula_vulgaris.pdf

http://www.snh.gov.uk/docs/B823176.pdf

An Introduction to Cephalotus follicularis - A Strange Carnivore From Australia

In a small corner of western Australia grows one of the most unique carnivorous plants in the world. Commonly referred to as the Albany pitcher plant, Cephalotus follicularis is, evolutionarily speaking, distinct among the pitcher plants. It is entirely unrelated to both the Sarraceniaceae and the Nepenthaceae.

This stunning case of convergent evolution stems from similar ecological limitations. Cephalotus grows in nutrient poor areas and thus must supplement itself with insect prey. It does so by growing modified leaves that are shaped into pitchers. The lid of each pitcher serves two purposes. It keeps rain from diluting the digestive enzymes within and it also confuses insects.

A close inspection of the lid will reveal that it is full of clear spots. These spots function as windows, allowing light to penetrate and confuse insects that have landed on the trap. As they fly upwards into the light, they crash into the lid and, with a little help from physics, fall down into the trap.

The relationship of Cephalotus to other plants has been the object of much scrutiny. Though it is unique enough to warrant its own family (Cephalotaceae), its position in the greater scheme of plant taxonomy originally had it placed in Saxifragales. Genetic analysis has since moved it out of there and now places it within the order Oxalidales. What is most intriguing to me is that the closest sister lineage to this peculiar little pitcher plant are a group of trees in the family Brunelliaceae. Evolution can be funny like that.

Regardless of its relationship to other plants, Cephalotus follicularis has gained quite a bit of attention over the last few years. Its strange appearance and carnivorous habit have earned it a bit of stardom in the horticultural trade. A single specimen can fetch a hefty price tag. As a result, collecting from wild populations has caused a decline in numbers that are already hurting due to habitat destruction. Luckily they are easy to culture in captivity, which will hopefully take pressure off of them in the wild.

What's more, the loss of Cephalotus from the wild is hurting more than just the plant. A species of flightless, ant-mimicking fly requires Cephalotus pitchers to rear its young. They don't seem to mind growing up in the digestive enzymes of the pitchers and to this date, their larvae have been found living nowhere else. If you are lucky enough to grow one of these plants, share the wealth. Captive reared specimens not only take pressure off wild populations, they are also much hardier. Lets keep wild Cephalotus in the wild!