The Ceropegias Welcome a New Member

Photos by David Styles

The genus Ceropegia is home to some of my favorite plants. Not only are they distant cousins of the milkweeds (Asclepias spp.), they sport some of the most interesting floral morphologies whose beauty is only exceeded by their fascinating pollination syndromes. Recently, Ceropegia expert and friend of the podcast Dr. Annemarie Heiduk brought to my attention the recent description of a species named in her honor.

Ceropegia heidukiae hails from KwaZulu-Natal, South Africa, and, at current, is believed to be endemic to a habitat type called the Northern Zululand Mistbelt Grassland. Morphologically, it has been described as an erect perennial herb. Unlike many of its cousins, C. heidukiae does not vine. Instead, it grows a slender stem with opposite, ovate leaves that just barely reaches above the surrounding grasses. By far the most striking feature of this plant are its flowers.

Photos by David Styles.

Ceropegia heidukiae produces elaborate trap flowers at the tips of its slender stems during the month of December (summer in the Southern Hemisphere). Each flower is comprised a greenish-gold, striped tube made of fused petals and topped with a purple, star-like structure with fine hairs. These flowers were the key indication that this species was previously unknown to science. Additionally, a sweet, acidic scent was detected during the relatively short blooming period.

Their beauty aside, the anatomy and scent of these flowers hints at what may very well be a complex and specific pollination syndrome. Indeed, scientists like Dr. Heiduk are revealing amazing chemical trickery within the flowers of this incredible genus, including one species that mimics the smell of dying bees. Who knows what kinds of relationships this new species has evolved in its unique habitat. Only plenty of observation and experimentation will tell and I anxiously await future studies.

A view of the Northern Zululand Mistbelt Grassland where Ceropegia heidukiae was found.

Sadly, C. heidukiae lives in one of South Africa’s most threatened habitat types. South Africa’s Biodiversity Act currently classifies the Northern Zululand Mistbelt Grassland as endangered due to factors like timber plantations and unsustainable grazing. Hopefully with the recognition of unique species like C. heidukiae, more attention can be given to sustainable use of the Northern Zululand Mistbelt Grassland such that both the people and the species that rely on it can continue to do so for generations to come.

Photo Credits: David Styles

Further Reading: [1] [2]

What an orchid that smells like rotting meat can tell us about carrion flies

Satyrium pumilum Photo by Bernd Haynold licensed by CC BY-SA 3.0

Orchids are really good at tricking pollinators. Take, for instance, this strange looking orchid from South Africa. Satyrium pumilum is probably obscure to most of us but it is doing fascinating things to ensure its own reproductive success. This orchid both smells and kind of looks like rotting meat, which is how it attracts its pollinators.

It is a bit strange to think of orchids living in arid climates like those found in South Africa but this family is defined by exceptions. That is not to say that Satyrium pumilum is a desert plant. To find this orchid, you must look in special microclimates where water sticks around long enough to support its growth. Populations of S. pumilum are most often found clustered near small streams or hidden under bushes throughout the western half of the greater Cape Floristic Region.

Satyrium pumilum blooms from the beginning of September until late October. As is typical in the orchid family, S. pumilum produces rather intricate flowers. Whereas the sepals are decked out in various shades of green, the interior of the flower is blood red in color. Also, unlike many of its cousins, S. pumilum doesn’t throw its flowers up on a tall stalk for all the world to see. Instead, its flowers open up at ground level and give off an unpleasant smell of rotting meat.

This is where pollinators enter into the picture. It has been found that carrion flies are the preferred pollinator for S. pumilum. By producing flowers at ground level that both look and smell like rotting meat, the plants are primed to attract these flies. The plants are tapping into the flies’ reproductive habits, a biological imperative so strong that they simply do not evolve a means of discriminating a rotting corpse from a flower that smells like one. This is the trick. Flies land on the flower thinking they have found a meal and a place to lay their eggs. They go through the motions as expected and pick up or deposit pollen in the process. Unfortunately for the flies, their offspring are doomed. There is not food to be found in these flowers.

What is most remarkable about the reproductive ecology of S. pumilum is that not just any type of fly will do. It appears that only a specific subset of flies actually visit the flowers and act as effective pollinators. Amazingly, this provides insights into some long-running hypotheses regarding carrion fly ecology.

(A) The habitat of S. pumilum (B) Satyrium pumilum in situ (scale bar = 1 cm). (C–E) Pollination sequence of a S. pumilum flower by a sarcophagid fly in an arena (scale bar for all three photos = 0·5 cm); (C) the fly carrying five pollinaria from other S. pumilum flowers enters an unpollinated flower (D) as the fly moves deeper into the flower towards the right-hand spur, it presses an attached pollinium against the stigma, and its thorax against the right-hand viscidium; (E) as it leaves the flower, the fly has deposited two massulae on the stigma (1), and removed a pollinarium (2) – it now carries six pollinaria. [SOURCE]

Apparently there has been a lot of debate in the fly community over why we see so many different species of carrion flies. Rotting meat is rotting meat, right? Probably not, actually. Fly ecologists have comes up with a few hypotheses involving niche segregation among carrion flies to explain their diversity on the landscape. Some believe that flies separate themselves out in time, with different species hatching out and breeding at different times of the year. Others have suggested that carrion flies separate themselves by specializing on carrion at different stages of decay. Still others have suggested that some flies specialize on large pieces of carrion whereas others prefer smaller pieces.

By studying the types of flies visiting the flowers of S. pumilum researchers did find evidence of niche segregation based on carrion size. It turns out that S. pumilum is exclusively pollinated by a group of flies known as sarcophagid carrion flies. These flies were regularly observed with orchid pollen sacs stuck to their backs and plants seemed to only set seed after they had been visited by members of this group. So, what is it about these flowers that makes them so specific to this group of flies?

The answer lies both in their size as well as the amount of scent they produce. It is likely that the quantity of scent compounds produced by S. pumilum most closely mimics that of smaller rotting corpses. The types of flies that visited these blooms were mostly females of species that lay relatively few eggs compared to other carrion flies. It could very well be that the smaller brood size of these flies allows them to effectively utilize smaller bits of carrion than other, more fecund species of fly. To date, this is some of the best evidence in support of the idea that flies avoid competition among different species by segregating out their feeding and reproductive niches.

Rotting meat smells are not uncommon in the plant world. Even within the home range of S. pumilum, there are other plants produce flowers that smell like carrion as well. It would be extremely interesting to look at what kinds of flies visit other carrion flowers and in what numbers. Like I mentioned earlier, reproductive is such a major part of any organisms life that it may simply be too costly for carrion flies to evolve a means of discriminating real and fake breeding sites. It is amazing to think of what we gain from trying to understand the reproductive biology of a small, obscure orchid growing tucked away in arid regions of South Africa.

Photo Credits: [1] [2]

Further Reading: [1]

A New Case of Lizard Pollination from South Africa

With its compact growth habit and small, inconspicuous flowers tucked under its leaves, it seems like Guthriea capensis doesn’t want to be noticed. Indeed, it has earned itself the common name of '“hidden flower.” That’s not to say this plant is unsuccessful. In fact, it seems to do just fine tucked in among high-elevation rock crevices of its home range along the Drakensberg escarpment of South Africa. Despite its cryptic nature, something must be pollinating these plants and recent research has finally figured that out. It appears that the hidden flower has a friend in some local reptiles.

Lizard pollination is not unheard of ([1] & [2]), however, it is by no means a common pollination syndrome. This could have something to do with the fact that we haven’t been looking. Pollination studies are notoriously tricky. Just because something visits a flower does not mean its an effective pollinator. To investigate this properly, one needs ample hours of close observation and some manipulative experiments to get to the bottom of it. Before we get to that, however, its worth getting to know this strange plant in a little more detail.

The hidden flower is a member of an obscure family called Achariaceae. Though a few members have managed to catch our attention economically, most genera are poorly studied. The hidden flower itself appears to be adapted to high elevation environments, hence its compact growth form. By hugging the substrate, this little herb is able to avoid the punishing winds that characterize montane habitats. Plants are dioecious meaning individuals produce either male or female flowers, never both. The most interesting aspect of its flowers, however, are how inconspicuous they are.

The hidden flower (Guthriea capensis) in situ.

Flowers are produced at the base of the plant, out of site from most organisms. They are small and mostly green in color except for the presence of a few bright orange glands near the base of the style, deep within the floral tube. What they lack in visibility, they make up for in nectar and smell. Each flower produced copious amounts of sticky, sugar-rich nectar. They are also scented. Taken together, these traits usually signal a pollination syndrome with tiny rodents but this assumption appears to be wrong.

Based on hours of video footage and a handful of clever experiments, a team of researchers from the University of KwaZulu-Natal and the University of the Free State have been able to demonstrate that lizards, not mammals, birds, or insects are the main pollinators of this cryptic plant. Two species of lizard native to this region, Pseudocordylus melanotus and Tropidosaura gularis, were the main floral visitors over the duration of the study period.

Pseudocordylus melanotus

Tropidosaura gularis photo © 2009 Serban Proches licensed under CC BY-SA 2.5

Visiting lizards would spend time lapping up nectar from several flowers before moving off and in doing so, picked up lots of pollen in the process. Being covered in scales means that pollen can have a difficult time sticking to the face of a reptile but the researchers believe that this is where the sticky pollen comes into play. It is clear that the pollen adheres to the lizards’ face thanks to the fact that they are usually covered in sticky nectar. By examining repeated feeding attempts on different flowers, they also observed that not only do the lizards pick up plenty of pollen, they deposit it in just the right spot on the stigma for pollination to be successful. Insect visitors, on the other hand, were not as effective at proper pollen transfer.

Conspicuously absent from the visitation roster were rodents. The reason for this could lie in some of the compounds produced within the nectar. The team found high levels of a chemical called safranal, which is responsible for the smell of the flowers. Safranal is also bitter to the taste and it could very well serve as a deterrent to rodents and shrews. More work will be needed to confirm this hypothesis. Whatever the case, safranal does not seem to deter lizards and may even be the initial cue that lures them to the plant in the first place. Tongue flicking was observed in visiting lizards, which is often associated with finding food in other reptiles.

Male flower (a) and female flower (b). Note the presence of the orange glands at the base.

Another interesting observation is that the color of the floral tube and the orange glands within appear to match the colors of one of the lizard pollinators (Pseudocordylus subviridis ). Is it possible that this is further entices the lizards to visit the flowers? Other reptile pollination systems have demonstrated that lizards appear to respond well to color patterns for which they already have some sort of sensory bias. Is it possible that these flowers evolved in response to such a bias? Again, more work will be needed to say for sure.

By excluding vertebrates from visiting the flowers, the team was able to show that indeed lizards appear to be the main pollinators of these plants. Without pollen transfer, seed set is reduced by 95% wheres the additional exclusion of insects only reduced reproductive success by a further 4%. Taken together, it is clear that lizards are the main pollinators of the enigmatic hidden flower. This discovery expands on our limited knowledge of lizard pollination syndromes and rises many interesting questions about how such relationships evolve.

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

Further Reading: [1] [2]

Meet the Fire Lily

Photo by Callan Cohen licensed under CC BY-SA 3.0

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

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

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

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

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

Photo by Callan Cohen licensed under CC BY-SA 3.0

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

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

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

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

Everlasting or Seven Years Little

Photo by Andrew massyn licensed under CC BY-SA 3.0

Common names are a funny thing. Depending on the region, the use, and the culture, one plant can take on many names. In other situations, many different plants can take on a single name. Though it isn't always obvious to those unfamiliar with them, the use of scientific names alleviates these issues by standardizing the naming of things so that anyone, regardless of where they are, knows what they are referring to. That being said, sometimes common names can be entertaining.

Take for instance, plants in the genus Syncarpha. These stunning members of the family Asteraceae are endemic to the fynbos region of the Eastern and Western Cape of South Africa. In appearance they are impossible to miss. In growth habit they have been described as "woody shrublets," forming dense clusters of woody stems covered in a coat of woolly hairs. Sitting atop their meter-high stems are the flower heads.

Each flower head consists of rings of colorful paper-like bracts surrounding a dense cluster of disk flowers. The flowering period of the various species can last for weeks and spans from October, well into January. Numerous beetles can be observed visiting the flowers and often times mating as they feed on pollen. Some of the beetles can be hard to spot as they camouflage quite well atop the central disk. Some authors feel that such beetles are the main pollinators for many species within this genus.

Photo by JonRichfield licensed under CC BY-SA 3.0

Their mesmerizing floral displays are where their English common name of "everlasting" comes from. Due to the fact that they maintain their shape and color for a long time after being cut and dried, various Syncarpha species have been used quite a bit in the cut flower industry. A name that suggests everlasting longevity stands in stark contrast to their other common name. 

These plants are referred to as "sewejaartjie" in Afrikaans, which roughly translates to "seven years little." Why would these plants be referred to as everlasting by some and relatively ephemeral by others? It turns out, sewejaartjie is a name that has more to do with their ecology than it does their use in the floral industry.

As a whole, the 29 described species of Syncarpha are considered fire ephemerals. The fynbos is known for its fire regime and the plants that call this region home have evolved in response to this fact. Syncarpha are no exception. They flower regularly and produce copious amounts of seed but rarely live for more than 7 years after germination. Also, they do not compete well with any vegetation that is capable of shading them out.

Photo by Andrew massyn licensed under CC BY-SA 3.0

Instead, Syncarpha invest heavily in seed banking. Seeds can lie dormant in the soil for many years until fires clear the landscape of competing vegetation and release valuable nutrients into the soil. Only then will the seeds germinate. As such, the mature plants don't bother trying to survive intense ground fires. They burn up along with their neighbors, leaving plenty of seed to usher in the next generation.

Research has shown that its not the heat so much as the smoke that breaks seed dormancy in these plants. In fact, numerous experiments using liquid smoke have demonstrated that the seeds are likely triggered by some bio-active chemical within the smoke itself.

So, there you have it. Roughly 29 plants with two common names, each referring back to an interesting aspect of the biology of these plants. Despite their familiarity and relative ease of committing to memory, the common names of various species only get us so far. That's not to say we should abolish the use of common names altogether. Learning about any plant should be an all encompassing endeavor provided you know which plant you are referring to.

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

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

Flowers That Mimic Flies

Photo by Claire Woods licensed under CC BY-NC-ND 2.0

Pollination is one of the major advantages flowering plants have over the rest of the botanical tree. With a few exceptions, flowers have cornered this market. It no doubt has played a significant role in their rise to dominance on the landscape. The importance of flowers is highlighted by the fact that they are costly structures. Because they don't photosynthesize, all plants take a hit on energy reserves when it comes time to flower. Sepals, petals, pollen, nectar, all of these take a lot of energy to produce which is why some plants cheat the system a bit. 

Sexual mimicry is one form of ruse that has evolved repeatedly. The flowers of such tricksters mimic receptive female insects waiting for a mate. The evolution of such a strategy taps into something far deeper in the mind of animals than food. It taps into the need to reproduce and that is one need animals don't readily forego. As such, sexually deceptive flowers usually do away with the production of costly substances such as nectar. They simply don't need it to attract their pollinators. 

Photo by Dr. Alexey Yakovlev licensed under CC BY-SA 2.0

By and large, the world of sexual mimicry in plants is one played out mainly by orchids. However, there exists an interesting exception to this rule. A daisy that goes by the scientific name Gorteria diffusa has evolved a sexually deceptive floral strategy of its own. Native to South Africa, this daisy is at home in its Mediterranean climate. It produces stunning orange flowers that very much look like those of a daisy. On certain petals of the ray florets, one will notice peculiar black spots. From region to region there seems to be a lot of variation in the expression of these spots but all are textured thanks to a complex of different cell types. 

The spots may seem like random patterns until the flowers are visited by their pollinator - a tiny bee-fly known scientifically as Megapalpus nitidus. With flies present, one can sort of see a resemblance. This would not be a mistake on the observers part. Indeed, when researchers removed or altered these spots, bee-fly visitation significantly decreased. Although this didn't seem to influence seed production, it nonetheless suggests that those spots are there for the flies. 

When researchers painted spots on to non-textured petals, the bee-flies ignored those as well. It appears that the texture of the spots makes a big difference to visiting flies. What's more, although female flies visited the flowers, a majority of the visits were by males. It appears that the presence of these spots is keying in on the mate-seeking and aggregation behavior of their bee-fly pollinators. Further investigation has revealed that the spots even reflect the same kind of UV light as the flies themselves, making the ruse all the more accurate. This case of sexual mimicry is unique among this family. No other member of the family Asteraceae exhibits such reproductive traits (that we know of). Although it doesn't seem like seed production is pollinator limited, it certainly increases the chance of cross pollination with unrelated individuals.

Photo Credits: [1] [2]

Further Reading: [1] [2]

The Shrubs of Iridaceae

Nivenia corymbosa

Did you know there are shrubs in the iris family? I didn't either until quite recently. I had the distinct honor of getting to tour the collections of Martin Grantham, a resident of the Bay Area and quite possibly the most talented horticulturist I have ever met. Martin has had quite a bit of luck with these plants and because of this, I was able to meet a handful of them growing quite happily in large containers. There are some things in life that your brain just simply isn't prepared to take in. The shrubby iriads are one of them.

The true shrubby species all hail from a subfamily of Iridaceae coined Nivenioideae. This is not a single grouping of all shrubby genera. It contains other genera that look a lot more like what we would consider an iris. Nivenioideae as a whole is considered to be pretty derived for the iris family, with the shrubby species serving as an excellent example of how bizarrely unique the subfamily really is. In total, there are three genera of shrubby iriads - Klattia, Nivenia, and Witsenia, all of which are native to South Africa. Klattia and Nivenia contain a small handful of species whereas Witsenia has only a single representative.

Once you get past the initial shock and awe of what you have just laid eyes on, their membership in the iris family becomes a bit more apparent. Though there is great variation in size, the species I encountered all looked roughly like long, slender sticks with multiple iris-like fans of leaves jutting out. Like most members of the family, the flowers of this group are spectacular. In the wild they are visited by long tongue bees and flies.

Overall this group is poorly understood. Some molecular phylogenetic work has been performed but it is by no means concrete. More attention may result in either the addition or subtraction of species. The most thorough treatment on the shrubby iriads comes from a monograph written by Dr. Peter Goldblatt as well as a handful of horticultural articles written by those lucky enough to have had some success in growing these plants (see Martin's essay on his experiences - http://bit.ly/2pStMZ4).

Like most of South Africa's unique flora, these plants are at threatened by habitat destruction, invasive species, and climate change. Luckily many of these species have caught the attention of folks like Martin who have put in the time and dedication into understanding their germination and growth requirements.

Seeing these plants in person was breathtaking. Not only was I completely flabbergasted at their appearance, the fact that plants like this exist is a testament to the wild diversity of life this planet supports. I never tire of meeting new plant species and this is one encounter I won't soon forget. Just when you think you are starting to understand plant diversity, plants like these show up to remind you that you have just barely scratched the surface.

Further Reading: [1] [2]

Dung Seeds

Midgley, J., White, J., Johnson, S. et al. Faecal mimicry by seeds ensures dispersal by dung beetles. Nature Plants 1, 15141 (2015). https://doi.org/10.1038/nplants.2015.141

Photo by Nicola van Berkel (Nicky vB)

There are a lot of interesting seed dispersal mechanisms out there. It makes sense too because effective seed dispersal is one of the most important factors in a plant's life cycle. It is no wonder then that plants have evolved myriad ways to achieve this. Everything from wind to birds to mammals and even ants have been recruited for this task. Now, thanks to a group of researchers in South Africa, we can add dung beetles to this list.

That's right, dung beetles. These little insects are famous the world over for their dung rolling lifestyle. These industrious beetles are quite numerous and play an important role in the decomposition of feces on the landscape. Without them, the world would be a gross place. They don't do this for us, of course. Instead, dung beetles both consume the dung and lay their eggs on the balls. They are often seen rolling these balls across the landscape until they find the perfect spot to bury it where other dung-feeding animals won't find it. It is this habit that a plant known scientifically as Ceratocaryum argenteum has honed in on.

The seeds of this grass relative are hard and pungent. Researchers questioned why the plant would produce such smelly seeds. After all, the scent would hypothetically make it easier for seed predators to find them. However, the typical seed predators of this region such as birds and rodents show no real interest in them. What's more, when offered seeds directly, rodents only ate seeds in which the tough, smelly coat had been removed. Using cameras, the researchers studied the behavior of these animals time and time again. It was only after viewing hours of video that they made their discovery.

Although they weren't big enough to trip the cameras themselves, incidental footage caught dung beetles checking out the seeds and rolling them away. As it turns out, the scent and appearance (which closely mimics that of antelope dung) tricks the dung beetles into thinking they found the perfect meal. As such, the dung beetles do exactly what the plant needs - they bury the seeds. This is a dead end for the dung beetle. Only after a seed has been buried do they realize that it is both inedible and an unsuitable nursery. Nonetheless, the drive for reproduction is so strong that the plant is able to successfully trick the dung beetles into dispersing their seeds.

Photo Credit: Nicky vB (bit.ly/1WVgs0G) and Nature Plants

Further Reading:
http://www.nature.com/articles/nplants2015141

The Curly-Whirly Plants of South Africa

Gethyllis villosa. Photo by Capetown Botanist: www.capetownbotanist.com

In a region of South Africa traditionally referred to as Namaqualand there exists a guild of plants that exhibit a strange pattern in their growth habits. These plants hail from at least eight different monocot families as well as the family Oxalidaceae. They are all geophytes, meaning they live out the driest months of the year as dormant, bulb-like structure underground. However, this is not the only feature that unites them.

A walk through this region during the growing season would reveal that members of this guild all produce leaves that at least one author has described as "curly-whirly." To the casual observer it would seem that they had left the natural expanse of the desert flora and entered into the garden of someone with very particular tastes.

What these plants have managed to do is to converge on a morphological strategy that allows them to take full advantage of their unique geographical location. The region along the coastal belt of Namibia is famous for being a "fog desert." Despite receiving very little rain, humid air blowing in from the southwestern Atlantic runs into colder air blowing down from the north and condenses, carrying fog inland. This produces copious amounts of dew.

Normally dew would be unavailable to most plants. It simply doesn't penetrate the soil enough to be useful for roots. This is where those curly-whirly leaves come in. Researchers have discovered that this leaf anatomy is specifically adapted for capturing and concentrating fog and dew. This has the effect of significantly improving their water budget in this otherwise arid region. What's more, the advantages are additive.

The most obvious advantage has to do with surface area. Curled leaves increase the amount of edge a leaf has. This provides ample area for capturing fog and dew. Also, by curling up, the leaves are able to reduce the overall size of the leaf exposed to the air, which reduces the amount of transpiration stress these plants encounter in their hot desert environment. Another advantage is direct absorption. Although no specific organs exist for absorbing water, the leaves of most of these species are nonetheless capable of absorbing considerable amounts.

Dipcadi crispum By roncorylus

Finally, each curled leaf acts like a mini gutter, channeling water to the base of the plant. Many of these plants have surprisingly shallow root zones. The lack of a deep taproot may seem odd until one considers the fact that dew dripping down from the leaves above doesn't penetrate too deeply into the soil. These roots are sometimes referred to as "dew roots."

I don't know about you but this may be one of the coolest plant guilds I have ever heard about. This is such a wonderfully clear example of just how strong of a selective pressure the combination of geography and climate can be. What's more, this is not the only region in the world where drought-tolerant plants have converged on this curly strategy. Similar guilds exist in other arid regions of Africa, as well as in Turkey, Australia, and Asia.

Albuca spiralis. Photo by Wolf G. licensed under CC BY-NC-ND 2.0

Photo Credits: Cape Town Botanist (http://bit.ly/1PzPkP7), www.ispotnature.org, roncorylus (http://bit.ly/1PzPoi6), and Wolf G. (http://bit.ly/1n4Mo6b)

Further Reading: [1]

Straight out of Seussville

Photo by Derek Keats licensed under CC BY-NC-ND 2.0

At first glance this photo seems fake. However, I assure you this is indeed a real plant. Meet Pachypodium namaquanum, the elephant's trunk. This bizarre member of the family Apocynaceae can be found growing in the dry rocky deserts of Richtersveld and southern Namibia in South Africa. Although it may seem better suited for life in a Dr. Seuss book, I assure you that all aspects of this plants strange appearance enable it to live in some of the harshest climates possible for a plant.

During the spring and summer months (November - March) temperatures in these regions can reach upwards of 50°C (122°F). It doesn't rain much either. What little water this plant does receive comes in the form of fog rolling in from the coast. Oddly enough, the elephant's trunk seems to prefer growing on the most exposed slopes possible, favoring spots where sun and wind are at their worst.

Photo by Rafael Medina licensed under CC BY-NC-ND 2.0

As such, everything about P. namaquanum seems to be focused on water conservation. The most obvious feature is that swollen trunk, which serves as a water storage organ. It is no surprise then that this valuable storage organ is covered in spines. These "trees" remain leafless during this time as well. This keeps valuable water reserves from evaporating in the summer heat.

There is at least one aspect of this plants physiology that seems to stand in the face of the harsh desert environment in which it lives. Anyone who has observed these plants in the wild may have noticed that their tips all seem to be pointing northwards. What's more, this inclination usually ranges between a 50° and 60° angle. This is strange because most desert plants usually prefer to minimized their exposure to solar radiation rather than face it head on.

The reason for this becomes more apparent with the onset of fall. Come April, the climate of this region becomes a bit more mild. Also, the sun begins to dip below the horizon for longer periods of time. It is around this time that the plant will produce leaves. A single whorl of velvety leaves emerges from the very tip of the stem. This is also the time in which it reproduces. Attractive yellow and red flowers spray out from between the leaves.

Because the success of the elephant's trunk is reliant on this relatively short growth period, the plant aims to maximize its gains. This is where the northern inclination comes into play. Such an orientation serves to maximize the amount of sunlight the leaves and the flowers receive. In this way, the leaves and flowers absorb twice as much sunlight than if they were vertically oriented. It is thought that the sunlight warms the flowers as well as brightens their display, making them impressive targets for local pollinators.

Like most members of this family, seeds are produced in pods and are borne on silky hairs. The slightest breeze can carry them a great distance. Though germination comes relatively easy to this species, it is nonetheless declining in the wild. Mining and livestock have taken up a lot of their available habitat. Poaching is second to these threats as its strange appearance makes it highly sought after by greedy gardeners.

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

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

Fly Guild

Photo by Rictor Norton & David Allen licensed under CC BY 2.0

Lapeirousia oreogena grows in the western portion of South Africa. Though it may be difficult to tell by looking at it, this little plant is a member of the iris family. Decked out in its striking shade of purple, the white spots on its petals really stand out. Shaped like arrowheads, it would almost seem as if the plant was trying to advertise the perfect place to grab a sip of nectar. Indeed, that is exactly what they are doing. Those white arrows serve as guides for a rather peculiar pollinator.

Photo by Peter Goldblatt

Prosoeca peringueyi is a pretty incredible little fly. For starters, its proboscis is 2 inches in length! It looks rather awkward buzzing around a patch of these beautiful irises. Seeing it in action may change your mind though. It is truly an ariel acrobat as it maneuvers itself above a flower and expertly dips its long proboscis down the slightly longer nectar tube of the flowers. How is the fly so adept at hitting its target every time? The answer lies in those white arrows. 

A team of researchers performed a series of experiments in which they covered up the white arrows of some flowers. As it turned out, the flies still approached the flowers but, with no arrows visible, successful insertion of the proboscis was drastically reduced. The arrows serve as a guide for the flies to tell them exactly where they are going to be able to get an energy rich drink.

How exactly does a system like this evolve? A clue to the answer lies in the fertility of these irises. Plants that aren't visited sequentially by these long-tongued flies do not set seed. As it turns out, the plants need the flies to be just out of reach of the bottom of the nectar tube for efficient transfer of pollen. Over time, an evolutionary arms race developed in which the proboscis of the flies gradually got longer to get as much nectar as possible and thus selecting for irises with longer and longer flower tubes.

This system seems to have had an effect on other plant species growing in this region too. Lapeirousia oreogena is only in bloom for a small window of time during the growing season. What happens to these long tongued flies when this window is closed? Interestingly, other plant species form what is referred to as a guild with L. oreogena. They all cater to these flies with varying lengths of elongated nectar tubes. In total, at least 28 plant species in this region have seemed to have converged on this pollination syndrome. To see more of these plants, click here.

Photo Credits: Rictor Norton, David Allen (http://bit.ly/1jzvHeK) and Peter Goldblatt

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