The Carnivorous Plant Guild Welcomes a New Member

Photo by Michael Kauffmann (www.backcountrypress.com)

It is a rare but special day when we can add a new plant to the relatively small list of carnivorous plants. It is even more exciting when that plant has been “hiding” in plain sight all this time. Meet the western false asphodel (Triantha occidentalis), a lovely monocot native to nutrient-poor wetlands in western North America.

Triantha occidentalis may seem like an odd carnivorous plant. At first glance, it doesn’t have much in the way of carnivorous adaptations; there are not pitfall traps, no sticky leaves, no snap traps, and no bladders anywhere on the plant. However, if you were to examine this species during its flowering season, you would notice that a lot of small insects seem to get stuck to its flowering stem.

Indeed, the ability of this species to trap insects has been known for quite some time. Even old herbarium collections of T. occidentalis are chock full of insect remains stuck to the scape. Magnify the flowering stem and you will see that it is covered in sticky hairs or trichomes that look a lot like miniature versions of those covering the leaves of more obvious carnivores like sundews (Drosera spp.). Observations such as these led scientists to investigate whether this wonderful little wetland monocot actually benefits from trapping all those arthropods.

Via a series of experiments using isotopes of nitrogen, scientists have revealed that T. occidentalis really does obtain a nutritional boost from the insects it traps. This isn’t a passive process on the part of the plant either. It was also discovered that the plant also secrets the digestive enzyme phosphatase, which helps break down the trapped insects. When the team examined what was going on within the tissues of the plant, they found even more evidence of its carnivorous nature.

Look closely and you can see sticky glands and trapped insects just below the flowers! Photo by Michael Kauffmann (www.backcountrypress.com)

It turns out that 64% of the nitrogen within the plant is obtained via insect digestion, which is comparable to that of other known carnivorous plants such as the aforementioned sundews. Interestingly, it appears that the insect nitrogen the plant obtains is first stored in the flowering stem and fruits but is then transported down into the roots and rhizome underground to be utilized in the following growing season. Why exactly the plant does this requires further investigations. Perhaps by using its flowering stems to obtain nutrients that are in short supply in its wetland habitat, the plant is able to better offset the cost of flowering each year.

By far the most remarkable aspect of this discovery is where carnivory occurs on the plant. With few exceptions, the vast majority of carnivorous plants keep their feeding organs away from their flowers. The leading hypothesis on this suggests that separating feeding and reproduction in space (and sometimes time) helps carnivorous plants avoid catching and digesting their pollinators. However, T. occidentalis does the opposite. It produces all of its sticky hairs very close to its blooming flowers.

Large floral visitors like butterflies appear to be the main pollinators and are too large to get stuck, whereas smaller insects like midges do. Photo by Michael Kauffmann (www.backcountrypress.com)

The key to this apparent morphological contradiction may lie in the stickiness of those hairs. It has been observed that the vast majority of insects trapped on the flowering stems of T. occidentalis are mostly midges and other small insects that don’t function as pollinators for the plant. It is possible that the larger bees and butterflies that could function as true pollinators are simply too large and strong to be trapped. Again, more research is needed to say for sure.

All in all, T. occidentalis represents a unique carnivorous plant whose true nature required solid natural history knowledge and observation to reveal. The fact that we are just learning about its carnivorous habit after all this time suggests that many more potentially carnivorous plants may also be “hiding” in plain sight (I’m looking at you, Silene), waiting for curious minds to collect the necessary data. This is also an exciting discovery from a taxonomic perspective as well. Up until now, all of the known carnivorous monocots hail from the order Poales. Therefore, T. occidentalis represents the first non-Poalean carnivorous monocot! For all these reasons and more, I am excited about future research on this plant and others like it.

Further Reading: [1]

Should We Be Calling Aquatic Bladderworts Omnivores Instead of Carnivores?

Photo by Leonhard Lenz licensed under CC BY-NC 2.0

As is so often the case in nature, the closer we start to look at things, the more interesting they become. Take, for instance, the diet of some carnivorous bladderworts (Utricularia spp.). These wonderful organisms cover their photosynthetic tissues in tiny bladder traps that rapidly spring open whenever a hapless invertebrate makes the mistake of coming too close to a trigger hair. The unlucky prey is quickly sucked into the trap and subsequently digested.

This is how most bladderworts supplement their growth. As cool as this mechanism truly is, our obsession with the idea that these plants are strict carnivores has historically biased the kinds of investigations scientists attempt with these plants. Over the last decade or so, closer inspection of the contents of aquatic bladderwort traps has revealed that a surprising amount of plant material gets trapped as well. Most of this material consists of single celled algae. Is it possible that at least some aquatic bladderworts also gain nutrients from all of that “vegetable” matter?

The answer to this question is a bit more nuanced than expected. Yes, it does appear that non-animal material frequently ends up in bladderwort traps. Much of this comes in the form of a wide variety of algae species. What’s more, it does appear that algae are broken down within the traps themselves, suggesting that the bladderworts are actively digesting this material. The main question that needs to be answered here is whether or not the bladderworts actually benefit from the breakdown of algae.

Evidence of a nutritive benefit from algae digestion is mixed. Some studies have found that the bladderworts don’t appear to benefit at all from the breakdown of algae within their traps. Alternatively, others have found that bladderworts may benefit from digesting at least some types of algae. These authors noted that there doesn’t seem to be any benefit in terms of additional nitrogen for the bladderwort but instead suggest that other trace nutrients might be obtained in this way.

One of the biggest hurdles in this line of research arises from the fact that we still don’t fully understand the digestive mechanisms of bladderworts. It is possible that some of the algal degradation within bladderwort traps has nothing to do with digestion at all. Instead, it could simply be that algae stuck in the traps eventually dies and rots away. Another major question raised by these observations is how tiny organisms like single celled algae even make it into the traps in the first place. What we can say for sure is most algae are far too small to actually trigger the bladder traps. As such, algae is either getting into the traps passively via some form of diffusion or they are sucked in when other, larger prey is captured.

Some research has even suggested that the benefit of trapping algae may depend on the habitats in which bladderworts are growing. Bladderworts living in more acidic water have shown to capture far more algae than bladderworts in more neutral or alkaline water. This has to do with acidity. Numerically speaking, there is far less zooplankton living in acidic water than algae, which means algae is more likely to end up in the bladders. It could be that the benefits of algae are thus greater for plants living in places where little zooplankton is available. Certainly more work will be needed before we can call bladderworts omnivores but the idea itself is exciting.

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

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

Encounters With a Rare White-Topped Carnivore

I am not a list maker. Never have been and never will be. That being said, there are always going to be certain plants that I feel I need to see in the wild before I die. The white-topped pitcher plant (Sarracenia leucophylla) was one such plant.

I will never forget the first time I laid eyes on one of these plants. It was at a carnivorous plant club meeting in which the theme had been “show and tell.” Local growers were proudly showcasing select plants from their collections and it was a great introduction to many groups which, at the time, I was unfamiliar with. Such was the case for the taller pitcher plants in the genus Sarracenia. Up until that point, I had only ever encountered the squat purple pitcher plant (S. purpurea).

I rounded the corner to a row of display tables and was greeted with a line of stunning botanical pitfall traps. Nestled in among the greens, reds, and yellows was a single pot full of tremendously white, green, and red pitcher plants. I picked my jaw up off the floor and inquired. This was the first time I had seen Sarracenia leucophylla. At that point I knew I had to see such a beauty in the wild.

More like white and red top…

It would be nearly a decade before that dream came true. On my recent trip to the Florida panhandle, I learned that there may be a chance to see this species in situ. Needless to say, this plant nerd was feeling pretty ecstatic. Between survey sites, we pulled down a long road and parked our vehicle. I could tell that there was a large clearing just beyond the ditch, on the other side of the trees.

The clearing turned out to be an old logging site. Apparently the site was not damaged too severely during the process as the plant diversity was pretty impressive. We put on our boots and slogged our way down an old two track nearly knee deep in dark, tanic water. All around us we could see amazing species of Sabatia, Lycopodiella, Drosera, and so much more. We didn’t walk far before something white caught my eye.

There to the left of me was a small patch of S. leucophylla. I had a hard time keeping it together. I wanted to jump up and down, run around, and let off all of the excited energy that had built up that morning. I decided to reign it in, however, as I had to be extra careful not to trample any of the other incredible plants growing near by. It is always sad to see the complete disregard even seasoned botanists have for plants that are unlucky enough to be growing next door to a species deemed “more exciting,” but I digress.

Sarracenia leucophylla flower. Photo by Noah Elhardt licensed by GNU Free Documentation License [SOURCE]

This was truly a moment I needed to savor. I took a few pictures and then put my camera away to simply enjoyed being in the presence of such an evolutionary marvel. If you know how pitcher plants work then you will be familiar with S. leucophylla. Its brightly colored pitchers are pitfall traps. Insects lured in by the bright colors, sweet smell, and tasty extrafloral nectar eventually lose their footing and fall down into the mouth of the pitcher. Once they have passed the rim, escape is unlikely. Downward pointing hairs and slippery walls ensure that few, if any, insects can crawl back out.

What makes this species so precious (other than its amazing appearance) is just how rare it has become. Sarracenia leucophylla is a poster child for the impact humans are having on this entire ecosystem. It can only be found in a few scattered locations along the Gulf Coast of North America. The main threat to this species is, of course, loss of habitat.

A large conservation population growing ex situ at the Atlanta Botanical Garden.

Southeastern North America has seen an explosion in its human population over the last few decades and that has come at great cost to wild spaces. Destruction from human development, agriculture, and timber production have seen much of its wetland habitats disappear. What is left has been severely degraded by a loss of fire. Fires act as a sort of reset button on the vegetation dynamics of fire-prone habitats by clearing the area of vegetation. Without fires, species like S. leucophylla are quickly out-competed by more aggressive plants, especially woody shrubs like titi (Cyrilla racemiflora).

Another major threat to this species is poaching, though the main reasons may surprise you. Though S. leucophylla is a highly sought-after species by carnivorous plant growers, its ease of propagation means seed grown plants are usually readily available. That is not to say poaching for the plant trade doesn’t happen. It does and the locations of wild populations are best kept secret.

Sarracenia leucophylla habitat. Photo by Brad Adler licensed by CC BY-SA 2.5 [SOURCE]

The main issue with poaching involves the cut flower trade. Florists looking to add something exotic to their floral displays have taken to using the brightly colored pitchers of various Sarracenia species. One or two pitchers from a population probably doesn’t hurt the plants very much but reports of entire populations having their pitchers removed are not uncommon to hear about. It is important to realize that not only do the pitchers provide these plants with much-needed nutrients, they are also the main photosynthetic organs. Without them, plants will starve and die.

I think at this point my reasons for excitement are pretty obvious. Wandering around we found a handful more plants and a few even had ripening seed pods. By far the coolest part of the encounter came when I noticed a couple damaged pitchers. I bent down and noticed that they had holes chewed out of the pitcher walls and all were positioned about half way up the pitcher.

I peered down into one of these damaged pitchers and was greeted by two tiny moths. Each moth was yellow with a black head and thick black bands on each wing. A quick internet search revealed that these were very special moths indeed. What we had found was a species of moth called the pitcher plant mining moth (Exyra semicrocea).

An adult pitcher plant mining moth (Exyra semicrocea) sitting within a pitcher!

Amazingly, the lives of these moths are completely tied to the lives of the pitcher plants. Their larvae feed on nothing else. As if seeing this rare plant wasn’t incredible enough, I was witnessing such a wonderfully specific symbiotic relationship right before my very eyes.

Fortunately, the plight of S. leucophylla has not gone unnoticed by conservationists. Lots of attention is being paid to protecting remaining populations, collecting seeds, and reintroducing plants to part of their former range. For instance, it has been estimated that efforts to protect this species by the Atlanta Botanical Garden have safeguarded most of the genetic diversity that remains for S. leucophylla. Outside of direct conservation efforts, many agencies both public and private are bringing fire back into the ecology of these systems. Fires benefit so much more than S. leucophylla. They are restoring the integrity and resiliency of these biodiverse wetland habitats.

LEARN MORE ABOUT WHAT PLACES LIKE THE ATLANTA BOTANICAL GARDEN ARE DOING TO PROTECT IMPORTANT PLANT HABITATS THROUGHOUT THE SOUTHEAST AND MORE.

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

Bacteria Help the Cobra Lily Subdue Prey

Photo by David Berry licensed under CC BY 2.0

The 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 as 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.

Those 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 pitcher 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 saves 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 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.

Some members of the microbial community release special 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 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 certainly makes a big difference for these carnivores living in such nutrient poor conditions.

Read more about the amazing world of carnivorous plants by picking up a copy of my book!

Photo Credit: [1] [2]

Further Reading: [1]

An Introduction to Cephalotus follicularis - A Strange Carnivore From Australia

Photo by H. Zell licensed under CC BY-SA 3.0

In a small corner of western Australia grows a truly unique carnivorous plant. 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 has two main functions. 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, which confuses insects that have landed on the trap. As they fly upwards into the light, they crash into the lid and fall back down into the trap.

Photo by Lucas Arrrrgh licensed under CC BY-NC-ND 2.0

The relationship of Cephalotus to other plants has been the object of much scrutiny. Though it is different 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 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!

Photo by Holger Hennern licensed under CC BY-SA 3.0

Photo Credits: Holger Hennern (Wikimedia Commons) and Lucas Arrrrgh (https://www.flickr.com/photos/chug/2121092119/)

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

Devil's Claws

Proboscidea louisianica

I would like to introduce you to the genus Proboscidea. These lovely, albeit sticky plants are collectively referred to as the Devil's claw plants. The common name comes from the nasty looking seed pods which likely evolved in response to large mammals that once roamed this continent. The genus Proboscidea has traditionally been placed into the sesame family (Pedaliaceae) due to superficial similarities in flower and seed morphology, but more recent work has moved it into the unicorn plant family, Martyniaceae. That's right... unicorn plants.

The entire family is found in the New World, with two species (P. lousianica & P. althaeifolia) hailing from arid parts of the southern portions of North America. At least two other species are readily naturalizing in this region as well. There are some aspects of these species that make them quite interesting to botanists. For starters, the apt name of Devil's claw was bestowed upon this genus because of the bizarre seed pods they produce. Similar to burs, they can become entangled in fur quite readily. The odd thing about this seed dispersal mechanism for some Devil's claws is how big those seed pods are. Until cattle were introduced to this continent, animals large enough to effectively disperse these massive seed pods seemed to be missing, having gone extinct at the end of the last ice age. It is believed that these plants may be an anachronism of this era.

Photo by T.K. Naliaka licensed under CC BY-SA 4.0

Photo by Roger Culos licensed under CC BY-SA 3.0

The flora we are familiar with today spent millennia co-evolving with ice age megafauna like mammoths and giant ground sloths. There is a growing school of thought that many close relationships probably developed over this time and have not yet been lost due to the relatively limited amount of time since the extinction of these large mammals. There are some people who will tell you that the seed pods are "designed" to ensnare small mammals like mice, causing them to die, which then provides the seeds a nutrient-rich, rotting corpses on which to germinate. I have never been able to find any evidence in support of these claims.

Another intriguing anatomical feature of this species are the countless sticky glands that cover the entire plant. These readily ensnare insects that land on or try to climb up the plant. Analysis of the fluids secreted by these glands show evidence of digestive enzymes but the jury still seems to be out on whether or not Devil's claws are undergoing any active carnivorous behavior.

Proboscidea althaeifolia. Public Domain

It is more likely that these glands are a form of defense against insect herbivores and indeed they work quite well. Even a brief run-in with this plant leaves you quite sticky and slimy. It is possible that by ensnaring herbivorous insects, the plant can attract carnivorous insects that will eat the herbivores and then "repay" the devil's claw with nutrient-rich feces. Another possibility is that the glands cause the plant to become covered in sand grains over time. Such sandy armor would get in the way of hungry herbivores. To ad insult to injury, the plant kind of smells. It has been likened to old gym clothes.

These are neat plants. I have had fun growing them in the past. They are an annual but may reseed if care is not taken to removing the seed pods before they pop open. Because of their lively appearance and the unique look of their seed pods, these plants are often grown as horticultural oddities. Be careful though, as they have escaped cultivation outside of their native range and can be considered a noxious weed!

Photo Credit: [1] [2] [3]

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

A New Look at a Common Bladderwort

Photo by Kevin Thiele licensed under CC BY 2.0

It is so often that common species are overshadowed by something more exotic. Indeed, we know more about some of the rarest plants on earth than we do about species growing in our own back yards. Every once in a while researchers break this pattern and sometimes this yields some amazing results. Nowhere has this been better illustrated in recent years than on the humped bladderwort, Utricularia gibba. 

This wonderful little carnivore can be found growing in shallow waters all over the world. Like all Utricularia, it uses tiny little bladders to capture its even tinier prey. Despite its diminutive size, U. gibba is nonetheless a very derived species. For all of its wonderful physical attributes, the real adventure begins at the microscopic level. As it turns out, U. gibba has some amazing genetic attributes that are shining light on some incredible evolutionary mechanisms. 

When researchers from the University at Buffalo, Universitat de Barcelona in Spain, and LANGEBIO in Mexico decided to sequence the genome of this plant, what they found was quite startling. For a rather complex little plant, the genome of U. gibba is incredibly small. What the researchers found is that U. gibba appears to be very efficient with its DNA. Let's back up for a moment and consider this fact. 

The genomes of most multicellular organisms contain both coding and non-coding DNA. For decades researchers have gone back and forth on how important non-coding DNA is. They do not code for any protein sequences but they may play a role in things like transcription and translation. For a long time this non-coding DNA has been referred to as junk DNA. 

This is where things get interesting. Sequencing of the U. gibba genome revealed that only 3% of its genome consisted of non-coding or junk DNA. For some reason the U. gibba lineage has managed to delete most of it. To put things in perspective, the human genome is comprised of roughly 98% non-coding or junk DNA. Despite its rather small and efficient genome, U. gibba nonetheless has more genes than plants with larger genomes. This may seem confusing but think of it this way, whereas U. gibba has a smaller overall genetic code, it is comprised of more genes that code for things like digestive enzymes (needed for digesting prey) and cell walls (needed to keep water out) than plants with more overall genetic code such as grapes or Arabidopsis. 

As one author put it, this tiny ubiquitous plant has revealed "a jewel box full of evolutionary treasures." It is a species many of us have encountered time and again at the local fishing hole or in your favorite swimming pond. Time and again we pass by the obvious. We overlook those organisms that are most familiar to us. We do so at the cost of so much knowledge. It would seem that the proverbial "Old Dog" has plenty of tricks to teach us. 

Photo Credit: Kevin Thiele (http://bit.ly/1Flouqd) and Reinaldo Aguilar (http://bit.ly/1B6mnHN)

Further Reading:

http://www.nature.com/nature/journal/v498/n7452/full/nature12132.html

http://mbe.oxfordjournals.org/content/early/2015/01/31/molbev.msv020

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

Slippery When Wet

Photo by Andrea Schieber licensed under CC BY-NC-ND 2.0

Pitcher plants in the genus Nepenthes have been getting a lot of attention in the literature as of late. Not only have researchers discovered the use of ultraviolet pigments around the rims of their pitchers, it has also been noted that the pitchers of many species aren't as slippery as we think they are. Indeed, scientists have noted that prey capture is at its highest only when the pitchers are wet. This seems counterintuitive. Why would a plant species that relies on the digestion of insects for most of its nitrogen and phosphorus needs produce insect traps that are only effective at certain times? After all, it takes a lot of energy for these plants to produce pitchers, which give little to nothing back in the way of photosynthesis. 

The answer to this peculiar conundrum may lie in the types of insects these plants are capturing. Ants are ubiquitous throughout the world. Their gregarious and exploratory nature has provided ample selection pressures for much of the plant kingdom. They are particularly well known for their military-esque raiding parties. It is this behavior that researchers have looked at in order to explain the intermittent effectiveness of Nepenthes pitchers. 

A recent study that looked at Nepenthes rafflesiana found that ants made up 65% of the prey captured, especially on pitchers produced up in the canopy. What's more, younger pitchers produced closer to the ground were found to be much more slippery (containing more waxy cells) than those produced farther up on the plant. When the pitchers of this species were kept wet, prey capture consisted mostly of individual insects such as flies. However, when allowed to dry between wettings, the researchers found that prey capture, specifically ants, increased dramatically. How is this possible?

It all goes back to the way in which ants forage. A colony sends out scouts in all directions. Once a scout finds food, it lays down a pheromone trail that other ants will follow. It is believed that this is the very behavior that Nepenthes are relying on. The traps produce nectar as a lure for their insect prey. As the traps dry up, the nectar becomes concentrated. Ants find this sugary treat irresistible. However, if the pitcher were to be slippery at all times, it is likely that most ant scouts would be killed before they could ever report back to the colony. By reducing the slippery waxes, especially around the rim of the trap, the Nepenthes are giving the ants a chance to "spread the news" about this new food source. Because these plants grow in tropical regions, humidity and precipitation can fluctuate wildly throughout a 24 hour period. If the scouting party returns at a time in which the pitchers are wet then the plant stands to capture far more ants than it did if it had only caught the scout. 

This is what is referred to as batch capture. The plants may be hedging their bets towards occasional higher nutrient input than constant low input. This is bolstered by the differences between pitchers produced at different points on the plant. Lower pitchers, especially on younger plants are far more waxy and thus are constantly slippery. This allows constant prey capture to fuel rapid growth into the canopy. Upper pitchers on older individuals want to maximize their yields via this batch capture method and therefore produce fewer waxy cells, relying on a humid climate to do the work for them. It is likely that this is a form of tradeoff which benefits different life cycle stages for the plant. 

Photo Credit: Andrea Schieber (http://bit.ly/1xUsGJk)

Further Reading:

http://rspb.royalsocietypublishing.org/content/282/1801/20142675

An Unlikely Carnivore from Brazil

There is something about a plant eating an animal that makes it all the more beautiful. Indeed, even without carnivory, the beauty of these highly adapted plant species is up there with the fanciest of horticultural creations. Nowhere is this fact more apparent than in a recently described species of plant from Brazil. Philcoxia minensis has only been known to science since 1981 and the way in which it has adapted to catching its prey is rather incredible.

Native to montane savannas of southeastern Brazil, these delicate members of the family Scrophulariaceae grow in nutrient poor, sandy habitats. They seem rather delicate with only a thin flowering stalk readily apparent above the soil line. The botanists who first discovered this species made an interesting observation, the leaves of this plant grow mostly underground. Though they do contain functional chloroplasts, it was initially assumed that they served little function. 

As it turns out, the leaves can in fact photosynthesize. The white sands that these plants grow in likely permit just enough light to penetrate down into the clear grains, allowing photosynthesis to happen. However, this is not the strangest thing about Philcoxia. Since this genus was first described, botanists have taken interest in the glandular stalks on the leaves. They noted that they were quite sticky and hypothesized that Philcoxia minensis may be carnivorous. 

Initial investigations into this were not conclusive. Recently, however, this has changed. A study published in 2012 used special nitrogen markers to look deeper into the potential carnivorous habits of this plant. What they found was quite amazing. As it turns out, there is very strong evidence that Philcoxia minensis uses its sticky traps to capture and eat nematodes under the soil. Not only is Philcoxia new to science, it also offers us yet another view into the many different ways plants have evolved to obtain precious nutrients in harsh environments. 

Photo Credit: Caio G. Pereiraa, Daniela P. Almenarab, Carlos E. Winterb, Peter W. Fritschc, Hans Lambersd, and Rafael S. Oliveira

Further Reading:
http://www.pnas.org/content/109/4/1154.abstract

http://www.jstor.org/discover/4117770?sid=21105606841053&uid=2

Carnivores in Amber

Carnivorous leaves from Eocene Baltic amber. (A) Overview of the leaf enclosed in amber showing the adaxial tentacle-free side in slightly oblique view and stalked glands at the margin and on the abaxial side; arrowhead points to the exceptional long tentacle stalk with several branched oak trichomes attached. (B) Overview of the leaf enclosed in amber, showing abundant tentacles on the abaxial side. (C) Margin of abaxial leaf surface with tentacles of different size classes and nonglandular trichomes [SOURCE]

Carnivorous plants are marvels of evolution. Adapting to nutrient poor conditions, these botanical curiosities have evolved myriad ways of capturing and digesting prey. For all of their extant diversity, the fossil record of carnivorous plants over the eons is pretty much non existent save for some highly contentious fossils from China as well as some fossilized seeds of the aquatic carnivore, Aldrovanda. However, a recent discovery out of Russia changes everything. Beautifully preserved in amber, we now have the first conclusive fossil evidence of a carnivorous plant.

The amber was found in a mine in Russia and is estimated to be between 35 and 47 million years old, during an epoch known as the Eocene. Inside are beautifully preserved leaves of what seems to be a species of Roridula. The leaves clearly show specialized stalked glands with a pore at the tip. The researchers who discovered the amber also found evidence of the sticky secretions that were used to capture its prey.

Overviews showing the tentacle-free adaxial surface and tentacles along the leaf margins (B & C). (D) Partial leaf tip showing different size classes of stalked glands. [SOURCE]

The resemblance of these leaves to the leaves of extant Roridula is uncanny. Modern Roridula do not directly digest their prey. Instead, they rely on a symbiotic relationship between a species of bug, which lives on the leaves without getting stuck. The bugs hunt down and eat trapped insects. As they eat, the bugs defecate and it is their nitrogen-rich feces that the plants absorb for sustenance. It is quite possible that the fossilized Roridula also relied on these insects as well, though no direct evidence of this was found. 

The most interesting aspect of this discovery is its location. Today, Roridula is found only in South Africa. Its presence in Russia hints at a historic distribution that is much wider than previously thought. It has long been assumed that Roridula is a neoendemic to South Africa, with the family having arisen there and nowhere else. This discovery now shows Roridula to be a paleoendemic, once having a much wider distribution but currently restricted to South Africa. This discovery is an excitingly huge step in our understanding of carnivorous plant evolution. 

Morphological comparison of the carnivorous leaf fossils from Baltic amber (Left) and extant Roridula species (Right). (A and B) Leaf tip ending in a sole tentacle. (C and D) Stalked glands of different size classes. (E and F) Hyaline unicellular nonglandular trichomes. (G and H) Epidermal cells and stomata. (I–L) Multicellulartentacles. (A, C, E, and G) (I and J). (B, D, K, and L) R. gorgonias. [SOURCE]

Photo Credit: Alexander R. Schmidt, University of Göttingen

Further Reading: [1]