Meet the Pygmy Clubmoss

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

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

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

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

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

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

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

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

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

A New Species of Waterfall Specialist Has Been Discovered In Africa

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At first glance, this odd plant doesn’t look very special. However, it is the first new member of the family Podostemaceae to be found in Africa in over 30 years. It has been given the name Lebbiea grandiflora and it was discovered during a survey to assess the impacts of a proposed hydroelectric dam. By examining the specimen, Kew botanists quickly realized this plant was unique. Sadly, if all goes according to plan, this species may not be long for this world unless something is done to preserve it.

Members of the family Podostemaceae are strange plants. Despite how delicate they look, these plants specialize in growing submersed on rocks in waterfalls, rapids, and other fast flowing bodies of water. They are generally small plants, though some species can grow to lengths of 3 ft. (1 m) or more. The best generalization one can make about this group is that they like clean, fast-flowing water with plenty of available rock surfaces to grow on.

Lebbiea grandiflora certainly fits this description. It is native to a small portion of Sierra Leone and Guinea where it grows on slick rock surfaces only during the wet season. As the dry season approaches and the rivers shrink in size, L. grandiflora quickly sets seed and dies.

As mentioned, the area in which this plant was discovered is slated for the construction of a large hydroelectric dam. The building of this dam will most certainly destroy the entire population of this plant. As soon as water slows, becomes more turbid, and sediments build up, most Podostemaceae simply disappear. Unfortunately, I appears this plant was in trouble even before the dam came into the picture.

 A. habit, whole plant, in fruit, showing the flat root, a pillar-like ‘haptera’, and a shoot with three inflorescences, B. detail of shoot with three branches, C. view of upper surface of a flattened root, with six short, erect shoots, each with 1–2 1-flowered inflorescences emerging from spathellum remains, D. side view of plant showing, on the lower surface of the flattened root, the pillar-like haptera, branched at base; upper surface of root with spathellum-sheathed inflorescence base, E. plant attached to rock by weft of thread-like root hairs (indicated with arrow) from base of pillar-like haptera; upper surface of flattened root with two shoots, F. side view of flower showing one of two tepals in full frontal view, G. as F. with tepal removed, exposing the gynoecium with, to left, the arched-over androecium, H. side view of flower with androecium in centre, two tepals flanking the gynoecium, I. androecium (leftmost of three anthers missing), J. transverse section of andropodium, K. view of gynoecium from above showing funneliform style-stigma base, L. fruit, dehisced, M. transverse section of bilocular fruit, showing septum and placentae, N. placentae with seeds, divided by septum, O. seeds, P. seed with mucilage outer layer. Drawn by Andrew Brown from  Lebbie  A2721  [SOURCE]

A. habit, whole plant, in fruit, showing the flat root, a pillar-like ‘haptera’, and a shoot with three inflorescences, B. detail of shoot with three branches, C. view of upper surface of a flattened root, with six short, erect shoots, each with 1–2 1-flowered inflorescences emerging from spathellum remains, D. side view of plant showing, on the lower surface of the flattened root, the pillar-like haptera, branched at base; upper surface of root with spathellum-sheathed inflorescence base, E. plant attached to rock by weft of thread-like root hairs (indicated with arrow) from base of pillar-like haptera; upper surface of flattened root with two shoots, F. side view of flower showing one of two tepals in full frontal view, G. as F. with tepal removed, exposing the gynoecium with, to left, the arched-over androecium, H. side view of flower with androecium in centre, two tepals flanking the gynoecium, I. androecium (leftmost of three anthers missing), J. transverse section of andropodium, K. view of gynoecium from above showing funneliform style-stigma base, L. fruit, dehisced, M. transverse section of bilocular fruit, showing septum and placentae, N. placentae with seeds, divided by septum, O. seeds, P. seed with mucilage outer layer. Drawn by Andrew Brown from Lebbie A2721 [SOURCE]

As mentioned, Podostemaceae need clean rock surfaces on which to germinate and grow. Without them, the seedlings simply can’t get established. Mining operations further upstream of the Sewa Rapids have been dumping mass quantities of sediment into the river for years. All of this sediment eventually makes it down into L. grandiflora territory and chokes out available germination sites.

Alarmed at the likely extinction of this new species, the Kew team wanted to try and find other populations of L. grandiflora. Amazingly, one other population was found growing in a river near Koukoutamba, Guinea. Sadly, the discovery of this additional population is bitter sweet as the World Bank is apparently backing another hydro-electric dam project on that river as well.

The only hope for the continuation of this species currently will be to (hopefully) find more populations and collect seed to establish ex situ populations both in other rivers as well as in captivity if possible. To date, no successful purposeful seeding of any Podostemaceae has been reported (if you know of any, please speak up!). Currently L. grandiflora has been given “Critically Endangered” status by the IUCN and the botanists responsible for its discovery hope that, coupled with the publication of this new species description, more can be done to protect this small rheophytic herb.

Photo Credit: [1] [2]

Further Reading: [1]

On the Flora of Antarctica

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Antarctica - the frozen continent. It is hard to think of a place on Earth that is less hospitable to life. Yet life does exist here and some of it is botanical. Though few in number, Anarctica’s diminutive flora is able to eke out an existence wherever the right conditions present themselves. It goes without saying that these plants are some of the hardiest around.

It is strange to think of Antarctica as having any flora at all. How many descriptions of plant families and genera say something to the effect of “found on nearly every continent except for Antarctica.” It didn’t always used to be this way though. Antarctica was once home to a diverse floral assemblage that rivaled anything we see in the tropics today. Millions upon millions of years of continental drift has seen this once lush landmass positioned squarely at Earth’s southern pole.

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Situated that far south, Antarctica has long since become a frozen wasteland of sorts. The landscape is essentially a desert. Instead of no precipitation, however, most water in this neck of the woods is completely locked up in ice for most of the year. This is one reason why plants have had such a hard time making a living here. That is not to say that some plants haven’t made it. In fact, a handful of species thrive under these conditions.

When anyone goes looking for plants in Antarctica, they must do so wherever conditions ease up enough for part of the year to allow terrestrial life to exist. In the case of this frozen continent, this means hanging out along the coast or one of handful of islands situated just off of the mainland. Here, enough land thaws during the brief summer months to allow a few plant species to take root and grow.

 Antarctic hair grass ( Deschamsia antarctica )

Antarctic hair grass (Deschamsia antarctica)

The flora of Antarctica proper consists of 2 flowering plant species, about 100 species of mosses, and roughly 30 species of liverwort. The largest of these are the flowering plants - a grass known as Antarctic hair grass (Deschamsia antarctica), and member of the pink family with a cushion-like growth habit called Antarctic pearlwort (Colobanthus quitensis). Whereas the hair grass benefits from being wind pollinated, the Antarctic pearlwort has had to get creative with its reproductive needs. Instead of relying on pollinators, which simply aren’t present in any abundance on Antarctica, it appears that the pearlwort has shifted over to being entirely self-pollinated. This seems to work for it because if the mother plant is capable of living on Antarctica, so too will its clonal offspring.

By far the dominant plant life on the continent are the mosses. With 100 species known to live on Antarctica, it is hard to make generalizations about their habits other than to say they are pretty tough plants. Most live out their lives among the saturated rocks of the intertidal zones. What we can say about these mosses is that they support a bewildering array of microbial life, from fungi and lichens to protists and tardigrades. Even in this frozen corner of the world, plants form the foundation for all other forms of life.

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 Antarctic pearlwort ( Colobanthus quitensis )

Antarctic pearlwort (Colobanthus quitensis)

The coastal plant communities of Antarctica represent hotbeds of biodiversity for this depauperate continent. They reach their highest densities on the Antarctic Peninsula as well as on coastal islands such as south Orkney Islands and the South Shetland Islands. Here, conditions are just mild enough among the various rocky crevices for germination and growth to occur. Still, life on Antarctica is no cake walk. A short growing season, punishing waves, blistering winds, and trampling by penguins and seals present quite a challenge to Antarctica’s botanical denizens. They are able to live here despite these challenges.

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Still, humans take their toll. The Antarctic Peninsula is experiencing some of the most rapid warming on the planet over the last century. As this region grows warmer and drier each year, plants are responding accordingly. Antarctic mosses along the peninsula are increasingly showing signs of stress. They are starting to prioritize the production of protective pigments in their tissues over growth and reproduction. Moreover, new species of moss are starting to take over. Rapid warming and drying of the Antarctic Peninsula appears to be favoring species that are more desiccation tolerant at the expense of the continents endemic moss species.

Changes in the structure and composition of Antarctica’s moss beds is far from being a scientific curiosity for only bryologists to ponder. It is a symptom of greater changes to come.

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

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

How a Tropical Conifer May Hold the Key to Kākāpō Recovery

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The plight of the kākāpō is a tragedy. Once the third most common bird in New Zealand, this large, flightless parrot has seen its numbers reduced to less than 150. In fact, for a time, it was even thought to be extinct. Today, serious effort has been put forth to try and recover this species from the brink of extinction. It has long been recognized that kākāpō breeding efforts are conspicuously tied to the phenology of certain trees but recent research suggests one in particular may hold the key to survival of the species.

The kākāpō shares its island homes (saving the kākāpō involved moving birds to rat-free islands) with a handful of tropical conifers from the families Podocarpaceae and Araucariaceae. Of these tropical conifers, one species is of particular interest to those concerned with kākāpō breeding - the rimu. Known to science as Dacrydium cupressinum, this evergreen tree represents one of the most important food sources for breeding kākāpō. Before we get to that, however, it is worth getting to know the rimu a bit better.

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Rimu are remarkable, albeit slow-growing trees. They are endemic to New Zealand where they make up a considerable portion of the forest canopy. Like many slow-growing species, rimu can live for quite a long time. Before commercial logging moved in, trees of 800 to 900 years of age were not unheard of. Also, they can reach immense sizes. Historical accounts speak of trees that reached 200 ft. (61 m) in height. Today you are more likely to encounter trees in the 60 to 100 ft. (20 to 35 m) range.

The rimu is a dioecious tree, meaning individuals are either male or female. Rimu rely on wind for pollination and female cones can take upwards of 15 months to fully mature following pollination. The rimu is yet another one of those conifers that has converged on fruit-like structures for seed dispersal. As the female cones mature, the scales gradually begin to swell and turn red. Once fully ripened, the fleshy red “fruit” displays one or two black seeds at the tip. Its these “fruits” that have kākāpō researchers so excited.

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As mentioned, it is a common observation that kākāpō only tend to breed when trees like the rimu experience reproductive booms. The “fruits” and seeds they produce are an important component of the diets of not only female kākāpō but their developing chicks as well. Because kākāpō are critically endangered, captive breeding is one of the main ways in which conservationists are supplementing numbers in the wild. The problem with breeding kakapo in captivity is that supplemental food doesn’t seem to bring them into proper breeding condition. This is where the rimu “fruits” come in.

Breeding birds desperately need calcium and vitamin D for proper egg production. As such, they seek out diets high in these nutrients. When researchers took a closer look at the “fruits” of the rimu, the kākāpō’s reliance on these trees made a whole lot more sense. It turns out, those fleshy scales surrounding rimu seeds are exceptionally high in not only calcium, but various forms of vitamin D once thought to be produced by animals alone. The nutritional quality of these “fruits” provides a wonderful explanation for why kākāpō reproduction seems to be tied to rimu reproduction. Females can gorge themselves on the “fruits,” which brings them into breeding condition. They also go on to feed these “fruits” to their developing chicks. For a slow growing, flightless parrot, it seems that it only makes sense to breed when food is this food source is abundant.

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Though far from a smoking gun, researchers believe that the rimu is the missing piece of the puzzle in captive kākāpō breeding. If these “fruits” really are the trigger needed to bring female kākāpō into good shape for breeding and raising chicks, this may make breeding kākāpō in captivity that much easier. Captive breeding is the key to the long term survival of these odd yet charismatic, flightless parrots. By ensuring the production and survival of future generations of kākāpō, conservationists may be able to turn this tragedy into a real success story. What’s more, this research underscores the importance of understanding the ecology of the organisms we are desperately trying to save.

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

Further Reading: [1] [2]

Gymnosperms and Fleshy "Fruits"

 Fleshy red aril surrounding the seeds of  Taxus baccata.

Fleshy red aril surrounding the seeds of Taxus baccata.

Many of us were taught in school that one of the key distinguishing features between gymnosperms and angiosperms is the production of fruit. Fruit, by definition, is a structure formed from the ovary of a flowering plant. Gymnosperms, on the other hand, do not enclose their ovules in ovaries. Instead, their unfertilized ovules are exposed (to one degree or another) to the environment. The word “gymnosperm” reflects this as it is Greek for “naked seed.” However, as is the case with all things biological, there are exceptions to nearly every rule. There are gymnosperms on this planet that produce structures that function quite similar to fruits.

 Cross section of a  Ginkgo  ovule with red arrow showing the integument.

Cross section of a Ginkgo ovule with red arrow showing the integument.

The key to understanding this evolutionary convergence lies in understanding the benefits of fruits in the first place. Fruits are all about packing seeds into structures that appeal to the palates of various types of animals who then eat said fruits. Once consumed, the animals digest the fruity bits and will often deposit the seeds elsewhere in their feces. Propagule dispersal is key to the success of plants as it allows them to not only to complete their reproductive cycle but also conquer new territory in the process. With a basic introduction out of the way, let’s get back to gymnosperms.

 “Fruits” of  Cephalotaxus fortunei  (Cephalotaxaceae)

“Fruits” of Cephalotaxus fortunei (Cephalotaxaceae)

There are 4 major gymnosperm lineages on this planet - the Ginkgo, cycads, gnetophytes, and conifers. Each one of these groups contains members that produce fleshy structures around their seeds. However, their “fruits” do not all develop in the same way. The most remarkable thing to me is that, from a developmental standpoint, each lineage has evolved its own pathway for “fruit” production.

  Ginkgo  “fruits” are full of butyric acid and smell like rotting butter or vomit.

Ginkgo “fruits” are full of butyric acid and smell like rotting butter or vomit.

For instance, consider ginkgos and cycads. Both of these groups can trace their evolutionary history back to the early Permian, some 270 - 280 million years ago, long before flowering plants came onto the scene. Both surround their developing seed with a layer of protective tissue called the integument. As the seed develops, the integument swells and becomes quite fleshy. In the case of Ginkgo, the integument is rich in a compound called butyric acid, which give them their characteristic rotten butter smell. No one can say for sure who this nasty odor originally evolved to attract but it likely has something to do with seed dispersal. Modern day carnivores seem to be especially fond of Ginkgo “fruits,” which would suggest that some bygone carnivore may have been the main seed disperser for these trees.

 “Fruits” contained within the female cone of a cycad ( Lepidozamia peroffskyana ).

“Fruits” contained within the female cone of a cycad (Lepidozamia peroffskyana).

The Gnetophytes are represented by three extant lineages (Gnetaceae, Welwitschiaceae, and Ephedraceae), but only two of them - Gnetaceae and Ephedraceae - produce fruit-like structures. As if the overall appearance of the various Gnetum species didn’t make you question your assumptions of what a gymnosperm should look like, its seeds certainly will. They are downright berry-like!

 Berry-like seeds of  Gnetum gnemon .

Berry-like seeds of Gnetum gnemon.

The formation of the fruit-like structure surrounding each seed can be traced back to tiny bracts at the base of the ovule. After fertilization, these bracts grow up and around the seed and swell to become red and fleshy. As you can imagine, Gnetum “fruits” are a real hit with animals. In the case of some Ephedra, the “fruit” is also derived from much larger bracts that surround the ovule. These bracts are more leaf-like at the start than those of their Gnetum cousins but their development and function is much the same.

 Red, fleshy bracts of  Ephedra distachya .

Red, fleshy bracts of Ephedra distachya.

Whereas we usually think of woody cones when we think of conifers, there are many species within this lineage that also have converged on fleshy structures surrounding their seeds. Probably the most famous and widely recognized example of this can be seen in the yews (Taxus spp.). Ovules are presented singly and each is subtended by a small stalk called a peduncle. Once fertilized, a group of cells on the peduncle begin to grow and differentiate. They gradually swell and engulf the seed, forming a bright red, fleshy structure called an “aril.” Arils are magnificent seed dispersal devices as birds absolutely relish them. The seed within is quite toxic so it usually escapes the process unharmed and with any luck is deposited far away from the parent plant.

 The berry-like cones of  Juniperus communis .

The berry-like cones of Juniperus communis.

Another great example of fleshy conifer “fruits” can be seen in the junipers (Juniperus spp.). Unlike the other gymnosperms mentioned here, the junipers do produce cones. However, unlike pine cones, the scales of juniper cones do not open to release the seeds inside. Instead, they swell shut and each scale becomes quite fleshy. Juniper cones aren’t red like we have seen in other lineages but they certainly garnish the attention of many a small animal looking for food.

I have only begun to scratch the surface of the fruit-like structures in gymnosperms. There is plenty of literary fodder out there for those of you who love to read about developmental biology and evolution. It is a fascinating world to uncover. More importantly, I think the fleshy “fruits” of the various gymnosperm lineages stand as a testament to the power of natural selection as a driving force for evolution on our planet. It is amazing that such distantly related plants have converged on similar seed dispersal mechanisms by so many different means.

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

Further Reading: [1] [2] [3] [4] [5] [6] [7]

Hydrostachyaceae: Enigmatic Rheophytes

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Today I would like to introduce you to an enigmatic family of aquatic angiosperms called Hydrostachyaceae. Though they kind of look like strange aquatic ferns or perhaps even lycopods, they are actually strange flowering plants. To find them, you need to hang out around waterfalls and rapids in either Madagascar or southern Africa.

Hydrostachyaceae is made up of roughly 22 species. This is a poorly understood group of plants and there is always a chance that more species await discovery. The various members of Hydrostachyaceae all take on a similar appearance. For much of the year they exist as a set of feathery, fern-like leaves that grow surprisingly large and look quite delicate, especially considering the types of habitats in which they grow.

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Their delicate appearance is deceptive. In fact, the feathery structure of their leaves is an adaptation to the waters in which they grow. These are plants that require fast moving, clean, fresh water. If they were to produce flat, unbroken leaves, the fast currents would quickly rip them to shreds. By producing long, feathery leaves, water simply flows right over them with minimal disturbance. However, their preferred habitats also make them extremely difficult to study. Hence we know very little about their ecology.

What we do know about these plants is that they need clean rock surfaces and clear water for germination and subsequent growth. Dump too much sediment in the stream and you can kiss these plants goodbye. When they dry season approaches and water levels begin to drop, these oddball plants go into flowering mode. To the best of my knowledge, nearly all members of this family are dioecious, meaning individual plants are either male or female. When it comes time to flower, each plant produces modest sized spikes densely packed with flower.

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The spikes themselves sit up and above the water line, which is how this family and genus got its name. Hydrostachys is Greek and roughly translates to “water spike.” I have not been able to track down any solid information on what might be pollinating these blooms, however, given their small, dense nature, and the extreme places in which they live, my bet would be on wind.

The ecology of Hydrostachyaceae isn’t the only mystery about these plants. Their position on the tree of life has also been cause for confusion ever since they were discovered. Morphologically speaking, aquatic angiosperms can offer a lot of confusion to taxonomists. Like whales, the ancestors of aquatic angiosperms lived out their lives on land. Making the move back into water comes with a lot of extremely specialized adaptations that can cloud our morphological interpretations of things.

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Some authors have put forth the idea that these plants belong to another family of highly derived aquatic angiosperms - the Podostemaceae. However, genetic analyses paint a much different story. When the Angiosperm Phylogeny Group got a hold of specimens, their molecular work suggested the Hydrostachyaceae were nestled in Cornales, somewhere near the Hydrangea family (Hydrangeaceae). Exactly where Hydrostachyaceae fits into this new classification is still up for debate but it just goes to show you how messy things can get when plant lineages return to water.

Sadly, like so many other plants, the various members of Hydrostachyaceae are under a lot of pressure in the wild. Basically anything that threatens the quality of streams and rivers is a threat to the ongoing survival of these species. Runoff pouring into water ways from agriculture and mining cloud up the water and bury available germination sites under layers of sediment. Things only get worse when hydroelectric projects are installed. The fate of these plants is unequivocally tied to water quality.

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

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

A Relictual Palm in the American Southwest

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Scattered throughout hidden oases nestled in the southwest corner of North America grows a glorious species of palm known to science as Washingtonia filifera. This charismatic tree goes by a handful of common names such as the desert fan palm, petticoat palm, and California fan palm. No matter what you call it, there is no denying that this palm is both unique and important to this arid region.

Populations of the desert fan palm are few and far between, occurring in a few scattered locations throughout the Colorado and Mojave Deserts. This palm can’t grow just anywhere in these deserts either. Instead, its need for water restricts it to small oases where springs, streams, or a perched water table can keep them alive.

Fossil evidence from Wyoming suggests that the restricted distribution of this palm is a relatively recent occurrence. Though not without plenty of debate, our current understanding of the desert fan palm is that it could once be found growing throughout a significant portion of western North America but progressive drying has seen its numbers dwindle to the small pockets of trees we know today.

The good news is that, despite being on conservation lists for its rarity, the desert fan palm appears to be expanding its range ever so slightly. One major component of this range expansion has to do with human activity. The desert fan palm makes a gorgeous specimen plant for anyone looking to add a tropical feel to their landscape. As such, it has been used in plantings far outside of its current range. Some reports suggest that it is even becoming naturalized in places like Death Valley, Sonoran Mexico, and even as far away as Florida and Hawai’i.

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Other aspects contributing to its recent range expansion are also attributable to human activity, though indirectly. For one, with human settlement comes agriculture, and with agriculture comes wells and other forms of irrigation. It is likely that the seeds of the desert fan palm can now find suitably wet areas for germination where they simply couldn’t before. Also, humans have done a great job at providing habitat for potential seed dispersers, especially in the form of coyotes and fruit-eating birds.

It’s not just an increase in seed dispersers that may be helping the desert fan palm. Pollinators may be playing a role in its expansion as well, though in a way that may seem a bit counterintuitive. With humans comes a whole slew of new plants in the area. This greatly adds to the floral resources available for insect pollinators like bees.

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Historically it has been noted that bees, especially carpenter bees, tend to be rather aggressive with palm inflorescences as they gather pollen, which may actually reduce pollination success. It is possible that with so many new pollen sources on the landscape, carpenter bees are visiting palm flowers less often, which actually increases the amount of pollen available for fertilizing palm ovules. This means that the palms could be setting more seed than ever before. Far more work will be needed before this mechanism can be confirmed.

Aside from its unique distribution, the desert fan palm has an amazing ecology. Capable of reaching heights of 80 ft. (25 m) or more and decked out in a skirt of dead fronds, the desert fan palm is a colossus in the context of such arid landscapes. It goes without saying that such massive trees living in desert environments are going to attract their fair share of attention. The thick skirt of dead leaves that cloaks their trunks serve as vital refuges for everything from bats and birds, to reptiles and countless of insects. Fibers from its leaves are often used to build nests and line dens.

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And don’t forget the fruit! Desert fan palms can produce copious amount of hard fruits in good years. These fruits go on to feed many animals. Coupled with the fact that the desert fan palm always grows near a water source and you can begin to see why these palms are a cornerstone of desert oases. There has been some concern over the introduction of an invasive red palm weevil (Rhynchophorus ferrugineus), however, researchers were able to demonstrate that the desert fan palm has a trick up its sleeve (leaf skirt?) for dealing with these pests.

It turns out that desert fan palms are able to kill off any of these weevils as they try to burrow into its trunk. The desert fan palm secretes a gummy resin into damaged areas, which effectively dissuaded most adults and killed off developing beetle larvae. For now it seems that resistance is enough to protect this palm from this weevil scourge.

It is safe to say that regardless of its limited distribution, the desert fan palm is one tough plant. Its towering trunks and large, fan-like leaves stand as a testament to the wonderful ways in which natural selection shapes organisms. It is a survivor and one that has benefited a bit from our obsession with cultivating palms.

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

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


Are Packrats Fumigating Their Homes Using Plants?

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Any organism that lives in one place for a long enough time is going to have to deal with pests. For mammals, this often means fleas and ticks. Nests, dens, and other roosting spots tend to accumulate high numbers of these blood suckers the longer they are in use. As such, anything that can cut down on pest loads in and around the home has the potential to confer great advantages. Evidence from California suggests that wood rats may be using the leaves of a shrub to do just that.

Dusky-footed wood rats (A.K.A. packrats) build giant nests out of twigs and other plant debris. These nests serve to protect packrats from both the elements and hungry predators. Packrat nests can last for quite a long time and reach monumental proportions considering the size of the rat itself. Because they use these stick nests for long periods of time, it should come as no surprise that they can build up quite a pest load. Fleas are especially problematic for these rodents.

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 A dusky-footed woodrat ( Neotoma fuscipes ) and its den.

A dusky-footed woodrat (Neotoma fuscipes) and its den.

When researchers took a closer look at what packrats were bringing into their nests, they realized that not all plant material was treated equally. Whereas packrats actively collect and feed on leaves from various oaks (Quercus spp.), conifers (Pinus spp., Juniperus spp., etc.), and toyon (Heteromeles arbutifolia), the packrats seemed to have a special affinity for the leaves of the California bay (Umbellularia californica). However, instead of taking huge bites out of bay leaves, the rats appear to nibble them along the margin and spread them throughout their nest. What’s more, fresh bay leaves are brought in every few days.

This led some researchers to suggest that, instead of packrats using bay leaves as food, they may be using them to fumigate their homes. Indeed, California bay is rather chemically active. It is an aromatic shrub noted for its resistance to insect infestation. Of special interest to the research team were a group of chemical compounds called monoterpenoids. They noted that bay leaves were especially high in two types of of these compounds - 1,8-cineole (which gives the shrub its characteristic odor), and umbellulone (which has shown to be quite toxic to rodents). Why else would packrats bring something potentially deadly into their home other than to drive off pests?

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Closer observation revealed that the packrats were in fact treating bay leaves differently than other leaves. For starters, bay leaves were disproportionately used to line the sleeping chambers within the stick nests. What’s more, the bay leaves were cycled out every 2 to 3 days. Even the nibbling patterns were significantly different. As mentioned above, bay leaves were merely nibbled along the leaf margins, which is an ideal place to nibble if releasing volatile compounds is the desired effect.

When researchers tested the effectiveness of a variety of leaves in the lab, their results added further evidence to the fumigation hypothesis. More than any other leaf found in packrat nests, bay leaves had clear negative effects on flea numbers. Flea survival in the lab was reduced by upwards of 75% when California bay leaves were present whereas flea survival was only reduced by less than 10% with all other leaves. It goes without saying that, whether they are conscious decisions or not, packrats definitely stand to benefit by decorating their homes with California bay leaves.

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

Further Reading: [1]

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 Upside Down World of Orchid Flowers

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Did you know that most orchid flowers you see are actually blooming upside down? That's right, referred to as "resupination," the lower lip of many orchid flowers is actually the top petal and, as the flower develops inside the bud, the whole structure makes a 180° rotation. How and why does this happen?

The lip of an orchid flower usually serves to attract pollinators as well as function as a landing pad for them. The flower of an orchid is an incredibly complex organ with an intriguing evolutionary history. Basically, the lip is the most derived structure on the flower and, in most cases, it is the most important structure in initiating pollination.

 The non-resupinate flowers of the grass pink ( Calopogon tuberosus ) showing the lip on top.

The non-resupinate flowers of the grass pink (Calopogon tuberosus) showing the lip on top.

As an orchid flower bud develops, it begins to exhibit gravitropic tendencies, meaning it responds to the pull of gravity. By removing specific floral organs like the column and pollinia, researchers found that they produce special hormones called auxins that tell the developing bud to begin the process of resupination. The ovary starts to twist, causing the flower to stand on its head.

Not all orchids exhibit resupinate flowers. Grass pinks (Calopogon tuberosus) famously bloom with the lip pointing up as it does in the early stages of bud development. It is an interesting mechanism and serves to demonstrate the stepwise tendencies that the forces of natural selection and evolution can manifest. But why does it occur at all? What is the evolutionary advantage of resupinate flowers?

 Not only are  Dracula  flowers resupinate, many species also face them towards the ground.

Not only are Dracula flowers resupinate, many species also face them towards the ground.

The most likely answer to this biological twist is that, for orchids, resupination places the lip in such a way that facilitates pollination by whatever the flowers are attracting. For many orchids, this means providing an elaborate landing strip in the form of the lip. For the grass pinks, which operate by slamming visiting bees downward onto the column to achieve pollination, placing the lip at the top makes more mechanical sense. When a bee visits the upward pointing lip thinking it will find a pollen-rich meal, the lip bend at the base like a hinge. Anything goes in evolution provided the genes are present for selection to act upon and nowhere is this fact more beautifully illustrated than in orchids.

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

Viper's Bugloss

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Throughout much of North America, brown fields, roadsides, and other waste places occasionally take on a wonderful blue hue. Often time the cause of this colorful display is none other than Echium vulgare, or as its commonly referred to, viper's bugloss. Viper’s bugloss is a member of the borage family and was originally native to most of Europe and Asia. However, humans introduced it to North America some time ago. It has since naturalized quite well and is even considered invasive in parts of Washington. No matter your views on this plant, the reproductive ecology of this species is quite interesting.

Viper's bugloss produces its flowers on spikes. Starting off pink and gradually changing to blue as they mature, the flowers ripen their male portions on their first day and ripen their female portions on the second day. This is known as "protandry." Plants that exhibit this lifestyle offer researchers a window into the advantages and disadvantages with regards to the fitness investment of each sex. What they have found in viper's bugloss is that there are clearly distinct strategies for each type of flower.

Male flowers are pollinator limited. They must hedge their bets towards increasing the number of visitors. Bees are the main pollinators of this species and the more bees that visit, the more pollen can be disseminated. Unlike female flowers, which are resource limited, male flowers can produce pollen and nectar quite cheaply. Because of this, male flowers produce significantly more nectar than female flowers to bring in more bees. As the anthers senesce and give way to receptive styles, things begin to change. The plant now has to redirect resources into producing seed. At this point, resources are everything. The plant produces considerably less nectar resources than pollen but the bees can’t know that without visiting.

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The other interesting aspect its reproductive ecology has to do with population size. Bees are notorious for favoring plants that are more numerous on the landscape. This makes a lot of sense. Why spend time looking for uncommon plants when they can go for easier, more numerous targets. This can be very detrimental to the fitness of rare plant species. However, plants like viper's bugloss don't seem to fall victim to this.

By looking at large and small populations, researchers found that pollination success pretty much evens out for viper's bugloss no matter how numerous it is in a given area. Large populations receive many more visits from bees but the bees spend less time on each flower. When viper's bugloss populations are small, flowers receive fewer visits but bees spend more time at each flower. This results is no significant difference in the reproductive fitness of either population.

Considering how efficient this plant is reproductively, it is no wonder it has done so well outside of its native range. Add to this its ability to grow in some of the worst soil conditions, it goes without saying that viper's bugloss is here to stay. If you find this species growing, certainly take time to get up close with the flowers. You will be glad you did.

Photo Credits: [1] [2]

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


The Genus Ceropegia Recently Got a Whole Lot Bigger

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The succulent and climbing members of the milkweed family (Apocynaceae) have been gaining a lot of popularity among houseplant growers and for good reason. These wonderful plants produce some of the most elaborate flowers most of us will ever encounter and many of them smell quite strongly. Whereas houseplant enthusiasts recognize multiple genera of these spectacular plants, recent taxonomic work suggests lumping them all into one single genus - Ceropegia.

Such a massive taxonomic move has caused its fair share of drama. Folks seem to get quite ornery when it comes to shifts in nomenclature, especially when it involves this many species. However, when you dive into this group of plants, you really start to see how shaky the ground was that supported the previous classification systems. Evolution, after all, is not a neat and tidy process and we can learn a lot from the succulent and climbing asclepiads regarding the importance of combining morphological and genetic data into our taxonomic decisions.

  Ceropegia (Stapelia) hirsuta

Ceropegia (Stapelia) hirsuta

Botanists have been obsessing over this group for decades. Historically speaking, four major groups have been recognized: those with caudiciform stems (genus Brachystelma), the stem succulent stapeliads (which include genera such as Stapelia, Huernia, Orbea, Caralluma, and others), the climbers (genus Ceropegia), and the so-called early divergent group (which include genera such as Anisotoma, Conomitra, Dittoceras, and others). Together these groups total something like 762 species and represent the tribe Ceropegieae.

The taxonomic status of the various members of Ceropegieae have always been up for debate. Early work was based on surprisingly few species and relied heavily on morphological characters such and corolla shape, stem anatomy, and pubescence. Since the 1950’s, many more species have been discovered and that is where a lot of the trouble began. Much of the early characters that were used to draw lines between various groups were suddenly blurred. Genera were created and absorbed by various authors in an attempt to get a handle on how this tribe evolved.

  Ceropegia  ( Brachystelma )  tuberosum

Ceropegia (Brachystelma) tuberosum

Things got even more complicated as various stapeliads and Ceropegia attracted the attention of horticulturists. As new species became available, many varieties were haphazardly named and genera such as Stapelia were further split to accommodate some of the peculiar nuances in floral shapes, colors, and sizes. It wasn’t until some genetic work was done that the need for a major overhaul of the Ceropegieae tribe became apparent.

Unfortunately, this early molecular work suffered from low resolution. Very few genera were used and among those, only a handful of gene regions were analyzed. Still, the picture that was developing was that the historical understanding of Ceropegieae was surprisingly misleading. For instance, the genera that made up the stapeliad group appeared to be nested quite firmly within the genus Ceropegia. Though equally as limited in scope, consecutive work in the early 2000’s added further evidence to the idea that the four groups that made up Ceropegieae were so genetically similar that most should be nested somewhere within Ceropegia.

  Ceropegia  ( Duvalia )  modesta

Ceropegia (Duvalia) modesta

Though not without controversy, this early molecular work convinced enough taxonomists to take a closer look at each of the four groups. With more resolution and a finer grasp on the diversity in form of these plants, taxonomists started to question the validity of some taxa. Indeed, the closer anyone looked, the more the lines between genera started to blur.

For example, Ceropegia and Brachystelma have long been separated on the basis of floral structure. Ceropegia were considered to adhere to a single corolla structure involving long, tubular flowers whereas Brachystelma were thought to be more variable in form. The discovery of new species clearly demonstrates that there are far too many exceptions to this system for it to be valid.

 Fig. 1. Variation in the corolla and corona in the traditional concept of  Ceropegia : A–C,  C. salicifolia , Nepal,  Bruyns 2507  (BM, K); D–E,  C. melanops , Ethiopia,  Gilbert 3050  (K); F—H,  C. meleagris , Nepal,  Bruyns 2496  (K); I–J,  C. loranthiflora , Ethiopia,  Gilbert 2851   (K). [scale-bars or subdivisions indicate mm; A, D, F, I, corolla from  side; B, G, corolla dissected to show location of corona; C, E, H, J,  corona from side].   [SOURCE]

Fig. 1. Variation in the corolla and corona in the traditional concept of Ceropegia: A–C, C. salicifolia, Nepal, Bruyns 2507 (BM, K); D–E, C. melanops, Ethiopia, Gilbert 3050 (K); F—H, C. meleagris, Nepal, Bruyns 2496 (K); I–J, C. loranthiflora, Ethiopia, Gilbert 2851 (K). [scale-bars or subdivisions indicate mm; A, D, F, I, corolla from side; B, G, corolla dissected to show location of corona; C, E, H, J, corona from side]. [SOURCE]

 Fig. 2. Variation in the corolla and corona in the traditional concept of  Brachystelma : A–C,  B. brevipedicellatum , South Africa,  Bruyns 2372 ; D–F,  B. mafekingense , Namibia,  Bruyns 1954  (K, WIND); G–J,  B. gymnopodum , South Africa,  Bruyns 2078   (NBG). [scale-bars or subdivisions indicate mm; A, corolla from front,  D, G, corolla from side; B, E, H, corolla dissected to show location of  corona; C, J, corona from front; F, I, corona from side].   [SOURCE]

Fig. 2. Variation in the corolla and corona in the traditional concept of Brachystelma: A–C, B. brevipedicellatum, South Africa, Bruyns 2372; D–F, B. mafekingense, Namibia, Bruyns 1954 (K, WIND); G–J, B. gymnopodum, South Africa, Bruyns 2078 (NBG). [scale-bars or subdivisions indicate mm; A, corolla from front, D, G, corolla from side; B, E, H, corolla dissected to show location of corona; C, J, corona from front; F, I, corona from side]. [SOURCE]

Such is also the case for other anatomical features such as whether plants climb or not. Again, there are plants in both genera that deviate from these patterns, thus making it impossible to nail down any set of characters that maintain the split between these two genera. Also, it would seem that some authors were trying to pull a fast one on readers. Back in 2007, Meve and Liede-Schumann claimed there were “a wide array of morphological features” that separate these two genera but failed to reveal any but those mentioned here. There are multiple species of Ceropegia and Brachystelma that simply do not conform to this historical classification.

Similarly, Ceropegia and the various stapeliads have been separated on the basis of stem and floral anatomy. Historically speaking, the stapeliads were thought to consist of fleshy, succulent stems with tubercules and reduced or absent leaves, whereas Ceropegia were considered to be slender climbers. Again, with more species having been discovered, these distinctions grew more and more blurry.

 The succulent stems of  Ceropegia cimiciodora .

The succulent stems of Ceropegia cimiciodora.

It turns out that there are many Ceropegia with fleshy, succulent stems and the only major difference between the two genera is the lack of angles in the stems of some Ceropegia. The structure and presentation of their flowers also stands on shaky ground. There is so much similarity between the flowers of some of the succulent Ceropegia and the early diverging stapeliads that one would be hard pressed to identify any character that clearly separates them.

Between all of the molecular work and the anatomical scrutiny, it was clear that something needed to be done to clean up the taxonomic status of Ceropegieae. Keeping things separate may make sense to some but considering the group as a whole instead of from a collector’s standpoint, trying to find enough distinct characters to preserve the historical treatment would make things way too messy. In 2017 it was suggested that because there are no clear differences between the four groups within this tribe, all members were to be lumped back in to the genus Ceropegia.

  Ceropegia  ( Stapelia )  flavopurpurea

Ceropegia (Stapelia) flavopurpurea

Although this most recent treatment still recognizes some morphological differences between these plants (thus multiple subsections are recognized), the lack of genetic differentiation between groups long thought to be distinct really does support this decision. Because of historical precedents, Ceropegia won out as the main generic classification.

Personally I find this work to be extremely exciting. It involved a lot of wonderful detective work and a whole lot of attention to detail. I think the end result paints a far better picture for our understanding of how these plants evolved. I am especially floored that some of the earlier morphological notes turned out to be quite useful in this modern understanding. Even more exciting is the fact that now we know that many of what we thought were “unique” characters amoung the various species actually evolved multiple times throughout the history of this group. This is why I will never get upset by taxonomic changes. They may be working documents but each step we take helps us understand evolution that much more.

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

Further Reading: [1]

The Wild World of Rattan Palms

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There are a lot of big organisms out there. A small handful of these are truly massive. When someone mentions big plants, minds will quickly drift to giant sequoias or coastal redwoods. These species are indeed massive. The tallest tree on record is a coastal redwood measuring 369 feet tall. That's a whole lot of tree! What some may not realize is that there are other plants out there that can grow much "taller" than even the tallest redwood. For instance, there is a group of palms that hail from Africa, Asia, and Australasia that grow to staggering lengths albeit without the mass of a redwood.

You are probably quite familiar with some of these palm species, though not as living specimens. If you have ever owned or sat upon a piece of wicker furniture then you were sitting on pieces of a rattan palm. Rattan palms do not grow in typical palm tree fashion. Rattans are climbers, more like vines. All palms grow from a central part of the plant called the heart. They grow as bromeliads do, from meristem tissue in the center of a rosette of leaves. As a rattan grows, its stem lengthens and grabs hold of the surrounding vegetation using some seriously sharp, hooked spikes. For much of their early life they generally sprawl across the forest floor but the real goal of the rattan is to reach up into the canopy where they can access the best sunlight.

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Rattans are not a single taxonomic unit. Though they are all palms, at least 13 genera contain palms that exhibit this climbing habit. With over 600 species included in these groups, it goes without saying that there is a lot of variation on the theme. The largest rattan palms hail from the genus Calamus and all but one are native to Asia.

Many species of rattan have whip-like stems that would be easy to miss in a lush jungle. Be aware of your surroundings though, because these spikes are quite capable of ripping clothes and flesh to pieces. The rattans are like any other vine, sacrificing bulk for an easy ride into the light at the expense of whatever it climbs on. Indeed some get so big that they break their host tree. It is this searching, sprawling nature of the rattans that allow them to reach some impressive lengths. Some species of rattan have been reported with stems measuring over 500 feet!

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Getting back to what I mentioned earlier about wicker furniture, rattans are a very important resource for the people of the jungles in which they grow. They offer food, building materials, shelter materials, an artistic medium, and a source of economic gain. In many areas, rattans are being heavily exploited as a result. This is bad for both the ecology of the forest and the locals who depend upon these species.

The global rattan trade is estimated at around $4 billion dollars. Because of this, rattans are harvested quite heavily and many are cut at too young of an age to re-sprout meaning little to no recruitment occurs in these areas. There is a lot of work being done by a few organizations to try to set up sustainable rattan markets in the regions that have been hit the hardest. More information can be found at sites like the World Wildlife Fund.

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

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

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]

Meet Pokeweed's Tree-Like Cousin

There is more than one way to build a tree. For that reason and more, “tree” is not a taxonomic designation. Arborescence has evolved independently throughout the botanical world and many herbaceous plants have tree-like relatives. I was shocked to learn recently of a plant native to the Pampa region of South America commonly referred to as ombú. At first glance it looks like some sort of fig, with its smooth bark and sinuous, buttressed roots. Deeper investigation revealed that this was not a fig. Ombú is actually an arborescent cousin of pokeweed!

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The scientific name of ombú is Phytolacca dioica. As its specific epithet suggests, plants are dioecious meaning individuals are either male or female. Unlike its smaller, herbaceous cousins, ombú is an evergreen perennial. Because they can grow all year, these plants can reach bewildering proportions. Heights upwards of 60 ft. (18 m.) are not unheard of and the crowns of more robust specimens can easily attain diameters of 40 to 50 ft. (12 - 18 m.)! What makes such sizes all the more impressive is the way in which ombú is able to achieve such growth.

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Ombú is thought to have evolved from an herbaceous ancestor. Cut into the trunk of one of these trees and you will see that this phylogenetic history has left its mark. Ombú do not produce what we think of as wood. Instead, much of the support for branches and stems comes from turgor pressure. Also, the way in which these trees grow is not akin to what you would see from something like an oak or a maple. Whereas woody trees undergo secondary growth in which the cambium layer differentiates into xylem and phloem, thus thickening stems and roots, ombú exhibits a unique form of stem and root thickening called “anomalous secondary thickening.”

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Essentially what this means is that instead of a single layer of cambium forming xylem and phloem, ombú cambium exhibits unidirectional thickening of the cambium layer. There are a lot of nitty gritty details to this kind of growth and I must admit I don’t have a firm grasp on the mechanics of it all. The point of the matter is that anomalous secondary thickening does not produce wood as we know it and instead leads to rapid growth of weak and spongy tissues. This is why turgor pressure is so important to the structural integrity of these trees. It has been estimated that the trunk and branches of an ombú is 80% water.

 A cross section of an ombú limb showing harder xylem tissues separated by spongy parenchyma that has since disintegrated.

A cross section of an ombú limb showing harder xylem tissues separated by spongy parenchyma that has since disintegrated.

Like all members of this genus, ombú is plenty toxic. Despite this, ombú appears to have been embraced and is widely planted as a specimen tree in parks, along sidewalks, and in gardens in South America and elswhere. In fact, it is so widely planted in Africa that some consider it to be a growing invasive issue. All in all I was shocked to learn of this species. It caused me to rethink some of the assumptions I hold onto with some lineages I only know from temperate regions. It is amazing what natural selection has done to this genus and I am excited to explore more arborescent anomalies from largely herbaceous groups.

Photo Credits: [1] [2]

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

Rodents as Pollinators

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It may come as a surprise to some that small mammals such as rodents, shrews, and even marsupials have been coopted by plants for pollination services. Far from being occasional evolutionary oddities, many plants have coopted small furry critters for their reproductive needs. Some of the best illustrations of this phenomenon occur in the Protea family (Proteaceae).

  Protea nana

Protea nana

The various members of Proteaceae are probably best known for their bizarre floral displays. Indeed, they are most often encountered outside of their native habitats as outlandish additions to the cut flower industry. Superficial interest in beauty aside, the floral structure of the various protea genera and species is complex to say the least. They are well adapted to ensure cross pollination regardless of what the inflorescence attracts. Most notable is the fact that pollen doesn’t stay on the anthers. Instead, it is deposited on the tip of a highly modified style, which is referred to as the pollen presenter. Usually these structures remain closed until some visiting animal triggers their release.

 The inconspicuous floral display of  Protea cordata .

The inconspicuous floral display of Protea cordata.

Although birds and insects have taken up a majority of the pollination needs of this family, small mammals have entered into the equation on multiple occasions. Pollination by rodents, shrews, and marsupials is collectively referred to as therophilly and it appears to be quite a successful strategy at that. Therophilous pollination has arisen in more than one genera within Proteaceae.

  Leucospermum arenarium  in the field and one of its pollinators,  Gerbillurus paeba,  feeding on flowers. (A) Pollen presenter contact on  G. paeba . (B)  G. paeba  foraging on  L. arenarium   [Source]

Leucospermum arenarium in the field and one of its pollinators, Gerbillurus paeba, feeding on flowers. (A) Pollen presenter contact on G. paeba. (B) G. paeba foraging on L. arenarium [Source]

A therophilous pollination syndrome appears to come complete with a host of unique morphological characters aimed at keeping valuable pollen and nectar away from birds and insects. The inflorescences of therophilous species like Protea nana, P. cordata, and Leucospermum arenarium are usually tucked deep inside the branches of these bushes, often at or near ground level. They are also quite robust and sturdy in nature, which is thought to be an adaptation to avoid damage incurred by the teeth of hungry mammals. The inflorescences of therophilous proteas also tend to have brightly colored or even shiny flowers surrounded by inconspicuous brown involucral bracts.

 (C) Flowering  L. arenarium  with dense, mat-forming inflorescences. (D) Geoflorous inflorescences. (E) Pendulous inflorescences above ground level.  [Source]

(C) Flowering L. arenarium with dense, mat-forming inflorescences. (D) Geoflorous inflorescences. (E) Pendulous inflorescences above ground level. [Source]

Contrasted against bird pollinated proteas, these inflorescences can seem rather drab but that is because small mammals like rodents and shrews are drawn in by another sense - smell. Therophilous proteas tend to produce inflorescences with strong musty or yeasty odors. They also produce copious amounts of sugar-rich, syrupy nectar. Small mammals, after all, need to take in a lot of calories throughout their waking hours and it appears that proteas use that to their advantage.

 A small mouse pollinating  Protea nana

A small mouse pollinating Protea nana

As a rodent or shrew slinks in to take a drink, its head gets completely covered in pollen. In fact, they become so dusted with pollen that, before small, easy to hide trail cameras became affordable, pollen loads in the feces of rodents were the main clue that these plants were attracting something other than birds or insects. What’s more, the flowering period of many of these therophilous proteas occurs in the spring, right around the time when many small mammals go into breeding mode. Its during this time that small mammals need all of the energy they can get.

  Protea humiflora  being pollinated by two different species of rodent in South Africa.

Protea humiflora being pollinated by two different species of rodent in South Africa.

As odd as it may seem, rodent pollination appears to be a successful strategy for a considerable amount of protea species. The proteas aren’t alone either. Other plants appear to have evolved therophilous pollination as well. Nature, after all, works with what it has available and small mammals like rodents make up a considerable portion of regional faunas. With that in mind, it is no wonder that more plants have not converged on a similar strategy. Likely many have, we just need to take the time to sit down and observe.

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

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



Glacier Mice

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At first glance the surface of a glacier hardly seems hospitable. Cold, barren, and windswept, glaciers appear to be the antithesis of life. However, this assumption is completely completely false. Glaciers are home to an interesting ecosystem of their own, albeit on a smaller scale than we normally give attention to.

From pockets of water on the surface to literal lakes of water sealed away inside, glaciers are home to a myriad microbial life. On some glaciers the life even gets a bit larger. Glaciers are littered with debris. As dust and gravel accumulate on the surface of the ice, they begin to warm ever so slightly more than the frozen water around them. Because of this, they are readily colonized by mosses such as those in the genus Racomitrium.

The biggest challenge to moss colonizers is the fact that glaciers are constantly moving, which anymore today means shrinking. As such, these bits of debris, along with the mosses growing on them, do not sit still as they would in say a forest setting. Instead they roll around. As the moss grows it spreads across the surface of the rock while the ice rotates it around. This causes the moss to grow on top of itself, inevitably forming a ball-like structure affectionately referred to as a "glacier mouse."

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Because the moss stays ever so slightly warmer than its immediate surroundings, glacier mice soon find themselves teaming with life. Everything from worms to springtails and even a few water bears call glacier mice home. In a study recently published in Polar Biology, researcher Dr. Steve Coulson found "73 springtails, 200 tardigrades and 1,000 nematodes" thriving in just a single mouse!

The presence of such a diverse community living in these little moss balls brings up an important question - how do these animals find themselves in the glacier mice in the first place? After all, life just outside of the mouse is quite brutal. As it turns out, the answer to this can be chalked up to how the mice form in the first place. As they blow and roll around the the surface of the glacier, they will often bump into one another and even collect in nooks and crannies together. It is believed that as this happens, the organisms living within migrate from mouse to mouse. The picture being painted here is that far from being a sterile environment, glaciers are proving to be yet another habitat where life prospers.

Photo Credit: [1] [2]

Further Reading: [1]

Raphides: A Gnarly Form of Plant Defense

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Take a bite out of a dumbcane (Dieffenbachia spp.) or a pothos (Philodendron spp.) and it won’t be long before your mouth and throat start to burn (please don’t actually do that). Eat enough of it and your symptoms may also include intense numbing, oral irritation, excessive drooling, localized swelling, and possibly even kidney and liver failure (again, please don’t). What you are experiencing is a brutal form of plant defense caused by tiny crystals called raphides.

Raphides are tiny, needle-shaped crystals made up of calcium oxalate. A lot of plants accumulate calcium oxalate. Research has shown that in doing so, plants are able to sequester excess calcium in their cells. Many plant lineages then use that calcium oxalate to make raphides. Not all raphides come in the form of needle-like crystals. Often they are ‘H’ shaped or even twinned. Others are blunt, kind of like tiny crystalline cigars.

 Cigar-shaped raphides found in the tissues of the polka dot plant ( Hypoestes phyllostachya ).

Cigar-shaped raphides found in the tissues of the polka dot plant (Hypoestes phyllostachya).

How raphides form within the plant is rather fascinating. As far as we can discern, raphide crystals form in vacuoles of specialized cells called “idioblasts.” It is thought that an exquisitely controlled scaffolding or matrix shapes the biomineralization process. To the best of my knowledge, no one has been able to reproduce this process in a laboratory setting. For now, plants are the undeniable masters of raphide manufacturing.

Within the cells, raphides are often associated with acrid and toxic proteins. Together, they comprise one hell of a defense against herbivory. Raphides are only the first part of the defensive equation. When plant tissues containing raphides are damaged, usually by chewing, the raphides shoot out of the idioblasts and into the oral cavity of the herbivore. This is where their needle shape comes in.

 Needle-like raphides extracted from the leaves of an  Epipremnum  species.

Needle-like raphides extracted from the leaves of an Epipremnum species.

Raphides wreak havoc on sensitive tissues. They literally act like tiny needles, cutting into and tearing the lining of the mouth, esophagus, and gut. This is only half of the story though. As mentioned, raphides are often packed in with acrid and toxic proteins. The laceration caused by the raphides allows these compounds to enter into the wounds. This is where things can get especially nasty. If the proteins are toxic enough, the herbivore now has far more to worry about than simply the burning sensation.

Raphides are not produced in equal amounts in all tissues. Stems tend to have more than leaves, but raphide content in leaves has also shown to be a function of leaf size. Raphides also differ from species to species. Not all plants that produce raphides produce them in the same shape and quantity. Still, more than 200 plant families contain species that have evolved this form of defense and many of our most prized houseplants fall into this category. However, this should not scare you away from these plants. Provided you or your loved ones don’t go nibbling on the leaves or stems, all will be fine. If anything, this remarkable form of plant defense should earn these plants even more respect than they already get.

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

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

The Strangest Maple

I love being humbled by plant ID. Confusion usually means I am going to end up learning something new. This happened quite recently during a trip through The Morton Arboretum. Admittedly trees are not my forte but I had spotted something that seemed off and needed further inspection. I was greeted by a small tree with leaves that screamed "birch family" (Betulaceae) yet they were opposite. Members of the birch family should have alternately arranged leaves. What the heck was I looking at?

It didn't take long for me to find the ID tag. As a plant obsessed person, the information on the tag gave me quite the thrill. What I was looking at was possible the strangest maple on the planet. This, my friends, was my first introduction to Acer carpinifolium a.k.a the hornbeam maple.

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The hornbeam maple is endemic to Japan where it can be found growing in mountainous woodlands and alongside streams. Maxing out around 30 feet (9 m) in height, the hornbeam maple is by no means a large tree. It would appear that it has a similar place in its native ecology as other smaller understory maples do here in North America. It blooms in spring and its fruits are the typical samaras one comes to expect from the genus.

It probably goes without saying that the thing I find most fascinating about the hornbeam maple are its leaves. As both its common and scientific names tell you, they more closely resemble that of a hornbeam (Carpinus spp.) than a maple. Unlike the lobed, palmately veined leaves of its cousins, the hornbeam maple produces simple, unlobed leaves with pinnate venation and serrated margins. They challenge everything I have come to expect out of a maple. Indeed, the hornbeam maple is one of only a handful of species in the genus Acer that break the mold for leaf shape. However, compared to the rest, I think its safe to say that the hornbeam maple is the most aberrant of them all. 

Not a lot of phylogenetic work has been done on the relationship between the hornbeam maple and the rest of its Acer cousins. At least one study suggests that it is most closely related to the mountain maple of neartheastern North America. More scrutiny will be needed before anyone can make this claim with certainty. Still, from an anecdotal standpoint, it seems like a reasonable leap to make considering just how shallow the lobes are on mountain maple leaves.

Regardless of who it is related to, running into this tree was truly a thrilling experience. I love it when species challenge long held expectations of large groups of plants. Hornbeam maple has gone from a place of complete mystery to me to being one of my favorite maples of all time. I hope you too will get a chance to meet this species if you haven't already!

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

Further Reading: [1] [2]

 

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]