Arctic Vegetation is Growing Taller & Why That Matters

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The Arctic ecosystem is changing and it is doing so at an alarming rate. Indeed, the Arctic Circle is warming faster than most other ecosystems on this planet. All of this change has implications for the plant communities that call this region home. In a landmark study that incorporated thousands of data points from places like Alaska, Canada, Iceland, Scandinavia, and Russia, researchers have demonstrated that Arctic vegetation is, on average, getting taller.

Imagine what it is like to be a plant growing in the Arctic. Extreme winds, low temperatures, a short growing season, and plenty of snow are just some of the hardships that characterize life on the tundra. Such harsh conditions have shaped the plants of this region into what we know and love today. Arctic plants tend to hug the ground, hunkering down behind whatever nook or cranny offers the most respite from their surroundings. As such, plants of Arctic-type habitats tend to be pretty small in stature. As you can probably imagine, if these limits to plant growth become less severe, plants will respond accordingly.

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That is part of what makes this new paper so alarming. The vegetation that comprise these Arctic communities is nearly twice as tall today as it was 30 years ago. However, the increase in height is not because the plants that currently grow there are getting taller but rather because new plants are moving northwards into these Arctic regions. New players in the system are usually cause for concern. Other studies have shown that it isn’t warming necessarily that hurts Arctic and alpine plants but rather competition. They simply cannot compete as well with more aggressive plant species from lower latitudes.

Taller plants moving into the Arctic may have even larger consequences than just changes in species interactions. It can also change ecosystem processes, however, this is much harder to predict. One possible consequence of taller plants invading the Arctic involves carbon storage. It is possible that as conditions continue to favor taller and more woody vegetation, there could actually be more carbon storage in this system. Woody tissues tend to sequester more carbon and shading from taller vegetation may slow decomposition rates of debris in and around the soil.

  Alopecurus alpinus  is one of the new tall plant species moving into the Arctic

Alopecurus alpinus is one of the new tall plant species moving into the Arctic

It is also possible that taller vegetation will alter snowpack, which is vital to the health and function of life in the Arctic. Taller plants with more leaf area could result in a reduced albedo in the surrounding area. Lowering the albedo means increased soil temperatures and reduced snowpack as a result. Alternatively, taller plants could also increase the amount of snowpack thanks to snow piling up among branches and leaves. This could very well lead (counterintuitively) to warmer soils and higher decomposition rates as snowpack acts like an insulating blanket, keeping the soil slightly above freezing throughout most of the winter.

It is difficult to make predictions on how a system is going to respond to massive changes in the average conditions. However, studies looking at how vegetation communities are responding to changes in their environment offer us one of the best windows we have into how ecosystems might change moving into the uncertain future we are creating for ourselves.

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

Further Reading: [1]

The Only True Cedars

  Cedrus deodara

Cedrus deodara

The only true cedars on this planet can be found growing throughout mountainous regions of the western Himalayas and Mediterranean. All others are cedars by name only. The so-called “cedars” we encounter here in North America are not even in the same family as the true cedars. Instead, they belong to the Cypress family (Cupressaceae). The true cedars all belong to the genus Cedrus and are members of the family Pinaceae. They are remarkable trees with tons of ecological and cultural value.

 J. White,1803-1824.

J. White,1803-1824.

The true cedars are stunning trees to say the least. They regularly reach heights of 100 ft. (30 m.) or more and can live for thousands of years. Cedars exhibit a dimorphic branching structure, with long shoots forming branches and smaller shoots carrying most of the needle load. The needles themselves are borne in dense, spiral clusters, giving the branches a rather aesthetic appearance. Each needle produces layers of wax, which vary in thickness depending on how exposed the tree is growing. This waxy layer helps protect the tree from sunburn and desiccation.

  Cedrus libani

Cedrus libani

  Cedrus libani

Cedrus libani

One of the easiest ways to identify a cedar is by checking out its cones. All members of the genus Cedrus produce upright, barrel-shaped cones. Male cones are smaller and don’t stay on the tree for very long. Female cones, on the other hand, are quite large and stay on the tree until the seeds are ripe. Upon ripening, the entire female cone disintegrates, releasing the seeds held within. Each seed comes complete with blisters full of distasteful resin, which is thought to deter seed predators.

 Male cones of  Cedrus atlantica

Male cones of Cedrus atlantica

 Female  Cedrus  cones.

Female Cedrus cones.

In total, there are only four recognized species of cedar - the Atlas cedar (Cedrus atlantica), the Cyprus cedar (C. brevifolia), the deodar cedar (C. deodara), and the Lebanon cedar (C. libani). I have heard arguments that C. brevifolia is no more than a variant of C. libani but I have yet to come across any source that can say this for certain. Much more work is needed to assess the genetic structure of these species. Even their place within Pinaceae is up for debate. Historically it seems that Cedrus has been allied with the firs (genus Abies), however, work done in the early 2000’s suggests that Cedrus may actually be sister to all other Pinaceae. We need more data before anything can be said with certainty.

  Cedrus atlantica

Cedrus atlantica

Regardless, two of these cedars - C. atlantica & C. libani - are threatened with extinction. Centuries of over-harvesting, over-grazing, and unsustainable fire regimes have taken their toll on wild populations. Much of what remains is not considered old growth. Gone is the heyday of giant cedar forests. Luckily, many populations are now located in protected areas and reforestation efforts are being put into place throughout their range. Still, the ever present threat of climate change is causing massive pest outbreaks in these forests. The future for these trees hangs in the balance.

Photo Credit: Wikimedia Commons

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

Getting to Know Sansevieria

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The houseplant hobby is experiencing something of a renaissance as of late. With their popularity on various social media platforms, easy to grow plant species and their cultivars are experiencing a level of popularity they haven't seen in decades. One genus of particular interest to houseplant hobbyists is Sansevieria.

Despite their popularity, the few Sansevieria species regularly found in cultivation come attached with less than appealing common names. Mother-in-law's tongue, Devil's tongue, and snake plant all carry with them an air of negativity for what are essentially some of the most forgiving houseplants on the market. What few houseplant growers realize is that those dense clumps of upright striped leaves tucked into a dark corner of their home belong to a fascinating genus worthy of our admiration. What follows is a brief introduction to these enigmatic houseplants.

  Sansevieria cylindrica

Sansevieria cylindrica

  Sansevieria ballyi

Sansevieria ballyi

The Sansevieria we encounter in most nurseries are just the tip of the iceberg. Sansevieria is a genus comprise of about 70 different species. I say 'about' because this group is a taxonomic mess. There are a couple reasons for this. For starters, the vast majority of Sansevieria species are painfully slow growers. It can take decades for an individual to reach maturity. As such, they have never really presented nursery owners with much in the way of economic gain and thus only a few have received any commercial attention.

Another reason has to do with the fiber market during and after World War II. In hopes of discovering new plant-based fibers for rope and netting, the USDA collected many Sansevieria but never formally described most of them. Instead, plants were assigned numbers in hopes that future botanists would take the time needed to parse them out properly.

A third reason has to do with the variety of forms and colors these plants can take. Horticulturists have been fond of giving plants their own special cultivar names. This complicates matters as it is hard to say which names apply to which species. Often the same species can have different names depending on who popularized it and when.

  Sansevieria grandis in situ .

Sansevieria grandis in situ.

Regardless of what we call them, all Sansevieria hail from arid regions of Africa, Madagascar and southern Asia. In the wild, many species resemble agave or yucca and, indeed, they occupy similar niches to these New World groups. Like so many other plants of arid regions, Sansevieria evolved CAM photosynthesis as a means of coping with heat and drought. Instead of opening up their stomata during the day when high temperatures would cause them to lose precious water, they open them at night and store CO2 in the form of an organic acid. When the sun rises the next day, the plants close up their stomata and utilize the acid-stored carbon for their photosynthetic needs.

 The wonderfully compact  Sansevieria pinguicula .

The wonderfully compact Sansevieria pinguicula.

Often you will encounter clumps of Sansevieria growing under the dappled shade of a larger tree or shrub. Some even make it into forest habitats. Most if not all species are long lived plants, living multiple decades under the right conditions. These are just some of the reasons that they make such hardy houseplants.

The various Sansevieria appear the sort themselves out along a handful of different growth forms. The most familiar to your average houseplant enthusiast is the form typified by Sansevieria trifasciata. These plants produce long, narrow, sword shaped leaves that point directly towards the sky. Many other Sansevieria species, such as S. subspicata and S. ballyi, take on a more rosetted form with leaves that span the gamut from thin to extremely succulent. Still others, like S. grandis and S. forskaalii, produce much larger, flattened leaves that grow in a form reminiscent of a leaky vase. 

  Sansevieria trifasciata  with berries .

Sansevieria trifasciata with berries.

Regardless of their growth form, a majority of Sansevieria species undergo radical transformations as they age. Because of this, adults and juveniles can look markedly different from one another, a fact that I suspect lends to some of the taxonomic confusion mentioned earlier. A species that illustrates this nicely is S. fischeri. When young, S. fischeri consists of tight rosettes of thick, mottled leaves. For years these plants continue to grow like this, reaching surprisingly large sizes. Then the plants hit maturity. At that point, the plant switches from its rosette form to producing single leaves that protrude straight out of the ground and can reach heights of several feet! Because the rosettes eventually rot away, there is often no sign of the plants previous form.

 A young  Sansevieria fischeri  exhibiting its rosette form.

A young Sansevieria fischeri exhibiting its rosette form.

 A mature  Sansevieria fischeri  with its large, upright, cylindrical leaves.

A mature Sansevieria fischeri with its large, upright, cylindrical leaves.

If patient, many of the Sansevieria will reach enormous sizes. Such growth is rarely observed as slow growth rates and poor housing conditions hamper their performance. It's probably okay too, considering the fact that, when fully grown, such specimens would be extremely difficult to manage in a home. If you are lucky, however, your plants may flower. And flower they do!

Though there is variation among the various species, Sansevieria all form flowers on either a simple or branched raceme. Flowers range in color from greenish white to nearly brown and all produce a copious amount of nectar. I have even noticed sickeningly sweet odors emanating from the flowers of some captive specimens. After pollination, flowers give way to brightly colored berries, hinting at their place in the family Asparagaceae.

 A flowering  Sansevieria hallii .

A flowering Sansevieria hallii.

As a whole, Sansevieria can be seen as exceptional tolerators, eking out an existence wherever the right microclimate presents itself in an otherwise harsh landscape. Their extreme water efficiency, tolerance of shade, and long lived habit has lent to the global popularity of only a few species. For the majority of the 70 or so species in this genus, their painfully slow growth rates means that they have never made quite a splash in the horticulture trade.

Nonetheless, Sansevieria is one genus that even the non-botanically minded among us can pick out of a lineup. Their popularity as houseplants may wax and wane but plants like S. trifasciata are here to stay. My hope is that all of these folks collecting houseplants right now will want to learn more about the plants they bring into their homes. They are more than just fancy decorations, they are living things, each with their own story to tell. 

Photo Credits: [1] [2] [3] [4] [5] [6] [7] [8] [9]

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

Maples, Epiphytes, and a Canopy Full of Goodies

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The forests of the Pacific Northwest are known for the grandeur. This region is home to one of the greatest temperate rainforests in the world. A hiker is both dwarfed and enveloped by greenery as soon as they hit the trail. One aspect of these forests that is readily apparent are the carpets of epiphytes that drape limbs and branches all the way up into the canopy. Their arboreal lifestyle is made possible by a combination of mild winters and plenty of precipitation. 

Weare frequently taught that the relationship between trees and their epiphytes are commensal - the epiphytes get a place to live and the trees are no worse for wear. However, there are a handful of trees native to the Pacific Northwest that are changing the way we think about the relationship between these organisms in temperate rainforests.

Though conifers dominate the Pacific Northwest landscape, plenty of broad leaved tree species abound. One of the most easily recognizable is the bigleaf maple (Acer macrophyllum). Both its common and scientific names hint at its most distinguishing feature, its large leaves. Another striking feature of this tree are its epiphyte communities. Indeed, along with the vine maple (A. circinatum), these two tree species carry the greatest epiphyte to shoot biomass ratio in the entire forest. Numerous species of moss, liverworts, lichens, and ferns have been found growing on the bark and branches of these two species.

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Epiphyte loads are pretty intense. One study found that the average epiphyte crop of a bigleaf maple weighs around 78 lbs. (35.5 Kg). That is a lot of biomass living in the canopy! The trees seem just fine despite all of that extra weight. In fact, the relationship between bigleaf and vine maples and their epiphyte communities run far deeper than commensalism. Evidence accumulated over the last few decades has revealed that these maples are benefiting greatly from their epiphytic adornments.

Rainforests, both tropical and temperate, generally grow on poor soils. Lots of rain and plenty of biodiversity means that soils are quickly leached of valuable nutrients. Any boost a plant can get from its environment will have serious benefits for growth and survival. This is where the epiphytes come in. The richly textured mix of epiphytic plants greatly increase the surface area of any branch they live on. And all of that added surface area equates to more nooks and crannies for water and dust to get caught and accumulate.

When researchers investigated just how much of a nutrient load gets incorporated into these epiphyte communities, the results painted quite an impressive picture. On a single bigleaf maple, epiphyte leaf biomass was 4 times that of the host tree despite comprising less than 2% of the tree's above ground weight. All of that biomass equates to a massive canopy nutrient pool rich in nitrogen, phosphorus, potassium, calcium, magnesium, and sodium. Much of these nutrients arrive in the form of dust-sized soil particles blowing around on the breeze. What's more, epiphytes act like sponges, soaking up and holding onto precious water well into the dry summer months.

Now its reasonable to think that nutrients and water tied up in epiphyte biomass would be unavailable to trees. Indeed, for many species, epiphytes may slow the rate at which nutrients fall to and enter into the soil. However, trees like bigleaf and vine maples appear to be tapping into these nutrient and water-rich epiphyte mats.

 A subcanopy of vine maple ( Acer circinatum ) draped in epiphytes.

A subcanopy of vine maple (Acer circinatum) draped in epiphytes.

Both bigleaf and vine maples (as well as a handful of other tree species) are capable of producing canopy roots. Wherever the epiphyte load is thick enough, bundles of cells just under the bark awaken and begin growing roots. This is a common phenomenon in the tropics, however, the canopy roots of these temperate trees differ in that they are indistinguishable in form and function from subterranean roots.

Canopy roots significantly increase the amount of foraging an individual tree can do for precious water and nutrients. Additionally, it has been found that canopy roots of the bigleaf maple even go as far as to partner with mycorrhizal fungi, thus unlocking even more potential for nutrient and water gain. In the absence of soil nutrient and water pools, a small handful of trees in the Pacific Northwest have unlocked a massive pool of nutrients located above us in the canopy. Amazingly, it has been estimated that mature bigleaf and vine maples with well developed epiphyte communities may actually gain a substantial fraction of their water and nutrient needs via their canopy roots.

 

Photo Credits: [1] [2]

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

 

The Plight of the African Violets

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For many of us, African violets (Saintpaulia spp.) are some of the first houseplants we learned how to grow. They are not true violets (Violaceae), of course, but rather members of the family Gesneriaceae. Nonetheless, their compact rosettes of fuzzy leaves coupled with regular sprays of colorful flowers has made them a multi-million dollar staple of the horticultural industry. Unfortunately their numbers in captivity overshadow a bleak future for this genus in the wild. Many African violets are teetering on the brink of extinction.

The genus Saintpaulia is endemic to a small portion of east Africa, with a majority of species being found growing at various elevations throughout the Eastern Arc Mountains of Kenya and Tanzania. Most of the plants we grow at home are clones and hybrids of two species, S. ionantha and S. confusa. Collected in 1892, these two species were originally thought to be the same species, S. ionantha, until a prominent horticulturist noted that there are distinct differences in the seed capsules each produced. Since the 1890's, more species have been discovered.

  Saintpaulia goetzeana

Saintpaulia goetzeana

Exactly how many species comprise this genus is still up for some debate. Numbers range from as many as 20 to as few as 6. Much of the early work on describing various Saintpaulia species involved detailed descriptions of the density and direction of hairs on the leaves. More recent genetic work considers some of these early delineations to be tenuous at best, however, even these modern techniques have resolved surprisingly little when it comes to a species concept within this group.

  Saintpaulia  sp.  in situ .

Saintpaulia sp. in situ.

Though it can be risky to try and make generalizations about an entire genus, there are some commonalities when it comes to the habitats these plants prefer. Saintpaulia grow at a variety of elevations but most can be found growing on rocky outcrops. Most of them prefer growing in the shaded forest understory, hence they do so well in our (often) poorly lit homes. Their affinity for growing on rocks means that many species are most at home growing on rocks and cliffs near streams and waterfalls. The distribution of most Saintpaulia species is quite limited, with most only known from a small region of forest or even a single mountain. Its their limited geographic distribution that is cause for concern.

  Saintpaulia ionantha  subsp.  grotei in situ.

Saintpaulia ionantha subsp. grotei in situ.

Regardless of how many species there are, one fact is certain - many Saintpaulia risk extinction if nothing is done to save them. Again, populations of Saintpaulia species are often extremely isolated. Though more recent surveys have revealed that a handful of lowland species are more widespread than previously thought, mid to highland species are nonetheless quite restricted in their distribution. Habitat loss is the #1 threat facing Saintpaulia. Logging, both legal and illegal, and farming are causing the diverse tropical forests of eastern Africa to shrink more and more each year. As these forests disappear, so do Saintpaulia and all of the other organisms that call them home.

There is hope to be had though. The governments of Kenya and Tanzania have recognized that too much is being lost as their forests disappear. Stronger regulations on logging and farming have been put into place, however, enforcement continues to be an issue. Luckily for some Saintpaulia species, the type localities from which they were described are now located within protected areas. Protection coupled with inaccessibility may be exactly what some of these species need to survive. Also, thanks to the ease in which Saintpaulia are grown, ex situ conservation is proving to be a viable and valuable option for conserving at least some of the genetic legacy of this genus.

  Saintpaulia intermedia

Saintpaulia intermedia

It is so ironic to me that these plants can be so common in our homes and offices and yet so rare in the wild. Despite their popularity, few recognize the plight of this genus. My hope is that, in reading this, many of you will think about what you can do to protect the legacy of plants like these and so many others. Our planet and the species that call it home are doomed without habitat in which to live and reproduce. This is why land conservation is an absolute must. Consider donating to a land conservation organization today. Here are two worth your consideration:

The Nature Conservancy

The Rainforest Trust

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

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

The Carnivorous Dewy Pine

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The dewy pine is definitely not a pine, however, it is quite dewy. Known scientifically as Drosophyllum lusitanicum, this carnivore is odd in more ways than one. It is also growing more and more rare each year.

One of the strangest aspects of dewy pine ecology is its habitat preferences. Whereas most carnivorous plants enjoy growing in saturated soils or even floating in water, the dewy pine's preferred habitats dry up completely for a considerably portion of the year. Its entire distribution consists of scattered populations throughout the western Iberian Peninsula and northwest Morocco.

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Its ability to thrive in such xeric conditions is a bit of a conundrum. Plants stay green throughout the year and produce copious amounts of sticky mucilage as a means of catching prey. During the summer months, both air and soil temperatures can skyrocket to well over 100°F (37 °C). Though they possess a rather robust rooting system, dewy pines don't appear to produce much in the way of fine roots. Because of this, any ground water presence deeper in the soil is out of their reach. How then do these plants manage to function throughout the driest parts of the year?

During the hottest months, the only regular supply of water comes in the form of dew. Throughout the night and into early morning, temperatures cool enough for water to condense out of air. Dew covers anything with enough surface area to promote condensation. Thanks to all of those sticky glands on its leaves, the dewy pine possesses plenty of surface area for dew to collect. It is believed that, coupled with the rather porous cuticle of the surface of its leaves, the dewy pine is able to obtain water and reduce evapotranspiration enough to keep itself going throughout the hottest months. 

 Dewy pine leaves unfurl like fern fiddle heads as they grow.

Dewy pine leaves unfurl like fern fiddle heads as they grow.

As you have probably guessed at this point, those dewy leaves do more than photosynthesize and collect water. They also capture prey. Carnivory in this species evolved in response to the extremely poor conditions of their native soils. Nutrients and minerals are extremely low, thus selecting for species that can acquire these necessities via other means. Each dewy pine leaf is covered in two types of glands: stalked glands that produce sticky mucilage, and sessile glands that secrete digestive enzymes and absorb nutrients.

Their ability to capture insects far larger than one would expect is quite remarkable. The more an insect struggles, the more it becomes ensnared. The strength of the dewy pines mucilage likely stems from the fact that the leaves do not move like those of sundews (Drosera spp.). Once an insect is stuck, there is not much hope for its survival. Living in an environment as extreme as this, the dewy pine takes no chances.

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The taxonomic affinity of the dewy pine has been a source of confusion as well. Because of its obvious similarity to the sundews, the dewy pine has long been considered a member of the family Droseraceae. However, although recent genetic work does suggest a distant relationship with Droseraceae and Nepenthaceae, experts now believe that the dewy pine is unique enough to warrant its own family. Thus, it is now the sole species of the family Drosophyllaceae.

Sadly, the dewy pine is losing ground fast. From industrialization and farming to fire suppression, dewy pines are running out of habitat. It is odd to think of a plant capable of living in such extreme conditions as being overly sensitive but that is the conundrum faced by more plants than just the dewy pine. Without regular levels of intermediate disturbance that clear the landscape of vegetation, plants like the dewy pine quickly get outcompeted by more aggressive plant species. Its the fact that dewy pine can live in such hostile environments that, historically, has kept its populations alive and well.

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What's more, it appears that dewy pines have trouble getting their seeds into new habitats. Low seed dispersal ability means populations can be cut off from suitable habitats that are only modest distances away. Without a helping hand, small, localized populations can disappear alarmingly fast. The good news is, conservationists are working hard on identifying what must be done to ensure the dewy pine is around for future generations to enjoy.

Changes in land use practices, prescribed fires, wild land conservation, and incentives for cattle farmers to adopt more traditional rather than industrial grazing practices may turn the table on dewy pine extinction. Additionally, dewy pines have become a sort of horticultural oddity over the last decade or so. As dedicated growers perfect germination and growing techniques, ex situ conservation can help maintain stocks of genetic material around the globe.

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

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

 

 

Cycad Pollinators

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When it comes to insect pollination, flowering plants get all of the attention. However, flowers aren't the only game in town. More and more we are beginning to appreciate the role insects play in the pollination of some gymnosperm lineages. For instance, did you know that many cycad species utilize insects as pollen vectors? The ways in which these charismatic gymnosperms entice insects is absolutely fascinating and well worth understanding in more detail.

Cycads or cycad-like plants were some of the earliest gymnosperm lineages to arise on this planet. They did so long before familiar insects like bees, wasps, and butterflies came onto the scene. It had long been assumed that, like a vast majority of extant gymnosperms, cycads relied on the wind to get pollen from male cones to female cones. Indeed, many species certainly utilize to wind to one degree or another. However, subsequent work on a few cycad genera revealed that wind might not cut it in most cases.

 White-haired cycad ( Encephalartos friderici-guilielm i)

White-haired cycad (Encephalartos friderici-guilielmi)

It took placing living cycads into wind tunnels to obtain the first evidence that something strange might be going on with cycad pollination. The small gaps on the female cones were simply too tight for wind-blown pollen to make it to the ovules. Around the same time, researchers began noting the production of volatile odors and heat in cycad cones, providing further incentives for closer examination.

Subsequent research into cycad pollination has really started to pay off. By excluding insects from the cones, researchers have been able to demonstrate that insects are an essential factor in the pollination of many cycad species. What's more, often these relationships appear to be rather species specific.

  Cycadophila yunnanensis ,  C. nigra , and other beetles on a cone of  Cycas  sp.

Cycadophila yunnanensis, C. nigra, and other beetles on a cone of Cycas sp.

By far, the bulk of cycad pollination services are being performed by beetles. This makes a lot of sense because, like cycads, beetles evolved long before bees or butterflies. Most of these belong to the superfamily Cucujoidea as well as the true weevils (Curculionidae). In some cases, beetles utilize cycad cones as places to mate and lay eggs. For instance, male and female cones of the South African cycad Encephalartos friderici-guilielmi were found to be quite attractive to at least two beetle genera. 

Beetles and their larvae were found on male cones only after they had opened and pollen was available. Researchers were even able to observe adult beetles emerging from pupae within the cones, suggesting that male cones of E. friderici-guilielmi function as brood sites. Adult beetles carrying pollen were seen leaving the male cones and visiting the female cones. The beetles would crawl all over the fuzzy outer surface of the female cones until they became receptive. At that point, the beetles wriggle inside and deposit pollen. Seed set was significantly lower when beetles were excluded.

 Male cone of  Zamia furfuracea  with a mating (lek) assembly of  Rhopalotria mollis  weevils.

Male cone of Zamia furfuracea with a mating (lek) assembly of Rhopalotria mollis weevils.

For the Mexican cycad Zamia furfuracea, weevils also utilize cones as brood sites, however, the female cones go to great lengths to protect themselves from failed reproductive efforts. The adult weevils are attracted to male cones by volatile odors where they pick up pollen. The female cones are thought to also emit similar odors, however, larvae are not able to develop within the female cones. Researchers attribute this to higher levels of toxins found in female cone tissues. This kills off the beetle larvae before they can do too much damage with their feeding. This way, the cycad gets pollinated and potentially harmful herbivores are eliminated. 

Beetles also share the cycad pollination spotlight with another surprising group of insects - thrips. Thrips belong to an ancient order of insects whose origin dates back to the Permian, some 298 million years ago. Because they are plant feeders, thrips are often considered pests. However, for Australian cycads in the genus Macrozamia, they are important pollinators.

  Macrozamia macleayi  female cone.

Macrozamia macleayi female cone.

Thrip pollination was studied in detail in at least two Macrozamia species, M. lucida and M. macleayi. It was noted that the male cones of these species are thermogenic, reaching peak temperatures of around   104 °F (40 °C). They also produce volatile compounds like monoterpenes as well as lots of CO2 and water vapor during this time. This spike in male cone activity also coincides with a mass exodus of thrips living within the cones.

 Thrips ( Cycadothrips chadwicki ) leaving a thermogenic pollen cone of  Macrozamia lucida.

Thrips (Cycadothrips chadwicki) leaving a thermogenic pollen cone of Macrozamia lucida.

Thrips apparently enjoy cool, dry, and dark places to feed and breed. That is why they love male Macrozamia cones. However, if the thrips were to remain in the male cones only, pollination wouldn't occur. This is where all of that male cone metabolic activity comes in handy. Researchers found that the combination of rising heat and humidity, and the production of monoterpenes aggravated thrips living within the male cones, causing them to leave the cones in search of another home.

Inevitably many of these pollen-covered thrips find themselves on female Macrozamia cones. They crawl inside and find things much more to their liking. It turns out that female Macrozamia cones do not produce heat or volatile compounds. In this way, Macrozamia are insuring pollen transfer between male and female plants.

 Thrips up close.

Thrips up close.

Pollination in cycads is a fascinating subject. It is a reminder that flowering plants aren't the only game in town and that insects have been providing such services for eons. Additionally, with cycads facing extinction threats on a global scale, understanding pollination is vital to preserving them into the future. Without reproduction, species will inevitably fail. Many cycads have yet to have their pollinators identified. Some cycad pollinators may even be extinct. Without boots on the ground, we may never know the full story. In truth, we have only begun to scratch the surface of cycads and their pollinators.

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

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

Meet the Blazing Stars

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Midsummer in North America is, among other things, Liatris season. These gorgeous plants are often referred to as blazing stars or gayfeathers, which hints at the impact their flowers have on our psyche. Whether in the garden or in the wild, Liatris are a group of plants worth getting to know a bit better.

Liatris is by and large a North American genus with only a single species occurring in the Bahamas. Though we often think of Liatris as prairie plants, the center of diversity for this group is in the southeastern United States. Taxonomically speaking, Liatris are a bit of a conundrum. Something like 40 different species have been described and, where ranges overlap, many putative hybrids have been named.

 Rocky Mountain blazing star ( Liatris ligulistylis )

Rocky Mountain blazing star (Liatris ligulistylis)

Authorities on this group cite ample confusion when it comes to drawing lines between species. Much of this confusion comes from the fact that numerous variants and intergradations exist between the various species. As mentioned, hybridization is not uncommon in this genus, which complicates matters quite a bit.

 Prairie blazing star ( Liatris pycnostachya )

Prairie blazing star (Liatris pycnostachya)

Liatris as a whole appears to have undergone quite an adaptive radiation in North America, with species adapting to specific soils and habitat types. Take, for instance, the case of cylindrical blazing star (L. cylindracea), marsh blazing star (L. spicata), and rough blazing star (L. aspera). The ranges of these species overlap to quite a degree, however, each prefers to grow in soils of specific texture and moisture. Marsh blazing star, as you may have guessed, prefers wetter soils whereas rough blazing star enjoys drier habitats. Cylindrical blazing star seems to enjoy intermediate soil conditions, especially where soil pH is a bit higher. As such, these three species often occur in completely different habitats. However, in places like the southern shores of Lake Michigan, they find themselves growing in close quarters and as a result, a fair amount of hybridization has occurred.

 Rough blazing star ( Liatris aspera )

Rough blazing star (Liatris aspera)

Another example of confusion comes from a species commonly known as the savanna blazing star (Liatris scariosa nieuwlandii). Many different ecotypes of this plant exist and some experts don't quite know how to deal with them all. Sometimes savanna blazing star is treated as a variant of another species called the northern blazing star (Liatris scariosa var. nieuwlandii) and sometimes it is treated as its own distinct species (Liatris nieuwlandii). Until proper genetic work can be done, it is impossible to say which, if any, are correct. 

 Glandular blazing star ( Liatris glandulosa )

Glandular blazing star (Liatris glandulosa)

Taxonomic confusion aside, the various Liatris species and variants are important components of the ecology wherever they occur. Numerous insects feed upon and raise their young on the foliage and few could argue against their flowers as pollinator magnets. All Liatris produce pink to purple flowers in splendid Asteraceae fashion. Every once in a while, an aberrant form is produced that sports white flowers. Though horticulturists have capitalized on this for the garden, at least one authority claims that these white forms are much weaker than their pink flowering parents. At least one species, the pinkscale blazing star (L. elegans), produces large, filamentous white bracts that very much resemble flowers.

 Check out the bracts on the pinkscale blazing star ( L. elegans )!

Check out the bracts on the pinkscale blazing star (L. elegans)!

Liatris are just as interesting below as they are above. The roots, foliage, and flowers all emerge from a swollen underground stem called a corm. The formation of these corms is one reason why some Liatris species have become so popular in our gardens. It makes them extremely hardy during the dormant season. In the spring, the corm starts forming roots. At the same time, tiny preformed buds at the top of the corm begin to grow this years crop of leaves and flowers. By the end of the growing season, the corm has reached its maximum size for that year and the plant draws down the rest of its reserves to wait out the winter.

 Cylindrical blazing star ( Liatris cylindracea )

Cylindrical blazing star (Liatris cylindracea)

During this time, some species form a layer of tissue along the edge of the corm that is much darker in coloration than what was laid down earlier in the season. This has led some to suggest that aging individual Liatris is possible. Experts believe that specimens can readily reach 30 to 40 years of age or more, however, the degree to which these dark bands indicate annual growth is up for a lot of debate. Others have found no correlation with plant age. Regardless, it is safe to say that many Liatris species can live for decades if left undisturbed.

 Scrub blazing star ( Liatris ohlingerae )

Scrub blazing star (Liatris ohlingerae)

All in all, Liatris is a very special, albeit slightly confusing, group of plants. It offers a little something for everyone. What's more, their beauty is only part of the story. These are ecologically important plants that support many great insect species. As summer wears on, make sure to get out there and enjoy the Liatris in your neck of the woods. You will be happy you did!

Photo Credits: [1] [2] [3] [4] [5] [6] [7] [8]

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

 

 

 

Life With Endophytic Fungi

 Endophytic fungi living in the cells of a grass leaf.

Endophytic fungi living in the cells of a grass leaf.

Talk about plants long enough and fungi eventually make their way into the conversation. These two walks of life are inextricably linked and probably have been since the earliest days. At this point we are well aware of beneficial fungal partners like mycorrhizae or pathogens like the cedar apple rust. Another type of relationship we are only starting to fully appreciate is that of plants and endophytic fungi living in their above ground tissues. 

Endophytic fungi have been discovered in many different types of plants, however, it is best studied in grasses. The closer we look at these symbiotic relationships, the more complex the picture becomes. There are many ways in which plants can benefit from the presence of these fungi in their tissues and it appears that some plants even stock their seeds with fungi, which appears to give their offspring a better chance at establishment. 

To start, the benefits to the fungi are rather straight forward. They get a relatively safe place to live within the tissues of a plant. They also gain access to all of the carbohydrates the plants produce via photosynthesis. This is not unlike what we see with mycorrhizae. But what about the plants? What could they gain from letting fungi live in and around their cells?

One amazing benefit endophytic fungi offer plants is protection. Fungi are famous for the chemical cocktails they produce and many of these can harm animals. Such benefits vary from plant to plant and fungi to fungi, however, the overall effect is largely the same. Herbivores feeding on plants like grasses that have been infected with endophytic fungi are deterred from doing so either because the fungi make the plant distasteful or downright toxic. It isn't just big herbivores that are deterred either. Evidence has shown that insects are also affected.

There is even some evidence to suggest that these anti-herbivore compounds might have influences farther up the food chain. It usually takes a lot of toxins to bring down a large herbivore, however, some of these toxins have the potential to build up in the tissues of some herbivores and therefore may influence their appeal to predators. Some have hypothesized that the endophytic fungal toxins may make herbivores more susceptible to predators. Perhaps the toxins make the herbivores less cautious or slow them down, making them more likely targets. Certainly more work is needed before anyone can say for sure.

 Italian ryegrass ( Lolium multiflorum ) is one of the most studied grasses that host endophytic fungi.

Italian ryegrass (Lolium multiflorum) is one of the most studied grasses that host endophytic fungi.

Another amazing example deals with parasitoids like wasps that lay their eggs in other insects. Researchers found that female parasitoid wasps can discriminate between aphids that have been feeding on plants with endophytic fungi and those without endophytic fungi. Wasp larvae developed more slowly and had a shorter lifespan when raised in aphids that have fed on endophytic fungi plants. As such, the distribution of plants with endophytic symbionts may have serious ramifications for parasitoid abundance in any given habitat.

Another benefit these endophytic fungi offer plants is increased photosynthesis. Amazingly, some grasses appear to photosynthesize better with endophytic fungi living in their tissues than plants without fungi. There are many mechanisms by which this may work but to simplify the matter, it appears that by producing defense compounds, endophytic fungi allow the plant to redistribute their metabolic processes towards photosynthesis and growth. In return, the plants produce more carbohydrates that then feed the fungi living in their tissues. 

One of the most remarkable aspects about the relationship between endophytic fungi and plants is that the plants can pass these fungi on to their offspring. Fungi are able to infect the tissues of the host plants' seeds and therefore can be carried with the seeds wherever they go. As the seedlings grow, so do the fungi. Some evidence suggests this gives infected seedlings a leg up on the competition. Other studies have not found such pronounced effects.

Still other studies have shown that it may not be fungi in the seeds that make a big difference but rather the fungi present in the decaying tissues of plants growing around them. Endophytic fungi have been shown to produce allelopathic compounds that poison neighboring plants. Areas receiving lots of plant litter containing endophytic fungi produced fewer plants but these plants grew larger than areas without endophytic fungi litter. Perhaps this reduces competition in favor of plant species than can host said endophytes. Again, this has potentially huge ramifications for the diversity and abundance of plant species living in a given area.

We are only beginning to understand the role of endophytic fungi in the lives of plants and the communities they make up. To date, it would appear that endophytic fungi are potentially having huge impacts on ecosystems around the globe. It goes without saying that more research is needed.

Photo Credits: [1] [2]

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

                                                        

Meet the Crypts

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If you have ever spent time in an aquarium store, you have undoubtedly come across a Cryptocoryne or two. Indeed, these plants are most famous for their indispensable role in aquascaping freshwater aquaria. As organisms, however, crypts receive considerably less attention. Nonetheless, a handful of dedicated botanists have devoted time and effort to understanding this wonderful genus of tropical Aroids. What follows is a brief introduction to the world of Cryptocoryne plants. 

Cryptocoryne is a genus that currently consists of around 60 - 65 species, all of which are native to tropical regions of Asia and New Guinea. Every few years it seems at least one or two new species are added to this list and without a doubt, more species await discovery. All crypts are considered aquatic to one degree or another. Ecologically speaking, however, species fall into four broad categories based on the types of habitats they prefer.

  Cryptocoryne cognata in situ .

Cryptocoryne cognata in situ.

The most familiar crypts grow along the banks of slow-moving rivers and streams and find themselves submerged for a large portion of their life. Others grow in seasonally flooded habitats and experience a pronounced dry season. These species usually go dormant until flood waters return. Still others can be found growing in swampy forested habitats, often in acidic peat swamps. Finally, a few crypts have adapted to living in tidal zones in both fresh and brackish waters.

Like all aquatic plants, crypts face a lot of challenges living in water. One of the biggest challenges is reproduction. Despite their aquatic nature, crypts will not flower successfully underwater. If growing submerged, most crypt species reproduce vegetatively via a creeping rhizome. As such, crypts often form large, clonal colonies in both the wild and in aquaria, a fact that has made a few crypts aggressive invaders in places like Florida.

  Cryptocoryne wendtii  is one of the most common species in the aquarium trade. Its textured leaves are thought to have a higher surface area, allowing this plant to thrive in shaded aquatic habitats.

Cryptocoryne wendtii is one of the most common species in the aquarium trade. Its textured leaves are thought to have a higher surface area, allowing this plant to thrive in shaded aquatic habitats.

Given proper hydrologic cycles, however, crypts will flower and when they do, it is truly a sight to behold. As is typical of aroids, crypts produce an inflorescence comprised of a spadix with whirls of male and female flowers covered by a decorative sheath called a spathe. This spathe is the key to successful flowering among the various crypt species.

 Species like  C. becketti  have become invasive in places like Florida, no doubt thanks to aquarium hobbyists.

Species like C. becketti have become invasive in places like Florida, no doubt thanks to aquarium hobbyists.

If the spathe were to open underwater, the inflorescence would quickly rot. Instead, most crypts seem to have an uncanny ability to sense water levels. At early stages of development, the spathe completely encloses the developing spadix in a water tight package. The tubular spathe continues to grow upward until the top has breached the surface. Consequently, the overall length of a crypt inflorescence is highly variable depending on the water level of its habitat. Crypts living in tidal zones take this a step further. Somehow they are able to time their flowering events to the ebb and flow of the tides, only producing flowers during periods of the month when tides are at their lowest.

  Cryptocoryne ligua

Cryptocoryne ligua

With the tip of the inflorescence safely above water, the spathe will finally open revealing their surprisingly complex anatomy and coloration. It is a shame that most crypt growers never get to see such floral splendor in person. The spathe of many crypt species emit a faint but unpleasant odor. Additionally, some species adorn the spathe with fringes that, coupled with stark coloration, is thought to improve the chances of pollinator visitation.

Pollinators are poorly studied among crypts, however, it is thought that small flies take up the bulk of the work. Lured in by the promise of a rotting meal on which they can feed and lay their eggs, the flies become trapped inside the long tube of the spathe. Like the pitfall traps of a pitcher plant, the inner walls of the spathe are coated in a waxy substance that keeps the insects from crawling out before they do their job.

In general, the female flowers mature first. If the insect inside has visited a crypt of the same species the day before, it is likely carrying pollen and thus deposits said pollen onto the stigmas of the current crypt. After the female flowers have had a chance at being fertilized, the male flowers then mature. The insects inside are then dusted with new pollen, the walls of the spathe lose their slippery properties, and the insects are released in hopes of repeated the process again.

 The fruit of a  Cryptocoryne  is called a syncarp.

The fruit of a Cryptocoryne is called a syncarp.

To the best of my knowledge, most crypts are not self-compatible. Instead, plants must receive pollen from unrelated individuals to set seed. Because large crypt colonies are often made up of clones of a single mother plant, sexual reproduction can be rather infrequent among the various species. Nonetheless sexual reproduction does occur and the seeds are produced in a different way than most other aroids. Instead of berries, crypts produce their seeds in a aggregated collection of fruits called a syncarp. When ripe, the syncarp opens like a little star and the seeds float away on the current.

One species, Cryptocoryne ciliata, takes seed production to a whole different level by producing viviparous seeds. Before the syncarp even opens, the seeds actually germinate on the mother plant. In this way, tiny seedlings complete with roots and leaves are released instead of seeds. Seedlings have a much greater surface area than seeds and readily get stuck in mud as well as other aquatic vegetation. In this way, C. ciliata offspring get a jump start on the establishment process. It is no wonder then that C. ciliata has one of the widest distributions of any of the crypt species.

  Cryptocoryne ciliata

Cryptocoryne ciliata

Despite plenty of overlap among the ranges of various crypt species, the genus displays an amazing array of variation. Some have likened crypts to Araceae's version of Darwin's finches in that the unique ecology of each species appears to have created barriers to species introgression. Though hybrids do occur, each crypt seems to maintain its own niche via a unique habitat requirement, differing flower phenology, or a specific set of pollinators. It would appear that much can be learned about the mechanics of speciation by studying the various Cryptocoryne and their habits.

Unfortunately, the limited geographic distribution and specific habitat requirements of crypt species is cause for concern. Many are growing more and more rare as human settlements expand and destroy valuable crypt habitat. As popular as some crypts may be in cultivation, many others have proven too idiosyncratic to grow on a commercial level. More work is certainly needed to properly assess populations and bring plants into cultivation as a form of ex situ conservation.

  Cryptocoryne cordata  Var. Siamensis 'Rosanervig' is a contoversial variety names recognized by the stark patterns of venation on its leaves.

Cryptocoryne cordata Var. Siamensis 'Rosanervig' is a contoversial variety names recognized by the stark patterns of venation on its leaves.

Proper study is further complicated by the fact that many crypt species are highly plastic. They have to be in order to survive the rigors of their aquatic environment. True species identification can really only be assessed when flowers are present and some populations seem to prefer vegetative over sexual reproduction a majority of the time. A multitude of subspecies exist, though the degree to which they should be formally recognized is up for debate.

I think it is safe to say that Cryptocoryne is a genus worth far more attention than it currently receives. They are without a doubt important components of the ecology of their native habitats and humans would do well to understand them a bit better. With a bit more attention from botanical gardens and other conservation organizations, perhaps the future for many crypts does not have to be so bleak.

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

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

 

The Rose of Jericho

To survive in a desert, plants must eek out an existence in specific microclimates that provide conditions that are only slightly better than the surrounding landscape. Such is the case for the Rose of Jericho (Anastatica hierochuntica). This tenacious little mustard is found throughout arid regions of the Middle East and the Saharan Desert and it has been made famous the world over for its "resurrection" abilities. It is also the subject of much speculation so today we are going to separate fact from fiction and reveal what years of research has taught about this desert survivor. 

Natural selection has shaped this species into an organism fully ready to take advantage of those fleeting moments when favorable growing conditions present themselves. A. hierochuntica makes its living in dry channels called runnels or wadis, which concentrate water during periods of rain. It is a desert annual meaning the growth period of any individual is relatively short. Once all the water in the sandy soil has evaporated, this plant shrivels up and dies. This is not the end of its story though. With a little luck, the plants were pollinated and multiple spoon-shaped fruits have formed on its stems.

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As the dead husk of the plant starts to dry out, its branches curl up into a ball-like mass with most of the fruits tucked away in the interior. There the plant will sit, often for many years, until rain returns. When rain does finally arrive, things happen fast. After all, who knows how long it will be before it rains again. Thanks to a quirk of physiology, the dried tissues of A. hierochuntica are extremely elastic and can return to their normal shape and position once hydrated. As the soil soaks up water, the dried up stems and roots just under the surface also begin taking up water and the stems unfurl.

To call this resurrection is being a bit too generous. The plant is not returning to life. Instead, its dead tissues simply expand as they imbibe liquid. Water usually does not come to the desert without rain and rain is exactly what A. hierochuntica needs to complete its life cycle. Unfurling of its stems exposes its spoon-shaped fruits to the elements. Their convex shape is actually an adaptation for seed dispersal by rain, a mechanism termed ombrohydrochory. When a raindrop hits the fruit, it catapults the seed outward from the dead parent.

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If rains are light, seeds do not get very far. They tend to cluster around the immediate area of their parent. If rains are heavy, however, seeds can travel quite a distance. This is why one will only ever find this species growing in channels. During the rare occasions when those channels fill with water, seeds quickly float away on the current. In fact, experts believe that the buoyancy of A. hierochuntica seed is an adaptation that evolved in response to flooding events. It is quite ironic that water dispersal is such an important factor for a plant growing in some of the driest habitats on Earth.

To aid in germination, the seeds themselves are coated in a material that becomes mucilaginous upon wetting. When the seeds eventually come into contact with the soil, the mucilage sticks to the ground and causes the seeds to adhere to the surface upon drying. This way, they are able to effectively germinate instead of blowing around in the wind.

Again, things happen fast for A. hierochuntica. Most of its seeds will germinate within 12 hours of rainfall. Though they are relatively drought tolerant, the resulting seedlings nonetheless cannot survive without water. As such, their quick germination allows them to make the most out of fleeting wet conditions.

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Occasionally, the balled up husks of these plants will become dislodged from the sand and begin to blow around the landscape like little tumbleweeds. This has led some to suggest that A. hierochuntica utilizes this as a form a seed dispersal, scattering seeds about the landscape as it bounces around in the wind. Though this seems like an appealing hypothesis, experts believe that this is not the best means of disseminating propagules. Seeds dispersed in this way are much less likely to end up in favorable spots for germination. Though it certainly occurs, it is likely that this is just something that happens from time to time rather than something the plant has evolved to do.

In total, the Rose of Jericho is one tough cookie. Thanks to quick germination and growth, it is able to take advantage of those rare times when its desert environment become hospitable.

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

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

The Curious Case of the Yellowwood Tree

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The immense beauty and grace of the yellowwood (Cladrastis kentukea) is inversely proportional to its abundance. This unique legume is endemic to the eastern United States and enjoys a strangely patchy distribution. Its ability to perform well when planted far outside of its natural range only deepens the mystery of the yellowwood.

The natural range of the yellowwood leaves a lot of room for speculation. It hits its highest abundances in the Appalachian and Ozark highlands where it tends to grow on shaded slopes in calcareous soils. Scattered populations can be found as far west as Oklahoma and as far north as southern Indiana but nowhere is this tree considered a common component of the flora.

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Though the nature of its oddball distribution pattern is open for plenty of speculation, it is likely that its current status is the result of repeated glaciation events and a dash of stochasticity. The presence of multiple Cladrastis species in China and Japan and only one here in North America is a pattern shared by multiple taxa that once grew throughout each continent. A combination of geography, topography, and repeated glaciation events has since fragmented the ranges of many genera and perhaps Cladrastis is yet another example.

The fact that yellowwood seems to do quite well as a specimen tree well outside of its natural range says to me that this species was probably once far more wide spread in North America than it was today. It may have been pushed south by the ebb and flow of the Laurentide Ice Sheet and, due to the stochastic nuances of seed dispersal, never had a chance to recolonize the ground it had lost. Again, this is all open to speculation as this point.

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Despite being a member of the pea family, yellowwood is not a nitrogen fixer. It does not produce nodules on its roots that house rhizobium. As such, this species may be more restricted by soil type than other legumes. Perhaps its inability to fix nitrogen is part of the reason it tends to favor richer soils. It may also have played a part in its failure to recolonize land scraped clean by the glaciers.

Yellowwood's rarity in nature only makes finding this tree all the more special. It truly is a site to behold. It isn't a large tree by any standards but what it lacks in height it makes up for in looks. Its multi-branched trunk exhibits smooth, gray bark reminiscent of beech trees. Each limb is decked out in large, compound leaves that turn bright yellow in autumn.

When mature, which can take upwards of ten years, yellowwood produces copious amounts of pendulous inflorescences. Each inflorescence sports bright white flowers with a dash of yellow on the petals. It doesn't appear that any formal pollination work has been done on this tree but surely bees and butterflies alike visit the blooms. The name yellowwood comes from the yellow coloration of its heartwood, which has been used to make furniture and gunstocks in the past.

Whether growing in the forest or in your landscape, yellowwood is one of the more stunning trees you will find in eastern North America. Its peculiar natural history only lends to its allure.

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

Further Reading: [1] [2]

The Mystery of the Ghost Plant

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As houseplants enjoy a resurgence in our culture, untold numbers of novice and expert growers alike will have undoubtedly tried their luck at a succulent or two. Succulent, of course, is not a taxonomic division, but rather a way of describing the anatomy of myriad plants adapted to harsh, dry environments around the world. One of the most common succulents in the trade is the ghost plant (Graptopetalum paraguayense).

I would bet that, if you are reading this and you grow houseplants, you have probably grown a ghost plant at one point or another. They are easy to grow and will propagate a whole new plant from only a single leaf. Despite its worldwide popularity, the ghost plant is shrouded in mystery and confusion. To date, we know next to nothing about its ecology. Much of this stems from poor record keeping and the fact that we have no idea exactly where this species originated.

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That's right, we do not know the location of its native habitat. Records indicate that the first plants to find their way into human hands were imported into New York in 1904. Apparently, they were growing as "weeds" at the base of some South American cacti. Plants were lucky enough to wind up in the hands of competent botanists and the species has ended up with the name Graptopetalum paraguayense. The specific epithet "paraguayense" was an indication of much confusion to come as it was thought that the ghost plant originated in Paraguay.

Time has barely improved our knowledge. Considering many of its relatives hail from Mexico, it gradually became more apparent that South America could not claim this species as its own. Luck changed only relatively recently with the discovery of a population of a unique color variant of the ghost plant on a single mountain in northeastern Mexico. A thorough search of the area did not reveal any plants that resemble the plant so many of us know and love. It has been suggested that the original population from which the type species was described is probably growing atop an isolated mountain peak somewhere nearby in the Chihuahuan Desert.

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Despite all of the mystery surrounding this species, we can nonetheless elucidate some aspects about its biology by observing plants in cultivation. It goes without saying that the ghost plant is a species of dry, nutrient-poor habitats. Its succulence and tolerance of a wide array of soil conditions is a testament to its hardy disposition. Also, if plants are grown in full sun, they develop a bluish, waxy coating on their leaves. This is likely a form of sunscreen that the plant produces to protect it from sun scorch. As such, one can assume that its native habitat is quite sunny, though its ability to tolerate shade suggests it likely shares its habitat with shrubby vegetation as well. Given enough time and proper care, ghost plants will produce sprays of erect, 5 pointed flowers. It is not known who might pollinate them in the wild.

It is always interesting to me that a plant can be so well known to growers while at the same time being a complete mystery in every other way. A search of the literature shows that most of the scientific attention given to the ghost plant centers on potentially useful compounds that can be extracted from its tissues. Such is the case for far too many plant species, both known and unknown alike. Perhaps, in the not too distant future, some intrepid botanist will at last scramble up the right mountain and rediscover the original habitat of this wonderful plant. Until then, I hope this small introduction provides you with a new found appreciation for this wonderfully adaptable houseplant.

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

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

 

Of Bluebells and Fungi

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Whether in your garden or in the woods, common bluebells (Hyacinthoides non-scripta) are a delightful respite from the dreary months of winter. It should come as no surprise that these spring geophytes are a staple in temperate gardens the world over. And, as amazing as they are in the garden, bluebells are downright fascinating in the wild.

Bluebells can be found growing naturally from the northwestern corner of Spain north into the British Isles. They are largely a woodland species, though finding them in meadows isn't uncommon. They are especially common in sites that have not experienced much soil disturbance. In fact, large bluebell populations are used as indicators of ancient wood lots.

Being geophytes, bluebells cram growth and reproduction into a few short weeks in spring. We tend to think of plants like this as denizens of shade, however, most geophytes get going long before the canopy trees have leafed out. As such, these plants are more accurately sun bathers. On warm days, various bees can be seen visiting the pendulous flowers, with the champion pollinator being the humble bumble bees.

The above ground beauty of bluebells tends to distract us from learning much about their ecology. That hasn't stopped determined scientists though. Plenty of work has been done looking at how bluebells make their living and get on with their botanical neighbors. In fact, research is turning up some incredible data regarding bluebells and mycorrhizal fungi.

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Bluebell seeds tend not to travel very far, most often germinating near the base of the parent. Germination occurs in the fall when temperatures begin to drop and the rains pick up. Interestingly, bluebell seeds actually germinate within the leaf litter and begin putting down their initial root before the first frosts. Often this root is contractile, pulling the tiny seedling down into the soil where it is less likely to freeze. During their first year, phosphorus levels are high. Not only does the nutrient-rich endosperm supply the seedling with much of its initial needs, abundant phosphorus near the soil surface supplies more than enough for young plants. This changes as the plants age and change their position within the soil.

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Over the next 4 to 5 years, the bluebell's contractile roots pull it deeper down into the soil, taking it out of the reach of predators and frost. This also takes them farther away from the nutrient-rich surface layers. What's more, the roots of older bluebells are rather simple structures. They do not branch much, if at all, and they certainly do not have enough surface area for proper nutrient uptake. This is where mycorrhizae come in.

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Bluebells partner with a group of fungi called arbuscular mycorrhiza, which penetrate the root cells, thus greatly expanding the effective rooting zone of the plant. Plants pay these fungi in carbohydrates produced during photosynthesis and in return, the fungi provide the plants with access to far more nutrients than they would be able to get without them. One of the main nutrients plants gain from these symbiotic fungi is phosphorus.

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For bluebells, with age comes new habitat, and with new habitat comes an increased need for nutrients. This is why bluebells become more dependent on arbuscular mycorrhiza as they age. In fact, plants grown without these fungi do not come close to breaking even on the nutrients needed for growth and maintenance and thus live a shortened life of diminishing returns. This is an opposite pattern from what we tend to expect out of mycorrhizal-dependent plants. Normally its the seedlings that cannot live without mycorrhizal symbionts. It just goes to show you that even familiar species like the bluebell can offer us novel insights into the myriad ways in which plants eke out a living.

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

Further Reading: [1] [2]

 

One Mustard, Many Flavors

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What do kale, broccoli, cauliflower, Brussel sprouts, and cabbage have in common? They are all different cultivars of the same species!

Wild cabbage (Brassica oleracea) is native to coastal parts of southern and western Europe. In its native habitat, wild cabbage is very tolerant of salty, limey soils but not so tolerant of competition. Because of this, it tends to grow mainly on limestone sea cliffs where few other plants can dig their roots in.

Despite their popularity as delicious, healthy vegetables, as well as their long history of cultivation, there is scant record of this plant before Greek and Roman times. Some feel that this is one of the oldest plants in cultivation. Along with the countless number of edible cultivars, the wild form of Brassica oleracea can be found growing throughout the world, no doubt thanks to its popularity among humans.

I am always amazed by how little we know about crop wild relatives. Despite the popularity of its many agricultural cultivars, relatively little attention has been paid to B. oleracea in the wild. What we do know is that at least two subspecies have been identified - B. oleracea ssp. bourgeaui and B. oleracea L. ssp. oleracea. As far as anyone can tell, subspecies 'oleracea' is the most wide spread in its distribution whereas subspecies 'bourgeaui'  is only known from the Canary Islands. 

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B. oleracea's long history with humans confuses matters quite a bit. Because it has been cultivated for thousands of years, identifying which populations represent wild individuals and which represent ancient introductions is exceedingly difficult. Such investigations are made all the more difficult by a lack of funding for the kind of research that would be needed to elucidate some of these mysteries. We know so little about wild B. oleracea that the IUCN considers is a species to be "data deficient."

It seems to appreciate cool, moist areas and will sometimes escape from cultivation if conditions are right, thus leading to the confusion mentioned above. It is amazing to look at this plant and ponder all the ways in which humans have selectively bred it into the myriad shapes, sizes, and flavors we know and love (or hate) today! However, we must pay more attention to the wild progenitors of our favorite crops. They harbor much needed genetic diversity as well as clues to how these plants are going to fare as our climates continue to change.

Photo Credit: [1] [2]

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

Trout Lily Appreciation

This video is a celebration of the white trout lily (Erythronium albidum) and its various spring ephemeral neighbors. We even talk about the threat that invasive species like garlic mustard (Alliara petiolata).

Producer, Editor, Camera: Grant Czadzeck (http://www.grantczadzeck.com)

Music by
Artist: Botanist
Track:
https://verdant-realm-botanist.bandcamp.com/

Prescribed Fire On An Illinois Prairie

Prairies are fire adapted ecosystems. For far too long, fires were sequestered. Today, more and more communities are coming around to the fact that fire can be used as a tool to bring life back to these endangered ecosystems. In this video, we get hands on experience with fire as a prairie restoration tool.

Producer, Editor, Camera: Grant Czadzeck (http://www.grantczadzeck.com)

Music by
Artist: Stranger In My Town
Track: Terra
https://strangerinmytown.bandcamp.com/

 

Early Spring Ephemerals

Join us as we go in search of some of the earliest spring ephemerals. In this episode we come face to face with the aptly named harbinger of spring (Erigenia bulbosa) and the lovely Hepatica nobilis.

Producer, Editor, Camera: Grant Czadzeck (http://www.grantczadzeck.com)

Music by
Artist: Stranger In My Town
Track: Air
https://strangerinmytown.bandcamp.com/

Life On a Floodplain

Floodplains can be pretty rough places for plant life. Despite readily a available water supply, the unpredictable, disturbance-prone nature of these habitats means that static lifeforms such as plants need to be quite adaptable to survive and persist. Join In Defense of Plants for a brief look at this sort of ecosystem.

Producer, Editor, Camera: Grant Czadzeck (http://www.grantczadzeck.com)

Music by
Artist: Somali Yacht Club
Track: Up In The Sky
http://somaliyachtclub.bandcamp.com

The Desert Mistletoe: Evolution In Action

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There are a multitude of mistletoes on this planet (for example: 1, 2, 3) and all of them are parasites to one degree or another. I find parasitic plants absolutely fascinating as there are many variations on this lifestyle as there are hosts to parasitize. On a recent botanical adventure in the Sonoran Desert, I met yet another representative of this group - the desert mistletoe (Phoradendron californicum). Once I knew what I was looking at, I could not wait to do some research. As it turns out, this species has garnered quite a bit of attention over the years and it is teaching us some interesting tidbits on how parasites may evolve.

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The desert mistletoe is not hard to spot, especially during the driest parts of the year when most of its host trees have shed their leaves. It looks like a leafless tangled mass of pendulous stems sitting among the branches of larger shrubs and trees. It can be found growing throughout both the Mojave and Sonoran deserts and appears to prefer leguminous trees including palo verde (Parkinsonia florida), mesquite (Prosopis spp.), and Acacia.

The desert mistletoe is a type of hemiparasite, which means it is capable of performing photosynthesis but nonetheless relies on its host tree for water and other nutrients. Lacking leaves, the desert mistletoe meets all of its photosynthetic needs via its green stems. Its leafless habit also makes its flowers and fruit all the more conspicuous. Despite their small size, its flowers are really worth closer inspection. When in bloom, a desert mistletoe comes alive with the hum of various insects looking for energy-rich nectar and pollen. Even before you spot them, you can easily tell if there is a blooming mistletoe nearby as the flowers give off a wonderfully sweet aroma. It appears that the desert mistletoe takes no chances when it comes to reproduction in such an arid climate.

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As I mentioned above, the desert mistletoe has been the subject of inquiry over the last few decades. Researchers interested in how parasitic plants evolve have illuminated some intriguing aspects of the biology of this species, especially as its relates to host preference. It would appear that our interest in this species seems to be situated at an important time in its evolutionary history. Not all populations of desert mistletoe "behave" in the same way. In fact, each seems to be heading towards more intense specialization based on its preferred host.

By performing seed transplant experiments, researchers have demonstrated that various populations of desert mistletoe seem to be specializing on specific tree species. For instance, when seeds collected from mistletoe growing on Acacia were placed on paleo verde or mesquite, they experienced significantly less germination than if they were placed on another Acacia. Though the exact mechanisms aren't clear at this point in time, evidence suggests that the success of desert mistletoe may be influenced by various hormone levels within the host tree, with isolated populations becoming more specialized on the chemistry of their specific host in that region.

Speaking of isolation, there is also evidence to show that populations of desert mistletoe growing on different host trees are reproductively isolated as well. Populations growing on mesquite trees flower significantly later than populations growing on Acacia or palo verde. Essentially this means that their genes never have the chance to mix, thus increasing the differences between these populations. Again, it is not entirely certain how the host tree may be influencing mistletoe flowering time, however, hormones and water availability are thought to play a role.

Another intriguing idea, and one that has yet to be tested, are the roles that seed dispersers may play out in this evolutionary drama. After pollination, the desert mistletoe produces copious amounts of bright red berries that birds find irresistible. Two birds in particular, the northern mockingbird and the Phainopepla, aggressively defend fruiting mistletoe shrubs within their territories. It could be possible that these birds may be influencing which trees the seeds of the desert mistletoe end up on. Again, this is just a hypothesis but one that certainly deserves more attention.

 A Phainopepla on the lookout for mistletoe berries.

A Phainopepla on the lookout for mistletoe berries.

Love them or hate them, there is something worth admiring about mistletoes. At the very least, they are important components of their native ecology. What's more, species like the desert mistletoe have a lot to teach us about the way in which species interact and what that means for biodiversity.

Photo Credit: [1]

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