Peculiar Pillworts

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As far as ferns are concerned, the pillworts are pretty unusual. Belonging to the genus Pilularia, there are something like 3 to 6 species depending who you ask. To find them, you need to have an eye for detail and be looking in the right kind of habitats. Pillworts won’t grow just anywhere, which is of growing concern for one species. Today I would like to give you a brief introduction to these peculiar semi-aquatic ferns.

Pillworts really challenge the notion of what a fern should look like. Instead of feathery fronds, pillworts produce narrow, grass-like leaves. Look closely and you will see that these leaves do in fact unfurl in fiddlehead fashion from a long stolon. Situated at the base of the leaves are small, hairy capsules called sporocarps, which house the spores. When presented with favorable growing conditions, pillworts can form large, creeping mats that resemble a shaggy lawn.

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No matter where you find them, pillworts largely require the same types of habitats to prosper. These tiny ferns are specialists on muddy banks of seasonal ponds. You see, pillworts simply cannot compete with more aggressive vegetation. For them to thrive, pond conditions must be maintained in an early successional state. The ideal pond for a pillwort fills with water during the winter and largely dries down to mud in the summer. Such fluctuations in water levels keeps competing vegetation at bay. Fully aquatic plants quickly dry out in the summer whereas more terrestrial species drown in the winter. In places like Europe, where Pilularia globulifera is native, grazing by large herbivores such as cattle play a big role as well. As cattle eat up and trample the vegetation around seasonal ponds, they create bare ground where pillworts can thrive.

One of the biggest threats to pillworts is pollution. As runoff from farms and residential areas dump massive quantities of nitrogen and phosphorus into the water, more aggressive plants start to take hold. As this happens, pillworts simply can’t keep up. The degradation and loss of seasonal ponds is causing severe declines in pillwort populations in Europe. Though Pilularia globulifera is still listed as a species of least concern, the rate at which it is being lost from its historical range is enough to place it on the watch list of many conservation organizations.

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Outside of the UK, pillworts are receiving much less attention. Little information exists on pillworts growing in Australia and New Zealand, and there is ongoing debate as to whether North American populations represent a single species or two distinct, albeit cryptic species. Such lack of attention and confusion coupled with its inconspicuous appearance could be bad news for this tiny plant. Without proper assessments of what species occur where and their relative abundance, few conservation measures can be put into place. What we can say for sure is that to protect pillworts, we must protect their habitat.

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

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

The Wacky World of Whisk Ferns

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The whisk ferns (Psilotum spp.) are a peculiar group of plants. If you hang out in greenhouses long enough, you are most likely to encounter them as “weeds” growing in pots with other plants. Though they aren’t often put on display by themselves, the whisk ferns are certainly worth a closer look.

Psilotum comprises two species, the far more common Psilotum nudum and the lesser known P. complanatum. These two species will also hybridize, resulting in Psilotum × intermedium. Together, the whisk ferns make up one of only two genera in the family Psilotaceae (the other being Tmesipteris). They are strange plants to look at as there doesn’t appear to be much to them besides stems. Indeed, their peculiar morphology has earned them a fair share of taxonomic attention over the last century but before we get into that, it is a good idea to take a closer look at their anatomy.

Psilotum nudum  with yellow sporagia.

Psilotum nudum with yellow sporagia.

What we see when we are looking at a whisk fern is the sporophyte generation. Like all sporophytes, its job is to produce the spores that will go on to make new whisk ferns. This part of the whisk fern lifecycle is pretty much all stem. Though these are in fact vascular plants, they do not produce true leaves. Instead, the branching stem takes up all of the photosynthetic work. What looks like tiny leaf-like scales are actually referred to as ‘enations.’ These structures do not contain any vascular tissue of their own. Instead, they bear a type of fused sporangia that house the spores. When mature, these will turn a bright yellow.

Underground, things aren’t much different. Whisk ferns produce a branching rhizome that is covered in hair-like projections called rhizoids. These structures not only help anchor the plant in place, they also function in a similar way to roots. Rhizoids interface with the soil environment allowing the plant to absorb nutrients and water. However, they don’t do this alone. Like so many other plants, whisk ferns partner with mycorrhizal fungi, which vastly increases the amount of surface area these plants have for absorbing what they need. In return, whisk ferns provide the fungi with carbohydrates they produce through photosynthesis. As lovely as this mutualistic relationship sounds, it actually starts off as parasitism.

A  Psilotum  rhizome with hair-like rhizoids.

A Psilotum rhizome with hair-like rhizoids.

When the spores find a suitable place to germinate, they will grow into the other half of the whisk fern lifecycle, the gametophyte. These resemble tiny versions of the rhizome and contain male and female reproductive organs. Living underground, the gametophytes do not photosynthesize. Instead, they completely rely on mycorrhizal fungi for all of their nutritional needs. This can go on for some time until the gametophytes are fertilized and grow a new sporophyte. Then and only then will the plant actually start giving back to the fungi that their lives depend on.

Psilotum complanatum  with its flattened stems.

Psilotum complanatum with its flattened stems.

Because the overall form of the whisk ferns appears so “simplistic.,” many have hypothesized that the genus Psilotum is an evolutionary throwback to the early days of vascular plant evolution. On a superficial level, the whisk ferns do appear to have a lot in common with rhyniophytes, a group of plants that arose during the early Devonian, some 419 to 393 million years ago. A more detailed inspection of the anatomy of each group would reveal that there are some significant and fundamental differences between the two lineages, which I won’t go into here. Also, subsequent molecular work has shown that the whisk ferns reside quite comfortably within the fern lineage and likely represent a sister group to the order that gives us the adder’s tongue ferns (Ophioglossales). It would appear that whisk ferns more accurately represent a reduction in the more “traditional” fern form rather than a holdover from the early days of land plant evolution.

What the genus Psilotum lacks in number of species, it makes up for with its wide distribution. The whisk ferns seem to have conquered most of the tropical and subtropical landmasses on our planet. In fact, I found it incredibly difficult to discern much in the way of a native distribution for these plants. In some areas they are fairly common components of the local flora whereas in others they are considered rare or even threatened. I am sure that at least some of their expansive distribution can be attributed to human assistance as we move soils and plants around the world. To find them in nature, one must look in the cracks of rocks or on the trunks and branches of trees. Though both species can be found growing on trees, P. complanatum in particular seems to prefer an epiphytic lifestyle.

Psilotum complanatum  (left) and  Psilotum nudum  (right) growing epiphytically.

Psilotum complanatum (left) and Psilotum nudum (right) growing epiphytically.

Whether you grow them on purpose, fight them as a greenhouse “weed,” or track them down in the wild, I hope you take a moment to appreciate these oddball plants. The whisk ferns are intriguing to say the least and certainly offer up a unique conversation piece for anyone curious about the botanical world. They are a genus worth admiring.

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

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

Süßwassertang: A Fern Disguised as a Liverwort

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If you enjoy planted aquariums, you may have crossed paths with a peculiar little plant called Süßwassertang. It can be propagated by breaking off tiny pieces, which eventually grow into a tangled carpet of tiny green thalli. One could be excused for thinking that Süßwassertang was some sort of liverwort and indeed, for quite some time was marketed as such. That all changed in 2009 when it was revealed that this was not a liverwort at all but rather the gametophyte of a fern.

Despite its German name, Süßwassertang appears to have originated in tropical parts of Africa and Asia. It is surprisingly hard to find out any information about this plant outside of its use in the aquarium trade. The name Süßwassertang translates to “freshwater seaweed” and indeed, that is exactly what it looks like. The fact that this is actually the gametophyte of a fern may seem startling at first but when you consider what they must deal with in nature, the situation makes a bit more sense.

A  Süßwassertang gametophyte.  B  An antheridium, showing a cap cell ( cc ), ring cell ( rc ), and basal cell ( bc ).  Bar : 20 µm.  C  Developing lateral branches with rhizoids ( arrowhead ) and meristems ( m )  Bar : 0.2 mm.  D  Ribbon-like, branched gametophyte ( g ) of  L. spectabilis  bearing a young sporophyte ( sp )  Bar : 1 cm

A Süßwassertang gametophyte. B An antheridium, showing a cap cell (cc), ring cell (rc), and basal cell (bc). Bar: 20 µm. C Developing lateral branches with rhizoids (arrowhead) and meristems (m) Bar: 0.2 mm. D Ribbon-like, branched gametophyte (g) of L. spectabilis bearing a young sporophyte (sp) Bar: 1 cm

Fern gametophytes are surprisingly hardy considering their small size and delicate appearance. They are amazing in their ability to tolerate harsh conditions like drought and freezing temperatures. Because of this, fern gametophytes sometimes establish themselves in places that would be unfavorable for their sporophyte generation. For some, this means never completing their lifecycle. Others, however, seem to have overcome the issue by remaining in their gametophyte stage forever. Though no sexual reproduction occurs for these permanent gametophytes, they nonetheless persist and reproduce by breaking off tiny pieces, which grow into new colonies.

The sporophyte of a related species,  Lomariopsis marginata , demonstrating the usual epiphytic habit of this genus.

The sporophyte of a related species, Lomariopsis marginata, demonstrating the usual epiphytic habit of this genus.

This appears to be the case for Süßwassertang. Amazingly, despite a few attempts, no sporophytes have ever been coaxed from any gametophyte. It would appear that this is yet another species that has given up its sporophyte phase for an entirely vegetative habit. What is most remarkable is what the molecular work says about Süßwassertang taxonomically. It appears that this plant its nestled into a group of epiphytic ferns in the genus Lomariopsis. How this species evolved from vine-like ferns living in trees to an asexual colony of aquatic gametophytes is anyones’ guess but it is an incredible jump to say the least.

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

Further Reading: [1]

Celebrating the Forked Spleenwort

What can I say, I am a total sucker for ferns with "untraditional" fronds. Whereas the tropics offer seemingly endless fern varieties, I find that there is something special about temperate ferns that, for lack of a better phrase, break the mold. I was recently introduced to such a fern. Known commonly as the forked spleenwort, Asplenium septentrionale looks more like a clump of grass than it does a fern.

A closer inspection, however, would reveal that it is indeed a Pteridophyte. It grows on rocky outcrops, including stone walls, throughout the northern hemisphere. Here in North America, it is predominantly found in the Rocky Mountains. It is a small fern that often forms dense clusters in cracks and crevices. Its stems are long, narrow, and grass-like, ending in a flattened leaf blade that often forks at the tip. In typical fractal fashion, these leaf blades fork again at the tips, forming minute pinnae.

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The forked spleenwort has gone through considerable taxonomic revisions since it was first described by Linnaeus in 1753. Originally it was named Acrostichum septentrionale, but was then moved into Asplenium a few decades later. Renewed interest in this species during the mid 20th century saw the forked spleenwort moved to the genus Chamaefilix followed by Tarachia, though these did not gain much scientific credence. As such, it has remained an Asplenium ever since.

Its taxonomic story does not end there, however, as genetic tests soon revealed that a much more subtle and nuanced revision was worth considering. It was discovered that the forked spleenwort existed in two genetically distinct types, a diploid (having two sets of chromosomes) and a tetraploid (having four sets of chromosomes). Researchers found that each group had its own distinct distribution with the diploids centered in southwest Asia and the tetraploids being circumboreal.

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It was clear that a subspecies division was worth considering. Further investigations in the early 2000's revealed the presence of sterile triploid individuals that are believed to be hybrids of the two mentioned above. What's more, the forked spleenwort has been found to hybridize with other members of its genus. It is believed that the more isolated populations owe their existence in part to the isolation of their preferred substrate - these ferns do best on acidic substrates where competition is low - and decent longevity. It has been speculated that genetic differences can be maintained when "mutant" individuals become established and persist undisturbed for long periods of time.  

Regardless of its taxonomic status, the forked spleendwort is nonetheless a charismatic little species. A simple image search will reveal just how pleasant this species is in situ. Even better, its beauty and splendor can be shared by botanical enthusiasts throughout the northern hemisphere. There is something to be said about such species.

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

Further Reading: [1]

Ferns Afloat

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My introduction to the genus Salvinia was as an oddball aquarium plant floating in a display tank at the local pet store. I knew nothing about plants at the time but I found it to be rather charming nonetheless. Every time the green raft of leaves floated under the filter outlet, water droplets would bead off them like water off of a ducks back. Even more attractive were the upside down forest of "roots" which were actively sheltering a bunch of baby guppies. 

I grew some Salvinia for a few years before my interest in maintaining aquariums faded. I had forgotten about them for quite some time. Much later as I was diving into the wild world of botany, I started revisiting some of the plants that I had grown in various aquariums to learn more about them. It wasn't long before the memory of Salvinia returned. A quick search revealed something astonishing. Salvinia are not flowering plants. They are ferns! 

The genus Salvinia is wide spread. They can be found growing naturally throughout North, Central, and South America, the West Indies, Europe, Africa, and Madagascar. Sadly, because of their popularity as aquarium and pond plants, a few species have become extremely aggressive invaders in many water ways. More on that in a bit. 

Salvinia comprises roughly 12 different species. Of these, at least 4 are suspected to be naturally occurring hybrids. As you have probably already gathered, these ferns live out their entire lives as floating aquatic plants. Their most obvious feature are the pairs of fuzzy green leaves borne on tiny branching stems. These leaves are covered in trichomes that repel water, thus keeping them dry despite their aquatic habit. 

These are not roots!

These are not roots!

Less obvious are the other types of leaves these ferns produce. What looks like roots dangling below the water's surface are actually highly specialized, finely dissected leaves! I was super shocked to learn this and to be honest, it makes me appreciate these odd little ferns even more. It is on those underwater leaves that the spores are produced. Specialized structures called sporocarps form like tiny nodules on the tips of the leaf hairs.

Sporocarps come in two sizes, each producing its own kind of spore. Large sporocarps produce megaspores while the smaller sporocarps produce microspores. This reproductive strategy is called heterospory. Microspores germinate into gametophytes containing male sex organs or "antheridia," whereas the megaspores develop into gametophytes containing female sex organs or "archegonia." 

As I mentioned above, some species of Salvinia have become aggressive invaders, especially in tropical and sub-tropical water ways. Original introductions were likely via plants released from aquariums and ponds but their small spores and vegetative growth habit means new introductions occur all too easily. Left unchecked, invasive Salvinia can form impenetrable mats that completely cover entire bodies of water and can be upwards of 2 feet thick!

Sporocarps galore! 

Sporocarps galore! 

Lots of work has been done to find a cost effective way to control invasive Salvinia populations. A tiny weevil known scientifically as Cyrtobagous singularis has been used with great success in places like Australia. Still, the best way to fight invasive species is to prevent them from spreading into new areas. Check your boots, check your boats, and never ever dump your aquarium or pond plants into local water ways. Provided you pay attention, Salvinia are rather fascinating plants that really break the mold as far as most ferns are concerned. 

Photo Credits: [1] [2] [3]

Further Reading: [1] [2] [3]

 

Tropical Ferns in Temperate North America

All plants undergo some form of alternation of generations. It is the process in which, through reproduction, they cycle between a haploid gametophyte stage and a diploid sporophyte stage. In ferns and lycophytes, this alternation of generations has been taken to the extreme. Instead of the sporophyte relying on the gametophyte for sustenance, the two generations are physically independent and thus separated from one another. In a handful of fern genera here in North America, this has led to some intriguing and, dare I say, downright puzzling distributions.

The presence of a small handful of tropical fern genera in temperate North America has generated multiple scientific investigations since the early 1900's. However, as is constantly happening in science, as soon as we answer one question, seemingly infinite more questions arise. At the very least, the presence of these ferns in temperate regions offers us a tantalizing window into North America’s ancient past.

To say any of these ferns offer the casual observer much to look at would be a bit of an exaggeration. They do not play out their lives in typical fern fashion. These out-of-place tropical ferns exists entirely as asexual colonies of gametophytes, reproducing solely by tiny bundles of cells called gemmae. What's more, you will only find them tucked away in the damp, sheltered nooks and crannies of rocky overhangs and waterfalls. Buffered by unique microclimates, it is very likely that these fern species have existed in these far away corners for a very, very long time. The last time their respective habitats approached anything resembling a tropical climate was over 60 million years ago. Some have suggested that they have been able to hang on in their reduced form for unthinkable lengths of time in these sheltered habitats. Warm, wet air gets funneled into the crevices and canyons where they grow, protecting them from the deep freezes so common in these temperate regions. Others have suggested that their spores blew in from other regions around the world and, through chance, a few landed in the right spots for the persistence of their gametophyte stages.

The type of habitat you can expect to find these gametophytes.

Aside from their mysterious origins, there is also the matter of why we never find a mature sporophyte of any of these ferns. At least 4 species in North America are known to exist this way - Grammitis nimbata, Hymenophyllum tunbridgense, Vittaria appalachiana, and a member of the genus Trichomanes, most of which are restricted to a small region of southern Appalachia. In the early 1980's, an attempt at coaxing sporophyte production from V. appalachiana was made. Researchers at the University of Tennessee brought a few batches of gametophytes into cultivation. In the confines of the lab, under strictly controlled conditions, they were able to convince some of the gametophytes to produce sporophytes. As these tiny sporophytes developed, they were afforded a brief look at what this fern was all about. It confirmed earlier suspicions that it was indeed a member of the genus Vittaria, or as they are commonly known, the shoestring ferns. The closest living relative of this genus can be found growing in Florida, which hints at a more localized source for these odd gametophytes. However, both physiology and subsequent genetic analyses have revealed the Appalachian Vittaria to be a distinct species of its own. Thus, the mystery of its origin remains elusive.

In order to see them for yourself, you have to be willing to cram yourself into some interesting situations. They really put the emphasis on the "micro" part of the microclimate phenomenon. Also, you really have to know what you are looking for. Finding gametophytes is rarely an easy task and when you consider the myriad other bryophytes and ferns they share their sheltered habitats with, picking them out of a lineup gets all the more tricky. Your best bet is to find someone that knows exactly where they are. Once you see them for the first time, locating other populations gets a bit easier. The casual observer may not understand the resulting excitement but once you know what you are looking at, it is kind of hard not to get some goosebumps. These gametophyte colonies are a truly bizarre and wonderful component of North American flora.

Photo Credit: [1] [2]

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

The Mighty 'Ama'u

We tend to think of ferns as fragile plants, existing in the shaded, humid understories of forests. This could not be farther from the truth. Their lineage arose on this planet some 360 million years ago and has survived countless extinctions. In truth, they exhibit a staggering array of lifestyles, each with its own degree of adaptability. Take the Hawaiian tree fern, Sadleria cyatheoides for example.

Known in Hawai'i as the 'Ama'u, this tree fern is one of the first species to colonize the barren lava flows that make the Big Island so famous. This is an incredibly harsh landscape and many challenges must be overcome in order to persist. This does not seem to be an issue for the 'Ama'u. It is just as much at home in these water-starved habitats as it is in wetter forests. It is easily the most successful species in this genus, having colonized every island in the archipelago.

Much of its success has to due with a part of its life cycle that is much less obvious to us - the gametophyte stage. The tree fern we see is only half of the story. It is the spore-producing phase conveniently referred to as the sporophyte. When a spore finds a suitable site for germination, it grows into the other half of the life cycle, the gametophyte. This minute structure looks like a tiny green heart and it houses the reproductive organs of the plant. When water is present, male gametophytes release their flagellated sperm, which swim around until they find a female gametophyte to fertilize. Once fertilized, the resulting embryos will then grow into a new tree fern and start the cycle anew.

What sets the 'Ama'u apart from its rarer cousins is the fact that its gametophyte appears to be quite capable of both outcrossing and self-fertilization. Outcrossing, of course, promotes genetic diversity, however, the ability to self-fertilize means that a new plant can grow from only a single spore. This is super advantageous when it comes to colonizing new habitats. Its cousins seem to lack this ability to self-fertilize successfully, restricting them to more localized areas. Taken together, I think it's safe to say that the 'Ama'u is one tough cookie. 

Photo Credits: [1] [2]

Further Reading: [1] [2]

 

Giant Ferns

Although the days of forests full of towering pteridophytes has long since vanished, a few giants still remain. Some of the largest ferns alive today hail from the genus Angiopteris and they are truly massive. To stand beneath their fronds is to be transported back hundreds of millions of years.

The mule's foot ferns (as they are commonly referred to) belong to an ancient lineage. The family, Marattiaceae, is thought to have diverged from the more familiar fern lineages very early on in their evolutionary history. As such, they have more in common with the grapeferns (Ophioglossales), whisk ferns (Psilotales), and horsetails (Equisetales) than they do more familiar extant ferns. One of the more bizarre qualities of this genus is the way in which they disperse their spores. A pressure differential is created inside the sporangium that eventually leads to cavitation. As the air space within implodes, the spores are launched outwards from the fronds at high speeds.

The most obvious feature, however, is their size. Angiopteris are some of the largest ferns on our planet. Arising from an odd looking globular mass are massive fiddle heads. These gradually unfurl into fronds of epic proportions. The record for frond size goes to Angiopteris evecta. An individual growing in Java produced fronds that were 29 feet 6 inches (9 meters) long! Amazingly enough, these fronds are capable of moving up or down depending on the weather.

Such movements are no small feat for a frond of that size. It is all thanks to an area of the petiole known as the pulvinus. The pulvini are swollen regions at the base of the petiole that expand or contract based on water pressure within. Angiopteris evecta produces the largest pulvini of any plant in the world.

Angiopteris can be found growing native from Madagascar and throughout vairous islands of the South Pacific. It is hard to get an accurate species count as the taxonomic status of many "species" are still up for debate. Although something like 200 species have been described, only a small handful of these are recognized in most modern floras. Sadly, many of these are threatened by habitat loss in their home range. The same can't be said elsewhere. Some Angiopteris have become quite invasive in places like Hawai'i and Jamaica. Because of their unique evolutionary history, their bizarre appearance, and their massive size, they been planted far outside of their native range. Research has shown that many of these ferns are much more tolerant of varying environmental conditions than that of their native forests, making any new introductions quite risky.

Photo Credits: [1] [2]

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

Floating Ferns

Not every tiny plant you see growing on the surface of ponds are duckweeds. Sometimes they are Azolla. Believe it or not, these are tiny, floating ferns! The genus Azolla is comprised of about 7 to 11 different species, all of which are aquatic. Despite being quite small they nonetheless exert a massive influence wherever they grow. 

Like all ferns, Azolla reproduce via spores. Unlike more familiar ferns, however, sexual reproduction in Azolla consists of two markedly different types of spores. When conditions are right, little structures called "sporocarps" are formed underneath the branches. These produce one of two types of sporangia. Male sporangia are small and are often referred to as microspores whereas female sporangia are, relatively speaking, quite large and are referred to as megaspores. The resulting gametophytes develop within and never truly leave their respective spores. Instead, male gameotphytes release motile sperm into the water column and female gametophytes peak out of the megaspore to intercept them. Thus, fertilization is achieved. 

Azolla are fast growing plants. Via asexual reproduction, these little floating ferns can double their biomass every 3 to 10 days. That is a lot of plant matter in a short amount of time. As such, entire water bodies quickly become smothered by a fuzzy-looking carpet. Depending on the species and the environmental conditions, the color of this carpet can range from deep green to nearly burgundy. They are able to float because of their overlapping scale-like leaves, which trap air. Below each plant hangs a set of roots. The roots themselves form a symbiotic relationship with a type of cyanobacterium, which fixes atmospheric nitrogen. Couple with their astronomic growth rate, this means that colonies of Azolla quickly reach epic proportions.

In fact, they can grow so fast that Azolla may have played a serious role in a massive global cooling event that occurred some 50 million years ago. During that time, Earth was much warmer than it is now. Global temperatures were so warm that tropical species such as palms grew all the way into the Arctic. There is fossil evidence that massive blooms of Azolla may have occurred in the Arctic Ocean during this time, which was a lot less saline than it is now.

Everything red in this picture is  Azolla .

Everything red in this picture is Azolla.

Though plenty of other factors undoubtedly played a role, it is believed that Azolla blooms would have been so large that they would have drawn down CO2 levels considerably over thousands of years. As these blooms died they sank to the sea floor, bringing with them all of the carbon they had locked up in their cells. In part, this may have led to a massive drop in atmospheric CO2 levels and led to a subsequent cooling period. Evidence for this is tantalizing, so much so that some researchers have taken to calling this "The Azolla Event." However, this is far from a smoking gun. Regardless, it is an important reminder than really big things often come in very small packages.

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

Further Reading: [1] [2]

 

An Awesome Ophioglossum


Sometimes I wonder how I must look to casual hikers. There I was sprawled out next to the trail, focusing all of my attention on a nondescript patch of leaves poking up where the trail ended and the grass began. This wasn't just any sort of leaf though. The object of my attention was an ancient member of the fern lineage commonly referred to as an adder's tongue. I will gladly look like a weirdo if it means spending time in the presence of such a cool plant. 

To be more specific, the species in question here is the southern adder's tongue (Ophioglossum pychnostichum). Though not overtly showy like its more derived cousins, this little fern is nonetheless quite the show stopper if you know what you're looking for. It is generally considered a grassland associate and is most often encountered growing alongside trails. I'm not sure if this has to do with some disturbance related factor or the fact that even modestly sized plants can overshadow it. 

Regardless, I felt very fortunate to be in the presence of at least one reproductive individual. For much of its life, the southern adder's tongue exists as a gametophyte followed by an underground fleshy rhizome. It can exist in this state for years, being nourished solely by an obligate association with mycorrhizal fungi. When a certain energy threshold is reached, individuals will then produce a single, sterile leaf. This can go on for season after season as the fern slowly stores away nutrients. When enough energy has been stored, mature individuals can then produce a spore bearing structure called a "sporophyll." 

Despite its common name, this particular species distributed throughout the Northern Hemisphere. It can be found growing in North America, Europe, and temperate Asia. Still, since it is such a nondescript little plant, it rarely gets the attention it deserves when it comes to conservation. It is of conservation concern in at least a handful of states. Because its lifecycle can be hard to predict, growing some years and not others, accurate estimates of population size and health can be difficult.

The family to which is belongs is quite interesting on a genetic level as well. Ophioglossaceae is known for having staggeringly large chromosome counts. One species in particular - Ophioglossum reticulatum - boasts a whopping set of 1260 chromosomes. To put that into perspective, we humans only have 46. I guess thats what can happen to a genome that has had millions upon millions of years of natural selection working upon it. 

Further Reading:

http://bit.ly/1SG2srH

http://bit.ly/24izBkD

http://1.usa.gov/1rcWWlU

Hyperabundant Deer Populations Are Reducing Forest Diversity

Synthesizing the effects of white-tailed deer on the landscape have, until now, been difficult. Although strong sentiments are there, there really hasn't been a collective review that indicates if overabundant white-tailed deer populations are having a net impact on the ecosystem. A recent meta-analysis published in the Annals of Botany: Plant Science Research aimed to change that. What they have found is that the overabundance of deer is having strong negative impacts on forest understory plant communities in North America.

White-tailed deer have become a pervasive issue on this continent. With an estimated population of well over 30 million individuals, deer have been managed so well that they have reached proportions never seen on this continent in the past. The effects of this hyper abundance are felt all across the landscape. As anyone who gardens will tell you, deer are voracious eaters.

Tackling this issue isn't easy. Raising questions about proper management in the face of an ecological disaster that we have created can really put a divide in the room. Even some of you may be experiencing an uptick in your blood pressure simply by reading this. Feelings aside, the fact of the matter is overabundant deer are causing a decline in forest diversity. This is especially true for woody plant species. Deer browsing at such high levels can reduce woody plant diversity by upwards of 60%. Especially hard hit are seedlings and saplings. In many areas, forests are growing older without any young trees to replace them.

What's more, their selectivity when it comes to what's on the menu means that forests are becoming more homogenous. Grasses, sedges, and ferns are increasingly replacing herbaceous cover gobbled up by deer. Also, deer appear to prefer native plants over invasives, leaving behind a sea of plants that local wildlife can't readily utilize. It's not just plants that are affected either. Excessive deer browse is creating trophic cascades that propagate throughout the food web.

For instance, birds and plants are intricately linked. Flowers attract insects and eventually produce seeds. These in turn provide food for birds. Shrubs provide food as well as shelter and nesting space, a necessary requisite for healthy bird populations. Other studies have shown that in areas that experience the highest deer densities songbird populations are nearly 40% lower than in areas with smaller deer populations. As deer make short work of our native plants, they are hurting far more than just the plants themselves. Every plant that disappears from the landscape is one less plant that can support wildlife.

Sadly, due to the elimination of large predators from the landscape, deer have no natural checks and balances on their populations other than disease and starvation. As we replace natural areas with manicured lawns and gardens, we are only making the problem worse. Deer have adapted quite well to human disturbance, a fact not lost on anyone who has had their garden raided by these ungulates. Whereas the deer problem is only a piece of the puzzle when it comes to environmental issues, it is nonetheless a large one. With management practices aimed more towards trophy deer than healthy population numbers, it is likely this issue will only get worse.

Photo Credit: tuchodi (http://bit.ly/1wFYh2X)

Further Reading:
http://aobpla.oxfordjournals.org/content/7/plv119.full

http://aobpla.oxfordjournals.org/content/6/plu030.full

http://www.sciencedirect.com/science/article/pii/S0006320705001722