Gooey Pitcher Fluids

Nepenthes_inermis4.jpg

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

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

Nepenthes_inermis1.jpg

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

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

Looking into the pitcher of  Nepenthes inermis .

Looking into the pitcher of Nepenthes inermis.

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

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

The upper pitcher of the closely related  Nepenthes dubia .

The upper pitcher of the closely related Nepenthes dubia.

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

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

Nepenthes jamban  takes the toilet bowl shape to the extreme.

Nepenthes jamban takes the toilet bowl shape to the extreme.

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

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

Photos via Wikimedia Commons

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

A Herbaceous Conifer From the Triassic

aleth1.jpg

It is hard to make broad generalizations about groups of related organisms. There are always exceptions to any rule. Still, there are some “facts” we can throw around that seem to apply pretty well to specific branches on the tree of life. For instance, all of the gymnosperm lineages we share our planet with today are woody, relatively slow to reach sexual maturity, and are generally long-lived. This has not always been the case. Fossil discoveries from France suggest that in the past, gymnosperms were experimenting with a more herbaceous lifestyle.

The fossils in question were discovered in eastern France back in the 1800’s. The strata from which they were excavated dates back to the Middle Triassic, some 247 million years ago. Immortalized in these rocks were numerous spindly plants with strap-like leaves and a few branches, each ending in what look like tiny cones. Early interpretations suggested that these may represent an extinct lycopod, however, further investigation suggested something very surprising - a conifer with an herbaceous growth habit.

Indeed, thanks to even more scrutiny, it is now largely agreed upon that what was preserved in these rocks were essentially herbaceous conifers. The fossils were given the name Aethophyllum stipulare. They are wonderfully complete, depicting roots, shoots, leaves, and reproductive organs. Moreover, the way in which they were fossilized preserved lots of fine-scale anatomical details. Taken together, there are plenty of clues available that allow paleobotanists to say a lot about how this odd conifer made a living.

For starters, they were not very big plants. Not a single specimen has been found that exceeds 2 meters (6.5 ft) in height. The main stem of these conifers only seem to branch a couple of times. Cones were formed at the tips of the upper branches and not a single specimen has been found that depicts subsequent growth following cone formation. This suggests that Aethophyllum exhibited determinate growth, meaning that individuals grew to a certain size, reproduced, and did not continue to grow after that. Female cones were situated at the tips of the upper most branches and male cones were situated at the tips of lower shoots. The smallest reproductive individuals that have been unearthed are only 30 cm (11 in) in height, which suggests that Aethophyllum  was capable of reproducing within a few months of germination.

Artists reconstruction of  Aethophyllum stipulare

Artists reconstruction of Aethophyllum stipulare

Amazingly, researchers were also able to extract fossilized pollen and seeds from some of the Aethophyllum cones. The pollen itself is saccate, much like what we see in many extant conifers. By comparing the morphology of the pollen extracted from the cones to other fossil pollen records, researchers now feel confident that Aethophyllum is the source of pollen grains discovered in sediments from western, central, and southern Europe, Russia, Northern Africa, and China, suggesting that Aethophyllum was pretty wide spread during the Middle Triassic. Aethophyllum seeds were small, ellipsoid, and were not winged, likely germinating a short distance from the parent.

The stems of Aethophyllum are interesting in the own right. Thanks to their preservation, cross sections have been made and they reveal that these plants only ever produced secondary tracheids and primary xylem. The only place on the plant where any signs of woody secondary xylem occur are at the base of the cones. This adds further confirmation that Aethophyllum was herbaceous at the onset of sexual maturity.

Another intriguing aspect of the stem is the presence of numerous large air spaces within the stem pith. Today, this anatomical feature is present in plants like bamboo, Equisetum, and the flowering stalks of Agave, all of which exhibit alarmingly fast growth rates for plants. This suggests that not only did Aethophyllum reproduce early in its life, it also likely grew extremely fast.

1. Smallest fertile plant in the Grauvogel and Gall collections, with two stems extending from the root, and terminal ovulate cone (OC) on one branch (scale bar=10 cm). 2. Cross-section of stem in the Grauvogel and Gall collections showing cauline bundles with scanty wood (at left, top and right) surrounding large pith with large, aerenchymatous lacunae and interspersed pith parenchyma cells. Vascular cambium, phloem, and more peripheral tissues are not preserved (scale bar=200 μm). 3.Seedling in the Grauvogel and Gall collections showing primary root (R), cotyledons (C) and stem (S) with apically borne leaves (scale bar=10 cm).  Quoted from SOURCE

1. Smallest fertile plant in the Grauvogel and Gall collections, with two stems extending from the root, and terminal ovulate cone (OC) on one branch (scale bar=10 cm). 2. Cross-section of stem in the Grauvogel and Gall collections showing cauline bundles with scanty wood (at left, top and right) surrounding large pith with large, aerenchymatous lacunae and interspersed pith parenchyma cells. Vascular cambium, phloem, and more peripheral tissues are not preserved (scale bar=200 μm). 3.Seedling in the Grauvogel and Gall collections showing primary root (R), cotyledons (C) and stem (S) with apically borne leaves (scale bar=10 cm). Quoted from SOURCE

Mature Aethophyllum aren’t the only fossils available either. Many seedlings have been discovered in close proximity to the adults. Seedlings were also exquisitely preserved, depicting hypocotyl, a primary root system, two two-veined cotyledons, and a short stem with four-veined leaves arranged in a helix. The fact that seedlings and adults were found in such close proximity lends to the idea that Aethophyllum populations were made up of multi-aged stands, not unlike some of the early successional plants we find in disturbed habitats today.

The sediments in which these plants were fossilized can also tell us something about the habitats in which Aethophyllum grew. The rock layers are made up of a mix of sediments typical of what one would find in a flood plain or delta. Also, Aethophyllum aren’t the only plant remains discovered. Many species known to grow in regularly disturbed, flood-prone habitats have also been found. Taken together these lines of evidence suggest that Aethophyllum was similar to what we would expect from herbaceous plants growing in similar habitats today. They grew fast, reproduced early, and had to jam as many generations in before the next flood ripped through and hit the reset button.

Aethophyllums small size, lack of wood, and rapid growth rate all point to a ruderal lifestyle. Today, this niche is largely filled by angiosperms. No conifers alive today can claim such territories. The discovery of Aethophyllum demonstrates that this was not always the case. The fact that pollen has been found far outside of France suggests that this ruderal lifestyle worked quite well for Aethophyllum.

The terrestrial habitats of the Middle Triassic were dominated by the distant relatives of modern day ferns, lycophytes, and gymnosperms. Needless to say, it was a very different world than anything that we are familiar with today. However, that does not mean that the pressures of natural selection were necessarily different. Aethophyllum is evidence that specific selection pressures, in this case regular flood disturbance, select for similar traits in plants through time. Why Aethophyllum went extinct is anyone’s guess. Despite how well they have been preserved, there is still a lot of mystery surrounding this plant.

Photo Credit: [1]

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



The Celery-Topped Conifers

I am only just starting to fully appreciate the diversity in form and habit exhibited by the gymnosperm lineages alive today. What I once thought of as a unidimensional group of plants is proving to be wonderfully diverse, despite being overshadowed by the angiosperms. For instance, imagine my surprise when I first laid eyes on a member of the genus Phyllocladus.

At first glance, these weird conifers look more like a broad-leaf angiosperm. This similarity is superficial, of course. Before we get to why they look the way they do, it is worth considering this group from a as a whole. The genus Phyllocladus comprises roughly 5 species spread out among New Zealand, Tasmania, and Malesia. They are somewhat variable in form but usually settle out somewhere between a good sized shrub and a medium sized tree. Where exactly this genus of oddball gymnosperms fits on the tree of life is subject to some debate.

Phyllocladus aspleniifolius

Phyllocladus aspleniifolius

Phyllocladus trichomanoides

Phyllocladus trichomanoides

For many years after its initial description, Phyllocladus was placed in a family of its own - Phyllocladaceae. Subsequent molecular work has only managed to add to the confusion. Despite its unique morphological characteristics, some authors feel this genus fits nicely into the family Podocarpaceae. At least one other study suggests that it doesn’t belong in Podocarpaceae but rather is situated as sister to the family. By the looks of it, this will not be cleared up any time soon. So, for now, let’s focus in on why these plants are so strange.

For starters we have the “leaves.” I place the word ‘leaves’ in quotes because they are not true leaves. The correct term for these structures are phylloclades (hence the generic name). A phylloclade is a flattened projection of a branch that takes on the form and function of a leaf. What we know of as leaves have been greatly reduced in the genus Phyllocladus. If you want to see them, you must look closely at the tips of the phylloclades. Early on in their development, the leaves exist as tiny brown scales. These scales are gradually lost over time as they serve no function for the plant.

Phyllocladus alpinus

Phyllocladus alpinus

Phyllocladus hypophyllus

Phyllocladus hypophyllus

Though no one has tested this directly (that I am aware of), the evolution of phylloclades over leaves likely has to do with energy conservation in one form or another. Why produce stems and leaves when you can co-opt stem-like structures to do the work for you? Oddly enough, some suggest that to consider them stems in the truest sense of the word is erroneous. Morphologically speaking, they share traits that are intermediate between branches and stems. However, I am going to need to do more homework before I feel comfortable elaborating on this point.

Only when it comes time for reproduction does their place among the gymnosperms become readily apparent, that is before the ovules are fertilized. All members of the genus Phyllocladus produce cones. Male cones are tiny, cylindrical structures located at the ends of their side branches whereas female cones are clustered into groups along the axils or margins of the phylloclades. Once fertilized, however, these plants offer another point of confusion for the casual observer.

The fleshy “fruits” of  Phyllocladus aspleniifolius

The fleshy “fruits” of Phyllocladus aspleniifolius

Phyllocladus is yet another genus of conifers that has converged on a fruit-like seed dispersal strategy. As the seed cones mature, the scales gradually swell and become berry-like. Poking out of the bright red and/or white aril is a single seed. These fleshy arils function in a similar way to fruit in that they attract birds, which then consume them, dispersing the seeds later on in their feces.

Another intriguing aspect of their morphology occurs below ground. The roots of this genus form nodules, which provide a home for bacteria that specializing in fixing atmospheric nitrogen. In return for a home and some carbohydrates from photosynthesis, these bacteria pay these trees with nitrogen that would otherwise be unavailable. Pretty remarkable stuff for a such an esoteric group of conifers!

Phyllocladus_aspleniifolius.jpg

Photo Credits: [1] [2]

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

The Largest Mistletoe

Nuytsia_floribunda_flowers_Dec_2014_02.jpg

When we think of mistletoes, we generally think about those epiphytic parasites living on branches way up in the canopy. The mistletoe we are discussing in this post, however, is a decent sized tree. Nuytsia floribunda is a native of western Australia where it is known locally as moojar or the Christmas tree. To the best of our knowledge, it is the largest mistletoe known to science.

Nuytsia floribunda is a member of the so-called showy mistletoe family (Loranthaceae). It along with all of its mistletoe cousins reside in the order Santalales but from a phylogenetic standpoint, the family Loranthaceae is considered sister to all other mistletoes. This has excited my botanists as it allows us a chance to better understand how parasitism may have evolved in this group as a whole.

Speaking of parasitism, there are some incredible things going on with N. floribunda that are worth talking about. For starters, it is not fully parasitic but rather hemiparasitic. As you can tell by looking at the tree decked out in a full canopy of leaves, N. floribunda is entirely capable of photosynthesizing on its own. In fact, experts feel that it is fully capable of meeting all of its own carbohydrate needs. Instead, it parasitizes other plants in order to acquire water and minerals. How it manages this is remarkable to say the least.

Nuytsia floribunda is a root parasite. Its own roots fan out into the surrounding soil looking for other roots to parasitize. Amazingly, exploratory roots of individual N. floribunda have been found upwards of 110 meters (360 ft.) or more away from the tree. When N. floribunda do find a suitable host root, something incredible happens. It begins to form specialized roots called “haustoria”, which to form a collar-like structure around the host’s roots.

Whole haustoria of Nuytsia (white [ha]) and host root (dark brown). * indicates `gland' and developing `cutting device.

Whole haustoria of Nuytsia (white [ha]) and host root (dark brown). * indicates `gland' and developing `cutting device.

The collar gradually swells and a small horn forms on the inside of the haustoria. Swelling of the haustoria is the result of an influx of water and as the pressure around the host root builds, the haustorial horn of N. floribunda physically cuts into its victim. Once this cut is formed, the haustoria form balloon-like outgrowths which intrude into the xylem tissues of the host root, thus forming the connection that allows N. floribunda to start stealing the water and minerals it needs.

Even more amazing is the fact that roots aren’t the only thing that N. floribunda will attempt to exploit. Many inanimate objects have been found wrapped up in a haustorial embrace including dead twigs, rocks, fertilizer granuals, and even electric cables! Its non-selective parasitic nature appears to have left it open to exploring other, albeit dead end options. I don’t want to paint the picture that this tree as the enemy of surrounding vegetation. It is worth noting that N. floribunda extracts very little from any given host so its impact is spread out among the surrounding vegetation, making its overall impact on host plants minimal most of the time.

Nuytsia_floribunda_-_Flickr_-_Kevin_Thiele.jpg

Provided its needs have been met, N. floribunda puts on one heck of a show around December. In fact, the timing of its blooms is the reason it earned the common name of Christmas tree. Flowering for this species is not a modest affair. Each tree is capable of producing multiple meter-long inflorescences decked out in sprays of bright orange to yellow flowers. The flowers themselves produce copious amounts of pollen and nectar, making it an important food source for resident pollinators. Though many different species have been documented visiting the flowers, it is thought that beetles and wasps are the most effective at pollination.

Seed dispersal for N. floribunda is mainly via wind. Each fruit is adorned with three prominent wings. After they detach from the tree, the fruits usually break apart into three samaras, each with its own wing. The key for success of any propagule is ending up in a site suitable for germination. According to some, this can be a bit tricky and attempts at cultivating this plant in captivity have not been terribly successful. It would seem that nature knows best when it comes to reproductive success in N. floribunda. It may be worth trying to figure it out though because recent evidence suggests that this species is not faring well with human development. As the surrounding landscapes of western Australia become more and more urbanized, plants like N. floribunda seem to be on the decline. Perhaps renewed interest in growing this species could change the tide for it as well as others.

Nuytsia_floribunda_-_The_Australian_Mistletoe.jpg

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

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

The Creeping Strawberry Pine

12170045845_ede1224ecf_o.jpg

With its small, creeping habit and bright red, fleshy female cones, it is easy to see how Microcachrys tetragona earned its common name “creeping strawberry pine.” This miniature conifer is as adorable as it is interesting. With a fossil history that spans 66 million years of Earth’s history, it also has a lot to teach us about biogeography.

Today, the creeping strawberry pine can only be found growing naturally in western Tasmania. It is an alpine species, growing best in what is commonly referred to as alpine dwarf scrubland, above 1000 m (3280 ft) in elevation. Like the rest of the plants in such habitats, the creeping strawberry pine does not grow very tall at all. Instead, it creeps along the ground with its prostrate branches that barely extend more than 30 cm (0.9 ft) above the soil. This, of course, is likely an adaptation to its alpine environment. Plants that grow too tall frequently get knocked back by brutal winds and freezing temperatures among other things.

The typical growth habit of the creeping strawberry pine.

The typical growth habit of the creeping strawberry pine.

The creeping strawberry pine is not a member of the pine family (Pinaceae) but rather the podocarp family (Podocarpaceae). This family is interesting for a lot of reasons but one of the coolest is the fact that they are charismatic representatives of the so-called Antarctic flora. Along with a handful of other plant lineages, it is thought that Podocarpaceae arose during a time when most of the southern continents were combined into a supercontinent called Gondwana. Subsequent tectonic drift has seen the surviving members of this flora largely divided among the continents of the Southern Hemisphere. By combining current day distributions with fossil evidence, researchers are able to use families such as Podocarpaceae to tell a clearer picture of the history of life on Earth.

What is remarkable is that among the various podocarps, the genus Microcachrys produces pollen with a unique morphology. When researchers look at pollen under the microscope, whether extant or fossilized, they can say with certainty if it belongs to a Microcachrys or not. The picture we get from fossil evidence paints an interesting picture for Microcachrys diversity compared to what we see today. It turns out, Microcachrys endemic status is a more recent occurrence.

This distinctive, small, trisaccate pollen grain is typical of what you find with  Microcachrys  whereas all other podocarps produce bisaccate pollen.

This distinctive, small, trisaccate pollen grain is typical of what you find with Microcachrys whereas all other podocarps produce bisaccate pollen.

The creeping strawberry pine is what we call a peloendemic, meaning it belongs to a lineage that was once far more widespread but today exists in a relatively small geographic location. Fossilized pollen from Microcachrys has been found across the Southern Hemisphere, from South America, India, southern Africa, and even Antarctica. It would appear that as the continents continued to separate and environmental conditions changed, the mountains of Tasmania offered a final refuge for the sole remaining species in this lineage.

Another reason this tiny conifer is so charming are its fruit-like female cones. As they mature, the scales around the cone swell and become fleshy. Over time, they start to resemble a strawberry more than anything a gymnosperm would produce. This is yet another case of convergent evolution on a seed dispersal mechanism among a gymnosperm lineage. Birds are thought to be the main seed dispersers of the creeping strawberry pine and those bright red cones certainly have what it takes to catch the eye of a hungry bird. It must be working well for it too. Despite how narrow its range is from a global perspective, the creeping strawberry pine is said to be locally abundant and does not face the same conservation issues that many other members of its family currently face. Also, its unique appearance has made it something of a horticultural curiosity, especially among those who like to dabble in rock gardening.

Mature female cones look more like angiosperm fruit than a conifer cone.

Mature female cones look more like angiosperm fruit than a conifer cone.

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

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

Meet the She-Oaks

628814411_ed018d2c14_o.jpg

No, what you are looking at here is not a type of conifer. Nor is it an oak. This odd plant belongs in its own family - Casuarinaceae. Despite their gymnosperm appearance, this is in fact a family of flowering plants. Though the name “she-oak” does hint at their larger position within the order Fagales, it was actually given to these trees in reference to the density of their wood in comparison to more commonly harvested oak species. Other common names for trees in this group include ironwood, bull-oak, beefwood.

As a whole this family sorts out as sister to Myricaceae in the order Fagales. It' is comprised of 4 genera (Allocasuarina, Casuarina, Ceuthostoma, and Gymnostoma) and roughly 91 species spread among Australia, Malaysia, and much of Polynesia. It is extremely difficult to make generalizations across so many species but there is one aspect of this family that makes them stand out - their appearance.

Gymnostoma  sp.

Gymnostoma sp.

Gymnostoma nobile  in Sarawak, Malaysia.

Gymnostoma nobile in Sarawak, Malaysia.

Without close inspection, one could be forgiven for thinking the various Casuarinaceae were species of conifer. For starters, their leaves have been reduced to tiny whorls surrounding their photosynthetic stems. The stems themselves have taken up the role of photosynthetic organs, which is one of the reasons this family is known for its drought tolerance. Reducing the surface area available for gas exchange helps to reduce water loss in the process. The stems themselves are arranged with whorls around the branches, giving them a rather bunched appearance. The photosynthetic branches are sometimes referred to as being ‘equisetiform’ as they superficially resemble the stems of Equisetum. They do not shed their photosynthetic branches and are therefore evergreen.

As mentioned, these are flowering plants. Their flowers themselves are aggregated into spike-like inflorescences near the tips of branches. Clusters of male flowers resemble catkin-like strobili and are often brightly colored. Female flowers are clustered into a more ovoid shape, with long, filamentous pistils sticking out like fiery, red pompoms. After fertilization, bracts at the base of the female flowers swell and the whole inflorescence starts to look more like some sort of a conifer cone than anything floral. This may have to do with the fact that, like conifers, the various Casuarinaceae are wind pollinated. Therefore, their reproductive structures have had to deal with similar selective forces related to optimizing pollen dispersal and capture.

Casuarina equisetifolia  with catkin-like male flowers and smaller, red female flowers.

Casuarina equisetifolia with catkin-like male flowers and smaller, red female flowers.

Allocasuarina distyla  female flowers and infructescence.

Allocasuarina distyla female flowers and infructescence.

Another interesting trait common to Casuarinaceae is the ability to fix nitrogen. The plants themselves don’t do the fixing, rather they form specialized nodules on their roots that house nitrogen-fixing bacteria. Unlike perennial legumes that regrow their nodules year after year, the members of Casuarinaceae hold onto their nodules, which can grow into impressive structures over time. This ability to house nitrogen-fixing bacteria is also shared with other members of the order Fagales, including members of Betulaceae and Myricaceae.

Thanks to the fact that they can tolerate drought, fix nitrogen, and have high timber value, species of Casuarinaceae have been introduced far outside of their native ranges. This has created yet another invasive species issue. Various Casuarinaceae have become serious pests in places like Central and South America, the Carribbean, and the Middle East. Control of such hardy plants can be extremely difficult once they reach a critical mass that maintains them on the landscape. Keep you eye out for these species. Not only are they interesting in their own right, knowing them can help you better understand their role in ecosystems both native and not.

Allocasuarina decaisneana  (Desert Oaks), Central Australia

Allocasuarina decaisneana (Desert Oaks), Central Australia

Photo Credits: [1] [2] [3] [4] [5] [6]

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

Crab Spiders and Pitcher Plants: A Dynamic Duo

Nepenthes_madagascariensis_-_Nepenthaceae_-_Katja_Rembold_(12)-2.JPG

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

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

4000507626_eed1e08da4_o.jpg

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

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

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

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

Nepenthes_gracilis_mass.jpg

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

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

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

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

Fossilized Flower Places Angiosperms in the Jurassic

1, style branches; 2, dendroid style; 3, sepal; 4, ovarian roof; 5, scale; 6, seed; 7, cup-form receptacle/ovary; 8, bract; 9, petal; 10, unknown organ (staminode?).  [SOURCE]

1, style branches; 2, dendroid style; 3, sepal; 4, ovarian roof; 5, scale; 6, seed; 7, cup-form receptacle/ovary; 8, bract; 9, petal; 10, unknown organ (staminode?). [SOURCE]

Despite their dominance on the landscape today, the origin of flowering plants is shrouded in mystery. The odds of any living material becoming fossilized is extremely rare and when you consider the delicate and ephemeral nature of most flowers, one can begin to understand why their fossils are so special. The last few decades have seen tantalizing evidence emerge from fossil beds dating to the Cretaceous Period but a recent set of fossils from China predate the oldest confirmed angiosperm fossils by 50 million years. That’s right, it would appear that flowering plants were already on the scene by the early Jurassic!

The fossils in question have been coined Nanjinganthus dendrostyla. They were discovered in China in a formation that dates back roughly 174 million years. To most of us they look like a bunch of dark, albeit elaborate smudges on the rocks. To a trained eye, however, these smudges reveal intricate anatomical details. Amazingly, the team of paleobotanists responsible for this discovery had a lot of material to work with. Descriptions were made on a whopping 264 specimens representing 198 individual flowers. This amount of data means that the declaration of angiosperm affinity stands on pretty solid ground.

A single  Nanjinganthus  flower  [SOURCE]

A single Nanjinganthus flower [SOURCE]

Aside from their age, there is a lot about these fossils that surprised researchers. Probably the biggest surprise is their overall appearance. Paleobotanists have long hypothesized that early angiosperm flowers likely resembled something akin to a modern day Magnolia and invoke floral features such as apocarpy, a superior ovary, and a lack of an obvious style as likely features to look for in ancient plant fossils. Surprisingly, Nanjinganthus does not seem to conform to many of these expectations.

One of the most striking features of these fossils are the styles. They are large and branched like tiny trees (hence the specific epithet “dendrostyla”). The tree-like appearance of the style suggests that early angiosperms likely did not rely on insects for pollination. The branches themselves greatly increase the amount of surface area available for pollen capture, which could mean that Nanjinganthus was wind pollinated.

Flowers of  Nanjinganthus  preserved in different states and their details. For specific details on each image, please see   SOURCE

Flowers of Nanjinganthus preserved in different states and their details. For specific details on each image, please see SOURCE

Another surprising feature is the presence of an inferior ovary that, by its very definition, sits below the sepals and petals. It has long been hypothesized that early angiosperms would exhibit superior ovaries so this discovery means that we must rethink our expectations of how flowers evolved. For instance, it suggests we may not be able to make broad inferences on the past based on what we see in extant angiosperm lineages. It could also suggest that the origin of flowering plants was not a single event but rather a series of individual occurrences. It could also be the case that the origin of flowering plants occurred much earlier than the Jurassic and that Nanjinganthus represents one of many derived forms. Only further study and more fossils can help us answer such questions.

Another way in which Nanjinganthus deviates from theoretical expectations is in the presence of both sepals and petals. Up until now, paleobotanists have been fond of the idea that petals arose much later in angiosperms, having evolved over time as leaves became more and more specialized for attracting pollinators. The fact that Nanjinganthus was likely wind pollinated yet had both sepals and petals is a bit of a conundrum and further emphasizes the need to revisit some of our long-held assumptions of flowering plant evolution.

Details of the sepal and petal as seen through different forms of microscopic analysis. For specific details on each image, please see  SOURCE .

Details of the sepal and petal as seen through different forms of microscopic analysis. For specific details on each image, please see SOURCE.

By far the most important feature present in these fossils are the ovaries. For any fossil to unequivocally qualify as an angiosperm, it must have seeds encased in an ovary. This, after all, is the main feature that separates angiosperms from gymnosperms. Indeed, Nanjinganthus does appear to fit this definition. Thanks to the sheer amount of fossils available for study, the team discovered that the seeds of Nanjinganthus were enclosed in a cup-like chamber that was sealed off from the outside world by a structure they refer to as an “ovarian roof.” This roof does not appear to have any sort of opening, which worked out quite nicely for paleobotanists as it prevented sediments from entering into the chamber, thus preserving the seeds or ovules (it is hard to tell where they were in the developmental process) for study. This feature more than all others secures its identity as a flowering plant.

Based on the sediments in which these flowers were fossilized, it appears that this plant grew close to water. Also, despite its abundance in this particular fossil layer, it very likely was not a common component of this Jurassic landscape. In reality we still have a lot to learn about Nanjinganthus. What we can say with some certainty at this point is that the presence of Nanjinganthus in the early Jurassic likely means that flowering plants arose even earlier. Nanjinganthus is most definitely not the first flower. We will probably never find the first of anything. It is an ancient flower though, predating all other discoveries by at least 50 million years. This is why paleontology is so incredible. Who knows what the next blow of a rock hammer will turn up!

 

EDIT (10/27/2018): Since writing this post it has come to my attention that there is quite a bit of controversy attached to the description of this fossil. Many have reached out informing me that these fossils may actually be a gymnosperm organ rather than a flower. Despite all of the outcry I have yet to see any published critiques on this particular controversy. I anxiously await more professional input on the subject but for now I have decided to keep the content of the original piece as is. Of course extraordinary claims require extraordinary evidence and not being a paleobotanist myself, I cannot trust hearsay on the internet as fact, no matter how vociferous, until I see it published in a peer reviewed outlet of some sort. Please stay tuned as this story develops! 

Photo Credits: [1]

Further Reading: [1]

The Smallest Clematis

Clematis_marmoraria_3.jpg

At first glance, the marble clematis (Clematis marmoraria) looks more like an anemone than it does a clematis. You would be forgiven by most for the mistaken ID because it is one of only a handful of the roughly 300 described species that do not exhibit a vining growth form. Also, they hail from the same family - Ranunculaceae. The marble clematis is odd in that it lives its life as a compact “shrub” that hugs the rocks of its alpine habitat. And compact it is! The marble clematis is the smallest in the genus.

The marble clematis exhibits a very limited distribution. It can only be found growing wild in the alpine zone of two sites within Kahurangi National Park in New Zealand. It has only been known to science for a relatively short period of time, having been discovered in 1975. Subsequent investigations have been able to elucidate that its restricted to specific rocky substrates, mainly marble, hence both its common name and specific epithet were given to reflect that.

Like many members of the genus, the marble clematis is dioecious, meaning individual plants are either male or female. Flowering begins in December, as the southern hemisphere summer kicks into high gear. Being restricted to an alpine habitat means that this species has to pack growth and reproduction into only a few short weeks before nasty weather returns and buries it under snow. Despite its herbaceous appearance, the marble clematis is more accurately described as a sub-shrub as it attains a rather woody habit as it matures.

Clematis_marmoraria_1.jpg

Other than its size, the fact that it is not a vine may be the most striking feature of the marble clematis. It is likely that natural selection simply doesn’t favor vine-like growth in such rocky terrain. There really isn’t a whole lot of neighboring vegetation to climb on and compete with so why both with an ambling habit? Also, its alpine environment doesn’t lend well to tall growth. Anything that scrambles up and over rocks is likely to be damaged by wind, sun, and freezing temperatures. As such, the marble clematis is more at home tucked into nooks and crannies than it is vining all over the place.

Unfortunately, its small size, slow growth rate, and limited distribution seem to be working against the marble clematis in our human-dominated world. Not only does climate change threaten its alpine habitat, human activity coupled with grazing by introduced goats and deer have seen populations of this unique species decline at an alarming rate. In 2009 the marble clematis was afforded ‘threatened’ status and is now considered Nationally Vulnerable by the New Zealand government. However, there is a silver lining to all of this and it lies in the hands of alpine garden enthusiasts.

It turns out, the marble clematis is fairly easy to grow. Together with its compact form and showy flowers, it has gained a lot of popularity among horticulturists and gardeners that enjoy rock gardening. Plants can easily be started by seeds or cuttings and, provided some basic soil needs are met (plenty of drainage), potted individuals can live long, healthy lives. Having plants in cultivation like this means that the risk of complete extinction is greatly minimized. Of course, ex situ collections are not a substitute for habitat conservation but it certainly helps mitigate at least some of the risks facing species like the marble clematis.

Photo Credits: [1] [2]

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

 

An Introduction to Hornworts

Anthoceros  sp.

Anthoceros sp.

When was the last time you thought about hornworts? Have you ever thought about hornworts? If you answered no, you aren’t alone. Despite their global distribution, these tiny plants receive hardly any attention and that is a shame. Hornworts (Anthocerotophyta) have been around for a very long time. In fact, it is likely that they were some of the first plants to colonize the land roughly 300 - 400 million years ago.

To be fair, hornworts aren’t known for their size. They are generally small plants, though their colonies can form impressive mats. To find them, one must try looking in and among rocks, bare patches of soil, or pretty much anywhere enough moisture builds up to supply their needs. They tend to enjoy nutrient-poor substrates but I would hesitate to say that with any certainty. No matter where you live, from the tundra to the tropics, there is probably a hornwort native to your neck of the woods.

Dendroceros  sp.

Dendroceros sp.

How many different species of hornwort there are is apparently the subject of some debate. Some authors recognize upwards of 300 species whereas others suggest the real number hangs somewhere around 150. Regardless of the exact numbers, hornworts belong to one of six genera: Anthoceros, Dendroceros, Folioceros, Megaceros, Notothylas and Phaeoceros. Fun fact, the suffix ‘ceros’ at the end of each genus is derived from the Latin word for ‘horn.’

The reason they are called hornworts is because of their reproductive structures or “sporophytes.” Similar to their moss and liverwort cousins, hornworts undergo an alternation of generations in order to reproduce sexually. The green gametophytes house the sexual organs - antheridia if they are male and archegonia if they are female. After fertilization, a sporophyte begins to grow, which will go on to produce and disseminate spores. However, the way in which the hornwort sporophyte forms is a bit different from what we see in mosses and liverworts.

Alternation of generations in hornworts.

Alternation of generations in hornworts.

Upon fertilization, the zygote begins to divide into a bulbous mass of cells affectionately referred to as "the foot.” This foot remains within the gametophyte throughout the lifetime of the hornwort, depending on the gametophyte for water and nutrients. Even more peculiar is the the fact that the growing point of the sporophyte is at the base rather than the tip. As such, the horn of each hornwort could continue to grow upwards until it is damaged in some way.

The horn itself is an amazing structure. Whereas the outside layers of tissue are merely structural, the internal tissues differentiate into two different types - spores and pseudo-elaters. Pseudo-elaters expand and contract as humidity fluctuates so as the sporophyte splits to release the spores, the pseudo-elaters dehydrate and snap like tiny spore catapults, thus aiding in their dispersal.

Megaceros flagellaris

Megaceros flagellaris

Of course, reproduction is the main goal but to get to that point, hornworts must grow and mature. How they manage to survive is incredible because it is a reminder that what are often thought of as “primitive” plants are actually far more advanced than we give them credit for. The main body of the hornwort gametophyte is a thin layer of cells that spread out to form a tiny, green mat. This is the structure you are most likely to encounter.

Inside each cell is a single chloroplast. In most hornworts, the chloroplast does not exist in isolation. Instead, it is fused with other organelles into a structure called a “pyrenoid.” The pyrenoid functions as both a center for photosynthesis and a food storage organ. This is unique as it relates to terrestrial plants but quite common in algae. Another odd fact about hornwort anatomy are the presence of tiny cavities scattered throughout their tissues. These cavities form as clusters of hornwort cells die. They then fill with a special mucilage that appears to invite colonization by nitrogen-fixing cyanobacteria. The cyanobacteria set up shop within the cavities and provides the hornwort with supplemental nitrogen in return for a place to live.

Anthoceros agrestis

Anthoceros agrestis

Cyanobacteria aren’t the only organisms to have partnered with hornworts either. Mycorrhizal fungi also enter into the picture. A study done back in 2013 actually found that a wide variety of fungi will partner with hornworts which suggests that this symbiotic relationship is much more ancient and versatile than we once thought. Fungi cluster around parts of the gametophyte that produce root-like structures called “rhizoids,” offering nutrients in return for carbohydrates.

All in all, I think it is safe to say that hornworts are remarkable little plants. Though they can sometimes be difficult to find and properly identify, they nonetheless offer plenty of inspiration for the botanically inclined mind. We can all do better by tiny plants like the hornworts. They have been on land for an incredible amount of time and they definitely deserve our respect and admiration.

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

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

Something Strange in Mexico

lac2.JPG

I assure you that what you are looking at here is indeed a plant. I would like you to meet the peculiar Lacandonia schismatica, one of roughly 55 species belonging to the family Triuridaceae. Not a single member of this family bothers with leaves or even chlorphyll. Instead, all members are mycoheterotrophic, meaning they make their living by parasitizing fungi in the soil. However, that is not why L. schismatica is so strange. Before we get to that, however, it is worth getting to know this plant a little bit better.

The sole member of its genus, Lacandonia schismatica grows in only a few locations in the Lancandon Jungle of southeastern Mexico. Its populations are quite localized and are under threat by encroaching agricultural development. Genetic analyses of the handful of known populations revealed that there is almost no genetic diversity to speak of among the individuals of this species. All in all, these factors have landed this tiny parasite on the endangered species list.

Mature flower of  Lacandonia schismatica . Three yellowish anthers (center) surrounded by rings of red carpels. Scale bar = 0.5cm.”  [SOURCE]

Mature flower of Lacandonia schismatica. Three yellowish anthers (center) surrounded by rings of red carpels. Scale bar = 0.5cm.” [SOURCE]

To figure out why L. schismatica is so peculiar, you have to take a closer look at its flowers. If you knew what to look for, you would soon realize that L. schismatica appear to be doing things in reverse. To the best of our knowledge, L. schismatica is the only plant in the world that known to have an inverted flower arrangement. The anthers of this species are clustered in the center of the flower surrounded by a ring of 60 or so pistils. The flowers are cleistogamous, which means they are fertilized before they even open, hence the lack of genetic diversity among individuals. 

Not all of its flowers take on this appearance. Researchers have found that in any given population, a handful of unisexual flowers will sometimes be produced. Even the bisexual flowers themselves seem to exhibit at least some variation in the amount of sexual organs present. Still, when bisexual flowers are produced, they only ever exhibit this odd inverted arrangement.

lac1.JPG

It is not quite clear how this system could have evolved in this species. Indeed, this unique floral morphology has made this species very hard to classify. Genetic analysis suggests a relation to the mycoheterotrphic family Triuridaceae. It was discovered that every once in a while, a closely related species known as Triuris brevistylis will sometimes produce flowers with a similar inverted morphology.

This suggests that the inversion evolved before the Lacandonia schismatica lineage diverged. One can only speculate at this point. The future of this species is quite uncertain. Climate change and habitat destruction could permanently alter the conditions so that this plant can no longer exist in the wild. This is further complicated by the fact that this species has proven to be quite difficult to cultivate. Only time will tell. For now, more research is needed on this peculiar plant.

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

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

The Golden Fuchsia: A Case Study in Why Living Collections Matter

6259203996_b0f81db866_o.jpg

The golden Fuchsia (Deppea splendens) is a real show stopper. It is impossible to miss this plant when it is in full bloom. Amazingly, if it were not for the actions of one person, this small tree may have disappeared without anyone ever knowing it existed in the first place. The golden Fuchsia is yet another plant that currently exists only in cultivation.

The story of the golden Fuchsia starts in the early 1970’s. During a trek through the mountains of southern Mexico, Dr. Dennis Breedlove, then the curator of botany for the California Academy of Sciences, stumbled across a peculiar looking shrub growing in a steep canyon. It stood out against the backdrop of Mexican oaks, pines, and magnolias. Standing at about 15 to 20 feet tall and adorned with brightly colored, pendulous inflorescences, it was clear that this species was something special indeed.

6414970581_5d1954daca_o.jpg

A subsequent expedition to Chiapas in the early 1980’s was aimed at collecting seeds of this wonderful plant. It turned out to be relatively easy to germinate and grow, provided it didn’t experience any hard frost events. Plants were distributed among botanical gardens and nurseries and it appeared that the golden Fuchsia was quickly becoming something of a horticultural treasure. Despite all of the attention it was paid, the golden Fuchsia was only properly described in 1987.

Sadly, around the same time that botanists got around to formally naming the plant, tragedy struck. During yet another trip to Chiapas, Dr. Breedlove discovered that the cloud forest that once supported the only known population of golden Fuchsia had been clear cut for farming. Nothing remained but pasture grasses. No other wild populations of the golden Fuchsia have ever been found.

Deppeasplendensagusten.jpg

If it was not for those original seed collections, this plant would have gone completely extinct. It owes its very existence to the botanical gardens and horticulturists that have propagated it over the last 30+ years. All of the plants you will encounter today are descendants of that original collection.

The role of ex situ living collections play in the conservation of species is invaluable. The golden Fuchsia is yet another stark reminder of this. If it were not for people like Dr. Breedlove and all of the others who have dedicated time and space to growing the golden Fuchsia, this species would have only been known as a curious herbarium specimen. The most alarming part about all of this is that as some botanical gardens continue to devalue living collections in favor of cheap landscaping and event hosting, living collections are getting pushed to the side, neglected, or even worse, destroyed. We must remember that living collections are a major piece of the conservation puzzle and their importance only grows as we lose more and more wild spaces to human expansion.

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

Further Reading: [1] [2]

Meet the Fire Lily

Cyrtanthus_ventricosus03.jpeg

The flora of the South African fynbos region is no stranger to fire. Many species have adapted to cope with and even rely on fire to complete their lifecycles. There is one species, however, that takes this to the extreme. It is a tiny member of the Amaryllidaceae aptly named the fire lily (Cyrtanthus ventricosus).

The fire lily is not a big plant by any means. Mature individuals can top out around 9 inches (250 mm) and for most of the year consist of a nothing more than a small cluster of narrow, linear leaves. As the dry months of summer approach, the leaves senesce and the plant more or less disappears until its time to flower. However, unlike other plants in this region that flower more regularly, the fire lily lies in wait for a very specific flowering cue - smoke.

It has been noted that fire lilies only seem to want to reproduce after a fire. No other environmental factor seems to trigger flowering. This has made them quite frustrating for bulb aficionados. Only after a fire burns over the landscape will a scape emerge topped with anywhere from 1 to 12 tubular red flowers.

2471_Cyrtanthus_ventricosus_(as_Cyrtanthus_pallidus).jpeg

This dependence on fire for flowering has garnered the attention of a few botanists concerned with conservation of pyrophytic geophytes. Obviously if we care about conserving species like the fire lily, it is extremely important that we understand their reproductive ecology. The question of fire lily blooming is one of triggers. What part of the burning process triggers these plants to bloom?

By experimenting with various burn and smoke treatments, researchers were able to deduce that it wasn’t heat that triggered flowering but rather something in the smoke itself. Though researchers were not able to isolate the exact chemical(s) responsible, at least we now know that fire lilies can be coaxed into flowering using smoke alone. This is a real boon to growers and conservationists alike.

Cyrtanthus_ventricosus00.jpeg

Seeing a population of fire lilies in full bloom must be an incredible sight. Within only a few days of a fire, huge patches of bright red flowers decorate the charred landscape. They are borne on hollow stalks which provide lots of structural integrity while being cheap to produce. The flowers themselves are not scented but they do produce a fair amount of nectar. The bright red inflorescence mainly attracts the Table Mountain pride butterfly as well as sunbirds.

Once flowering is complete, seeds are produced and the plants return to their dormant bulbous state until winter when leaves emerge again. Flowering will not happen again until fire returns to clear the landscape. This strategy may seem inefficient on the part of the plant. Why not attempt to reproduce every year? The answer is competition. By waiting for fire, this tiny plant is able to make a big impact despite being so small. It would be impossible to miss their enticing floral display when all other vegetation has been burned away.

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

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

A Passionflower With a Taste for Insects?

Passiflora_foetida_1.jpg

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?

Passiflora_foetida_3.jpg

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.

P_foetida_fruit.jpg

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 Rise and Fall of the Scale Trees

SS2139210.jpg

If I had a time machine, the first place I would visit would be the Carboniferous. Spanning from 358.9 to 298.9 million years ago, this was a strange time in Earth’s history. The continents were jumbled together into two great landmasses - Laurasia to the north and Gondwana to the south and the equatorial regions were dominated by humid, tropical swamps. To explore these swamps would be to explore one of the most alien landscapes this world has ever known.

The Carboniferous was the heyday for early land plants. Giant lycopods, ferns, and horsetails formed the backbone of terrestrial ecosystems. By far the most abundant plants during these times were a group of giant, tree-like lycopsids known as the scale trees. Scale trees collectively make up the extinct genus Lepidodendron and despite constantly being compared to modern day club mosses (Lycopodiopsida), experts believe they were more closely related to the quillworts (Isoetopsida).

Carboniferous coal swamp reconstruction dating back to the 1800’s

Carboniferous coal swamp reconstruction dating back to the 1800’s

It is hard to say for sure just how many species of scale tree there were. Early on, each fragmentary fossil was given its own unique taxonomic classification; a branch was considered to be one species while a root fragment was considered to be another and juvenile tree fossils were classified differently than adults. As more complete specimens were unearthed, a better picture of scale tree diversity started to emerge. Today I can find references to anywhere between 4 and 13 named species of scale tree and surely more await discovery. What we can say for sure is that scale tree biology was bizarre.

The name “scale tree” stems from the fossilized remains of their bark, which resembles reptile skin more than it does anything botanical. Fossilized trunk and stem casts are adorned with diamond shaped impressions arranged in rows of ascending spirals. These are not scales, of course, but rather they are leaf scars. In life, scale trees were adorned with long, needle-like leaves, each with a single vein for plumbing. Before the started branching, young trees would have resembled a bushy, green bottle brush.

Juvenile scale tree on the left & the adult on the right

Juvenile scale tree on the left & the adult on the right

As scale trees grew, it is likely that they shed their lower leaves, which left behind the characteristic diamond patterns that make their fossils so recognizable. How these plants achieved growth is rather fascinating. Scale tree cambium was unifacial, meaning it only produced cells towards its interior, not in both directions as we see in modern trees. As such, only secondary xylem was produced. Overall, scale trees would not have been very woody plants. Most of the interior of the trunk and stems was comprised of a spongy cortical meristem. Because of this, the structural integrity of the plant relied on the thick outer “bark.” Many paleobotanists believe that this anatomical quirk made scale trees vulnerable to high winds.

Scale trees were anchored into their peaty substrate by rather peculiar roots. Originally described as a separate species, the roots of these trees still retain their species name. Paleobotanists refer to them as “stigmaria” and they were unlike most roots we encounter today. Stigmaria were large, limb-like structures that branched dichotomously in the soil. Each main branch was covered in tiny spots that were also arranged in rows of ascending spirals. At each spot, a rootlet would have grown outward, likely partnering with mycorrhizal fungi in search of water and nutrients.

A preserved  Lepidodendron  stump

A preserved Lepidodendron stump

Eventually scale trees would reach a height in which branching began. Their tree-like canopy was also the result of dichotomous branching of each new stem. Amazingly, the scale tree canopy reached staggering heights. Some specimens have been found that were an estimated 100 ft (30 m) tall! It was once thought that scale trees reached these lofty heights in as little as 10 to 15 years, which is absolutely bonkers to think about. However, more recent estimates have cast doubt on these numbers. The authors of one paper suggest that there is no biological mechanism available that could explain such rapid growth rates, concluding that the life span of a typical scale tree was more likely measured in centuries rather than years.

Regardless of how long it took them to reach such heights, they nonetheless would have been impressive sites. Remarkably, enough of these trees have been preserved in situ that we can actually get a sense for how these swampy habitats would have been structured. Whenever preserved stumps have been found, paleobotanists remark on the density of their stems. Scale trees did not seem to suffer much from overcrowding.

leps.PNG

The fact that they spent most of their life as a single, unbranched stem may have allowed for more success in such dense situations. In fact, those that have been lucky enough to explore these fossilized forests often comment on how similar their structure seems compared to modern day cypress swamps. It appears that warm, water-logged conditions present similar selection pressures today as they did 350+ million years ago.

Like all living things, scale trees eventually had to reproduce. From the tips of their dichotomosly branching stems emerged spore-bearing cones. The fact that they emerge from the growing tips of the branches suggests that each scale tree only got one shot at reproduction. Again, analyses of some fossilized scale tree forests suggests that these plants were monocarpic, meaning each plant died after a single reproductive event. In fact, fossilized remains of a scale tree forest in Illinois suggests that mass reproductive events may have been the standard for at least some species. Scale trees would all have established at around the same time, grown up together, and then reproduced and died en masse. Their death would have cleared the way for their developing offspring. What an experience that must have been for any insect flying around these ancient swamps.

The fossilized strobilus of a Lepidodendron

The fossilized strobilus of a Lepidodendron

Compared to modern day angiosperms, the habits of the various scale trees may seem a bit inefficient. Nonetheless, this was an extremely successful lineage of plants. Scale trees were the dominant players of the warm, humid, equatorial swamps. However, their dominance on the landscape may have actually been their downfall. In fact, scale trees may have helped bring about an ice age that marked the end of the Carboniferous.

You see, while plants were busy experimenting with building ever taller, more complex anatomies using compounds such as cellulose and lignin, the fungal communities of that time had not yet figured out how to digest them. As these trees grew into 100 ft monsters and died, more and more carbon was being tied up in plant tissues that simply weren’t decomposing. This lack of decomposition is why we humans have had so much Carboniferous coal available to us. It also meant that tons of CO2, a potent greenhouse gas, were being pulled out of the atmosphere millennia after millennia.

A fossilized root or “stigmaria”

A fossilized root or “stigmaria”

As atmospheric CO2 levels plummeted and continents continued to shift, the climate was growing more and more seasonal. This was bad news for the scale trees. All evidence suggests that they were not capable of keeping up with the changes that they themselves had a big part in bringing about. By the end of the Carboniferous, Earth had dipped into an ice age. Earth’s new climate regime appeared to be too much for the scale trees to handle and they were driven to extinction. The world they left behind was primed and ready for new players. The Permian would see a whole new set of plants take over the land and would set the stage for even more terrestrial life to explode onto the scene.

It is amazing to think that we owe much of our industrialized society to scale trees whose leaves captured CO2 and turned it into usable carbon so many millions of years ago. It seems oddly fitting that, thanks to us, scale trees are once again changing Earth’s climate. As we continue to pump Carboniferous CO2 into our atmosphere, one must stop to ask themselves which dominant organisms are most at risk from all of this recent climate change?

Photo Credits: [1] [2] [3] [4] [5] [6] [7]

Further Reading: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14]

The Japanese Umbrella Pine

3697679747_7ed29f76fb_o.jpg

My first impression of the Japanese umbrella pine was that I was looking at a species of yew (Taxus spp.). Sure, its features were a bit more exaggerated than I was used to but what do I know? Trying to understand tree diversity is a recent development in my botanical obsession so I don’t have much to base my opinions on. Regardless, I am glad I gave the little sapling I was looking at a closer inspection. Turns out, the Japanese umbrella pine is most definitely not a yew. It is actually unique in its taxonomic position as the only member of the family Sciadopityaceae.

The Japanese umbrella pine goes by the scientific name of Sciadopitys verticillata. Both common and scientific names hint at the whorled arrangements of its “leaves.” I place leaves in quotes because they are not leaves at all. One of the most remarkable features of this tree is the fact that those whorled leaves are actually thickened, photosynthetic extensions of the stem known as “cladodes.”

Those tiny bumps along the stems are actually highly reduced leaves whereas the whorls of photosynthetic “leaves” are actually modified extensions of the stem called “cladodes.”

Those tiny bumps along the stems are actually highly reduced leaves whereas the whorls of photosynthetic “leaves” are actually modified extensions of the stem called “cladodes.”

Sciadopitys_verticillata3.jpg

It seems that the true leaves of the Japanese umbrella pine have, through evolutionary time, been reduced to tiny, brown scales that clasp the stems. I am not sure what evolutionary advantage(s) cladodes infer over leaves, however, at least one source suggested that cladodes may have fewer stomata and therefore can help to reduce water loss. Until someone looks deeper into this mystery, we cannot say for sure.

As a tree, the Japanese umbrella pine is slow growing. Records show that young trees can take upwards of a decade to reach average human height. However, given time, the Japanese umbrella pine can grow into an impressive specimen. In the forests of Japan, it is possible to come across trees that are 65 to 100 ft (20 – 35 m) tall. It was once wide spread throughout much of southern Japan, however, an ever-increasing human population has seen that range reduced.

A 49.5 million years old fossil of a  Sciadopitys  cladode.

A 49.5 million years old fossil of a Sciadopitys cladode.

The gradual reduction of this species is not solely the fault of humans. Fossil evidence shows that the genus Sciadopitys was once wide spread throughout parts of Europe and Asia as well. Whereas the current diversity of this genus is limited to a single species, fossils of at least three extinct species have been found in rocks dating back to the Triassic Period, some 230 million years ago. It would appear that this obscure conifer family, like so many other gymnosperm lineages, has been on the decline for quite some time.

Despite the obscure strangeness of the Japanese umbrella tree, it has gained considerable popularity as a unique landscape tree. Because it hails from a relatively cool regions of Japan, the Japanese umbrella tree adapts quite well to temperate climates around the globe. Enough people have grown this tree that some cultivars even exist. Whether you see it as a specimen in an arboretum or growing in the wild, know that you are looking at something quite special. The Japanese umbrella tree is a throwback to the days when gymnosperms were the dominant plants on the landscape and we are extremely lucky that it made it through to our time.

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

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

Resurrecting Café Marron

402010371_aad20102df_o.jpg

Back in 1980, a school teacher on the island of Rodrigues sent his students out to look for plants. One of the students brought back a cutting of a shrub that astounded the botanical community. Ramosmania rodriguesii, more commonly known as café marron, was up until that point only known from one botanical description dating back to the 1800's. The shrub, which is a member of the coffee family, was thought to have been extinct due to pressures brought about during the colonization of the island (goats, invasive species, etc.). What the boy brought back was indeed a specimen of café marron but the individual he found turned out to be the only remaining plant on the island.

News of the plant quickly spread. It started to attract a lot of attention, not all of which was good. There is a belief among the locals that the plant is an herbal remedy for hangovers and venereal disease (hence its common name translates to ‘brown coffee’) and because of that, poaching was rampant. Branches and leaves were being hauled off at a rate that was sure to kill this single individual. It was so bad that multiple layers of fencing had to be erected to keep people away. It was clear that more was needed to save this shrub from certain extinction.

Café-marron-flowers-and-leaves.jpg

Cuttings were taken and sent to Kew. After some trial and tribulation, a few of the cuttings successfully rooted. The clones grew and flourished. They even flowered on a regular basis. For a moment it looked like this plant had a chance. Unfortunately, café marron did not seem to want to self-pollinate. It was looking like this species was going to remain a so-called “living dead” representative of a species no longer able to live in the wild. That is until Carlos Magdalena (the man who saved the rarest water lily from extinction) got his hands on the plants.

The key to saving café marron was to somehow bypass its anti-selfing mechanism. Because so little was known about its biology, there was a lot of mystery surrounding its breeding mechanism. Though plenty of flowers were produced, it would appear that the only thing working on the plant were its anthers. They could get viable pollen but none of the stigmas appeared to be receptive. Could it be that the last remaining individual (and all of its subsequent clones) were males?

carlos.JPG

This is where a little creativity and a lot of experience paid off. During some experiments with the flowers, it was discovered that by amputating the top of the stigma and placing pollen directly onto the wound one could coax fertilization ans fruiting. From that initial fruit, seven seeds were produced. These seeds were quickly sent to the propagation lab but unfortunately the seedlings were never able to establish. Still, this was the first indication that there was some hope left for the café marron.

After subsequent attempts at the stigma amputation method ended in failure, it was decided that perhaps something about the growing conditions of the first plant were the missing piece of this puzzle. Indeed, by repeating the same conditions the first individual was exposed to, Carlos and his team were able to coax some changes out of the flowering efforts of some clones. Plants growing in warmer conditions started to produce flowers of a slightly different morphology towards the end of the blooming cycle. After nearly 300 attempts at pollinating these flowers, a handful of fruits were formed!

cm2.JPG

From these fruits, over 100 viable seeds were produced. What’s more, these seeds germinated and the seedlings successfully established. Even more exciting, the seedlings were a healthy mix of both male and female plants. Carlos and his team learned a lot about the biology of this species in the process. Thanks to their dedicated work, we now know that café marron is protandrous meaning its male flowers are produced before female flowers.

However, the story doesn’t end here. Something surprising happened as the seedlings continued to grow. The resulting offspring looked nothing like the adult plant. Whereas the adult plant has round, green leaves, the juveniles were brownish and lance shaped. This was quite a puzzle but not entirely surprising because the immature stage of this shrub was not known to science. Amazingly, as the plants matured they eventually morphed into the adult form. It would appear that there is more to the mystery of this species than botanists ever realized. The question remained, why go through such drastically different life stages?

A young café marron showing its brown, mottled, lance-shaped leaves.

A young café marron showing its brown, mottled, lance-shaped leaves.

The answer has to do with café marron's natural predator, a species of giant tortoise. The tortoises are attracted to the bright green leaves of the adult plant. By growing dull, brown, skinny leaves while it is still at convenient grazing height, the plant makes itself almost invisible to the tortoise. It is not until the plant is out of the range of this armoured herbivore that it morphs into its adult form. Essentially the young plants camouflage themselves from the most prominent herbivore on the island.

Thanks to the efforts of Carlos and his team at Kew, over 1000 seeds have been produced and half of those seeds were sent back to Rodrigues to be used in restoration efforts. As of 2010, 300 of those seed have been germinated, opening up many more opportunities for reintroduction into the wild. Those early trials will set the stage for more restoration efforts in the future. It is rare that we see such an amazing success story when it comes to such an endangered species. We must celebrate these efforts because they remind us to keep trying even if all hope seems to be lost. My hat is off to Carlos and the dedicated team of plant conservationists and growers at Kew.

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

Further Reading: [1] [2]

Meet the Pygmy Clubmoss

Phylloglossum+drummondii+++005.jpg

No, these are not some sort of grass or rush. What you are looking at here is actually a member of the clubmoss family (Lycopodiaceae). Colloquially known as the pygmy clubmoss, this odd little plant is the only species in its genus - Phylloglossum drummondii. Despite its peculiar nature, very little is known about it.

The pygmy clubmoss is native to parts of Australia, Tasmania, and New Zealand but common it is not. From what I can gather, it grows in scattered coastal and lowland sites where regular fires clear the ground of competing vegetation. It is a perennial plant that makes its appearance around July and reaches reproductive size around August through to October.

Reproduction for the pygmy clubmoss is what you would expect from this family. In dividual plants will produce a reproductive stem that is tipped with a cone-like structure. This cone houses the spores, which are dispersed by wind. If a spore lands in a suitable spot, it germinates into a tiny gametophyte. As you can probably imagine, the gametophyte is small and hard to locate. As such, little is known about this part of its life cycle. Like all gametophytes, the end goal of this stage is sexual reproduction. Sperm are released and with any luck will find a female gametophyte and fertilize the ovules within. From the fertilized ovule emerges the sporophytes we see pictured above.

Phylloglossum-drummondii-04.jpg

As dormancy approaches, this strange clubmoss retreats underground where it persists as a tiny tuber-like stem. Though it is rather obscure no matter who you ask, there has been some scientific attention paid to this odd little plant, especially as it relates to its position on the tree of life. Since it was first described, its taxonomic affinity has moved around a bit. Early debates seemed to center around whether it belonged in Lycopodiaceae or its own family, Phylloglossaceae.

image_thumb-663.png

Recent molecular work put this to rest showing that genetically the pygmy clubmoss is most closely related to another genus of clubmoss - Huperzia. This was bolstered by the fact that it shares a lot of features with this group such as spore morphology, phytochemistry, and chromosome number. The biggest difference between these two genera is the development of the pygmy clubmoss tuber, which is unique to this species. However, even this seems to have its roots in Lycopodiaceae.

If you look closely at the development of some lycopods, it becomes apparent that the pygmy clubmoss most closely resembles an early stage of development called the “protocorm.” Protocorms are a tuberous mass of cells that is the embryonic form of clubmosses (as well as orchids). Essentially, the pygmy clubmoss is so similar to the protocorm of some lycopods that some experts actually think of it as a permanent protocorm capable of sexual reproduction. Quite amazing if you ask me.

Phylloglossum drummondii   003.jpg

Sadly, because of its obscurity, many feel this plant may be approaching endangered status. There have been notable declines in population size throughout its range thanks to things like conversion of its habitat to farmland, over-collection for both novelty and scientific purposes, and sequestration of life-giving fires. As mentioned, the pygmy clubmoss needs fire. Without it, natural vegetative succession quickly crowds out these delicate little plants. Hopefully more attention coupled with better land management can save this odd clubmoss from going the way of its Carboniferous relatives.

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

Further Reading: [1] [2] [3] [4] [5] [6]