An Endangered Iris With An Intriguing Pollination Syndrome

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The Golan iris (Iris hermona) is a member of the Oncocyclus section, an elite group of 32 Iris species native to the Fertile Crescent region of southwestern Asia. They are some of the showiest irises on the planet. Sadly, like many others in this section, the Golan iris is in real danger of going extinct.

The Golan iris has a rather limited distribution. Despite being named in honor of Mt. Hermon, it is restricted to the Golan Heights region of northern Israel and southwestern Syria. Part of the confusion stems from the fact that the Golan iris has suffered from a bit of taxonomic uncertainty ever since it was discovered. It is similar in appearance to both I. westii and I. bismarckiana with which it is frequently confused. In fact, some authors still consider I. hermona to be a variety of I. bismarckiana. This has led to some serious issues when trying to assess population numbers. Despite the confusion, there are some important anatomical differences between these plants, including the morphology of their rhizomes and the development of their leaves. Regardless, if these plants are in fact different species, it means their respective numbers in the wild decrease dramatically. 

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Like other members of the Oncocyclus group, the Golan iris exhibits an intriguing pollination syndrome with a group of bees in the genus Eucera. Their large, showy flowers may look like a boon for pollinators, however, close observation tells a different story. The Golan iris and its relatives receive surprisingly little attention from most of the potential pollinators in this region.

One reason for their lack of popularity has to do with the rewards (or lack thereof) they offer potential visitors. These irises produce no nectar and very little pollen. Because of this and their showy appearance, most pollinators quickly learn that these plants are not worth the effort. Instead, the only insects that ever pay these large blossoms any attention are male Eucerine bees. These bees aren't looking for food or fragrance, however. Instead, they are looking for a place to rest. 

A Eucerine bee visiting a nectar source. 

A Eucerine bee visiting a nectar source. 

The Oncocyclus irises cannot self pollinate, which makes studying potential pollinators a bit easier. During a 5 year period, researchers noted that male Eucerine bees were the only insects that regularly visited the flowers and only after their visits did the plants set seed. The bees would arrive at the flowers around dusk and poke around until they found one to their liking. At that point they would crawl down into the floral tube and would not leave again until morning. The anatomy of the flower is such that the bees inevitably contact stamen and stigma in the process. Their resting behavior is repeated night after night until the end of the flowering season and in this way pollination is achieved. Researchers now believe that the Golan iris and its relatives are pollinated solely by these sleeping male bees.

Sadly, the status of the Golan iris is rather bleak. As recent as the year 2000, there were an estimated 2,000 Golan irises in the wild. Today that number has been reduced to a meager 350 individuals. Though there is no single smoking gun to explain this precipitous decline, climate change, cattle grazing, poaching, and military activity have exacted a serious toll on this species. Plants are especially vulnerable during drought years. Individuals stressed by the lack of water succumb to increased pressure from insects and other pests. Vineyards have seen an uptick in Golan in recent years as well, gobbling up viable habitat in the process.

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It is extremely tragic to note that some of the largest remaining populations of Golan irises can be found growing in active mine fields. It would seem that one of the only safe places for these endangered plants to grow are places that are extremely lethal to humans. It would seem that our propensity for violent tribalism has unwittingly led to the preservation of this species for the time being.

At the very least, some work is being done not only to understand what these plants need in order to germinate and survive, but also assess the viability of relocated plants that are threatened by human development. Attempts at transplanting individuals in the past have been met with limited success but thankfully the Oncocyclus irises have caught the eye of bulb growers around the world. By sharing information on the needs of these plants in cultivation, growers can help expand on efforts to save species like the Golan iris.

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

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

 

The Carnivorous Waterwheel

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Bladderworts (Utricularia spp.) aren't the only carnivorous plants stalking prey below the water surface. Meet the waterwheel (Aldrovanda vesiculosa). At first glance it looks rather unassuming but closer inspection will reveal that this carnivore is well equipped for capturing unsuspecting prey. 

The waterwheel never bothers with roots. Instead, it lives out its life as a free floating sprig, its stem is covered in whorls of filamentous leaves, each tipped with a tiny trap. The trapping mechanism is a bit different from its bladderwort neighbors. Instead of bladders, the waterwheel produces snap traps that closely resemble those of the Venus fly trap (Dionaea muscipula). These traps function in a similar way. When zooplankton or even a small fish trigger the bristles along the rim, the trap snaps shut and begins the digestion process.

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This similarity to the Venus fly trap is more than superficial. DNA analysis reveals that they are in fact close cousins. Together with the sundews, these plants make up the family Droseraceae. The evolutionary history of this clade is a bit confusing thanks to a limited fossil record. Today, the waterwheel is the only extant member of the genus Aldrovanda but fossilized seeds and pollen reveal that this group was once a bit more diverse during the Eocene. Whenever these genera diverged, it happened a long time ago and little evidence of it remains.

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At one point in time, the waterwheel could be found growing in wetland habitats throughout Africa, Europe, Asia, and even Australia. Today it is considered at risk of extinction. Its numbers have been severely reduced thanks to wetland degradation and destruction. Of the 379 known historical populations, only about 50 remain intact today and many of these are in rough shape. Agricultural and industrial runoff are exacting a significant toll on its long term survival. To make matters worse, sexual reproduction in the waterwheel is a rare event. Most often this plant reproduces vegetatively, reducing genetic diversity. What's more, natural dispersal into new habitats is extremely limited. 

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Oddly enough, populations of this plant have popped up in a few locations in eastern North America. These introductions were not a mistake either. Carnivorous plant enthusiasts concerned with the plight of this species in its native habitat began introducing it into water ways in New Jersey, New York, and Virginia where it is now established. Oddly enough, these introductions have performed far better than any of the reintroduction attempts made in its native range in Europe. Of course, this is always cause for concern. Endangered or not, the introduction of a species into new habitat is always risky. Still, there is hope yet for this species. Its popularity among plant growers has led to an increase in numbers in cultivation. At least folks have learned how to cultivate it until more comprehensive and effective conservation measures can be put into place. 

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

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

The Giant Genomes of Geophytes

Canopy plant ( Paris japonica )

Canopy plant (Paris japonica)

A geophyte is any plant with a short, seasonal lifestyle and some form of underground storage organ ( bulb, tuber, thick rhizome, etc.). Plants hailing from a variety of families fall into this category. However, they share more than just a similar life history. A disproportionate amount of geophytic plants also possess massive genomes. 

As we have discussed in previous posts, life isn't easy for geophytes. Cold temperatures, a short growing season, and plenty of hungry herbivores represent countless hurdles that must be overcome. That is why many geophytes opt for rapid growth as soon as conditions are right. However, they don't do this via rapid cell division. 

Dutchman's breeches ( Dicentra cucullaria ) emerging with preformed buds.

Dutchman's breeches (Dicentra cucullaria) emerging with preformed buds.

Instead, geophytes spend the "dormant" months pre-growing all of their organs. What's more, the cells that make up their leaves and flowers are generally much larger than cells found in non-geophytes. This is where that large genome comes into plant. If they had to wait until the first few weeks of spring to start their development, a large genome would only get in the way. Their dormant season growth means that these plants don't have to worry about streamlining the process of cellular division. They can take their time. 

As such, an accumulation of genetic material isn't detrimental. Instead, it may actually be quite beneficial for geophytes. Associated with large genomes are things like larger stomata, which helps these plants better regulate their water needs. The large genomes may very well be the reason that many geophytic plants are so good at taking advantage of such ephemeral growing conditions. 

When the right conditions present themselves, geophytes don't waste time. Pre-formed organs like leaves and flowers simply have to fill with water instead of having to wait for tissues to divide and differentiate. Water is plentiful during the spring so geophytes can rely on turgor pressure within their large cells for stability rather than investing in thick cell walls. That is why so many spring blooming plants feel so fleshy to the touch. 

Taken together, we can see how large genomes and a unique growth strategy have allowed these plants to exploit seasonally available habitats. It is worth noting, however, that this is far from the complete picture. With such a wide variety of plant species adopting a geophytic lifestyle, we still have a lot to learn about the secret lives of these plants.

Photo Credits: [1] [2]

Further Reading: [1]

An Ancient Hawaiian Moss

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The cloud forests of Kohala Mountain on the island of Hawai'i are home to a unique  botanical community. One plant in particular is quite special as it may be one of the most ancient clonal organisms in existence. Look down at your feet and you may find yourself surrounded by a species of moss known as Sphagnum palustre. Although this species enjoys a broad distribution throughout the northern hemisphere, its presence on this remote volcanic island is worth closer inspection. 

Hawai'i is rather depauperate in Sphagnum representatives and those that have managed to get to this archipelago are often restricted to growing in narrow habitable zones between 900 to 1,900 meters in elevation as these are the only spots that are cool and wet enough to support Sphagnum growth. Needless to say, successful colonization of the Hawaiian Islands by Sphagnum has been a rare event.  The fact that Sphagnum palustre was one of the few that did should not come as any surprise. What should surprise you, however, is how this particular species has managed to persist. 

Mounds of  S. palustre  in its native habitat. 

Mounds of S. palustre in its native habitat. 

Hawaiian moss aficionados have long noted that the entire population of Kohala's S. palustre mats never seem to produce a single female individual. Indeed, this moss is dioicous, meaning individuals are either male or female. As such, many have suspected that the mats of S. palustre growing on Kohala represented a single male individual that has been growing vegetatively ever since it arrived as a spore on the island. The question then becomes, how long has this S. palustre individual been on Kohala?

To answer that, researchers decided to take a look at its DNA. What they discovered was surprising in many ways. For starters, all plants were in fact males of a single individual. A rare genetic trait was found in the DNA of every population they sampled. This trait is so rare that the odds of it turning up in any number by sheer chance is infinitesimally small. What this means is that every S. palustre population found on Kohala is a clone of a single spore that landed on the mountain at some point in the distant past. Exactly how distant was the next question the team wanted to answer. 

A lush cloud forest on the slopes of Kohala.

A lush cloud forest on the slopes of Kohala.

The first clue to this mystery came from peat deposits found on the slopes of the mountain. Researchers found remains of S. palustre in peat deposits that were dated to somewhere around 24,000 years old. So, it would appear that S. palustre has been growing on Kohala since at least the late Pleistocene. But how long before that time did this moss arrive?

Again, DNA was the key to unlocking this mystery. By studying the rate at which mutations arise and fix themselves within the genetic code of this plant, they were able to estimate the average rate of mutation through time. By sampling different moss populations on Kohala, they could then use those estimates to figure out just how long each mat has been growing. Their estimates suggest that the ancestral male sport arrived on Hawai'i somewhere between 49,000 and 50,000 years ago and it has been cloning itself ever since. 

A large mat of  S. palustre

A large mat of S. palustre

As if that wasn't remarkable in and of itself, their thorough analysis of the genetic diversity within S. palustre revealed a remarkable amount of genetic diversity for a clonal organism. Though not all genetic mutations are beneficial, enough of them have managed to fix themselves into the DNA of the moss clones over thousands of years. The DNA of S. palustre is challenging long-held assumptions about genetic diversity of asexual organisms.

Of course, no conversation about Hawaiian botany would be complete without mention of invasive species. As one can expect at this point, Kohala's S. palustre populations are being crowded out by more aggressive vegetation introduced from elsewhere in the world. Unlike a lot of Hawaiian plants, however, the clonal habit of S. palustre puts a more nuanced twist to this story. 

Because Sphagnum is spongy yet durable, it has often been used as packing material. Packages stuffed with S. palustre from Kohala have been sent all over the island and because of this, S. palustre is now showing up en masse on other islands in the archipelago. Sadly, when it starts to grow in habitats that have never experienced the ecosystem engineering traits of a Sphagnum  moss, S. palustre gets pretty out of hand. It's not just packages that spread it either. All it takes is one sprig of the moss stuck on someone's boot to start a new colony elsewhere. The unique flora elsewhere in the Hawaiian archipelago have not evolved to compete with S. palustre and as a result, escaped populations are rapidly changing the ecology to the detriment of other endemic Hawaiian plants. 

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

Further Reading: [1] [2] 

The Pima Pineapple Cactus

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The Pima pineapple cactus (Coryphantha robustispina) is a federally endangered cactus native to the Sonoran Desert. It is a relatively small cactus by most standards, a fact that can make it hard to find even with a trained eye. Sadly, the plight of this cactus is shared by myriad other plant species of this arid region. Urbanization, fire, grazing, and illegal collection are an ever present threat thanks to our insatiable need to gobble up habitat we should never have occupied in the first place. 

Deserts are lands of extremes and the Pima pineapple cactus seems ready for whatever its habitat can throw its way (naturally). Plants are usually found growing individually but older specimens can take on a clustered clonal habit. During the winter months, the Pima pineapple cactus shrivels up and waits until warmth returns. Come spring, the Pima pineapple cactus begins anew. On mature specimens, flower buds begin to develop once the plant senses an increase in daylight. 

The flower buds continue to develop well into summer but seem to stop after a certain point. Then, with the onset of the summer monsoons, flower buds quickly mature and open all at once. It is thought that this evolved as a means of synchronizing reproductive events among widely spaced populations. You see, seed set in this species is best achieved via cross pollination. With such low numbers and a lot of empty space in between, these cacti must maximize the chances of cross pollination.

If they were to flower asynchronously, the chances of an insect finding its way to two different individuals is low. By flowering together in unison, the chances of cross pollination are greatly increased. No one is quite sure exactly how these cacti manage to coordinate these mass flowering events but one line of reasoning suggests that the onset of the monsoon has something to do with it. It is possible that as plants start to take up much needed water, this triggers the dormant flower buds to kick into high gear and finish their development. More work is needed to say for sure.

Seed dispersal for this species comes in the form of a species of hare called the antelope jackrabbit. Jackrabbits consume Pima fruits and disperse them across the landscape as they hop around. However, seed dispersal is just one part of the reproductive process. In order to germinate and survive, Pima pineapple cacti seeds need to end up in the right kind of habitat. Research has shown that the highest germination and survival rates occur only when there is enough water around to fuel those early months of growth. As such, years of drought can mean years of no reproduction for the Pima.

Taken together, it is no wonder then why the Pima pineapple cactus is in such bad shape. Populations can take years to recover if they even manage to at all. Sadly, humans have altered their habitat to such a degree that serious action will be needed to bring this species back from the brink of extinction. Aside from the usual suspects like habitat fragmentation and destruction, invasive species are playing a considerable role in the loss of Pima populations. 

Lehmann lovegrass (Eragrostis lehmanniana) was introduced to Arizona in the 1930's and it has since spread to cover huge swaths of land. What is most troubling about this grass is that it has significantly altered the fire regime of these desert ecosystems. Whereas there was once very little fuel for fires to burn through, dense stands of Lehmann lovegrass now offer plenty of stuff to burn. Huge, destructive fires can spread across the landscape and the native desert vegetation simply cannot handle the heat. Countless plants are killed by these burns.

Sometimes, if they are lucky, large cacti can resprout following a severe burn, however, all too often they do not. Entire populations can be killed by a single fire. What few plants remain are frequent targets of poaching. Cacti are quite a hit in the plant trade and sadly people will pay big money for rare specimens. The endangered status of the Pima pineapple cactus makes it a prized target for greedy collectors. 

The future of the Pima pineapple cactus is decidedly uncertain. Thankfully its placement on the endangered species list has afforded it a bit more attention from a conservation standpoint. Still, we know very little about this plant and more data are going to be needed if we are to develop sound conservation measures. This, my friends, is why land conservation is so important. Plants like the Pima pineapple cactus need places to grow. If we do not work harder on setting aside wild spaces, we will lose so much more than this species. 

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

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

How Air Plants Drink

  Tillandsia tectorum

 Tillandsia tectorum

Air plants (genus Tillandsia) are remarkable organisms. All it takes is seeing one in person to understand why they have achieved rock star status in the horticulture trade. Unlike what we think of as a "traditional" plant lifestyle, most species of air plants live a life free of soil. Instead, they attach themselves to the limbs and trunks of trees as well as a plethora of other surfaces. 

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Living this way imposes some serious challenges. The biggest of these is the acquisition of water. Although air plants are fully capable of developing roots, these organs don't live very long and they are largely incapable of absorbing anything from the surrounding environment. The sole purpose of air plant roots is to anchor them to whatever they are growing on. How then do these plants function? How do they obtain water and nutrients? The answer to this lies in tiny structures called trichomes. 

Trichomes are what gives most air plants their silvery sheen. To fully appreciate how these marvelous structures work, one needs some serious magnification. A close inspection would reveal hollow, nail-shaped structures attached to the plant by a stem. Instead of absorbing water directly through the leaf tissues, these trichomes mediate the process and, in doing so, prevent the plant from losing more water than it gains. 

The trichomes themselves start off as living tissue. During development, however, they undergo programmed cell death, leaving them hollow. When any amount of moisture comes into contact with these trichomes, they immediately absorb that water, swelling up in the process. As they swell, they are stretched out flat along the surface of the leaf. This creates a tiny film of water between the trichomes and the rest of the leaf, which only facilitates the absorption of more water. 

Trichomes up close.  

Trichomes up close.  

Because the trichomes form a sort of conduit to the inside of the leaf, water and any nutrients dissolved within are free to move into the plant until the reach the spongy mesophyll cells inside. In this way, air plants get all of their water needs from precipitation and fog. Not all air plants have the same amount of trichomes either. In fact, trichome density can tell you a lot about the kind of environment a particular air plant calls home. 

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The fuzzier the plant looks, the drier the habitat it can tolerate. Take, for instance, one of the fuzziest air plants - Tillandsia tectorum. This species hails from extremely arid environments in the high elevation regions of Ecuador and Peru. This species mainly relies on passing clouds and fog for its moisture needs and thus requires lots of surface area to collect said water. Now contrast that with a species like Tillandsia bulbosa, which appears to have almost no trichome cover. This smoother looking species is native to humid low-land habitats where high humidity and frequent rain provide plenty of opportunities for a drink. 

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Absorbing water in this way would appear to have opened up a plethora of habitats for the genus Tillandsia. Air plants are tenacious plants and worthy of our admiration. One could learn a lot from their water savvy ways. 

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

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

Mt. Cuba Center Puts Nativars to the Test

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By this point, most gardeners will have undoubtedly heard about the importance of using native plants in our landscapes. Though the idea is not new, Doug Tallamy’s landmark publication “Bringing Nature Home” put native plants on the radar for more gardeners than ever. There is no debate that utilizing native plants in our landscapes offers us a chance to bring back some of the biodiversity that was lost when our homes and work places were built. And, at the end of the day, who doesn’t love the sight of a swallowtail butterfly flitting from flower to flower or a pair of warblers nesting in their Viburnum? The rise of native plants in horticulture and landscaping is truly something worth celebrating.

At the same time, however, capitalism is capitalism, and many nurseries are starting to jump on the bandwagon in alarming ways. The rise of native cultivars or “nativars” is troubling to many. Nativars are unique forms, colors, and shapes of our beloved native plants which have been selected and propagated by nurseries and plant breeders. This has led many to denounce the practice of planting nativars as a slap in the face to the concept of native gardening.

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Nativars are frequently seen as unnatural mutant versions of their wild counterparts whose use overlooks the whole point of natives in the first place. Take, for instance, the popularity of double flowered nativars. These plants have been selected for an over-production of sepals and petals that can be so dense that they preclude visitation by pollinators. Another example that will be familiar to most are the bright blue hydrangeas that have become to popular. These shrubs have been selected for producing bright, showy flowers that, depending on your soil chemistry, exhibit a stunning blue coloration. The downside here is that all of those flowers are sterile and produce no nectar or pollen for visiting insects.

It would seem that nativars are a slippery slope to yet another sterile landscape incapable of supporting biodiversity. However, anecdotes don’t equal data and that is where places like Mt. Cuba Center come in. Located in northern Delaware, Mt. Cuba is doing something quite amazing for the sake of environmentally friendly landscaping – they are putting plants to the test.

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Mt. Cuba has been running trial garden research and experiments on native plants and their nativars for over a decade. The goal of this research is to generate and analyze data in order to help the public make better, more sustainable choices for their yards. Mt. Cuba aims to better understand and quantify the horticultural and ecological value of native plants and related nativars in order to better understand the various ecosystem services these plants provide. In collaboration with academic institutions in the region, popular nativars are established and grown under similar conditions to those experienced in the yards of your average gardener. They are monitored for years to assess their overall health, performance, and ability to support wildlife. Thanks to the help of countless volunteers, these trial gardens paint a holistic picture of each plant and related nativars that is sorely lacking from the gardening lexicon.

This is very exciting research to say the least. The data coming out of the Mt. Cuba trial gardens may both surprise and excite gardeners throughout the mid-Atlantic region of North America. For instance, their latest report looked at some of the most common Phlox varieties on the market. At the top of this list is Garden Phlox (Phlox paniculata). This lovely species is native throughout much of the eastern United States and has become quite a rockstar in the nursery trade. Over 580 cultivars and hybrids have been named to date and no doubt many more will be introduced in the future. Amazingly, many of these Phlox nativars are being developed in the Netherlands. As such, Phlox arriving in regions of the US with vastly different climates often fall victim to novel diseases they never encountered in Europe. What’s more, people often plant these nativars in hopes of attracting butterflies to their garden. Despite their popularity for attracting various lepidopterans, no one has ever tested whether or not the nativars perform as well as their native progenitor.

Phlox paniculata  'Delta Snow'

Phlox paniculata 'Delta Snow'

Starting in 2015, Mt. Cuba began trials on 66 selections and hybrids of Garden Phlox along with 28 other sun-loving types of Phlox. The plants were observed on a regular basis to see which of the nativars experienced the least amount of disease and attracted the most insects. The clear winner of these trails is a nativar known as Phlox paniculata ‘Jeana’. This particular selection was discovered growing along the Harpeth River in Tennessee and is known for having the smallest flowers of any of the Garden Phlox varieties. It also has the reputation for being rather resistant to powdery mildew. Alongside other selections such as Delta Sno’ and David, Jeana really held up to this reputation.

As far as butterflies are concerned, Jeana blew its competition out of the water. Throughout the observation period, Jeana plants received over 530 visits from butterflies whereas the second place selection, Lavelle, received 117. A graduate student at the University of Delaware is studying why exactly the various nativars of Phlox paniculata differ so much in insect visitation. Though they haven’t zeroed in on a single cause at this point, they suggest that the popularity of Jeana might actually have something to do with its small flower size. Perhaps the density of smaller flowers allows butterflies to access more nectar for less effort.

Phlox paniculata  ‘Jeana’

Phlox paniculata ‘Jeana’

Monarda is another genus of North American native plants that has seen an explosion in nativars and hybrids over the last few decades. The popularity of these mints is no surprise to anyone who has spent time around them. Their inflorescence seems to be doing their best impression of a fireworks display, an attribute that isn’t lost on pollinators. These plants are popular with a wide variety of wildlife from solitary bees to voracious hummingbirds. Even after flowering, their seeds provide food for seed-eating birds and many other animals.

As with Garden Phlox, a majority of the commercial selection and hybridization of Monarda occurs in Europe. As a result, resistance to North American plant diseases is not top priority. Many of us have experienced this first hand as our beloved bee balm patch succumbs to aggressive strains of powdery mildew. Though there are many species of Monarda native to North America, most of the plants we encounter are nativars and hybrids of two species – Monarda didyma and Monarda fistulosa.

Monarda fistulosa  'Claire Grace'

Monarda fistulosa 'Claire Grace'

Again, Mt. Cuba’s trial gardens put these plants to the test. A total of 40 different Monarda selections were grown, observed, and ranked based on their overall growth and vigor, pollinator attractiveness, and disease resistance. The clear winner of these trials was a naturally-occurring form of M. fistulosa affectionately named ‘Claire Grace.’ Its floral display lasts a total of 3 weeks without waning and managed to attract over 130 visits by butterflies and moths. Though plenty of other insects such as short-tongued bees visited the flowers during the trial period, they are too small to properly access the nectar inside the flower tubes and are therefore not considered effective pollinators.

Another clear winner in terms of pollinators was possibly one of the most stunning Monarda selections in existence – Monarda didyma ‘Jacob Cline’. This tall, red-flowering nativar was a major hit with hummingbirds. During the observation period, Jacob Cline received over 270 visits from these brightly colored birds. Researchers are still trying to figure out why exactly this particular selection was such a hit but they speculate that the large flower size presents ample feeding opportunities for tenacious hummingbirds.

Monarda didyma  'Jacob Cline'

Monarda didyma 'Jacob Cline'

Claire Grace and Jacob Cline also outperformed most of the other selections in terms of disease resistance. Even in the crowded conditions experienced by plants in the trail garden, both selections faired quite well against the dreaded powdery mildew. Though they aren’t completely resistant to it, these and others did not succumb like some selections tend to do. Interestingly enough, most of the other pure species tested in the trial faired quite well against powdery mildew as well. It would appear that Mother Nature better equips these plants than European breeders.

These reports are but two of the many trials that Mt. Cuba has undertaken and there are many, many more on the way. Thanks to the hard work of staff and volunteers, Mt. Cuba is finally putting numbers behind some of our most commonly held assumptions about gardening with native plants and their cultivars. It is impressive to see a place so dedicated to making our landscapes more sustainable and environmentally friendly.

If you would like to find out more about Mt. Cuba’s trial garden as well as download your own copies of the trial garden reports, please make sure to check out https://mtcubacenter.org/research/trial-garden/

Saving Bornean Peatlands is a Must For Conservation

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The leading cause of extinction on this planet is loss of habitat. As an ecologist, it pains me to see how frequently this gets ignored. Plants, animals, fungi - literally every organism on this planet needs a place to live. Without habitat, we are forced to pack our flora and fauna into tiny collections in zoos and botanical gardens, completely disembodied from the environment that shaped them into what we know and love today. That’s not to say that zoos and botanical gardens don’t play critically important roles in conservation, however, if we are going to stave off total ecological meltdown, we must also be setting aside swaths of land.

There is no way around it. We cannot have our cake and eat it too. Land conservation must be a priority both at the local and the global scale. Wild spaces support life. They buffer it from storms and minimize the impacts of deadly diseases. Healthy habitats filter the water we drink and, for many people around the globe, provide much of the food we eat. Every one of us can think back to our childhood and remember a favorite stretch of stream, meadow, or forest that has since been gobbled up by a housing development. For me it was a forested stream where I learned to love the natural world. I would spend hours playing in the creek, climbing trees, and capturing bugs to show my parents. Since that time, someone leveled the forest, built a house, and planted a lawn. With that patch of forest went all of the insects, birds, and wildflowers it once supported.

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Scenarios like this play out all too often and sadly on a much larger scale than a backyard. Globally, forests have felt taken the brunt of human development. Though it is hard to get a sense of the scope of deforestation on a global scale, the undisputed leaders in deforestation are Brazil and Indonesia. Though the Amazon gets a lot of press, few may truly grasp the gravity of the situation playing out in Southeast Asia.

Deforestation is a clear and present threat throughout tropical Asia. This region is growing both in its economy and population by about 6% every year and this growth has come at great cost to the environment. Indonesia (alongside Brazil) accounts for 55% of the world’s deforestation rates. This is a gut-wrenching statistic because Indonesia alone is home to the most extensive area of intact rainforest in all of Asia. So far, nearly a quarter of Indonesia’s forests have been cleared. It was estimated that by 2010, 2.3 million hectares of peatland forests had been felled and this number shows little signs of slowing. Experts believe that if these rates continue, this area could lose the remainder of its forests by 2056.

Consider the fact that Southeast Asia contains 6 of the world’s 25 biodiversity hotspots and you can begin to imagine the devastating blow that the levelling of these forests can have. Much of this deforestation is done in the name of agriculture, and of that, palm oil and rubber take the cake. Southeast Asia is responsible for 86% of the world’s palm oil and 87% of the world’s natural rubber. What’s more, the companies responsible for these plantations are ranked among some of the least sustainable in the world.

Palm oil plantations where there once was rainforest. 

Palm oil plantations where there once was rainforest. 

Borneo is home to a bewildering array of life. Researchers working there are constantly finding and describing new species, many of which are found nowhere else in the world. Of the roughly 15,000 plant species known from Borneo, botanists estimate that nearly 5,000 (~34%) of them are endemic. This includes some of the more charismatic plant species such as the beloved carnivorous pitcher plants in the genus Nepenthes. Of these, 50 species have been found growing in Borneo, many of which are only known from single mountain tops.

It has been said that nowhere else in the world has the diversity of orchid species found in Borneo. To date, roughly 3,000 species have been described but many, many more await discovery. For example, since 2007, 51 new species of orchid have been found. Borneo is also home to the largest flower in the world, Rafflesia arnoldii. It, along with its relatives, are parasites, living their entire lives inside of tropical vines. These amazing plants only ever emerge when it is time to flower and flower they do! Their superficial resemblance to a rotting carcass goes much deeper than looks alone. These flowers emit a fetid odor that is proportional to their size, earning them the name “carrion flowers.”

Rafflesia arnoldii  in all of its glory.

Rafflesia arnoldii in all of its glory.

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If deforestation wasn’t enough of a threat to these botanical treasures, poachers are having considerable impacts on Bornean botany. The illegal wildlife trade throughout southeast Asia gets a lot of media attention and rightfully so. At the same time, however, the illegal trade of ornamental and medicinal plants has gone largely unnoticed. Much of this is fueled by demands in China and Vietnam for plants considered medicinally valuable. At this point in time, we simply don’t know the extent to which poaching is harming plant populations. One survey found 347 different orchid species were being traded illegally across borders, many of which were considered threatened or endangered. Ever-shrinking forested areas only exacerbate the issue of plant poaching. It is the law of diminishing returns time and time again.

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But to lump all Bornean forests under the general label of “rainforest” is a bit misleading. Borneo has multitude of forest types and one of the most globally important of these are the peatland forests. Peatlands are vital areas of carbon storage for this planet because they are the result of a lack of decay. Whereas leaves and twigs quickly breakdown in most rainforest situations, plant debris never quite makes it that far in a peatland. Plant materials that fall into a peatland stick around and build up over hundreds and thousands of years. As such, an extremely thick layer of peat is formed. In some areas, this layer can be as much as 20 meters deep! All the carbon tied up in the undecayed plant matter is carbon that isn’t finding its way back into our atmosphere.

Sadly, tropical peatlands like those found in Borneo are facing a multitude of threats. In Indonesia alone, draining, burning, and farming (especially for palm oil) have led to the destruction of 1 million hectares (20%) of peatland habitat in only one decade. The fires themselves are especially worrisome. For instance, it was estimated that fires set between 1997-1998 and 2002-2003 in order to clear the land for palm oil plantations released 200 million to 1 billion tonnes of carbon into our atmosphere. Considering that 60% of the world’s tropical peatlands are found in the Indo-Malayan region, these numbers are troubling.

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The peatlands of Borneo are totally unlike peatlands elsewhere in the world. Instead of mosses, gramminoids, and shrubs, these tropical peatlands are covered in forests. Massive dipterocarp trees dominate the landscape, growing on a spongey mat of peat. What’s more, no water flows into these habitats. They are fed entirely by rain. The spongey nature of the peat mat holds onto water well into the dry season, providing clean, filtered water where it otherwise wouldn’t be available.

This lack of decay coupled with their extremely acidic nature and near complete saturation makes peat lands difficult places for survival. Still, life has found a way, and Borneo’s peatlands are home to a staggering diversity of plant life. They are so diverse, in fact, that when I asked Dr. Craig Costion, a plant conservation officer for the Rainforest Trust, for something approaching a plant list for an area of peatland known as Rungan River region, he replied:

“Certainly not nor would there ever be one in the conceivable future given the sheer size of the property and the level of diversity in Borneo. There can be as many as a 100 species per acre of trees in Borneo... Certainly a high percentage of the species would only be able to be assigned to a genus then sit in an herbarium for decades until someone describes them.”

And that is quite remarkable when you think about it. When you consider that the Rungan River property is approximately 385,000 acres, the number of plant species to consider quickly becomes overwhelming. To put that in perspective, there are only about 500 tree species native to the whole of Europe! And that’s just considering the trees. Borneo’s peatlands are home to myriad plant species from liverworts, mosses, and ferns, to countless flowering plants like orchids and others. We simply do not know what kind of diversity places like Borneo hold. One could easily spend a week in a place like the Rungan River and walk away with dozens of plant species completely new to science. Losing a tract of forest in such a biodiverse is a huge blow to global biodiversity.

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Nepenthes ampullaria  relies on decaying plant material within its pitcher for its nutrient needs.

Nepenthes ampullaria relies on decaying plant material within its pitcher for its nutrient needs.

Also, consider that all this plant diversity is supporting even more animal diversity. For instance, the high diversity of fruit trees in this region support a population of over 2,000 Bornean orangutans. That is nearly 4% of the entire global population of these great apes! They aren’t alone either, the forested peatlands of Borneo are home to species such as the critically endangered Bornean white-bearded gibbon, the proboscis monkey, the rare flat-headed cat, and the oddly named otter civet. All these animals and more rely on the habitat provided by these forests. Without forests, these animals are no more.

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The flat-headed cat, an endemic of Borneo. 

The flat-headed cat, an endemic of Borneo. 

At this point, many of you may be feeling quite depressed. I know how easy it is to feel like there is nothing you can do to help. Well, what if I told you that there is something you can do right now to save a 385,000 acre chunk of peatland rainforest? That’s right, by heading over to the Rainforest Trust’s website (https://www.rainforesttrust.org/project/saving-stronghold-critically-endangered-bornean-orangutan/) you can donate to their campaign to buy up and protect the Rungan River forest tract.

Click on the logo to learn more!

Click on the logo to learn more!

By donating to the Rainforest Trust, you are doing your part in protecting biodiversity in one of the most biodiverse regions in the world. What’s more, you can rest assured that your money is being used effectively. The Rainforest Trust consistently ranks as one of the top environmental protection charities in the world. Over their nearly three decades of operation, the Rainforest Trust has protected more than 15.7 million acres of land in over 20 countries. Like I said in the beginning, habitat loss is the leading cause of extinction on this planet. Without habitat, we have nothing. Plants are that habitat and by supporting organizations such as the Rainforest Trust, you are doing your part to fight the biggest threats our planet faces. 

Further Reading: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]

Photo Credits: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12]

Ferns Afloat

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

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

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

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

These are not roots!

These are not roots!

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

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

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

Sporocarps galore! 

Sporocarps galore! 

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

Photo Credits: [1] [2] [3]

Further Reading: [1] [2] [3]

 

Fish: The Unsung Heroes of Seed Dispersal

Fruits of the tucum palm.

Fruits of the tucum palm.

It goes without saying that effective seed (and spore) dispersal is vital for thriving plant populations. Without it, plant populations will stagnate and disappear. Whereas we know quite a bit about the role animals like birds, bats, and ants play in this process, there is another group of seed dispersers that are proving to be vital to the long-term health and survival of tropical forests around the globe - fish. 

The idea of seed dispersing fish may come as a shock to some but mounting evidence is showing that fruit-eating fish play a major role in the reproductive cycle of many tropical plant species. This is especially true in seasonally flooded tropical forests. To date, more than 100 different fish species have been found with viable seeds in their guts. In fact, some fish species, such as the pacu (Piaractus mesopotamicus), specialize on eating fruits.

A big ol' pacu looking for its next fruit meal.

A big ol' pacu looking for its next fruit meal.

By monitoring how fruit-eating fish like the pacu behave in their environment, scientists are painting a picture of tropical seed dispersal that is quite remarkable. Take, for instance, the tucum palm (Bactris glaucescens). Native to Brazil's Pantanal, this palm produces large, red fruits and everything from peccaries to iguanas will consume them. However, when eaten by these animals, the seed either don't make it through the gut in one piece or they end up being pooped out into areas unsuitable for germination. Only when the seeds have been consumed by the pacu do they end up in the right place in the right condition. It appears that pacus are the main seed dispersal agent for this palm. 

A beautiful tucum palm in the dry season.

A beautiful tucum palm in the dry season.

The tucum palm isn't alone either. The seeds of myriad other plant species known to inhabit such seasonally flooded habitats seem to germinate and grow most effectively only after having been dispersed by fish. Pacus are also responsible for a considerable amount of seed dispersal for plants such as Tocoyena formosa (Rubiaceae), Licania parvifolia (Chrysobalanaceae), and Inga uruguensis (Fabaceae). Even outside of the tropics, fish like the channel catfish (Ictalurus punctatus) are being found to be important seed dispersers of riparian plants such as the eastern swampprivet (Forestiera acuminata).

Camu-camu ( Myrciaria dubia )

Camu-camu (Myrciaria dubia)

Without fish, these plants would have a hard time with seed dispersal in such seasonally flooded habitats. Lacking a dispersal agent, these seeds would be stuck at the bottom of a river, buried in anoxic mud. As fish migrate into flooded forests, they can move seeds remarkable distances from their parents. When the flood waters recede, the seeds find themselves primed and ready to usher in the next generation.

Fruits of the Camu-camu ( Myrciaria dubia ) also benefit from dispersal by fish.

Fruits of the Camu-camu (Myrciaria dubia) also benefit from dispersal by fish.

Not all fish perform this task equally as well. Even within a species, there are differences in the effectiveness of seed dispersal services. Scientists are finding that large fish are most effective at proper seed dispersal. Not only can they consume whole fruits with little to no issue, they are also the fish that are most physically capable of moving large distances. Sadly, humans are seriously disrupting this process in a lot of ways.

For starters, dams and other impediments are cutting off the migratory routs of many fish species. Large fish are no longer able to make it into flooded regions of forest far upstream once a dam is in place. What's more, dams keep large tracts of forest from flooding entirely. As such, fish are no longer able to migrate into these regions, which means less seeds are making it there as well. This is bad news for forest regeneration.

"Gimme fruit" says local channel cat.

"Gimme fruit" says local channel cat.

It's not just dams hurting fish either. Over-fishing is a serious issue in most water ways. Pacus, for instance, have seen precipitous declines throughout the Amazon over the last few decades. Specifically targeted are large fish. Unfortunately, regulations that were put into place in order to help these fish may actually be harming their seed dispersal activities. Fish under a certain size must be released from any catch, thus a disproportionate amount of large fish are being removed from the system.

Logging is taking a serious toll as well. Floodplain forests have been hit especially hard by logging, both legal and illegal. The lower Amazon River, for example, has almost no natural floodplain forests left. Reports from fish markets in these areas have shown fewer and fewer frugivorous fish each year. It would appear that large fruit-eating fish are disappearing in the areas that need seed dispersal the most. It is clear that something drastic needs to happen. At the very least, fruit-eating fish need more recognition for the ecosystem services they provide.

Forest health and management is a holistic endeavor. We cannot think of organisms in isolation. This is why ecological literacy is so important. We are only now starting to realize the role of large fish in forest regeneration and who knows what kinds of discoveries are just over the horizon. This is why land conservation efforts are so important. We must move to protect wild spaces before they are lost for good. Please consider donating to one of the many great land conservancy agencies around the globe. 

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

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

 

The Strangest Wood Sorrel

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For me, wood sorrels are a group of plants I usually have to look down to find. This is certainly not the case for Oxalis gigantea. Native to the coastal mountains of northern Chile, this bizarre Oxalis has forgone the traditional herbaceous habit of its cousins in exchange for a woody shrub-like growth form.

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When I first laid eyes on O. gigantea, I thought I was looking at some strange form of Ocotillo. In front of me was a shrubby plant consisting of multiple upright branches that were covered in a dense layer of shiny green leaves occasionally interrupted by yellow flowers. You would think that at this point in my life, aberrant taxa would not longer surprise me. Think again. 

O. gigantea is one of the largest of the roughly 570 Oxalis species known to science. Its woody branches can grow to a height of 2 meters (6 feet)! The branches themselves are quite interesting to look at. They are covered in woody spurs from which clusters of traditional Oxalis-style leaves emerge. Each stem is capable of producing copious amounts of flowers all throughout the winter months. The flowers are said to be pollinated by hummingbirds but I was not able to find any data on this. 

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This shrub is but one part of the Atacama Desert flora. This region of Chile is quite arid,  experiencing a 6 to 10 month dry season every year. What rain does come is often sparse. Any plant living there must be able to cope. And cope O. gigantea does! This oddball shrub is deciduous, dropping its leaves during the dryer months. During that time, these shrubs look pretty ragged. You would never guess just how lush it will become once the rains return. Also, it has a highly developed root system, no doubt for storing water and nutrients to tide them over.  

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O. gigantea has enjoyed popularity as a horticultural oddity over the years. In fact, growing this shrub as a container plant is said to be quite easy. Despite its garden familiarity, O. gigantea is noticeably absent from the scientific literature. In writing this piece, I scoured the internet for any and all research I could find. Sadly, it simply isn't there.

This is all too often the case for unique and interesting plant species like O. gigantea. Like so many other species, it has suffered from the disdain academia has had for organismal research over the last few decades. We humans can and must do better than that. For now, what information does exist has come from horticulturists, gardeners, and avid botanizers from around the world. 

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

Further Reading: [1] [2] 

 

On the Ecology of Krameria

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There is something satisfying about saying "Krameria." Whereas so many scientific names act as tongue twisters, Krameria rolls of the tongue with a satisfying confidence. What's more, the 18 or so species within this genus are fascinating plants whose lifestyles are as exciting as their overall appearance. Today I would like to give you an overview of these unique parasitic plants.

Commonly known as rhatany, these plants belong to the family Krameriaceae. This is a monotypic clade, containing only the genus Krameria. Historically there has been a bit of confusion as to where these plants fit on the tree of life. Throughout the years, Krameria has been placed in families like Fabaceae and Polygalaceae, however, more recent genetic work suggests it to be unique enough to warrant a family status of its own. 

Regardless of its taxonomic affiliation, Krameria is a wonderfully specialized genus of plants with plenty of offer the biologically curious among us. All 18 species are shrubby, though at least a couple species can sometimes barely qualify as such. They are a New World taxon with species growing native as far south as Paraguay and Chile and as far north as Kansas and Colorado. They generally inhabit dry habitats.

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As I briefly mentioned above, most if not all of the 18 species are parasitic in nature. They are what we call "hemiparasites" in that despite stealing from their hosts, they are nonetheless fully capable of photosynthesis. It is interesting to note that no one has yet been able to raise these plants in captivity without a host. It would seem that despite being able to photosynthesize, these plants are rather specialized parasites. 

That is not to say that they have evolved to live off of a specific host. Far from it actually. A wide array of potential hosts, ranging from annuals to perennials, have been identified. What I find most remarkable about their parasitic lifestyle is the undeniable advantage it gives these shrubs in hot, dry environments. Research has found that despite getting a slow start on growing in spring, the various Krameria species are capable of performing photosynthesis during extremely stressful periods and for a much longer duration than the surrounding vegetation. 

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The reason for this has everything to do with their parasitic lifestyle. Instead of producing a long taproot to reach water reserves deep in the soil, these shrubs invest in a dense layer of lateral roots that spread out in the uppermost layers of soil seeking unsuspecting hosts. When these roots find a plant worth parasitizing, they grow around its roots and begin taking up water and nutrients from them. By doing this, Krameria are no longer limited by what water or other resources their roots can find. Instead, they have managed to tap into large reserves that would otherwise be locked away inside the tissues of their neighbors. As such, the Krameria do not have to worry about water stress in the same way that non-parasitic plants do. 

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By far the most stunning feature of the genus Krameria are the flowers. Looking at them it is no wonder why they have been associated with legumes and milkworts. They are beautiful and complex structures with a rather specific pollination syndrome. Krameria flowers produce no nectar to speak of. Instead, they have evolved alongside a group of oil-collecting bees in the genus Centris.

One distinguishing feature of Krameria flowers are a pair of waxy glands situated on each side of the ovary. These glands produce oils that female Centris bees require for reproduction. Though Centris bees are not specialized on Krameria flowers, they nonetheless visit them in high numbers. Females alight on the lip and begin scraping off oils from the glands. As they do this, they inevitably come into contact with the stamens and pistil. The female bees don't feed on these oils. Instead, they combine it with pollen and nectar from other plant species into nutrient-rich food packets that they feed to their developing larvae.  

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Following fertilization, seeds mature inside of spiny capsules. These capsules vary quite a bit in form and are quite useful in species identification. Each spine is usually tipped in backward-facing barbs, making them excellent hitchhikers on the fur and feathers of any animal that comes into contact with them.  

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

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

The Bladderwort Microbiome Revealed

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The bladderworts (Utricularia spp.) are among the most cosmopolitan groups of carnivorous plants on this planet. Despite their popularity, their carnivorous habits have been subject to some debate. Close observation reveals that prey capture rates are surprisingly low for most species. This has led some to suggest that the bladderworts may be benefiting from more passive forms of nutrient acquisition. To better understand how these plants utilize their traps, a team of researchers decided to take a closer look at the microbiome living within. 

The team analyzed the trap fluid of a handful of floating aquatic bladderwort species - U. vulgaris, U. australis, and U reflexa. In doing so, they uncovered a bewildering variety of microorganisms perfectly at home within the bladderwort traps. Thanks to sophisticated genetic tools, they were able to classify these microbes in order to investigate what exactly they might be doing inside the traps. 

Their findings were quite astonishing to say the least. The traps of these plants harbor extremely rich microbial communities, far richer than the microbial diversity of other carnivorous plant traps. In fact, the richness of these microbial communities were more akin to the richness seen in the rooting zone of terrestrial plants or the gut of a cow. In terms of the species present, the microbial communities of bladderwort traps most closely resembled that of the pitchers of Sarracenia species as well as the guts of herbivorous iguanas.

The similarities with herbivore guts is quite remarkable. Its not just coincidental either. The types of microbes they found weren't new to science but their function was a bit of a surprise. A large percentage of the bacteria living within the fluid are famously known for producing enzymes that digest complex plant tissues. Similarly, the team found related microbe groups that specialize on anaerobic fermentation. These types of microbes in particular are largely responsible for the breakdown of plant materials in the rumen of cattle.

As it turns out, the microbes living within the traps of these bladderworts are serving a very important purpose for the plant - they are breaking down plant and algae cells that find their way into the traps each time they open and close. In doing so, they give off valuable nutrients that the bladderworts can then absorb and utilize. Let me say that again, the bacteria living in bladderwort traps are digesting algae and other plant materials that these carnivorous plants can then absorb.

Now these bacteria are also responsible for producing a lot of methane in the process. Interestingly enough, the team was not able to detect measurable levels of methane leaving the traps. This would be odd if it wasn't for the community of methane-feeding microbes also discovered living within the traps. The team believes that these organisms metabolize all of the methane being produced before it can escape the traps. 

As remarkable as these findings are, I don't want to give the impression that these carnivorous plants have taken up a strict vegetarian lifestyle. The team also found myriad other microorganisms within the bladder traps, many of them being carnivores themselves. The team also found a rich protist community. A majority of these were euglenids and ciliates. 

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These sorts of protists are important microbial predators and the numbers recorded within the traps suggest that they are a rather significant component of these trap communities. As they chase down and consume bacteria and other protists, they release valuable nutrients that the plants can absorb and utilize. Numbers of these predatory protists were much higher in older traps, which have had much more time to accumulate a diverse microbiome. Astonishingly, it is estimated that the protist communities can cycle the entire contents of the bladderwort traps upwards of 4 or 5 times in a 24 hour period. That is some serious turnover of nutrients!

The protists weren't the only predators found within the traps either. There are also a considerable amount of bacterial predators living there as well. These not only cycle nutrients in similar ways to the protist community, it is likely they also exhibit strong controls on the biodiversity within this miniature ecosystem. In other words, they are considered keystone predators of these microcosms.

Also present within the traps were large amounts of fungal DNA. None of the species they found are thought to actually live within the traps. Rather, it is thought that they are taken up as spores blown in from the surrounding environment. Exactly how these organisms find themselves living inside bladderwort traps is something worth considering. The plants themselves are known for being covered in biomfilms. It is likely that many of the organisms living within the traps were those found living on the plants originally. 

Taken together, the remarkable discovery of such complex microbial communities living on and within these carnivorous plants shows just how complex the ecology of such systems really are. Far from the active predators we like to think of them as, the bladderworts nonetheless rely on a mixture of symbiotic orgnaisms to provide them with the nutrients that they need. The fact that these plants are in large part digesting plant and algae materials is what I find most astonishing.

Essentially, one can almost think of bladderworts as plants adorned with tiny, complex cow stomachs, each utilizing their microbial community to gain as much nutrients as they can from their living environment. The bladderworts gain access to nutrients and the microbes get a place to live. The bladderworts really do seem to be cultivating a favorable habitat for these organisms as well. Analysis of the bladder fluid demonstrated that the plants actively regulate the pH of the fluid to maintain their living community of digestive assistants. In doing so, they are able to offset the relative rarity of prey capture. Keep in mind that this research was performed on only three species of bladderwort originating from similar habitats. Imagine what we will find in the traps of the multitude of other Utricularia species.

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

Further Reading: [1]

 

Getting to Know Elodea

When I think back on it, one of the first plants I ever actively tried growing was waterweed (Elodea canadensis). My 4th grade teacher had invested in a unit on the ecosystem concept. We all brought in 2 liter soda bottles that we craftily turned into mini terrariums. The top half of the terrarium was filled with soil and planted with some grass seed. The bottom half was filled with water and some gravel. In that portion we placed a single guppy and a few sprigs of Elodea

The idea was to teach us about water and nutrient cycles. It didn't work out too well as most of my classmates abandoned theirs not long after the unit was over. Being the avid little nerd that I was, I fell deeply in love with my new miniature ecosystem. The grass didn't last long but the guppy and the Elodea did. Since then, I have kept Elodea in various aquariums throughout the years but never gave it much thought. It is easy enough to grow but it never did much. Today I would like to make up for my lack of concern for this plant by taking a closer look at Elodea

An example of the soda bottle terrariums

An example of the soda bottle terrariums

The genus Elodea is one of 16 genera that make up the family Hydrocharitaceae and is comprised of 6 species. All 6 of these plants are native to either North or South America, with Elodea canadensis preferring the cooler regions of northern North America. They are adaptable plants and can grow both rooted or floating in a variety of aquatic conditions. It is this adaptability that has made them so popular in the aquarium trade. It is also the reason why the genus is considered a nasty aquatic invasive throughout the globe. For this reason, I do not recommend growing this plant outdoors in any way, shape, or form unless that species is native to your region. 

Believe it or not, Elodea are indeed flowering plants. Small white to pink flowers are borne on delicate stalks at the water's surface. They are attractive structures that aren't frequently observed. In fact, it is such a rare occurrence that trying to figure out what exactly pollinates them proved to be quite difficult. What we do know is that sexual reproduction and seed set is not the main way in which these plants reproduce. 

Anyone who has grown them in an aquarium knows that it doesn't take much to propagate an Elodea plant. They have a remarkable ability for cloning themselves from mere fragments of the stem. This is yet another reason why they can become so invasive. Plants growing in temperate waterways produce a thick bud at the tips of their stems come fall. This is how they overwinter. Once favorable temperatures return, this bud "germinates" and grows into a new plant. In more mild climates, these plants are evergreen. 

One of the most interesting aspects of Elodea ecology is that at least two species, E canadensis and E. nuttallii, are considered allelopathic. In other words, these plants produce secondary chemicals in their tissues that inhibit the growth of other photosynthetic organisms. In this case, their allelopathic nature is believed to be a response to epiphytic algae and cyanobacteria.

Slow growing aquatic plants must contend with films of algae and cyanobacteria building up on their leaves. Under certain conditions, this buildup can outpace the plants' ability to deal with it and ends up completely blocking all sunlight reaching the leaves. Researchers found that chemicals produced by these two species of Elodea actually inhibited the growth of algae and cyanobacteria on their leaves, thus reducing the competition for light in their aquatic environments. 

Elodea make for a wonderful introduction to the world of aquatic plants. They are easy to grow and, if cared for properly, look really cool. Just remember that their hardy nature also makes them an aggressive invader where they are not native. Never ever dump the contents of an aquarium into local water ways. Provided you keep that in mind, Elodea can be a wonderful introduction to the home aquarium. If you are lucky enough to see them in flower in the wild, take the time to enjoy it. Who knows when you will see it again. 

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

Further Reading: [1] [2] 

The Extraordinary Catasetum Orchids

Male  Catasetum osculatum

Male Catasetum osculatum

Orchids, in general, have perfect flowers in that they contain both male and female organs. However, in a family this large, exceptions to the rules are always around the corner. Take, for instance, orchids in the genus Catasetum. With something like 166 described species, this genus is interesting in that individual plants produce either male or female flowers. What's more, the floral morphology of the individual sexes are so distinctly different from one another that some were originally described as distinct species. 

Female  Catasetum osculatum

Female Catasetum osculatum

In fact, it was Charles Darwin himself that first worked out that plants of the different sexes were indeed the same species. The genus Catasetum enthralled Darwin and he was able to procure many specimens from his friends for study. Resolving the distinct floral morphology wasn't his only contribution to our understanding of these orchids, he also described their unique pollination mechanism. The details of this process are so bizarre that Darwin was actually ridiculed by some scientists of the time. Yet again, Darwin was right. 

Catasetum longifolium

Catasetum longifolium

If having individual male and female plants wasn't strange enough for these orchids, the mechanism by which pollination is achieved is quite explosive... literally. 

Catasetum orchids are pollinated by large Euglossine bees. Attracted to the male flowers by their alluring scent, the bees land on the lip and begin to probe the flower. Above the lip sits two hair-like structures. When a bee contacts these hairs, a structure containing sacs of pollen called a pollinia is launched downwards towards the bee. A sticky pad at the base ensures that once it hits the bee, it sticks tight. 

Male Catasetum flower in action. Taken from BBC's Kingdom of Plants.

Male Catasetum flower in action. Taken from BBC's Kingdom of Plants.

Bees soon learn that the male flowers are rather unpleasant places to visit so they set off in search of a meal that doesn't pummel them. This is quite possibly why the flowers of the individual sexes look so different from one another. As the bees visit the female flowers, the pollen sacs on their back slip into a perfect groove and thus pollination is achieved. 

Eulaema polychroma  visiting  Catasetum integerrimum

Eulaema polychroma visiting Catasetum integerrimum

The uniqueness of this reproductive strategy has earned the Catasetum orchids a place in the spotlight among botanists and horticulturists alike. It begs the question, how is sex determined in these orchids? Is it genetic or are there certain environmental factors that push the plant in either direction? As it turns out, light availability may be one of the most important cues for sex determination in Catasetum

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A paper published back in 1991 found that there were interesting patterns of sex ratios for at least one species of Catasetum. Female plants were found more often in younger forests whereas the ratios approached an even 1:1 in older forests. What the researchers found was that plants are more likely to produce female flowers under open canopies and male flowers under closed canopies. In this instance, younger forests are more open than older, more mature forests, which may explain the patterns they found in the wild. It is possible that, because seed production is such a costly endeavor for plants, individuals with access to more light are better suited for female status. 

Catasetum macrocarpum

Catasetum macrocarpum

Aside from their odd reproductive habits, the ecology of these plants is also quite fascinating. Found throughout the New World tropics, Catasetum orchids live as epiphytes on the limbs and trunks of trees. Living in the canopy like this can be stressful and these orchids have evolved accordingly. For starters, they are deciduous. Most of the habitats in which they occur experience a dry season. As the rains fade, the plants will drop their leaves, leaving behind a dense cluster of green pseudobulbs. These bulbous structures serve as energy and water stores that will fuel growth as soon as the rains return. 

Catasetum silvestre in situ

Catasetum silvestre in situ

The canopy can also be low in vital nutrients like nitrogen and phosphorus. As is true for all orchids, Catasetum rely on an intimate partnership with special mychorrizal fungi to supplement these ingredients. Such partnerships are vital for germination and growth. However, the fungi that they partner with feed on dead wood, which is low in nitrogen. This has led to yet another intricate and highly specialized relationship for at least some members of this orchid genus. 

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Mature Catasetum are often found growing right out of arboreal ant nests. Those that aren't will often house entire ant colonies inside their hollowed out pseudobulbs. This will sometimes even happen in a greenhouse setting, much to the chagrin of many orchid growers. The partnership with ants is twofold. In setting up shop within the orchid or around its roots, the ants provide the plant with a vital source of nitrogen in the form of feces and other waste products. At the same time, the ants will viciously attack anything that may threaten their nest. In doing so, they keep many potential herbivores at bay.  

Female  Catasetum planiceps

Female Catasetum planiceps

To look upon a flowering Catasetum is quite remarkable. They truly are marvels of evolution and living proof that there seems to be no end to what orchids have done in the name of survival. Luckily for most of us, one doesn't have to travel to the jungles and scale a tree just to see one of these orchids up close. Their success in the horticultural trade means that most botanical gardens house at least a species or two. If and when you do encounter a Catasetum, do yourself a favor and take time to admire it in all of its glory. You will be happy that you did. 

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

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

Poinsettias Wild Origins

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Poinsettias are famous the world over for the splash of color they provide indoor spaces during the colder months of the year. The name "poinsettia" is seemingly synonymous with the holiday season. They are so common that it is all too easy to write them off as another disposable houseplant whose only purpose is to dazzle us with a few short weeks of reds and whites. With all of the focus on those colorful bracts, it is easy to lose sight of the fact that these plants have wild origins. What exactly is a poinsettia and where do they come from?

Poinsettia is the common name given to a species of shrub known scientifically as Euphorbia pulcherrima. No one quite knows the exact origin of our cultivated house guests but the species itself is native to the mountains of the Pacific slope of Mexico. It is a scraggly shrub that lives in seasonally dry tropical forests. Mature specimens can grow to be so large and lanky that they almost resemble vines. 

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These shrubs flower throughout winter and into spring. What we think of as large, showy, red and white flower petals are not petals at all. They are actually leafy bracts. Like a vast majority of Euphorbia species, E. pulcherrima produces tiny yellow flowers. They aren't much to look at with the naked eye but take a hand lens to them and you will reveal rather intriguing little structures. The bracts themselves serve similar functions as petals in that their stunning colors are there to attract potential pollinators. 

The bracts also caught the attention of horticulturists as well. Because of their beauty, E. pulcherrima is one of the most widely cultivated plants in human history. As many a poinsettia owner has come to realize, the bracts do not stay colored up all year. In fact, the whole function of these bracts is to save energy on flower production by coloring up leaves that are already in place. The key to the color change lies in the relative amount of daylight. 

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As days grow shorter, the plants begin to mature their flowers. At the same time, changes within the leafy bracts cause them to start producing pigments. When the days become shorter than the nights, the plants go into full reproductive mode. Both red- and white-colored bracts have been found in the wild. As soon as the days start to grow longer than the nights, the plants switch out of reproductive mode and the dazzling color fades. In captivity, this change is mimicked by plunging plants into complete darkness for a minimum of 12 hours per day.

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Another aspect worth considering about this species is its sap. Whereas most plants hailing from Euphorbiacea or spurge family contain toxic sap, the sap of E. pulcherrima is very mild in its toxicity and an absurd amount of plant material would have to be consumed to suffer any serious side effects. Certainly it serves an anti-herbivore purpose in the wild, however, as long as you're not a tiny insect or a gluttonous deer, you have nothing to worry about from this species at least. So there you have it, some food for thought if you feel the urge to purge some spurge in a post-holiday cleanse.

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

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

The Beech Aphid Poop-Eater

Interactions between organisms are what got me into ecology. After all, no living thing operates in a vacuum. I recently had an experience that reminded me of this on a recent hike with some friends. We stumbled across a strange black growth on the limb of a beech tree. It was like a crusty black stalagmite on the branch. Luckily, my friend Kristen happened to be there. Her expertise in plant/fungal interactions was exactly what this moment called for. What we had found was one of the most unique fungi I have seen in a long time. What's more, it only lives on American beech trees (Fagus grandifolia).  

The fungus in question is a type of sooty mold known scientifically as Scorias spongiosa. I'm not sure if it has a widely used common name but at least one source I referenced lovingly referred to it as "the beech aphid poop-eater." Though that name doesn't come close to rolling off the tongue, it nonetheless describes the life cycle of this bizarre fungus quite accurately. 

A  Scorias spongiosa  colony changing from its asexual phase (beige) to its sexual phase (black)

A Scorias spongiosa colony changing from its asexual phase (beige) to its sexual phase (black)

We begin with an aphid called the beech blight aphid (Grylloprociphilus imbricator). It is not the insect responsible for beech bark disease but it is specific to American beech. These aphids are gregarious little creatures and large populations can quickly accumulate on beech trees. They secrete a white woolly substance, making them quite easy to spot. Like all aphids, they feed on sap and poop out mass quantities of honeydew (sugary aphid poop) in the process. 

A colony of beech blight aphids

A colony of beech blight aphids

It is this honeydew that the sooty mold feeds on. Spores that manage to land on the accumulation of aphid poop begin to grow fungal hyphae. At first, the fungus takes on a beige coloration. Gradually it forms a tangled mass of fungal tissues. It is important to note that it is not a parasite on the beech tree whatsoever.  S. spongiosa simply feeds on the sugary beech blight aphid poop. The reason S. spongiosa can grow into such a large formation has to do with the colonial nature of the beech blight aphid. The more aphid poop that accumulates, the lager S. spongiosa will grow.

By mid summer, some S. spongiosa resemble large sponges on the branches and trunks of beech trees. At this point they are producing asexual spores. Later in the year, the fungus switches over to producing sexual spores. This shift also causes the fungal mass to produce more melanin, which gives it its black coloration. It also becomes much more durable, meaning there is a good chance of finding this fungus outside of the growing season. 

Patches of  Scorias spongiosa  covering the bark of a beech tree

Patches of Scorias spongiosa covering the bark of a beech tree

What amazes me the most is that this fungus will only ever be found on American beech trees. The reason for this is because it feeds only on the poop of the beech blight aphid, which, as its common name suggests, feeds only on beech trees. This is but one example of the myriad ecological interactions that makeup life on this planet. It is also a reminder that single species conservation efforts forget most of what makes a species special. 

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

Further Reading: [1] [2]

This Is Not The Bamboo You Are Looking For...

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She has one, he has one, you have one, I have one, the office has one... lets just say "lucky bamboo" has made its way into many a home, office, and waiting room. Popularized by the practice of feng shui and sold for pennies on the dime by New Age stores all over the world, these plants seem to thrive on neglect. It may come as a surprise then that these plants are not a bamboo at all.

These ubiquitous home decorations are actually a species of Dracaena, Dracaena braunii to be exact. It isn't even from the same taxonomical order as bamboo. Whereas bamboo are a type of grass, D. braunii is actually more closely related to lilies. Hailing from Africa, D. braunii grows as an understory shrub in rainforests. This may explain why it does so well in the nutrient poor, low light conditions of most homes. 

In the wild, it can grow upwards of 5 feet tall. In captivity, however, it rarely exceeds 3 feet.. While most people grow theirs in a container of water and pebbles, D. braunii can do equally as well, if not better in potting mix.

Photo Credit: Benoit Giroux

Further Reading: [1]

The Traveler's Palm

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This nifty looking tree is commonly referred to as the traveler's palm (Ravenala madagascariensis). In reality, it is not a palm at all but rather a close cousin of the bird of paradise plants (Strelitziaceae). It is endemic to Madagascar and the only member of its genus. Even more fascinating is its relationship with another uniquely Madagascan group - the lemurs. But first we must ask, what's in a name?

The name "traveler's palm" has two likely explanations. The first has to do with the orientation of that giant fan of leaves. The tree is said to align its photosynthetic fan in an east-west orientation, which can serve as a crude compass, allowing weary travelers to orient themselves. I found no data to support this. The other possibility comes from the fact that this tree collects a lot of water in its nooks and crannies. Each of its hollow leaf bases can hold upwards of a quart of rain water! Get to it quick, though, because these water stores soon stagnate.

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Flowers are produced between the axils of the leaves and closely resemble those of its bird of paradise cousins. Closer observation will reveal that they are nonetheless unique. For starters, they are large and contained within stout green bracts. Also, they are considerably less showy than the rest of the family. They don't produce any strong odors but they do fill up with copious amounts of sucrose-rich nectar. Finally, the flowers remain closed, even when mature and are amazingly sturdy structures. It may seem odd for a plant to guard its flowers so tightly until you consider how they are pollinated.

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It seems fitting that an endemic plant like the traveler's palm would enter into a pollination syndrome with another group of Madagascar endemics. As it turns out, lemurs seem to be the preferred pollinators of this species. Though black lemurs, white fronted lemurs, and greater dwarf lemurs have been recorded visiting these blooms, it appears that the black-and-white ruffed lemur manages a bulk of the pollination services for this plant.

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Watching the lemurs feed, one quickly understands why the flowers are so stout. Lemurs force open the blooms to get at the nectar inside. The long muzzles of the black-and-white ruffed lemur seem especially suited for accessing the energy-rich nectar within. The flowers themselves seem primed for such activity as well. The enclosed anthers are held under great tension. When a lemur pries apart the petals, the anthers spring forward and dust its muzzle with pollen. Using both its hands and feet, the lemur must wedge its face down into the nectar chamber in order to take a sip. In doing so, it inevitably comes into contact with the stigma. Thus, pollination is achieved. Once fertilized, the traveler's palm produces seeds that are covered in beautiful blue arils.

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All in all, this is one unique plant. Though its not the only plant to utilize lemurs as pollinators, it is nonetheless one of the more remarkable examples. Its stunning appearance has made it into something of a horticultural celebrity and one can usually find the traveler's palm growing in larger botanical gardens around the world. Though the traveler's palm itself is not endangered, its lemur pollinators certainly are. As I have said time and again, plants do not operate in a vacuum. To save a species, one must consider the entirety of its habitat. This is why land conservation is so vitally important. Support a land conservancy today!

Photo Credits: [1] [2]

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

 

The Other Balsaminaceae

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Have you heard of Hydrocera triflora? I hadn't until just recently. To my surprise, Hydocera is one of only two genera that make up the family Balsaminaceae. What's more, it is a monotypic genus, with this lovely species being the single representative. There is no question that H. triflora has been completely overshadowed by its cousins, the Impatiens. In fact, literature on this species is quite scant across the board.

The first question you may be asking is what differentiates Hydrocera from the Impatiens? The differences are rather subtle. I don't know if I would have considered this plant unique enough to warrant its own genus, however, closer botanical observations tell a more nuanced story. The biggest differences between Hydrocera and Impatiens has to do with flower and fruit morphology.

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For starters, the flowers of Hydrocera consist of a full compliment of 5 sepals and 5 petals. The petals themselves are all free from one another. Contrast this with Impatiens, whose flowers mostly consist of 3 sepals and 4 petals that are fused into pairs. The second major difference lies in the fruits. Many of us will be familiar with the explosive capsules of the various Impatiens species, each of which contains many seeds. Hydrocera on the other hand, produces berries that contain 5 seeds. Such vastly different developmental pathways in reproductive structures appear to be enough to warrant the taxonomic separation between the two genera.

The next question one might asking is why are Impatiens so diverse while Hydrocera contains only a single species? This is anyone's guess, really, but there has been at least a few hypotheses put forward that sound plausible. One has to do with habitat preference. Impatiens are largely plants of upland forests and montane environments. Such habitats may offer more potential for diversification due to high heterogeneity in resources and lots of potential for isolation of various populations. Contrast this with the habitat of H. triflora. Though it occurs throughout a wide swath of lowland Asia and India, it is semi-aquatic and these types of habitats may be more restrictive for diversification.

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Another possibility has to do with seed dispersal. As mentioned above, Impatiens produce lots of seeds per capsule and, with their explosive habit, can disperse them over relatively large distances. Contrast this with Hydrocera. When the berries mature, they fall into the water and sink. They remain submerged until rot or various aquatic organisms eat away at the fleshy coating. Once the seeds have been freed, air sacs cause them to float on the currents until seasonal drying brings them back into contact with the mud. Though this is certainly an effective method for dispersal, the lower seed production rate coupled with being at the mercy of the currents means that Hydrocera is probably considerably less likely to find itself in new habitats.

Again, this is largely speculation at this point. We simply don't know enough about this oddball of the balsam world to make any serious conclusions. Luckily H. triflora is not a species under immediate threat. It seems to do quite well throughout its range, frequently occurring in flooded ditches and rice patties. Still, such stories underlie the importance of fostering and funding organism-focused research.

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

Further Reading: [1] [2]