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 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.
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.
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.
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.
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.
Most pitcher plants in the genus Nepenthes seem pretty adept at catching prey. These plants specialize in nutrient-poor soils and their carnivorous habit evolved as a means of supplementing their nutritional needs. Despite the highly evolved nature of their pitfall traps (which are actually modified leaves), Nepenthes aren’t perfect killing machines. In fact, some get a helping hand from seemingly unlikely partners.
Spend enough time reading about Nepenthes in the wild and you will see countless mentions of arthropods hanging around their pitchers. Some of these inevitably become prey, however, there are others that appear to be taking advantage of the plant. Nepenthes don’t passively trap arthropods. Instead, they lure them in with bright colors and the promise of tasty treats like nectar. This is not lost on predators like spiders, who are frequent denizens of pitcher mouths.
Most notable to Nepenthes specialists are some of the crab spiders that frequently haunt Nepenthes traps. These wonderful arachnids sit at the mouth of the pitcher and ambush any insects that try to pay it a visit. Often times both predator and prey fall down into the pitcher, however, thanks to a strand of silk, the spiders easily climb back out with their meal. This may seem like bad news for the pitcher, however, recent research based out of the National University of Singapore has shown that this relationship is not entirely one sided.
By studying the interactions between spiders and pitcher plants both in the lab and in the field, ecologists discovered that at least one species of pitcher plant (Nepenthes gracilis) appears to benefit greatly from the presence of crab spiders. The key to understanding this relationship lies in the types of prey N. gracilis is able to capture when crab spiders are and are not present.
Not only did the presence of a resident crab spider increase the amount of prey in each Nepenthes pitcher, it also changed the types of insects that were being captured. Crab spiders are ambush predators that frequently attack prey much larger than themselves. It may seem as if this is a form of food robbery on the part of the crab spider but the spiders can’t eat everything. When they have eaten their fill, the spiders discard the carcass into the pitcher where the plant can make quick work digesting it for its own benefit.
Over time, simply having a spider hunting on the trap led to a marked increase in the number of insects in each pitcher compared to those without a spider. Even if these meals are already half eaten, the plant still gains nutrients. Additionally, the types of prey captured by pitchers with and without crab spiders changed. The spiders were able to capture and subdue insects like flesh flies, which normally aren’t captured by Nepenthes pitchers. As such, the resident crab spiders make available a larger suite of potential prey than would be available if they weren’t using the pitchers as hunting grounds.
The crab spiders may benefit the pitcher plant in other ways as well. Research on crab spiders has shown that their bodies are covered in pigments that register high in the UV spectrum. Insects can see UV light and often use it as a means of finding flowers as plants often produce UV-specific pigments in their floral tissues. The wide array of UV patterns on flowers are there to guide their pollinators into position. Researchers have documented that insects are actually more likely to visit flowers with crab spiders than those without, which has led to the idea that UV pigments in crab spiders actually act as insect attractants. Visiting insects simply cannot resist the UV stimulus and quickly fall victim to the resident crab spider.
Could it be that by taking up residence on a Nepenthes pitcher, the crab spiders are increasing the likelihood of insects visiting the traps? This remains to be seen as such questions did not fall under the scope of this investigation. That being said, it certainly offers tantalizing evidence that there is more to the Nepenthes-crab spider relationship. More work is needed to say for sure but the closer we look at such interactions, the more spectacular they become!
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.
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.
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.
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!
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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.
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.
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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.
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.
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.
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.
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.
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.
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.
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.
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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.
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.
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.
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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.
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.
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.
For a plant to be considered carnivorous, it must possess one or more traits unequivocally adapted for attracting, capturing, and/or digesting prey. It also helps to demonstrate that the absorption of nutrients has a clear positive impact on growth or reproductive effort. For plants like the Venus fly trap or any of the various pitcher plants out there, this distinction is pretty straight forward. For many other species, the line between carnivorous or not can be a little blurry. Take, for instance, the case of the stinking passionflower (Passiflora foetida).
At first glance, P. foetida seems par for the course as far as passionflowers are concerned. It is a vining species native from the southwestern United States all the way down into South America. It enjoys edge habitats where it can scramble up and over neighboring vegetation. It produces large, showy flowers followed by edible fruits. When the foliage is damaged, it emits a strong odor, earning it the specific epithet “foetida.”
Not until you inspect the developing floral buds of this passionflower will the question of carnivory enter into your mind. Covering the developing flowers and eventually the fruit are a series of feathery bracts, which are covered in glandular hairs. The hairs themselves are quite sticky thanks to the secretion of fluids. As insects crawl across the hairs, they become hopelessly entangled and eventually die. So, does this make P. foetida a carnivore?
Many different plants produce sticky hairs or glands on their tissues. Often this is a form of defense. Herbivorous insects looking to take a bite out of such a plant either get stuck outright or have their mouth parts completely gummed up in the process. This form of defense seems to work quite well for such plant species so simply trapping insects doesn’t mean the plant is a carnivore. Worth noting, however, is the fact that it appears that many carnivorous plant traits have simply been retooled from defense traits.
The question remains as to what happens to the trapped insects after they are ensnared by P. foetida. Observations in the field suggest that there is more to these sticky hairs than simply defense. This led a team of researchers to look closer at the interactions between P. foetida and insects. What they found is rather fascinating.
It turns out that most of the insects captured by P. foetida bracts are herbivores that would have made an easy meal of the flowers and fruits. However, after getting stuck, the insect bodies quickly decay. Laboratory analyses revealed that indeed, the fluids secreted by the sticky hairs contained lots of digestive enzymes, mainly proteases and acid phosphatases. Still, this does not mean the plant is eating the insects. It makes sense from a defensive standpoint that a plant would not benefit from having lots of rotting corpses stuck to its buds. As such, digesting them removes the possibility of fungal or bacterial attack. To investigate whether P. foetida benefits from trapping insects beyond simply avoiding herbivory, the team needed to know if any nutritional benefit was being had.
The team took amino acids marked with a special carbon isotope and smeared it onto the bracts. Then they waited to see if any of the labelled amino acids showed up in the plant tissues. Indeed they did. The amino acids were absorbed by the bracts and translocated to the calyx, corolla, anthers, and finally to the developing ovules. This is probably not too surprising to those of us that spend time growing plants as numerous plant species can uptake at least some nutrients through their leaves. This is why foliar feeding can work as a means of fertilizing potted plants. Nonetheless, these results are enticing as it shows that P. foetida is not only capturing and dissolving insects, it also seems capable of absorbing at least some amino acids from its victims.
So, should we call P. foetida a carnivore? To be honest, I am not sure. Certainly all of the evidence suggests there is more going on than simply defense. However, does garnering the attention of hungry herbivores constitute prey attraction? Certainly other carnivores utilize food deception as a means of prey capture. Does simply being a palatable plant count as a lure? Does absorbing nutrients constitute carnivory? In some instances, yes, however, as mentioned, plenty of plant species can absorb nutrients from organs other than their roots.
I think the main question is whether P. foetida sees a marked increase in growth or reproduction due to the addition of the dead herbivores. What I think we can say is that the sticky bracts surrounding the flowers and fruits serve a dual purpose - defense against herbivores and potentially a nutrient boost as well. If anything, I think this should qualify as a form of protocarnivory.
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).
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.
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.
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.
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.
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.
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?
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.”
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.
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.
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.
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?
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!
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?
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.
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.
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.
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.
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.
At first glance, this odd plant doesn’t look very special. However, it is the first new member of the family Podostemaceae to be found in Africa in over 30 years. It has been given the name Lebbiea grandiflora and it was discovered during a survey to assess the impacts of a proposed hydroelectric dam. By examining the specimen, Kew botanists quickly realized this plant was unique. Sadly, if all goes according to plan, this species may not be long for this world unless something is done to preserve it.
Members of the family Podostemaceae are strange plants. Despite how delicate they look, these plants specialize in growing submersed on rocks in waterfalls, rapids, and other fast flowing bodies of water. They are generally small plants, though some species can grow to lengths of 3 ft. (1 m) or more. The best generalization one can make about this group is that they like clean, fast-flowing water with plenty of available rock surfaces to grow on.
Lebbiea grandiflora certainly fits this description. It is native to a small portion of Sierra Leone and Guinea where it grows on slick rock surfaces only during the wet season. As the dry season approaches and the rivers shrink in size, L. grandiflora quickly sets seed and dies.
As mentioned, the area in which this plant was discovered is slated for the construction of a large hydroelectric dam. The building of this dam will most certainly destroy the entire population of this plant. As soon as water slows, becomes more turbid, and sediments build up, most Podostemaceae simply disappear. Unfortunately, I appears this plant was in trouble even before the dam came into the picture.
As mentioned, Podostemaceae need clean rock surfaces on which to germinate and grow. Without them, the seedlings simply can’t get established. Mining operations further upstream of the Sewa Rapids have been dumping mass quantities of sediment into the river for years. All of this sediment eventually makes it down into L. grandiflora territory and chokes out available germination sites.
Alarmed at the likely extinction of this new species, the Kew team wanted to try and find other populations of L. grandiflora. Amazingly, one other population was found growing in a river near Koukoutamba, Guinea. Sadly, the discovery of this additional population is bitter sweet as the World Bank is apparently backing another hydro-electric dam project on that river as well.
The only hope for the continuation of this species currently will be to (hopefully) find more populations and collect seed to establish ex situ populations both in other rivers as well as in captivity if possible. To date, no successful purposeful seeding of any Podostemaceae has been reported (if you know of any, please speak up!). Currently L. grandiflora has been given “Critically Endangered” status by the IUCN and the botanists responsible for its discovery hope that, coupled with the publication of this new species description, more can be done to protect this small rheophytic herb.
Further Reading: 
Antarctica - the frozen continent. It is hard to think of a place on Earth that is less hospitable to life. Yet life does exist here and some of it is botanical. Though few in number, Anarctica’s diminutive flora is able to eke out an existence wherever the right conditions present themselves. It goes without saying that these plants are some of the hardiest around.
It is strange to think of Antarctica as having any flora at all. How many descriptions of plant families and genera say something to the effect of “found on nearly every continent except for Antarctica.” It didn’t always used to be this way though. Antarctica was once home to a diverse floral assemblage that rivaled anything we see in the tropics today. Millions upon millions of years of continental drift has seen this once lush landmass positioned squarely at Earth’s southern pole.
Situated that far south, Antarctica has long since become a frozen wasteland of sorts. The landscape is essentially a desert. Instead of no precipitation, however, most water in this neck of the woods is completely locked up in ice for most of the year. This is one reason why plants have had such a hard time making a living here. That is not to say that some plants haven’t made it. In fact, a handful of species thrive under these conditions.
When anyone goes looking for plants in Antarctica, they must do so wherever conditions ease up enough for part of the year to allow terrestrial life to exist. In the case of this frozen continent, this means hanging out along the coast or one of handful of islands situated just off of the mainland. Here, enough land thaws during the brief summer months to allow a few plant species to take root and grow.
The flora of Antarctica proper consists of 2 flowering plant species, about 100 species of mosses, and roughly 30 species of liverwort. The largest of these are the flowering plants - a grass known as Antarctic hair grass (Deschamsia antarctica), and member of the pink family with a cushion-like growth habit called Antarctic pearlwort (Colobanthus quitensis). Whereas the hair grass benefits from being wind pollinated, the Antarctic pearlwort has had to get creative with its reproductive needs. Instead of relying on pollinators, which simply aren’t present in any abundance on Antarctica, it appears that the pearlwort has shifted over to being entirely self-pollinated. This seems to work for it because if the mother plant is capable of living on Antarctica, so too will its clonal offspring.
By far the dominant plant life on the continent are the mosses. With 100 species known to live on Antarctica, it is hard to make generalizations about their habits other than to say they are pretty tough plants. Most live out their lives among the saturated rocks of the intertidal zones. What we can say about these mosses is that they support a bewildering array of microbial life, from fungi and lichens to protists and tardigrades. Even in this frozen corner of the world, plants form the foundation for all other forms of life.
The coastal plant communities of Antarctica represent hotbeds of biodiversity for this depauperate continent. They reach their highest densities on the Antarctic Peninsula as well as on coastal islands such as south Orkney Islands and the South Shetland Islands. Here, conditions are just mild enough among the various rocky crevices for germination and growth to occur. Still, life on Antarctica is no cake walk. A short growing season, punishing waves, blistering winds, and trampling by penguins and seals present quite a challenge to Antarctica’s botanical denizens. They are able to live here despite these challenges.
Still, humans take their toll. The Antarctic Peninsula is experiencing some of the most rapid warming on the planet over the last century. As this region grows warmer and drier each year, plants are responding accordingly. Antarctic mosses along the peninsula are increasingly showing signs of stress. They are starting to prioritize the production of protective pigments in their tissues over growth and reproduction. Moreover, new species of moss are starting to take over. Rapid warming and drying of the Antarctic Peninsula appears to be favoring species that are more desiccation tolerant at the expense of the continents endemic moss species.
Changes in the structure and composition of Antarctica’s moss beds is far from being a scientific curiosity for only bryologists to ponder. It is a symptom of greater changes to come.
The plight of the kākāpō is a tragedy. Once the third most common bird in New Zealand, this large, flightless parrot has seen its numbers reduced to less than 150. In fact, for a time, it was even thought to be extinct. Today, serious effort has been put forth to try and recover this species from the brink of extinction. It has long been recognized that kākāpō breeding efforts are conspicuously tied to the phenology of certain trees but recent research suggests one in particular may hold the key to survival of the species.
The kākāpō shares its island homes (saving the kākāpō involved moving birds to rat-free islands) with a handful of tropical conifers from the families Podocarpaceae and Araucariaceae. Of these tropical conifers, one species is of particular interest to those concerned with kākāpō breeding - the rimu. Known to science as Dacrydium cupressinum, this evergreen tree represents one of the most important food sources for breeding kākāpō. Before we get to that, however, it is worth getting to know the rimu a bit better.
Rimu are remarkable, albeit slow-growing trees. They are endemic to New Zealand where they make up a considerable portion of the forest canopy. Like many slow-growing species, rimu can live for quite a long time. Before commercial logging moved in, trees of 800 to 900 years of age were not unheard of. Also, they can reach immense sizes. Historical accounts speak of trees that reached 200 ft. (61 m) in height. Today you are more likely to encounter trees in the 60 to 100 ft. (20 to 35 m) range.
The rimu is a dioecious tree, meaning individuals are either male or female. Rimu rely on wind for pollination and female cones can take upwards of 15 months to fully mature following pollination. The rimu is yet another one of those conifers that has converged on fruit-like structures for seed dispersal. As the female cones mature, the scales gradually begin to swell and turn red. Once fully ripened, the fleshy red “fruit” displays one or two black seeds at the tip. Its these “fruits” that have kākāpō researchers so excited.
As mentioned, it is a common observation that kākāpō only tend to breed when trees like the rimu experience reproductive booms. The “fruits” and seeds they produce are an important component of the diets of not only female kākāpō but their developing chicks as well. Because kākāpō are critically endangered, captive breeding is one of the main ways in which conservationists are supplementing numbers in the wild. The problem with breeding kakapo in captivity is that supplemental food doesn’t seem to bring them into proper breeding condition. This is where the rimu “fruits” come in.
Breeding birds desperately need calcium and vitamin D for proper egg production. As such, they seek out diets high in these nutrients. When researchers took a closer look at the “fruits” of the rimu, the kākāpō’s reliance on these trees made a whole lot more sense. It turns out, those fleshy scales surrounding rimu seeds are exceptionally high in not only calcium, but various forms of vitamin D once thought to be produced by animals alone. The nutritional quality of these “fruits” provides a wonderful explanation for why kākāpō reproduction seems to be tied to rimu reproduction. Females can gorge themselves on the “fruits,” which brings them into breeding condition. They also go on to feed these “fruits” to their developing chicks. For a slow growing, flightless parrot, it seems that it only makes sense to breed when food is this food source is abundant.
Though far from a smoking gun, researchers believe that the rimu is the missing piece of the puzzle in captive kākāpō breeding. If these “fruits” really are the trigger needed to bring female kākāpō into good shape for breeding and raising chicks, this may make breeding kākāpō in captivity that much easier. Captive breeding is the key to the long term survival of these odd yet charismatic, flightless parrots. By ensuring the production and survival of future generations of kākāpō, conservationists may be able to turn this tragedy into a real success story. What’s more, this research underscores the importance of understanding the ecology of the organisms we are desperately trying to save.
Many of us were taught in school that one of the key distinguishing features between gymnosperms and angiosperms is the production of fruit. Fruit, by definition, is a structure formed from the ovary of a flowering plant. Gymnosperms, on the other hand, do not enclose their ovules in ovaries. Instead, their unfertilized ovules are exposed (to one degree or another) to the environment. The word “gymnosperm” reflects this as it is Greek for “naked seed.” However, as is the case with all things biological, there are exceptions to nearly every rule. There are gymnosperms on this planet that produce structures that function quite similar to fruits.
The key to understanding this evolutionary convergence lies in understanding the benefits of fruits in the first place. Fruits are all about packing seeds into structures that appeal to the palates of various types of animals who then eat said fruits. Once consumed, the animals digest the fruity bits and will often deposit the seeds elsewhere in their feces. Propagule dispersal is key to the success of plants as it allows them to not only to complete their reproductive cycle but also conquer new territory in the process. With a basic introduction out of the way, let’s get back to gymnosperms.
There are 4 major gymnosperm lineages on this planet - the Ginkgo, cycads, gnetophytes, and conifers. Each one of these groups contains members that produce fleshy structures around their seeds. However, their “fruits” do not all develop in the same way. The most remarkable thing to me is that, from a developmental standpoint, each lineage has evolved its own pathway for “fruit” production.
For instance, consider ginkgos and cycads. Both of these groups can trace their evolutionary history back to the early Permian, some 270 - 280 million years ago, long before flowering plants came onto the scene. Both surround their developing seed with a layer of protective tissue called the integument. As the seed develops, the integument swells and becomes quite fleshy. In the case of Ginkgo, the integument is rich in a compound called butyric acid, which give them their characteristic rotten butter smell. No one can say for sure who this nasty odor originally evolved to attract but it likely has something to do with seed dispersal. Modern day carnivores seem to be especially fond of Ginkgo “fruits,” which would suggest that some bygone carnivore may have been the main seed disperser for these trees.
The Gnetophytes are represented by three extant lineages (Gnetaceae, Welwitschiaceae, and Ephedraceae), but only two of them - Gnetaceae and Ephedraceae - produce fruit-like structures. As if the overall appearance of the various Gnetum species didn’t make you question your assumptions of what a gymnosperm should look like, its seeds certainly will. They are downright berry-like!
The formation of the fruit-like structure surrounding each seed can be traced back to tiny bracts at the base of the ovule. After fertilization, these bracts grow up and around the seed and swell to become red and fleshy. As you can imagine, Gnetum “fruits” are a real hit with animals. In the case of some Ephedra, the “fruit” is also derived from much larger bracts that surround the ovule. These bracts are more leaf-like at the start than those of their Gnetum cousins but their development and function is much the same.
Whereas we usually think of woody cones when we think of conifers, there are many species within this lineage that also have converged on fleshy structures surrounding their seeds. Probably the most famous and widely recognized example of this can be seen in the yews (Taxus spp.). Ovules are presented singly and each is subtended by a small stalk called a peduncle. Once fertilized, a group of cells on the peduncle begin to grow and differentiate. They gradually swell and engulf the seed, forming a bright red, fleshy structure called an “aril.” Arils are magnificent seed dispersal devices as birds absolutely relish them. The seed within is quite toxic so it usually escapes the process unharmed and with any luck is deposited far away from the parent plant.
Another great example of fleshy conifer “fruits” can be seen in the junipers (Juniperus spp.). Unlike the other gymnosperms mentioned here, the junipers do produce cones. However, unlike pine cones, the scales of juniper cones do not open to release the seeds inside. Instead, they swell shut and each scale becomes quite fleshy. Juniper cones aren’t red like we have seen in other lineages but they certainly garnish the attention of many a small animal looking for food.
I have only begun to scratch the surface of the fruit-like structures in gymnosperms. There is plenty of literary fodder out there for those of you who love to read about developmental biology and evolution. It is a fascinating world to uncover. More importantly, I think the fleshy “fruits” of the various gymnosperm lineages stand as a testament to the power of natural selection as a driving force for evolution on our planet. It is amazing that such distantly related plants have converged on similar seed dispersal mechanisms by so many different means.