California Bumblebee Decline Linked to Feral Honeybees

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Worldwide, pollinators are having a rough go of it. Humans have altered the landscape to such a degree that many species simply can't keep up. The proverbial poster child for pollinator issues is the honeybee (Apis mellifera). As a result, countless native pollinators get the short shrift when it comes to media attention. This isn't good because outside of intense industrial agriculture, native pollinators make up the bulk of pollination services. Similarly, honeybee fandom often overshadows any potential negative effects these introduced insects might be having on native pollinators.

Long term scientific investigations are starting to paint a more nuanced picture of the impact introduced honeybees are having on native ecosystems. For instance, research based out of California is finding that honeybees are playing a big role in the decline of native bumblebee populations. What's more, these negative impacts are only made worse in the light of climate change.

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For over 15 years, ecologist Dr. Diane Thompson has been studying bumblebee populations in central California. At no point during those early years did any of the bumblebee species she focuses on show signs of decline. In fact, they were quite common. Then, around the year 2000, feral honeybees started to establish themselves in the area. Honeybee colonies were becoming more and more numerous each and every year and that is when she started noticing changes in bumblebee behavior and numbers.

You see, honeybees are extremely successful foragers. They are generalists, which means they can visit a wide variety of flower types. As a result, they are extremely good at competing for floral resources compared to native bumblebees. Her results show that increases in the number of honeybee colonies caused not only a reduction in foraging among the native bumblebees, they also caused a reduction in bumblebee colony success. The native bumblebees simply weren't raising as many young as they were before honeybees entered the system.

Decreased rainfall cause a decline in flower densities of Scrophularia californica, a key resource for native bumblebees in this system.

Decreased rainfall cause a decline in flower densities of Scrophularia californica, a key resource for native bumblebees in this system.

Climate change is only making things worse. As drought years become not only more severe but also more intense, the amount of flowers available during the growing season also declines. With fewer flowers on the landscape, bumblebees and honeybees are forced into closer proximity for foraging and the clear winner in most foraging disputes are the tenacious honeybees. As such, bumblebees are chased off the already diminishing floral displays. By 2014, Dr. Thompson had quantified a significant decline in native bumblebee populations as a result.

It would be all too convenient to say that this research represents an isolated case. It does not. More and more research is finding that honeybees frequently out-compete native pollinators for resources such as food and nesting sites. Such effects are especially pronounced in rapidly changing ecosystems. Although honeybees are here to stay, it is important that we realize the impacts that these feral insects are having on our native ecosystems and begin to better appreciate and facilitate the services provided by our native pollinators. 

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

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

Are Algae Plants?

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I was nibbling on some nori the other day when a thought suddenly hit me. I don't know squat about algae. I know it comes in many shapes, sizes, and colors. I know it is that stuff that we used to throw at each other on the beach. I know that it photosynthesizes. That's about it. What are algae? Are they even plants?

The shortest answer I can give you is "it depends." The term algae is a bit nebulous in and of itself. In Latin, the word "alga" simply means "seaweed." Algae are paraphyletic, meaning they do not share a recent common ancestor with one another. In fact, without specification, algae may refer to entirely different kingdoms of life including Plantae (which is often divided in the broad sense, Archaeplastida and the narrow sense, Viridiplantae), Chromista, Protista, or Bacteria.

Caulerpa racemosa, a beautiful green algae.

Caulerpa racemosa, a beautiful green algae.

Taxonomy being what it is, these groupings may differ depending on who you ask. The point I am trying to make here is that algae are quite diverse from an evolutionary standpoint. Even calling them seaweed is a bit misleading as many different species of algae can be found in fresh water as well as growing on land.

Cyanobacteria are photosynthetic bacteria, not plants.

Cyanobacteria are photosynthetic bacteria, not plants.

Take for instance what is referred to as cyanobacteria. Known commonly as blue-green algae, colonies of these photosynthetic bacteria represent some of the earliest evidence of life in the fossil record. Remains of colonial blue-green algae have been found in rocks dating back more than 4 billion years. As a whole, these types of fossils represent nearly 7/8th of the history of life on this planet! However, they are considered bacteria, not plants.

Diatoms (Chromista)

Diatoms (Chromista)

Diatoms (Chromista) are another enormously important group. The single celled, photosynthetic organisms are encased in beautiful glass shells that make up entire layers of geologic strata. They comprise a majority of the phytoplankton in the world's oceans and are important indicators of climate. However, they belong to their own kingdom of life - Chromista or the brown algae.

To bring it back to what constitutes true plants, there is one group of algae that really started it all. It is widely believed that land plants share a close evolutionary history with a branch of green algae known as the stoneworts (order Charales). These aquatic, multicellular algae superficially resemble plants with their stalked appearance and radial leaflets.

A nice example of a stonewort (Chara braunii).

A nice example of a stonewort (Chara braunii).

It is likely that land plants evolved from a Chara-like ancestor that may have resembling modern day hornworts that lived in shallow freshwater inlets. Estimates of when this happen go back as far as 500 million years before present. Unfortunately, fossil evidence is sparse for this sort of thing and mostly comes in the form of fossilized spores and molecular clock calculations.

Porphyra umbilicalis  - One of the many species of red algae frequently referred to as nori.

Porphyra umbilicalis  - One of the many species of red algae frequently referred to as nori.

Now, to bring it back to what started me down this road in the first place. Nori is made from algae in the genus Porphyra, which is a type of Rhodophyta or red algae. Together with Chlorophyta (the green algae), they make up some of the most familiar groups of algae. They have also been the source of a lot of taxonomic debate. Recent phylogenetic analyses place the red algae as a sister group to all other plants starting with green algae. However, some authors prefer to take a broader look at the tree and thus lump red algae in a member of the plant kingdom. So, depending on the particular paper I am reading, the nori I am currently digesting may or may not be considered a plant in the strictest sense of the word. That being said, the lines are a bit blurry and frankly I don't really care as long as it tastes good.

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

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

 

How a Giant Parasitic Orchid Makes a Living

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Imagine a giant vine with no leaves and no chlorophyll scrambling over decaying wood and branches of a warm tropical forest. As remarkable as that may seem, that is exactly what Erythrorchis altissima is. With stems that can grow to upwards of 10 meters in length, this bizarre orchid from tropical Asia is the largest mycoheterotrophic plant known to science.

Mycoheterotrophs are plants that obtain all of their energy needs by parasitizing fungi. As you can probably imagine, this is an extremely indirect way for a plant to make a living. In most instances, this means the parasitic plants are stealing nutrients from the fungi that were obtained via a partnership with photosynthetic plants in the area. In other words, mycoheterotrophic plants are indirectly stealing from photosynthetic plants.

In the case of E. altissima, this begs the question of where does all of the carbon needed to build a surprising amount of plant come from? Is it parasitizing the mycorrhizal network associated with its photosynthetic neighbors or is it up to something else? These are exactly the sorts of questions a team from Saga University in Japan wanted to answer.

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All orchids require fungal partners for germination and survival. That is one of the main reasons why orchids can be so finicky about where they will grow. Without the fungi, especially in the early years of growth, you simply don't have orchids. The first step in figuring out how this massive parasitic orchid makes its living was to identify what types of fungi it partners with. To do this, the team took root samples and isolated the fungi living within.

By looking at their DNA, the team was able to identify 37 unique fungal taxa associated with this species. Most surprising was that a majority of those fungi were not considered mycorrhizal (though at least one mycorrhizal species was identified). Instead, the vast majority of the fungi associated with with this orchid are involved in wood decay.

Stems climbing on fallen dead wood (a) or on standing living trees (b). A thick and densely branched root clump (c) and thin and elongate roots (d) [Source]

Stems climbing on fallen dead wood (a) or on standing living trees (b). A thick and densely branched root clump (c) and thin and elongate roots (d) [Source]

To ensure that these wood decay fungi weren't simply partnering with adult plants, the team decided to test whether or not the wood decay fungi were able to induce germination of E. altissima seeds. In vitro germination trials revealed that not only do these fungi induce seed germination in this orchid, they also fuel the early growth stages of the plant. Further tests also revealed that all of the carbon and nitrogen needs of E. altissima are met by these wood decay fungi.

These results are amazing. It shows that the largest mycoheterotrophic plant we know of lives entirely off of a generalized group of fungi responsible for the breakdown of wood. By parasitizing these fungi, the orchid has gained access to one of the largest pools of carbon (and other nutrients) without having to give anything back in return. It is no wonder then that this orchid is able to reach such epic proportions without having to do any photosynthesizing of its own. What an incredible world we live in!

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Photo Credits: [1] [2]

Further Reading: [1]

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 start 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]

Rein In Those Seeds

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Plants living on islands face a bit of a conundrum. In order to get to said islands, the ancestors of those plants had to exhibit extreme seed or spore dispersal strategies. However, if plants are to persist after arriving to an island, long-distance dispersal becomes rather risky. In the case of oceanic islands, seeds or spores that travel too far end up in the water. As such, we often observe an evolutionary reduction in dispersal ability for island residents. 

Islands, however, are not always surrounded by water. You can have "islands" on land as well. The easiest example for most to picture would be the alpine zone of a mountain. Species adapted to these high-elevation habitats find it hard to compete with species native to low-elevation habitats and are therefore stuck on these "islands in the sky." Less obvious are islands created by a specific soil type. 

Take, for instance, gypseous soils. Such soils are the result of large amounts of gypsum deposits at or near the soil surface. Gypseous soils are found in large quantities throughout parts of western North America, North and South Africa, western Asia, Australia, and eastern Spain. They are largely the result of a massive climatic shift that occurred during the Eocene, some 50 million years ago. 

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Massive mountain building events during that time were causing a large reductions in atmospheric CO2 concentrations. The removal of this greenhouse gas via chemical weathering caused a gradual decline in average temperatures around the world. Earth was also becoming a much drier place and throughout the areas mentioned above, hyper-saline lakes began to dry up. As they did, copious amount of minerals, including gypsum, were left behind. 

These mineral-rich soils differ from the surrounding soils in that they contain a lot of salts. Salt makes life incredibly difficult for most terrestrial plants. Life finds a way, however, and a handful of plant species inevitably adapted to these mineral-rich soils, becoming specialists in the process. They are so specialized on these types of soils that they simply cannot compete with other plant species when growing in more "normal" soils. 

Essentially, these gypseous soils function like soil or edaphic islands. Plants specialized in growing there really don't have the option to disperse far and wide. They have to rein it in or risk extirpation. For a group of plants growing in gypseous soils in western North America, this equates to changes in seed morphology. 

Mentzelia is a genus of flowering plants in the family Loasaceae. There are somewhere around 60 to 70 different species, ranging from annuals to perennials, and forbs to shrubs (they are often referred to as blazing stars but since that would lead to too much confusion with Liatris, I will continue to refer to them as Mentzelia).

For most species in this genus, seed dispersal is accomplished by wind. Plants growing on "normal" soils produce seeds with a distinct wing surrounding the seed. A decent breeze will dislodge them from their capsule, causing them blow around. With any luck some of those seeds will land in a suitable spot fer germination, far from their parents. Such is not the case for all Mentzelia though. When researchers took a closer look at species that have specialized on gypseous soils, they found something quite intriguing. 

Mentzelia phylogeny showing reduction in seed wings.

Mentzelia phylogeny showing reduction in seed wings.

The wings surrounding the seeds of gypseous Mentzelia were either extremely reduced in size or had disappeared altogether. Just as it makes no sense for a plant living on an oceanic island to disperse its seeds far out into the ocean, it too makes no sense for gypseous Mentzelia to disperse their seeds into soils in which they cannot compete. It is thought that limited dispersal may help reinforce the types of habitat specialization that we see in species like these Mentzelia. The next question that must be answered is whether or not such specialization and limited dispersal comes at the cost of genetic diversity. More work will be needed to understand such dynamics. 

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

Further Reading: [1] [2]

 

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/

Hydatellaceae: The Other Basal Angiosperms

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Though rather obscure to most of the world, the genus Trithuria has enjoyed somewhat of a celebrity status in recent years. A paper published in 2007 lifted this tiny group of minuscule aquatic plants out of their spot in Poales and granted them a place among the basal angiosperm lineage Nymphaeales. This was a huge move for such little plants. 

The genus Trithuria contains 12 species, the majority of which reside in Australia, however, two species, T. inconspicua and T. konkanensis, are native to New Zealand and India. They are all aquatic herbs and their diminutive size and inconspicuous appearance make them easy to miss. For quite some time these odd plants were considered to be a group of highly reduced monocots. Their original placement was in the family Centrolepidaceae. All of that changed in 2007.

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Close inspection of Trithuria DNA told a much different story. These were not highly reduced monocots after all. Instead, multiple analyses revealed that Trithuria were actually members of the basal angiosperm lineage Nymphaeales. Together with the water lilies (Nymphaeaceae) and the fanworts (Cabombaceae), these plants are living representatives of some of the early days in flowering plant evolution. 

Of course, DNA analysis cannot stand on its own. The results of the new phylogeny had to be corroborated with anatomical evidence. Indeed, closer inspection of the anatomy of Trithuria revealed that these plants are truly distinct from members of Poales based on a series of features including furrowed pollen grains, inverted ovules, and abundant starchy seed storage tissues. Taken together, all of these lines of evidence warranted the construction of a new family - Hydatellaceae.

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The 12 species of Trithuria are rather similar in their habits. Many live a largely submerged aquatic lifestyle in shallow estuarine habitats. As you may have guessed, individual plants look like tiny grass-like rosettes. Their small flower size has lent to some of their taxonomic confusion over the years. What was once thought of as individual flowers were revealed to be clusters or heads of highly reduced individual flowers. 

Reproduction for these plants seems like a tricky affair. Some have speculated that water plays a role but close inspections of at least one species revealed that very little pollen transfer takes place in this way. Wind is probably the most common way in which pollen from one plant finds its way to another, however, the reduced size of these flowers and their annual nature means there isn't much time and pollen to go around. It is likely that most of the 12 species of Trithuria are self-pollinated. This is probably quite useful considering the unpredictable nature of their aquatic habitats. It doesn't take much for these tiny aquatic herbs to establish new populations. In total, Trithuria stands as living proof that big things often come in small packages. 

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

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

 

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 quite astonishing. Salvinia are not flowering plants. They are ferns! 

The genus Salvinia is quite 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 is comprised of 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 quite shocked to learn this and to be honest, it makes me appreciate these odd little ferns even more. Its on these 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 these types of habitats. Without something moving them around, 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 floods 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 quite a 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]

 

How Trees Fight Disease

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Plants do not have immune systems like animals. Instead, they have evolved an entirely different way of dealing with infections. In trees, this process is known as the "compartmentalization of decay in trees" or "CODIT." CODIT is a fascinating process and many of us will recognize its physical manifestations.

In order to understand CODIT, one must know a little something about how trees grow. Trees have an amazing ability to generate new cells. However, they do not have the ability to repair damage. Instead, trees respond to disease and injury  by walling it off from their living tissues. This involves three distinct processes. The first of these has to do with minimizing the spread of damage. Trees accomplish this by strengthening the walls between cells. Essentially this begins the process of isolating whatever may be harming the living tissues.

This is done via chemical means. In the living sapwood, it is the result of changes in chemical environment within each cell. In heartwood, enzymatic changes work on the structure of the already deceased cells. Though the process is still poorly understood, these chemical changes are surprisingly similar to the process of tanning leather. Compounds like tannic and gallic acids are created, which protect tissues from further decay. They also result in a discoloration of the surrounding wood. 

The second step in the CODIT process involves the construction of new walls around the damaged area. This is where the real compartmentalization process begins. The cambium layer changes the types of cells it produces around the area so that it blocks that compartment off from the surrounding vascular tissues. These new cells also exhibit highly altered metabolisms so that they begin to produce even more compounds that help resist and hopefully stave off the spread of whatever microbes may be causing the injury. Many of the defects we see in wood products are the result of these changes.

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The third response the tree undergoes is to keep growing. New tissues grow around the infected compartment and, if the tree is healthy enough, will outpace further infection. You see, whether its bacteria, fungi, or a virus, microbes need living tissues to survive. By walling off the affected area and pumping it full of compounds that kill living tissues, the tree essentially cuts off the food supply to the disease-causing organism. Only if the tree is weakened will the infection outpace its ability to cope.

Of course, CODIT is not 100% effective. Many a tree falls victim to disease. If a tree is not killed outright, it can face years or even decades of repeated infection. This is why we see wounds on trees like perennial cankers. Even if the tree is able to successfully fight these repeat infections over a series of years, the buildup of scar tissues can effectively girdle the tree if they are severe enough.

CODIT is a well appreciated phenomenon. It has set the foundation for better tree management, especially as it relates to pruning. It is even helping us develop better controls against deadly invasive pathogens. Still, many of the underlying processes involved in this response are poorly understood. This is an area begging for deeper understanding.

Photo Credits: kaydubsthehikingscientist & Alex Shigo

Further Reading: [1]

Meet The Ghostworts

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I love parasitic plants and I love liverworts. Imagine my excitement then when I learned that there are at least two species of parasitic liverworts! These bizarre little plants are currently the only parasitic non-vascular plants known to science. 

The first description of a ghostwort dates back to 1919. Although no description of habitat was given, the account describes a set of liverwort thalli containing no chlorophyll and whose cells were full of mycorrhizal fungi. They were assigned to the genus Aneura and that was that. Further descriptions of this plant would not be made for more than a decade.

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Proper attention was not given to this group until the 1930's. More plants started turning up among the humus and mosses of forests and wetlands throughout Finland, Sweden, and Scotland. A more thorough workover of specimens was made and the plants were moved into their own genus, Cryptothallus, which accurately captured their subterranean habit. They were given the name Cryptothallus mirabilis.

Another species of Cryptothallus was discovered in Costa Rica in 1977. It was named Cryptothallus hirsutus. Only one other collection of these species was made and it remains the lesser known of the two species. It is interesting to note the disparity between their ranges, with C. mirabilis inhabiting northern portions of Europe, and C. hirsutus only known from those two collections in Central America. Regardless, these odd liverworts have received a bit more attention in recent years.

It seems that the ghostworts manage to capture the attention of anyone who looks hard enough. For instance, a handful of attempts have been made to cultivate ghostworts in a controlled lab setting. Originally, plants were grown exposed to varying levels of light but try as the may, researchers were never able to coax the plants into producing chlorophyll. It would appear that these tiny liverworts are in fact some sort of parasite.

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Proper evidence of their parasitic lifestyle was finally demonstrated 2003. Researchers were able to grow C. mirabilis in specialized observation chambers in order to understand what is going on under the soil. As it turns out, those numerous mycorrhizal connections mentioned in the original description are the key to survival for the ghostworts. The team showed that the ghostwort tricks fungi in the genus Tulasnella into forming mycorrhizal connections with its cells. These fungi also happen to be hooked up to a vast network of pine and birch tree roots.

By tricking the fungi, into an association, the ghostworts are able to steal carbohydrates that the fungi gain from the surrounding trees. Like all mycoheterotrophs, the ghostworts are essentially indirect parasites of photosynthetic plants. Their small size and relative rarity on the landscape likely helps these plants go unnoticed by the fungi but much more work needs to be done to better understand such dynamics.

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In 2008, phylogenetic attention was paid to the ghostworts in order to better understand where they fit on the liverwort branch of the tree. As it turns out, Cryptothallus appears to be nestled quite comfortably within the genus Aneura. Because of this, the authors suggest disposing of the genus Cryptothallus altogether. Outside of simply placing this species back in its originally described genus, it affiliation with Aneura is quite interesting from an evolutionary standpoint.

Other liverworts in the genus Aneura are also known to form mycorrhizal relationships with Tulasnella. Unlike the ghostworts, however, these liverworts are fully capable of photosynthesis. Because these intimate fungal relationships were already in place before the ghostworts began evolving towards a fully parasitic lifestyle, it suggests that the saprophytic nature of Tulasnella fungi may have actually facilitated this jump. 

The cryptic nature of the ghostworts has left many a botanist wanting. Their subterranean habit makes them incredibly hard to find. Who knows what secrets this group still holds. Future discoveries could very well add more species to the mix or, at the very least, greatly expand the known range of the other two.

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

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]

 

This Isn't Even My Final Form! A Pothos Story

Pothos might be one of the most widely cultivated plants in modern history. These vining aroids are so common that I don't think I can name a single person in my life that hasn't had one in their house at some point or another. Renowned for their hardy disposition and ability to handle extremely low light conditions, they have become famous the world over. They are so common that it is all too easy to forget that they have a wild origin. What's more, few of us ever get to see a mature specimen. The plants living in our homes and offices are mere juveniles, struggling to hang on as they search for a canopy that isn't there.

Trying to find information on the progenitors of these ubiquitous houseplants can be a bit confusing. To do so, one must figure out which species they are talking about. Without a proper scientific name, it is nearly impossible to know which plant to refer to. Common names aside, pothos have also undergone a lot of taxonomic revisions since their introduction to the scientific community. Also, what was thought to be a single species is actually a couple.

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To start with, the plants you have growing in your home are no longer considered Pothos. The genus Pothos seemed to be a dumping ground for a lot of nondescript aroid vines throughout the last century. Many species were placed there until proper materials were thoroughly scrutinized. Today, what we know as a "Pothos" has been moved into the genus Epipremnum. This revision did not put all controversies to rest, however, as the morphological changes these plants go through as they age can make things quite tricky.

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As I mentioned, the plants we keep in our homes are still in their juvenile form. Like all plants, these vines start out small. When they find a solid structure in a decent location, they make their bid for the canopy. Up in a tree in reach of life giving sunlight, these vines really hit their stride. They quickly grow their own version of a canopy that consists of massive leaves nearing 2 feet in length! This is when these plants begin to flower. 

As is typical for the family, the inflorescence consists of a spadix covered by a leafy spathe. The spadix itself is covered in minute flowers and these are the key to properly identifying species. When pothos first made its way into the hands of botanists, all they had to go on were the small, juvenile leaves. This is why their taxonomy had been such a mess for so long. Materials obtained in 1880 were originally named Pothos aureus. It was then moved into the genus Scindapsus in 1908.

Controversy surrounding a proper generic placement continued throughout the 1900's. Then, in the early 1960's, an aroid expert was finally able to get their hands on an inflorescence. By 1964, it was established that these plants did indeed belong in the genus Epipremnum. Sadly, confusion did not end there. The plasticity in forms and colors these vines exhibit left many confusing a handful of species within the group. At various times since the late 1960's, E. aureum and E. pinnatum have been considered two forms of the same species as well as two distinct species. The latest evidence I am aware of is that these two vines are in fact distinct enough to warrant species status. 

The plant we most often encounter is E. aureum. Its long history of following humans wherever they go has led to it becoming an aggressive invader throughout many regions of the world. It is considered a noxious weed in places like Australia, Southeast Asia, India, Pakistan, and Hawai'i (just to name a few). It does so well in these places that it has been a little difficult to figure out where these plants originated. Thanks to some solid detective work, E. aureum is now believed to be native to Mo'orea Island off the west coast of French Polynesia. 

Epipremnum pinnatum is similar until you see an adult plant

Epipremnum pinnatum is similar until you see an adult plant

It is unlikely that most folks have what it takes to grow this species to its full potential in their home. They are simply too large and require ample sunlight, nutrients, and humidity to hit their stride. Nonetheless there is something to be said for the familiarity we have with these plants. They have managed to enthrall us just enough to be a fixture in so many homes, offices, and shopping centers. It has also helped them conquer far more than the tiny Pacific island on which they evolved. Becoming an invasive species always seems to have a strong human element and this aroid is the perfect example.

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

Further Reading: [1] [2] [3] 

 

Gnetum Are Neat!

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As much as I hate to admit it, when I think of gymnosperms my mind autopilots to conifers and ginkgos. I too easily forget about some of the other extant gymnosperm lineages with which we share space on this planet. Whereas one can easily pick out a conifer or a ginkgo from a lineup, some of the other gymnosperms aren't readily recognized as such. One group in particular challenges my gymnosperm search image to the extreme. I am, of course, talking about a family of gymnosperms known as Gnetaceae.

Gnetaceae is home to a single genus, Gnetum, of which there are about 40 species. They can be found growing in tropical forests throughout South America, Africa, and Southeast Asia. Gnetum essentially come in two forms, small trees and larger, scrambling vines. To most passersby, the various Gnetum species appear to be yet another tropical angiosperm with elliptical evergreen leaves. Indeed, the various species of Gnetum exhibit features that suggest a close link with flowering plants. This has led some to hypothesize that they represent a sort of living "link" between gymnosperms and angiosperms. We will get to that in a bit. First, we must taker a closer look at these odd plants.

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We will start with their leaves. They are quite strange by gymnosperm standards. Gnetum produce elliptical leaves with reticulate or web-like venation. Also, their vascular tissues contain vessel elements. Such traits are usually associated with dicotyledonous angiosperms. Characteristics such as these explain why the taxonomic position of Gnetaceae has floundered a bit over the years. What about reproduction? Surely that can help gain a better understanding of where this groups stands taxonomically.

Gnetum reproductive bits require a bit of scrutiny. They are certainly not what we would call flowers. They aren't quite cones either. The technical term for gymnosperm reproductive structures are stobili. In Gnetum, these arise from the axils of the leaves. They are strange looking structures to say the least. Male strobili are long and cylindrical. They, of course, produce pollen. They also contain infertile ovules whose function I will get to in a minute. Female strobili, on the other hand, are larger and consist of ovules enclosed in a thin tissue or integument.

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Pollination in Gnetum is largely accomplished via insects, though wind plays a significant role for some species as well. In insect pollinated species, the female strobili emit a strong odor and secret tiny beads of liquid called "pollination droplets." Pollination droplets are also secreted from the sterile ovules on the male strobili. It was observed that moths were the main visitors for at least two species of Gnetum.  The reason both sexes produce pollination droplets is to ensure that moths will visit multiple individuals in their search for food.

Following pollen transfer, even more angiosperm-like activity takes place. Some Gentum undergo a type of double fertilization that is quite unique among gymnosperms. Double fertilization is largely considered a defining feature of flowering plants. It is a process by which two sperm cells unite with an egg and become the embryo and the nutritive endosperm that will fuel seedling growth. Along with its cousin Ephedra, Gnetum double fertilization also involves two sperm cells, though the end result is a bit different. Instead of forming an embryo and an endosperm, double fertilization in Gentum (and Ephedra) results in the formation of two viable zygotes and no endosperm.

Fertilized seeds gradually swell into large drupe-like structures. Integument tissues develop with the seed, covering it in a fruit-like substance that turns from green to red as it matures. As far as anyone knows, birds are the main seed dispersal agents for most Gnetum species. 

Taken together, their peculiar anatomy and intriguing pollination have led many to suggest that Gnetum are more closely allied to flowering plants than they are gymnosperms. Certainly it is easy to draw lines from one dot to another in this case but the real test lies in DNA. Are they highly derived gymnosperms or possibly a so-called missing link? 

No. Recent work by the Angiosperm Phylogeny Group found that Gnetaceae are more closely related to the family Pinaceae than they are any of the sister angiosperm lineages. Their work also revealed that, although this lineage arose some 250 million years ago, much of the diversity we see today is the result of rapid speciation events during the Oligocene and Miocene. It would appear that these derived gymnosperms are not the missing link they we once thought to be. In fact, the whole concept of an evolutionary missing link is flawed to begin with. 

Still, this should not take away from fully appreciating the bizarre nature of this family. The uniqueness of the genus Gnetum is certainly worth celebrating. They serve as a reminder of just how diverse gymnosperms once were. Today they are a mere shadow of their former glory, overshadowed by the bewildering diversity of angiosperms. If you encounter a Gnetum, take the time to appreciate it as a representative of just how strange gymnosperms can be. 

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

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

 

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] 

A Surprising Realization About Leaf Windows

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I will never forget the first time I laid eyes on a Lithops. These odd little succulents are truly marvels of evolution. The so-called "living stones" really do earn their name as most are exquisitely camouflaged to match the gravelly soils in which they grow. If bizarre color patterns weren't enough, Lithops, as well as many other succulents, live their lives almost completely buried under the soil. All one ever really sees is the very tip of their succulent leaves and the occasional flower.

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It is the tips of those leaves that make people swoon. Lithops belong to a hodgepodge mix of succulent genera and families that produce windowed leaves. Aside from their striking patterns, the tips of their leaves are made up of layers of translucent cells, which allow light to penetrate into the interior of the leaf where the actual photosynthetic machinery is housed. Their semi-translucent leaves, coupled with their nearly subterranean habit, have led to the assumption that the leaf windows allow the plants to continue photosynthesis all the while being mostly buried. Despite the popularity of this assumption, few tests had been performed to see whether or not the windows function as we think. All of that changed back in the year 2000.

As hinted at above, a variety of succulent plants have converged on a similar leaf morphology. This is where things get a bit strange. Not all plants that exhibit the leaf window trait find themselves buried in the soil. Others, such as Peperomia graveolens for example, produce the photosynthetic tissues well above the soil. Examples like this led at least some researchers to second guess the common assumption of windows increasing photosynthesis and the resulting investigations were surprising to say the least. 

Peperomia graveolens

Peperomia graveolens

A duo of researchers decided to test the assumption that leaf windows increase photosynthesis by channeling light directly to the photosynthetic machinery inside. The researchers used tape to cover the leaf windows of a variety of succulent plant species. When they compared photosynthetic rates between the two groups, not a single difference was detected. Plants who had their leaves covered photosynthesized the same amount as plants with uncovered leaves. These data were quite shocking. Because they tested this assumption across a variety of plant species, the results suggested that the function of windowed leaves isn't as straight forward as we thought. These findings raised more questions than they solved.

Subsequent experiments only served to reinforce the original findings. What's more, some even showed that plants with covered windows actually photosynthesized more than plants with uncovered windows. It seems that windowed leaves function in a completely opposite manner than the popular assumption. The key to this patterns may lie in heat exchange. When the researchers took the temperature of the interior of the leaves in each group, they found that internal leaf temperatures were significantly higher in the uncovered group and this has important implications for photosynthesis for these species.

Fenestraria rhopalophylla

Fenestraria rhopalophylla

High leaf temperatures can be extremely damaging to photosynthetic proteins. If too much light filters through, leaf temperatures can actually hit damaging levels. This is one reason that many of these plant species have adopted this bizarre semi-subterranean habit. Plants that experienced such high temperatures throughout the course of a day had permanent damage done to their photosystems. This led to a reduction of fitness over time. Such lethal temperature spikes did not happen to leaves that had been covered.

Haworthia truncata

Haworthia truncata

If you're anything like me, at this point you must be questioning the role of the leaf windows entirely. Why would they be there if they may actually hurt the plants in the long run? Well, this is where knowing something about the habitat of each species comes into play. Not all leaf windows are created equal. The patterns of their windows vary quite a bit depending on where the plants evolved. In 2012, a paper was published that looked at the patterns of Lithops leaf windows in relation to their place of origin. Not all Lithops grow in the same conditions and various species hail from regions with vastly different climates.

What the paper was able to demonstrate was that Lithops native to regions that experience more acerage annual rainfall have much larger window areas on their leaves than Lithops native to drier regions. Again, the underpinnings of this discovery nonetheless have to do with light availability. Wetter areas experience more cloud cover than drier areas so Lithops growing where its cloudy have to cope with a lot less sun than their more xeric-growing cousins. As such, having a larger window allows more diffuse light into the leaf for photosynthesis without having to worry about the damaging temperatures.

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The reverse is true for Lithops from drier climates. They have smaller leaf windows because they experience more days with direct sun. These species tended to have much smaller windows, which reduced the amount of sunlight entering the leaf. This serves to keep internal leaf temperatures within a much safer range, thus protecting the delicate proteins inside. As it turns out, leaf windows seem to represent a trade-off between photosynthesis and overheating. What's more, some window-leaved species seem to be evolving away from the light transmitting function of their cousins living in shadier conditions. If anything, this serves as a reminder that simply because something seems obvious, that doesn't mean its always true. Stay curious, my friends!

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

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

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 rather unique 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 rather 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. The 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 quite 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. This 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 sport 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]