Sea Oats: Builder of Dunes & Guardian of the Coast

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Coastal habitats can be really unforgiving to life. Anything that makes a living along the coast has to be tough and they don’t come much tougher than sea oats (Uniola paniculata). This stately grass can be found growing along much of the Atlantic coast of North America as well as along the Gulf of Mexico. What’s more, its range is expanding. Not only is this grass extremely good at living on the coast, it is a major reason coastal habitats like sand dunes exist in the first place. Its presence also serves to protect coastlines from the damaging effects of storm surges. What follows is a celebration of this amazing ecosystem engineer.

Sea oats is a dominant player in coastal plant communities. Few other species can hold a candle to its ability to survive and thrive in conditions that are lethal to most other plants. The ever-present winds that blow off the ocean bring with them plenty of sand and salt spray. Sea oats takes this in strides. Not only are its tissues extremely tough, they also help prevent too much water loss in a system defined by desiccation.

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The life cycle of sea oats begins with seeds. Its all about numbers for this species and seat oats certainly produces a lot of seed. Surprisingly, many of the seeds produced are not viable. What’s more, most will never make it past the seedling stage. You see, sea oat seeds require just the right amount of burial in sand to germinate and establish successfully. Too shallow and they are either picked off by seed predators or the resulting seedlings quickly dry up. Too deep and the limited reserves within mean the seedling exhausts itself before it can ever reach the surface.

Still, enough seeds germinate from year to year that new colonies of sea oats are frequently established. Given the right amount of burial, seedlings focus much of their first few months on developing a complex, albeit shallow root system. Within two months of germination, a single sea oat can grow a root system that is as much as 10 times the size of the rest of the plant. This is because sand is not a forgiving growing medium. Sand is constantly shifting, it does not hold on to water very long, and it is usually extremely low in nutrients. By growing a large, shallow root system, sea oats are able to not only anchor themselves in place, they are also able to take advantage of what limited water and nutrients are available.

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It is also this intense root growth that makes sea oats such an important ecosystem engineer in coastal habitats. All of those roots hold on to sand extremely well. Add to that some vast mychorrhizal fungi partnerships and you have yourself a recipe for serious erosion control. The interesting thing is that as sea oats grow larger, they trap more sand. As more sand builds up around the plants, they grow even larger to avoid burial. This process snowballs until an entire dune complex develops. As the dunes stabilize, more plants are able to establish, which in turn attracts more organisms into the community. A literal ecosystem is built from sand thanks to the establishment of a single species of grass.

As sea oats mature, they will begin to produce flowers, and the process repeats itself over and over again. As mentioned above, the sea oats seeds are subject to a lot of seed predation. This means that as sea oat populations grow, more and more animals can find food in and among the dunes. So, not only do sea oats build the habitat, they also supply it with plenty of resources for organisms to utilize.

The power of sea oats does not end there. Because they are so good at controlling erosion, they help stabilize the shoreline from the punishing blow of storm surges. Dune systems, especially those of barrier islands, help reduce the amount of erosion and the momentum of wave action reaching coastal communities. Many states here in North America are starting to realize this and are now protecting sea oat populations as a result.

Sea oats, though tough, are not indestructible. We humans can do a lot of damage to these plants and the communities they create simply by walking or driving on them. Pathways from foot and vehicle traffic kill off the dune vegetation and create a path of least resistance for wind, which quickly erodes the dunes. Apart from that, development and resulting runoff also destroy sensitive dune communities, making our coastlines that much more vulnerable to the inevitable storms that threaten their very existence.

As our climate continues to change at an unprecedented rate and storms grow ever stronger, it is very important that we recognize the role important species like sea oats play in not only providing habitat, but also protecting our coastlines. Dune stabilization and restoration projects are growing in popularity as a cost effective solution to some of the threats facing coastal communities. Among the many techniques for restoring dunes is the planting of native dune building species like sea oats. If you live near or simply like to enjoy the coast, please stay off the dunes. Foot and vehicle traffic make quick work of these habitats and we simply cannot afford less of them.


Watch our short film DUNES to learn more about these incredible ecosystems.


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

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




Eelgrass Sex is Strange

Pollination may seem like a strange thing to us humans. Whereas we only require two of us to accomplish reproduction, plants have to utilize a third party. The most familiar cases include insects like bees and butterflies. Unique examples include birds, bats, and even lizards. Many plants forego the need of an animal and instead rely on wind to broadcast copious amounts of pollen into the air in hopes that it will randomly bump into a receptive female organ.

This has worked very well for terrestrial plants but what about their aquatic relatives? Water proves to be quite an obstacle for the methods mentioned above. Some species get around this by thrusting their flowers above the surface but others don't bother. One genus in particular has evolved a truly novel way of achieving sexual reproduction without having to leave its aquatic environment in any way.

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Meet the Vallisnerias. Commonly referred to as tape or eelgrasses, this genus of aquatic plants has been made famous the world over by their use in the aquarium trade. In the wild they grow submerged with their long, grass-like leaves dancing up into the water column. Where they are native, eelgrasses function as an important component of aquatic ecology. Everything from fish and crustaceans all the way up to manatees utilize tape grass beds for both food and shelter. Eelgrasses stabilize stream beds and shorelines and even act as water filters.

All this is quite nice but, to me, the most interesting aspect of Vallisneria ecology is their reproductive strategy. Whereas they will reproduce vegetatively by throwing out runners, it is their method of sexual reproduction that boggles the mind. Vallisneria are dioecious, meaning individual plants produce either male or female flowers. The female flowers are borne on long stalks that reach up to the water surface. Once there they stop growing and start waiting. Because of their positioning, water tension causes a slight depression around the flowers at the surface. The depression resembles a little dimple with a tiny white flower in the center.

A female  Vallisneria  flower

A female Vallisneria flower

Male  Vallisneria  flowers floating on the water surface.

Male Vallisneria flowers floating on the water surface.

Male flowers are very different. Much smaller than the female flowers, a single inflorescence can contain thousands of individual male organs. As they mature underwater, the male flowers break off from the inflorescence and float to the surface. Similar to wind pollinated terrestrial plants, Vallisneria use water currents to disperse their pollen. Once at the surface, the tiny male flowers float around like little pollen-filled rafts.

If a male flower floats near the dimple created by a female flower, it will slide down into the funnel-like depression where it will contact with the female flowers. This is how pollination is achieved. Once pollinated, hormonal changes signal the stem of the female flower to begin to coil up like a spring, drawing the developing seeds safely underwater where they will mature. Eventually hundreds of seeds are released into the water currents.

After pollination, the stem of the female flower coils up, drawing the ripening ovaries safely underwater.

After pollination, the stem of the female flower coils up, drawing the ripening ovaries safely underwater.

The Vallisneria are incredible aquatic plants. Their bizarre reproductive strategy has ensured that these plants never really have to leave the water. The fact that they can also reproduce vegetatively means that many species are very successful plants. In fact, some species have become noxious invasive weeds where they have been introduced far outside of their native range. If you own these plants in any way, do take the necessary measures to ensure that they never have the chance to become invasive.

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

Further Reading: [1]

Path Rush

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Path rush (Juncus tenuis) is one of those plants that has really benefited from human expansion. Originally native to North America, it can now be found in numerous countries around the globe. It owes much of its success to both its ability to tolerate lots of disturbance as well as an ingenious seed dispersal mechanism. If you like to hike, there is a good chance you have encountered path rush somewhere along the way. There is also a strong chance that you have dispersed its seeds.

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Path rush is a relatively small species, topping out around 60 cm in height. Because it frequently grows where foot traffic is heavy, plants don’t always reach such stature. Like most rushes, it has round stems and surprisingly attractive flowers, though one would need a hand lens to fully appreciate their beauty. Flowering for path rush occurs during the summer and it is thought that wind is the main pollination mechanism for this species.

The darker vegetation running along the path is all path rush!

The darker vegetation running along the path is all path rush!

Following pollination, each flower is replaced by a tiny capsule filled with tiny seeds. Each seed is covered in a substance that turns into a sticky mucilage when wet. This mucilage is how path rush manages to move around the landscape so easily. The sticky seeds glom onto pretty much everything from fur to feathers, boots to car tires. This is why you most often find path rush on, well, paths! Its sticky seeds are carried far and wide by foot traffic. It is also why you can now find path rush growing well outside of North America.

Path rush enjoying a crack in the sidewalk.

Path rush enjoying a crack in the sidewalk.

Path rush frequents more habitats than simply paths too. The key to its success is soil disturbance. Anywhere the soil has been compacted and disturbed, path rush can find its niche. With little competition from surrounding vegetation, this tiny rush can grow into impressive colonies. Even cracks in asphalt can harbor a plant or two. Aside from its ability to tolerate soil disturbance, its tough, stringy foliage is not fed on by a lot of herbivores, which gives it yet another leg up on potential competitors. All in all, this is one tough little plant.

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

Further Reading: [1] [2]



Meeting the Elusive Three Birds Orchid

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Rare but locally abundant has to be the only proper way of describing the distribution of this peculiar little orchid. I have known about the three birds orchid (Triphora trianthophoros) for some time now. I'm generally not a jealous person but I did find myself quite envious of those who have encountered it. Even with ample herbarium records I simply could not seem to locate any individuals of this species.

The best advice for finding it that I was ever given was to not go looking for it. This secretive little plant is something you almost have to stumble upon. And stumble I did. While surveying some vegetation plots that I had combed over all summer back in 2016 I noticed something new poking up. The slender red stalks had tiny green leaves and elongated flower buds at the top. I knew instantly that this could only mean one thing - I had finally found some three birds.

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Both the common and scientific name hint at the fact that these plants are often seen with three flowers. This is not a rule by any means as plants can be found with as few as one flower or as many as 10. Regardless of the amount, finding them is only part of the battle. The other challenge is to catch them in bloom.

The secretive nature of this orchid has led to some interesting tips on how to get your timing right. Some say to check a known population after the first big rain of August. Another more pervasive tip claims that one must take to the forest after nighttime temperatures take a sudden dip. Despite this entertaining advice, it would seem that you just have to be in the right place at the right time.

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What is known about the flowering habits of the three birds orchid is that populations tend to flower in unison. The buds all develop to a certain point and stop. They will sit and wait for the right conditions (whatever they might be) to arise. Once that crucial condition is hit, they rapidly bloom en masse. This is a wonderful strategy for a flowering plant that lives tucked away on the shady forest floor.

Concealed among the forest debris, one or two flowers wouldn't get much attention. Hundreds of bright white and pink flowers, however, certainly do! Juxtaposed against the shade of the forest, these little orchids almost glow like little neon signs. Despite this mass effort, it has been found that pollination rates are usually very low. Instead, this orchid most often reproduces vegetatively by budding off tiny plantlets from the main root stock. Because of this, it is not uncommon to find literally hundreds of plants of various sizes clustered together within inches of each other. This is an impressive sight to behold.... again, if you are lucky enough to find it.

Like many of its orchid cousins, this species is no stranger to the disappearing act. Because they rely so heavily on mycorrhizal fungi for their nutrient needs, exhausted plants will often go dormant under the soil for years until they gain enough energy to produce stems, leaves, and flowers again. If you come across the three birds orchid during your travels, do yourself a favor and take some time to relish the moment. It may be a long time before you ever see them again.

Further Reading: [1] [2]

A Tiny Passionflower with a Hardy Disposition

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Passionflowers barely need an introduction. Who hasn't marveled at the beautiful splendor of their intricate blossoms. Thought largely tropical in their distribution, there are a couple members of the genus Passiflora that have tackled temperate North America. My favorite of these is small and not nearly as gaudy as its cousins but that is kind of what makes me like it so much. Today, I would like to introduce you to the yellow passionflower (Passiflora lutea).

Did I mention this was a small plant? Whereas it can vine itself over surrounding vegetation very effectively, it is by no means a bulky plant. Even more incredible are its flowers. Anyone familiar with the anatomy of Passiflora flowers will be shocked to see all of that detail miniaturized into a yellow-green bloom about the size of your thumbnail. You must be quick to catch these in flower as they themselves are only open for about a day.

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As I mentioned above, Passiflora don't come any hardier than the yellow passionflower (except maybe P. incarnata). With a range that extends as far north as Pennsylvania, this lovely little vine can handle winter temperatures as low as −30 °C (-22 °F)! This has earned it the designation of the northernmost species of Passiflora. Even then, I have heard reports of people growing this hardy little plant farther north in Canada.

Pollination for this species works in much the same way as it does for the genus as a whole. The flowers require an insect large enough to contact the peculiar arrangement of anthers and stigmas. The strange yet beautiful filaments that ring the center of the bloom are collectively referred to as the corona and it is believed that these guide insects to the nectar and thus into perfect position for pollination.

A visiting passionflower bee ( Anthemurgus passiflorae )

A visiting passionflower bee (Anthemurgus passiflorae)

By far the most peculiar aspect of this plant is the relationship it has formed in part of its range with a tiny bee aptly named the passionflower bee (Anthemurgus passiflorae). Native from central Texas to North Carolina and north to Illinois, this tiny black bee is the only member of its genus. What's more, it absolutely requires the yellow passionflower for its reproduction. It feeds its larvae solely on pollen from the yellow passionflower. If that wasn't strange enough, despite its highly specific foraging habits, the diminutive size of the bee has led experts to believe that the passionflower bee contributes very little in the way of pollination for the plant.

Photo Credit: [3]

Further Reading: [1] [2]

The Pine Lily

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The pine lily (Lilium catesbaei) is one of North America’s finest species of lily. It produces the largest flowers of the genus on this continent and to see one in person is a breathtaking experience. The pine lily is endemic to the Southeastern Coastal Plain where it prefers to grow in mesic to wet flatwoods, wet prairies, and savannas. Though it enjoys a relatively wide distribution, today it rarely occurs in any abundance.

The pine lily’s rarity may be a relatively recent status change for this wonderful plant. Historical records indicate that it was once quite abundant in states like Florida. Today it occurs in scattered localities and predicting its presence from year to year has been a bit tricky. Indeed, the pine lily appears to be very picky when it comes to growing and flowering.

One aspect of its biology that might lend to its limited appearance is the fact that it can remain underground in a dormant state for years. Like other members of this genus, the pine lily emerges from a bulb. This underground storage structure is small by lily standards, which means that most pine lilies are operating on marginal stores of energy in any given year.

Some have estimated that individual bulbs can remain dormant for upwards of 5 years before the right conditions for growth flowering present themselves. Of course, such dormancy can be a nightmare for proper conservation of such a unique plant. Aside from the individual flower borne at the tip of a long, slender stem, the rest of the plant is very dainty. In fact, its flowers can be so heavy compared to the rest of the plant that some stems simply topple to the ground before they can set seed. The slender stem, small leaves, and tiny bulb equate to a small operating budget in terms of energy stores. That being said, we are starting to get a clearer picture of what pine lilies need to thrive and it all comes down to fire.

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The key to acquiring enough energy for growth and reproduction appears to be a proper amount of sunlight. Without it, plants languish. This is where fire comes in. The pine lily lives in a region of North America that historically would have burned with some frequency. Wildfires sweep through an area, burning away competing vegetation like saw palmetto (Serenoa repens) and clearing the ground of accumulated debris like sticks and leaves. By burning away the competition, fire creates open areas where delicate plants like the pine lily can eke out an existence. Indeed, research has shown that pine lilies produce more flowers and seed immediately following ground-clearing burn followed by a subsequent decline in flowering and seed set as the surrounding vegetation begins to grow back.

If a pine lily does have enough energy to flower, then one of the most stunning flowers in all of North America is presented with its face towards the sky. Its 6 large petals are brightly colored and taper down into what looks like tiny tubes. Nectar is produced within these tubes and, coupled with the bright coloration, attract numerous insect visitors.

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Not all insects are capable of successfully pollinating such a large flower. In fact, it would appear that only a couple of species take up the bulk of the pollination of this incredible plant. As far as we know, the Palamede swallowtail butterfly (Papilio palamedes) and perhaps the spicebush swallowtail (P. troilus) are the only species large enough to properly contact both anthers and stigma while feeding at the flowers. The large wingspan of these butterflies do all of the work in picking up and depositing pollen. All other insects are simply too small to adequately achieve such feats.

Though we still have a lot more to learn about the pine lily, what we do know tells us a story that is repeated for fire-dependent ecosystems throughout the world. Without regular disturbance from fire, biodiversity drops. The pine lily is not alone in this either. Its fate is intertwined with countless other unique plant species that call the coastal plains their home.

Photo Credits: [2]

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

Dodder: Parasite & Gene Thief Extraordinaire

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Apparently dodder (Cuscuta spp.) steals more than just water and nutrients from their hosts. They also steal genetic material. The movement of genetic material from the genome of one organism into the genome of another is called ‘horizontal gene transfer’ and it is surprisingly common in nature. Microbes like bacteria do it all the time and more and more we are finding examples in more complex organisms like plants (here and here). For plants, there is little evidence that the acquired genes serve many, if any, functions. This is not the case for dodder. It appears that many of the foreign genes within the dodder genome are being utilized.

Dodder are obligate parasites. They produce no chlorophyl nor any roots. Instead, they tap into their hosts vascular tissues via specialized structures on their stems called haustoria. It may be the intimacy of this parasitic connection that facilitates such high rates of gene transfer. Regardless of how they got there, the amount of genetic foreign material in the dodder genome is shocking. What’s more, much of it is functional.

Researchers have identified over 100 genes that have been added to the dodder genome via horizontal gene transfer. These genes comes from a wide variety of host lineages, including representatives from the orders Malpighiales, Caryophyllales, Fabales, Malvales, Rosales, and Brassicales. Interestingly, between 16 and 20 of these genes are thought to have been retained from the common ancestor of all living dodder species, which suggests that horizontal gene transfer occurred early on in the evolution of these parasites.

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Amazingly, the function of many of these genes appear to have been co-opted by dodder for use in their own biology. Not only were many of these genes complete copies, they were being actively transcribed by the dodder genome and are therefore functional. These include genes being used for the development of houstoria, genes being used for defense responses, and genes being used for amino acid metabolism. Researchers also found an instance of a gene that codes for micro RNAs. The micro RNAs are actually sent back into the host plant and may play a role in silencing host defense genes, allowing dodder to be a more successful parasite.

The plants themselves may not be able to select which genes get transferred. Indeed, some 42 regions of the stolen genome appear to have no function at all. Still, natural selection appears to be acting on newly acquired genes, incorporating those that serve a useful function and silencing the rest. We still don’t know exactly how this process unfolds over time, nor if gene transfer from host to parasite is largely a one-way street. Still, the evidence suggests that horizontal gene transfer is an important process in parasitic plant species and may contribute to their success through evolutionary time.

Photo Credits: [1] [2]

Further Reading: [1] [2]

Surprising Genetic Diversity in Old Growth Trees

Long-lived trees face a lot of challenges throughout their lives. Many trees can live for centuries, which can be a problem because plants cannot get up and move when conditions become unfavorable. This should equate to a slower rates of adaptation and evolution for long lived trees but that isn’t always the case. Many trees are often superbly capable of adapting to local conditions. Recently, a team of researchers from the University of British Columbia have provided some insights into the genetic mechanisms that may underpin such adaptive potential.

Genetic insights came from a species of conifer many will be familiar with - the Sitka spruce (Picea sitchensis). Researchers were interested in these trees because they live for a long time (upwards of 500 years or more) and can grow to heights of over 70 meters (230 ft.). They wanted to understand how genetic mutations work in trees like the Sitka spruce because plants are doing things a bit different than animals in that department.

Plants are modular organisms, meaning they grow by producing multiple copies of discrete units. This equates to a branching structure whose overall shape is in large part determined by environmental influences. It also means that when genetic mutations occur in one branch, they can be carried on throughout the growth of those tissues independent of what is going on throughout the rest of the plant. This means that older trees can often accumulate a surprising amount of genetic diversity throughout the entire body of the plant.

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When researchers sampled the DNA of tissues from the trunks and the needles of tall, old growth Sitka spruce, they were shocked by what they had found. From the base of the tree to the needles in the canopy, an old growth Sitka spruce can show as much as 100,000 genetic differences. That is a lot of genetic diversity for a single organism. Though plenty of other trees have been found to exhibit varying levels of genetic differences within individuals, this is one of the highest mutation rates ever found in a single eukaryotic organism. This could also explain why such long-lived organisms can survive in a changing world for their entire lives.

Now, it is important to note that many mutations are likely either neutral or potentially harmful. Also, the rates of mutation may differ depending on where you look on this tree. For instance, needles at the top of a Sitka spruce are going to be exposed to far more gene-altering UV radiation than bark tissues near the base. Still, over the lifetime of a single tree, rare beneficial mutations can and do accumulate. Imagine a scenario in which one branch mutation results in needles that are more resistant to say an insect pest. Those needles could hypothetically receive less damage than needles elsewhere on the tree. This odd form of selection is occurring within the lifetime of that tree and may even have implications for the future offspring of that tree thanks again to the quirks of how tree reproductive cells develop.

Many trees also do not have segregated germlines. What this means is that unlike animals whose reproductive cells develop from separate cell lineages than the rest of their body cells, the reproductive cells of trees develop from somatic cells, which are the same cells that form stems, leaves, and branches. This means that if a mutation occurs on the germline of a branch that eventually goes on to produce cones, these mutations can be passed on in the seeds of those cones. This obviously needs a lot of evidence to substantiate but now that a mechanism is in place, we know where and what to look for.

Photo Credits: [1] [2]

Further Reading: [1] [2]

Let's Talk About Recruitment

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For any species to be considered successful, it must replace itself generation after generation. We call this process recruitment and it is very important. After all, reproduction is arguably the most fundamental aspect of life in a Darwinian sense. For plants, this can be done either vegetatively or sexually via seeds and spores. Though vegetative reproduction is a fundamental process for many plants around the globe, seed or spore germination is arguably the most important. To truly understand what a plant needs, we have to understand its germination requirements.

Recruitment is a considerable limiting factor for plant populations. In fact, it is the first major bottleneck plants must pass through. It is estimated that a majority of plant mortality occurs during the germination and seedling stages. However, not all plants are equal in this way. Some plants are considered seed or propagule limited whereas others are habitat limited.

If a plant is seed limited, it means that its ability to expand its population or colonize new habitats its limited by the ability of seeds (or spores) to make it to a new location. Once there, nature takes its course and germination occurs with little impediment. If a plant is habitat limited, however, things get a bit more tricky. For habitat limited plants, simply getting seeds to a new location is not enough. Some other aspect of the environment (soil moisture, texture, temperature, disturbance, etc.) limit successful germination. Only when the right conditions are present can habitat limited plants germinate and begin to grow.

Habitat limitation is probably the most common limit to plant establishment. Simply put, not all plants will be successful everywhere. Even the successful growth and persistence of adult plants can be poor predictors of seedling success. Many plants can live for decades or even centuries and the conditions that were present when they germinated may have long since changed. Even the presence of the adults themselves can make a site unsuitable for germination. Think of all of those fire adapted species out there that require the entire community to burn before their seeds will ever germinate.

In reality, it is likely that most plants are habitat limited to some degree. These are not binary categories after all, rather they are aligned along a spectrum of possibilities. The fact that most plants don’t completely take over an area once seeds or spores arrive is proof of the myriad limits to plant establishment. As such, recruitment limitation is extremely important to study. It can make a huge difference in the context of conservation and restoration. Even the successful establishment of adult plants is no guarantee that seedlings stand a chance. Without successful recruitment, all you have left is a nice garden that is doomed to run its course. By understanding the limits to plant recruitment, we can do much more than just improve on our ability to protect and bolster plant populations, we can also gain insights into why so many plants remain rare on the landscape and so few ever rise to dominance.

Photo Credits: [1]

Further Reading: [1] [2]

There's Metal in Them Thar Trees!

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Whereas most plants can take up metals from their environment on some level, there are a handful of plants species on this planet that are surprisingly good at it. We call these plants “hyperaccumulators,” and the levels of heavy metals in their tissues would be fatal to most organisms. It may seem strange that plants would willingly accumulate toxic levels of metal in their tissues until you consider both where these plants live and why they may be doing it.

Generally speaking, hyperaccumulators hail from regions of the world rich in metalliferous soils such as serpentine. These soils are difficult for plants to live in because of their naturally high metal content. The plants that do grow in metalliferous soils are often very restricted in their distribution and either cannot grow anywhere else or get out-competed in less toxic soils. Hyperaccumulators have been found to take up a variety of metals including nickel, zinc, cadmium, and many others. Some do this to such a degree that it actually changes the color of their sap.

Pycnandra acuminata  (top) is so good at taking up nickle from the soil in which it grows that its sap its blue-green in color (bottom).

Pycnandra acuminata (top) is so good at taking up nickle from the soil in which it grows that its sap its blue-green in color (bottom).

One of the most famous examples of a hyperaccumulator species is a tree endemic to the island of New Caledonia called Pycnandra acuminata. New Caledonia is a hot spot for metalliferous soils so finding such a tree there is not terribly surprising. What is surprising is just how much metal this tree accumulates. One study found that its blue-green sap contains upwards of 25% nickel. A similar example can be seen in a different species of tree known to science as Phyllanthus balgooyi, which is native to Borneo. Not only is this tree strange thanks to the fact that its leaves are not leaves at all, but rather flattened photosynthetic stems, but it is also a hyperaccumulator of nickel. Recent work suggests that its sap can contain upwards of 16% nickel, which also gives it a distinctive blue-green hue.

Again, there are several examples of plants that do this. It is by no means restricted to just nickel nor the islands of New Caledonia and Borneo. That is not to say its a common trait either. Despite its occurrence across different plant lineages, hyperaccumulation is still quite rare. To date, it is estimated that only about 0.2% of all angiosperms are capable of this feat. Also, it appears to be most common in tropical regions of the world. What is most amazing is that it doesn’t appear to be limited by the amount of metal in the soil. Researchers have found that many hyperaccumulators are able to maintain high levels of metal in their tissues across a wide range of soil metal concentrations. How they deal with this biologically is a topic for another post but the question remains, why concentrate toxic levels of heavy metals in your tissues?

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Phyllanthus balgooyi  (top) also takes up so much nickle from its environment that its sap is blue-green in color (bottom).

Phyllanthus balgooyi (top) also takes up so much nickle from its environment that its sap is blue-green in color (bottom).

The answer is likely defense. Whereas the high concentrations of heavy metals in their tissues are not toxic to the plants themselves, they are certainly toxic to anything that may want to eat them. One way that hyperaccumulation can work as a defense mechanism is by deterring herbivores outright. Insects and other herbivores may be able to detect heavy metals within the tissues and will actively avoid feeding on those plants. If no other options are available, then eating such plants can straight up harm herbivores. One study found that locusts feeding on tissues containing high levels of heavy metals exhibited significant reductions in growth and development.

There is still a lot to learn about hyperaccumulation in plants. How this trait evolves, why we see it in some lineages and not others, and how plants are able to tolerate toxic levels of heavy metals are but a few of the questions that scientists are actively working on answering. One exciting avenue of research is understanding how some of these plants can be used to clean soils polluted by human activities such as mining. They call the process “phytomining” and it involves planting certain hyperaccumulators in polluted soils, allowing them to absorb metals, and then removing that biomass, taking all of the accumulated metals along with it. Certainly this needs a lot more work before it can be used effectively.

We need to act fast, however, as so many botanical hyperaccumulators are under threat of extinction. Because so many of these plants grow on restricted soil types in remote corners of the world, they are at great risk from habitat destruction. Places like New Caledonia are being strip mined at an unsustainable rate to get at the very metals that these plants have evolved to tolerate. If something is not done to protect these unique places and the flora they support, there is no telling what Earth stands to lose. This is yet another reason why we must support land conservation at all costs!

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

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

The Round Leaved Orchid

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In the northern temperate regions of North America, late June marks the beginning of what I like to call orchid season. If you're lucky you may stumble across one of these rare beauties in full bloom. Their diversity in shape and size are mainly a result of the intricate evolutionary relationships they have formed with their pollinators. I spend much of my time botanizing trying to locate and photograph these botanical curiosities and any time I get to meet a new species is a very special time indeed. 

Take the round leaved orchid (Platanthera orbiculata) for example. For years I have only known this species as two round leaves that are slightly reminiscent of the phaleanopsis orchids you see for sale in nurseries and grocery stores. The leaves can be quite large too. With their glossy appearance, they are the easiest way to locate this plant.

When conditions are right and the plants have enough stored energy they will begin to flower. Rising from the middle of the pair of leaves is a decent sized inflorescence loaded with greenish white flowers. The flowers are interesting structures. Not particularly colorful, they have a long white lip and considerable green nectar spurs. There are said to be two varieties of this species, each being characterized by the length of the nectar spur. Unlike many orchids that offer no reward to pollinators, P. orbiculata produces nectar. The flowers are pollinated by noctuid moths, which is probably why they are white in color. Whereas most lepidopteran pollinated orchid attach their pollinia to the proboscis of the butterfly or moth, P. orbiculata attaches its pollinia to the eyes of visiting moths. 

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If this isn't strange enough, the pollinia themselves have some of their own intriguing adaptations. Visiting moths take a certain amount of time to successfully access the nectar from the nectar spur. If the plant is to avoid wasting precious pollen on itself, then it must find a way to delay this process. The pollinia are the solution to this. When first attached to the eyes, the pollinia stick straight up. This keeps them away from the female parts of the plant as the moth feeds. Only after enough time has elapsed will the stalks of the pollinia begin to bend forward. At this point the moth will hopefully have moved on to the flowers of an unrelated individual. Pointing straight forward, they are now perfectly positioned to transfer pollen. 

Like all orchids, P. orbiculata relies on specialized mycorrhizal fungi for germination and survival. At the beginning of its life, P. orbiculata relies solely on the fungi for sustenance. Once it has enough energy to produce leaves it will repay the fungi by providing carbohydrates. However, the relationship is not over at this point. Every spring, P. orbiculata produces a new set of leaves as well as a whole new root system. The fungi supply a lot of energy for this process and if the plant is disturbed (ie. dug up by greedy poachers) or browsed upon, it is likely that it will not recover from the stress and it will die. The mycorrhizal fungi it relies on live on rotting wood so finding well rotted logs is a good place to start searching for this species. With declining populations throughout much of its range, it is important to remember to enjoy it where it grows. Leave wild orchids in the wild!

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

A Poop-Loving Moss Discovered Living on Poop-Eating Pitcher Plants

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Poop mosses are strange to say the least. They hail from the family Splachnaceae and most live out their entire (short) lives growing on poop. Needless to say, they are fascinating plants. Recently, one species of poop moss known to science as Tayloria octoblepharum was discovered growing in Borneo for the first time. As if this range expansion wasn’t exciting enough, their growing location was very surprising. Populations of this poop-loving moss were found growing in the pitchers of two species of poop-eating pitcher plants in the genus Nepenthes!

The pitcher of  Nepenthes lowii  both look and function like a toilet bowl.

The pitcher of Nepenthes lowii both look and function like a toilet bowl.

The wide pitcher mouth of  Nepenthes macrophylla  offer a nice seating area for visiting tree shrews.

The wide pitcher mouth of Nepenthes macrophylla offer a nice seating area for visiting tree shrews.

The pitchers of both Nepenthes lowii and N. macrophylla get a majority of their nutrient needs not by trapping and digesting arthropods but instead from the feces of tree shrews. They have been coined toilet pitchers as they exhibit specialized adaptations that allow them to collect feces. Tree shrews sit on the mouth of the pitcher and lap up sugary secretions from the lid. As they eat, they poop down into the pitcher, providing the plant with ample food rich in nitrogen. Digestion is a relatively slow process so much of the poop that enters the pitcher sticks around for a bit.

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During a 2013 bryophyte survey in Borneo, a small colony of poop moss was discovered growing in the pitcher of a N. lowii. This obviously fascinated botanists who quickly made the connection between the coprophagous habits of these two species. On a return trip, more poop moss was discovered growing in a N. macrophylla pitcher. This population was fertile, indicating that it was able to successfully complete its life cycle within the pitcher environment. It appears that these two toilet pitchers offer ample niche space for this tiny, poop-loving moss. If this doesn’t convince you of just how incredible and complex the botanical world is, I don’t know what will!

Pick up your very own Shrew Lew Sticker here!

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

Further Reading: [1]




Can Cultivation Save the Canary Island Lotuses?

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Growing and propagating plants is, in my opinion, one of the most important skills humanity has ever developed. That is one of the reasons why I love gardening so much. Growing a plant allows you to strike up a close relationship with that species, which provides valuable insights into its biology. In today’s human-dominated world, it can also be an important step in preventing the extinction of some plants. Such may be the case for four unique legumes native to the Canary Islands provided it is done properly.

The Canary Islands are home to an impressive collection of plants in the genus Lotus, many of which are endemic. Four of those endemic Lotus species are at serious risk of extinction. Lotus berthelotii, L. eremiticus, L. maculatus, and L. pyranthus are endemic to only a few sites on this archipelago. Based on old records, it would appear that these four were never very common components of the island flora. Despite their rarity in the wild, at least one species, L. berthelotii, has been known to science since it was first described in 1881. The other three were described within the last 40 years after noting differences among plants being grown locally as ornamentals.

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All four species look superficially similar to one another with their thin, silvery leaves and bright red to yellow flowers that do a great impression of a birds beak. The beak analogy seems apt for these flowers as evidence suggests that they are pollinated by birds. In the wild, they exhibit a creeping habit, growing over rocks and down overhangs. It is difficult to assess whether their current distributions truly reflect their ecological needs or if they are populations that are simply hanging on in sites that provide refugia from the myriad threats plaguing their survival.

None of these four Lotus species are doing well in the wild. Habitat destruction, the introduction of large herbivores like goats and cattle, as well as a change in the fire regime have seen alarming declines in their already small populations. Today, L. eremiticus and L. pyranthus are restricted to a handful of sites on the island of La Palma and L. berthelotii and L. maculatus are restricted to the island of Tenerife. In fact, L. berthelotii numbers have declined so dramatically that today it is considered nearly extinct in the wild.

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Contrast this with their numbers in captivity. Whereas cultivation of L. eremiticus and L. pyranthus is largely restricted to island residents, L. berthelotii and L. maculatus and their hybrids can be found in nurseries all over the world. Far more plants exist in captivity than in their natural habitat. This fact has not been lost on conservationists working hard to ensure these plants have a future in the wild. However, simply having plants in captivity does not mean that the Canary Island Lotus are by any means safe.

One of the biggest issues facing any organism whose numbers have declined is that of reduced genetic diversity. Before plants from captivity can be used to augment wild populations, we need to know a thing or two about their genetic makeup. Because these Lotus can readily be rooted from cuttings, it is feared that most of the plants available in the nursery trade are simply clones of only a handful of individuals. Also, because hybrids are common and cross-pollination is always a possibility, conservationists fear that the individual genomes of each species may run the risk of being diluted by other species’ DNA.

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Luckily for the Canary Island Lotus species, a fair amount of work is being done to not only protect the remaining wild plants, but also augment existing as well as establish new populations. To date, many of the remaining plants are found within the borders of protected areas of the island. Also, new areas are being identified as potential places where small populations or individuals may be hanging on, protected all this time by their inaccessibility. At the same time, each species has been seed banked and entered into cultivation programs in a handful of botanical gardens.

Still, one of the best means of ensuring these species can enjoy a continued existence in the wild is by encouraging their cultivation. Though hybrids have historically been popular with the locals, there are enough true species in cultivation that there is still reason for hope. Their ease of cultivation and propagation means that plants growing in peoples’ gardens can escape at least some of the pressures that they face in the wild. If done correctly, ex situ cultivation could offer a safe haven for these unique species until the Canary Islands can deal with the issues facing the remaining wild populations.

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

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

The Cypress-Knee Sedge

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Sedges (Carex spp.) simply do not get the attention they deserve. I am part of this problem because like so many others, I have breezed over them in vegetation surveys as “just another graminoid.” This is truly a shame because not only are sedges absolutely fascinating organisms, they are immensely important ecologically as well. I am working hard to get to know sedges better so that I too can fully appreciate their place in our ecosystems. One of the coolest specialist sedges I just recently learned about is the so-called cypress-knee sedge (Carex decomposita). For all intents and purposes, this sedge is considered something of an epiphyte!

The cypress-knee sedge has a fondness for growing on wood. Most often you will find it rooted to the buttresses and knees of bald cypress (Taxodium distichum) or the swollen trunk of a swamp tupelo (Nyssa aquatica). It can also be found growing out of rotting logs that float on the surface of the water. It is a long lived species, with individuals having records stretching back through decades of wetland plant surveys. When supplied with the conditions it likes, populations can thrive. That is not to say that it does well everywhere. In fact, it has declined quite a bit throughout its range.

Juvenile cypress-knee sedges establishing in moss along the water line of a bald cypress.

Juvenile cypress-knee sedges establishing in moss along the water line of a bald cypress.

One of the key wetland features that the cypress-knee sedge needs to survive and prosper is a stable water level. If water levels change too much, entire populations can be wiped out either by drowning or desiccation. Even before the sedge gets established, its seeds require stable water levels to even get to suitable germination sites. Each achene (fruit) comes complete with a tiny, corky area at its tip that allows the seeds to float. Floating seeds are how this species gets around. With any luck, some seeds will end up at the base of a tree or on a floating log where they can germinate and grow. If water levels fluctuate too much, the seeds simply can’t reach such locations.

Its dependence on high quality wetlands is one of the major reasons why the cypress-knee sedge has declined so much in recent decades. Aside from outright destruction of wetlands, changes in wetland hydrology can have dire consequences for its survival. One of the major issues for the cypress-knee sedge is boat traffic. Boat wakes create a lot of disturbance in the water that can literally scour away entire populations from the base of trees and logs. Another major threat are changes to upstream habitats. Any alteration to the watersheds of wetland habitats can spell disaster for the cypress-knee sedge. Alterations to creeks, streams, and rivers, as well as changes in ground water infiltration rates can severely alter the water levels in the swamps that this sedge depends on for survival.

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Closeups of the infructescence showing details of the perigynia (fruit).

Closeups of the infructescence showing details of the perigynia (fruit).

Less obvious threats also include changes in plant cover. If the wetlands in which it grows become too dense, the cypress-knee sedge quickly gets out-competed. To thrive, the cypress-knee sedge needs slightly more sunlight than a densely forested wetland can provide. In fact, some have even noted that cypress-knee sedge populations can explode after selective logging of such wetlands. Such explosions have been attributed to not only extra sunlight but also the addition of woody debris, which provides much needed germination sites. That being said, such explosions can only be maintained if woody debris is left in place and further wetland disturbances do not continue.

The plight of the cypress-knee sedge stands as a reminder of just how poorly we treat wetlands around the globe. Aside from providing valuable ecosystem services for the human environment (flood control, water filtration, etc.), wetlands are home to countless unique species. Only by treating wetlands betters and attempting to restore some of what has been lost will we ever do better by wetland species like the cypress-knee sedge. Hopefully by showcasing species like this, people will begin to feel a little more compassion towards the ecosystems on which they depend. Please consider supporting a wetland conservation and restoration initiative in your region!

Photo Credits : LDWF Natural Heritage Program [1] & Paul Marcum (Midwest Graminoides) [2] [3] [4]

Further Reading: [1] [2]


Pitcher Plants with a Taste for Salamanders?

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The thought of a carnivorous plant trapping and digesting a vertebrate may seem more like fiction than reality. Though rumors have circulated over the years that some pitcher plants have a taste for animals larger than an insect, this has been hard to prove as evidence has been notoriously lacking. That is not to say it does not happen from time to time. Small mammals have indeed been found in the pitchers of some of the larger tropical pitcher plants in the genus Nepenthes. Still, these seem more incidental than regular. However, recent observations from Canada suggest that vertebrates may actually make up a bigger part of the menu of some pitcher plants than we previously thought at least under certain circumstances.

The observations were made in Algonquin Provincial Park, Ontario. The carnivore responsible is North America’s most abundant pitcher plant - the purple pitcher plant (Sarracenia purpurea). In late summer of 2017, researchers discovered that some pitchers contained recently metamorphosed salamanders. Some of the salamanders were alive but a few others were dead and undergoing digestion. This was very exciting because despite plenty of study, there has been almost no substantiated evidence of vertebrate prey capture in the purple pitcher plant.

Subsequent surveys were done to figure out if the purple pitcher plants were indeed capturing salamanders on a regular basis or if the salamanders were one-off events. It turns out that, at least for the pitcher plants growing in this bog, salamanders may make up a considerable proportion of their prey! Researchers found that recently metamorphosed spotted salamanders were present in nearly 20% of the pitcher plants they surveyed!

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Not all of the salamanders they found were dead. Some were found in a relatively lively state, retreating down into the bottom of the pitcher whenever they were disturbed. Some of the larger dead specimens showed signs of putrefaction, which is probably because they were simply too large to be properly digested. Still, many of the dead salamanders showed signs of digestion, which suggests that the plants are in fact benefiting from salamander capture. In fact, it has been estimated that a single salamander could contribute as much nitrogen to the pitcher plant as the entire contents of three pitchers combined.

Taken together, the team found enough evidence to suggest that salamanders not only make up a portion of the pitcher plants’ diet in this bog, but also that pitcher plants are a significant source of mortality for young salamanders in this system. How the salamanders are caught is up for some debate. It could be that the salamanders are looking for a safe, wet place to hide, however, the complexity of the bog habitat means that there is no shortage of safe places for a young salamander to hide that won’t end in death.

It could also be that salamanders are attracted to all of the invertebrates that these plants capture or that salamanders are accidental victims, having fallen into the trap randomly as they explore their habitat. However, some pitchers not only contained more than one salamander, the plants position and stature within the bog means that most salamanders would have had to actively climb up and into the pitcher in order to end up inside. It very well may not be random chance after all. Certainly this will require more tests to say for sure.

What we can say for now is that within the confines of this Algonquin bog, salamanders are being trapped and digested by the purple pitcher plant. How much of this is unique to the circumstances of this particular bog and how much of this is something going on in other areas within the range of the purple pitcher plant is a subject for future research. It is possible that vertebrate prey may be more common among carnivorous plants than we ever thought!

Photo Credits: [1] [2]

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

The Dual Benefits of Smelling Like Frightened Aphids

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If you garden, you have probably dealt with aphids. These tiny sap-suckers not only drain the plant of valuable sap, they can also serve as vectors for disease. Plants must contend with the ever-present threat of aphid infestation throughout the growing season and have evolved some amazing defenses against these insects. Recently an incredible form of defense against aphids has been described in pyrethrum (Tanacetum cinerariifolium) and it involves smelling like a frightened aphid colony.

Aphids produce their own alarm pheromones when attacked. Because aphids form large, clonal colonies, these pheromones can help warn their kin of impending doom. Other aphids will also eavesdrop on these alarm signals and will avoid settling in on plants where aphids are being attacked. Aphids aren’t the only ones honing in on these scents either. Aphid predators and parasitoids will also use these compounds to locate aphid colonies. As such, these pheromones are helpful to the host plant because it can mean a reduction in aphid numbers.

An alate (winged) green peach aphid (Myzus persicae).

An alate (winged) green peach aphid (Myzus persicae).

The selection pressured imposed by aphids on plants is so strong that it appears that at least one species of pyrethrum has actually evolved a means of producing these pheromones themselves. Pyrethrum is a member of the aster family (Asteraceae) native to southern portions of Eurasia. Like all flowering plants, its flowers are the most precious organs. They are the key to getting their genes into the next generation and therefore protecting them from herbivore damage is of utmost importance.

It has been discovered that pyrethrums produce an aphid alarm pheromone called ( E )-β-farnesene or EβF for short. The pheromone is not produced in every tissue of the plant but rather it is concentrated near the inflorescence. What’s more, pheromone production is not constant throughout the duration of flowering. Researchers found that it production reaches its peak just before the inflorescence opens to reveal the flowers within.

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The production of EβF in pyrethrum appears to serve a dual function. For starters, it actually results in reduced aphid infestation during the early stages of flowering. When the initial aphid attack begins, these insects consume some of the EβF as they feed and release it as they excrete honeydew. Other aphids detect EβF within the honeydew and will actually avoid the plant, likely due to the perception that the aphids feeding there are already under attack.

That does not mean that predators are not to be found. In fact, the other benefit of producing EβF in the inflorescence is that it appears to lure in one of the most voracious aphid predators on the planet - ladybird beetles. The ladybird beetles are able to detect EβF in the air and will come from far and wide to investigate in hopes of finding a tasty aphid meal. The ladybird beetles were most frequently found on plants during the early stages of floral development, which suggests that EβF production in the floral tissues is the main attractant.

A 7-spot ladybird beetle (Coccinella septempunctata).

A 7-spot ladybird beetle (Coccinella septempunctata).

Interestingly, it has been found that constant production of EβF is less effective at deterring aphids than pulses of EβF. It is thought that just as humans can get used to certain background levels of scent, so too can aphids. If aphids are exposed to high levels of EβF for long periods of time, they simply recognize it as the safe background level and will continue to feed. This may explain why pyrethrum plants only produce EβF for a short period of time during the most crucial stages of floral development. Research like this not only improves our understanding of the myriad ways in which plants defend themselves, it also offers us new avenues for researching more natural ways of defending the plants we rely on from unwanted pests.

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

Further Reading: [1]


The Fungus-Mimicking Mouse Plant

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The mouse plant (Arisarum proboscideum) is, to me, one of the most charming aroids in existence. Its small stature and unique inflorescence are a joy to observe. It is no wonder that this species has attained a level of popularity among those of us who enjoy growing oddball plants. Its unique appearance may be reason enough to appreciate this little aroid but its pollination strategy is sure to seal the deal.

The mouse plant is native to shaded woodlands in parts of Italy and Spain. It is a spring bloomer, hitting peak flowering around April. It has earned the name “mouse plant” thanks to the long, tail-like appendage that forms at the end of the spathe. That “tail” is the only part of the inflorescence that sticks up above the arrow-shaped leaves. The rest of the structure is presented down near ground level. From its stature and position, to its color, texture, and even smell, everything about the inflorescence is geared around fungal mimicry.

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The mouse plant is pollinated by fungus gnats. However, it doesn’t offer them any rewards. Instead, it has evolved a deceptive pollination syndrome that takes advantage of a need that all living things strive to attain - reproduction. To draw fungus gnats in, the mouse plant inflorescence produces compounds that are said to smell like fungi. Lured by the scent, the insects utilize the tail-like projection of the spathe as a sort of highway that leads them to the source.

Once the fungus gnats locate the inflorescence, they are presented with something incredibly mushroom-like in color and appearance. The only opening in the protective spathe surrounding the spadix and flowers is a tiny, dark hole that opens downward towards the ground. This is akin to what a fungus-loving insect would come to expect from a tiny mushroom cap. Upon entering, the fungus gnats are greeted with the tip of the spadix, which has come to resemble the texture and microclimate of the underside of a mushroom.

Anatomy of a mouse plant inflorescence  [SOURCE]

Anatomy of a mouse plant inflorescence [SOURCE]

This is exactly what the fungus gnats are looking for. After a round of courtship and mating, the fungus gnats set to work laying eggs on the tip of the spadix. Apparently the tactile cues are so similar to that of a mushroom that the fungus gnats simply don’t realize that they are falling victim to a ruse. Upon hatching, the fungus gnat larvae will not be greeted with a mushroomy meal. Instead, they will starve and die within the wilting inflorescence. The job of the adult fungus gnats is not over at this point. To achieve pollination, the plant must trick them into contacting the flowers themselves.

Both male and female flowers are located down at the base of the structure. As you can see in the pictures, the inflorescence is two-toned - dark brown on top and translucent white on the bottom. The flowers just so happen to sit nicely within the part of the spathe that is white in coloration. In making a bid to escape post-mating, the fungus gnats crawl/fly towards the light. However, because the opening in the spathe points downward, the lighted portion of the structure is down at the bottom with the flowers.

The leaves are the best way to locate these plants.

The leaves are the best way to locate these plants.

Confused by this, the fungus gnats dive deeper into the inflorescence and that is when they come into contact with the flowers. Male and female flowers of the mouse plants mature at the exact same time. That way, if visiting fungus gnats happen to be carrying pollen from a previous encounter, they will deposit it on the female flowers and pick up pollen from the male flowers all at once. It has been noted that very few fungus gnats have ever been observed within the flower at any given time so it stands to reason that with a little extra effort, they are able to escape and with any luck (for the plant at least) will repeat the process again with neighboring individuals.

The mouse plant does not appear to be self-fertile so only pollen from unrelated individuals will successfully pollinate the female flowers. This can be a bit of an issue thanks to the fact that plants also reproduce vegetatively. Large mouse plant populations are often made up of clones of a single individual. This may be why rates of sexual reproduction in the wild are often as low as 10 - 20%. Still, it must work some of the time otherwise how would such a sophisticated form of pollination syndrome evolve in the first place.

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

Further Reading: [1] [2]

A Palm With a Unique Pollination Syndrome

I would like to introduce you to the coligallo palm (Calyptrogyne ghiesbreghtiana). The coligallo palm is a modest palm, living out its life in the understory of wet, tropical forests from Mexico to Panama. To the casual observer, this species doesn’t present much of anything that would seem out of the ordinary. That is, until it flowers. Its spike-like inflorescence is covered in fleshy white flowers that smell of garlic and as far as we know, the coligallo palm is the only palm that requires bats for pollination.

Flowering for this palm occurs year round. At first glance, the inflorescence doesn’t appear out of the ordinary but that is where close observation comes in handy. The more scrutiny they are given, the more strange they appear. As mentioned, the flowers are bright white in color and they smell strongly of garlic. Also, they are protandrous, meaning the male flowers are produced before the female flowers.

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After the male flowers have shed their pollen, there is a period of a few days in which no flowers are produced. Then, after 3 to 4 nights of no flowers, female flowers emerge, ready to receive pollen. Each flower only opens at night and does not last for more than a single evening. Protandry is an excellent strategy to avoid self-pollination. By separating male and female flowers in time, each plant can assure that its own pollen will not be deposited back onto its own stigmas. The fact that the coligallo palm flowers year-round means that there is always a receptive plant somewhere in the forest.

The oddities do not end there. Both male and female flowers are covered in a fleshy tube that must be removed for pollination to occur successfully. Removal of the tube is what actually exposes the reproductive organs and allows pollen transfer to occur. Often times, the flowers of the coligallo palm are dined upon by katydids and other insect herbivores. This does not result in pollination as they completely destroy the flower as they eat. Considering the success of this plant across its range, it stands to reason that something else must provide ample pollination services.

Two species of bat visiting coligallo palm inflorescences: A) A perching  Artibeus  bat feeding on male flowers and B) a hovering  Glossophaga  bat feeding on female flowers.

Two species of bat visiting coligallo palm inflorescences: A) A perching Artibeus bat feeding on male flowers and B) a hovering Glossophaga bat feeding on female flowers.

As it turns out, bats are that pollinator. The job of pollination is not accomplished by a single species of bat either. A few species have been observed visiting the inflorescences. Apparently the bright color and strong odor of the flowers acts as a calling card for flower-feeding bats throughout these forests. Interestingly, the feeding mechanism of each species of bat differs as well. Some bats hover at the inflorescence like hummingbirds, chewing off the fleshy tube from individual flowers as they go. Other bats prefer to perch on the inflorescence itself, crawling all over it as they eat. These different feeding behaviors actually result in different levels of pollination. Though both forms do result in seed set, perching bats appear to be the most effective pollinators of the coligallo palm.

The reason for this is due to the fact that perching bats not only spend more time on the inflorescence, their bodies come into contact with far more flowers as they feed. Hovering bats, on the other hand, only manage to contact a few flowers with their snout at a time. So, despite the variety of bats recorded visiting coligallo palms, the perching bats appear to provide the best pollination services.

A coligallo palm infructescence showing signs of ample pollination.

A coligallo palm infructescence showing signs of ample pollination.

The role of perching bats in the ecology of this palm species does not end with pollination either. It turns out, they also play a crucial role in the dispersal of certain mites that live on the palm flowers. Flower mites live on plants and consume tiny amounts of pollen and nectar. As you can imagine, their small size makes it incredibly difficult for them to find new feeding grounds. This is where perching bats come into play.

It was discovered that besides pollen, perching bats also carried considerable loads of flower mites in their fur. The mites crawl onto the bat as they visit one inflorescence and climb off when they visit another. This is called phoresy. The bats are not harmed by these hitchhikers but are essential to the mite lifecycle. Thanks to their bat transports, the mites are able to make it to new feeding grounds far away from their original location. Though little is known about these mites, it has been suggested that the mites living on the coligallo palm are unique to that species and probably feed on no other plants.

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

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




Botanical Buoys

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American featherfoil (Hottonia inflata) is a fascinating aquatic plant. It can be found in wetlands ranging from the coastal plains of Texas all the way up into Maine. Though widespread, American featherfoil is by no means common. Today I would like to introduce you to this gorgeous member of the primrose family (Primulaceae).

American featherfoil may look like a floating plant but it is not. It roots itself firmly into the soil and spends much of its early days as a vegetative stem covered in wonderful feathery leaves. It may be hard to find during this period as no part of it sticks above the water. To find it, one must look in shallow waters of ponds, ditches, and swamps that have not experienced too much disturbance. More on this in a bit.

American featherfoil lives life in the fast lane. It is what we call a winter annual. Seeds germinate in the fall and by late October, juveniles can be seen sporting a few leaves. There it will remains throughout the winter months until early spring when warming waters signal the growth phase. Such growth is rapid. So rapid, in fact, that by mid to late April, plants are beginning to flower. To successfully reproduce, however, American featherfoil must get its flowers above water.

The need to flower out of water is exactly why this plant looks like it is free floating. The flower stalks certainly do float and they do so via specialized stems, hence the specific epithet “inflata.” Each plant grows a series of large, spongy flowering stalks that are filled with air. This helps buoy the stems up above the water line. It does not float about very much as its stem and roots still anchor it firmly into place. Each inflorescence consists of a series of whorled umbels that vary in color from white to yellow, and even violet. Following pollination, seeds are released into the water where they settle into the mud and await the coming fall.

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As I mentioned above, American featherfoil appreciates wetland habitats that haven’t experienced too much disturbance. Thanks to our wanton disregard for wetlands over the last century or so, American featherfoil (along with countless other species) has seen a decline in numbers. One of the biggest hits to this species came from the trapping of beavers. It turns out, beaver ponds offer some of the most ideal conditions for American featherfoil growth. Beaver ponds are relatively shallow and the water level does not change drastically from month to month.

Historically unsustainable levels of beaver trapping coupled with dam destruction, wetland draining, and agricultural runoff has removed so much suitable habitat and with it American featherfoil as well as numerous wetland constituents. Without habitat, species cannot persist. Because of this, American featherfoil has been placed on state threatened and endangered lists throughout the entirety of its range. With the return of the beaver to much of its former range, there is hope that at least some of the habitat will again be ready for American featherfoil. Still, our relationship with wetlands remains tenuous at best and until we do more to protect and restore such important ecosystems, species like American featherfoil will continue to suffer. This is why you must support wetland protection and restoration in your region!

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

Further Reading: [1] [2]

 

Twinspurs & Their Pollinators

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Garden centers and nurseries always have something to teach me. Though I am largely a native plant gardener, the diversity of plant life offered up for sale is always a bit mind boggling. Perusing the shelves and tables of myriad cultivars and varieties, I inevitably encounter something new and interesting to investigate. That is exactly how I came to learn about the twinspurs (Diascia spp.) and their peculiar floral morphology. Far from being simply beautiful, these herbaceous plants have evolved an interesting relationship with a small group of bees.

Diascia whiteheadii

Diascia whiteheadii

The genus Diascia comprises roughly 70 species and resides in the family Scrophulariaceae. They are native to a decent chunk of southern Africa and have adapted to a range of climate conditions. Most are annuals but some have evolved a perennial habit. The reason these plants caught my eye was not the bright pinks and oranges of their petals but rather the two spurs that hang off the back of each bloom. Those spurs felt like a bit of a departure from other single-spurred flowers that I am used to so I decided to do some research. I fully expected them to be a mutation that someone had selectively bred into these plants, however, that is not the case. It turns out, those two nectar spurs are completely natural and their function in the pollination ecology of these plants is absolutely fascinating.

Diascia rigescens

Diascia rigescens

Not all Diascia produce dual spurs on each flower but a majority of them do. The spurs themselves can vary in length from species to species, which has everything to do with their specific pollinator. The inside of each spur is not filled with nectar as one might expect. Instead, the walls are lined with strange trichomes and that secrete an oily substance. It’s this oily substance that is the sole reward for visiting Diascia flowers.

Diascia megathura  (a) inflorescenc with arrows indicating spurs and (b) cross sectioned spur showing the trichomes secreting oil (Photos: G. Gerlach).

Diascia megathura (a) inflorescenc with arrows indicating spurs and (b) cross sectioned spur showing the trichomes secreting oil (Photos: G. Gerlach).

If you find yourself looking at insects in southern Africa, you may run into a genus of bees called Rediviva whose females have oddly proportioned legs. The two front legs of Rediviva females are disproportionately long compared to the rest of their legs. They look a bit strange compared to other bees but see one in action and you will quickly understand what is going on. Rediviva bees are the sole pollinators of Diascia flowers. Attracted by the bright colors, the bees alight on the flower and begin probing those two nectar spurs with each of their long front legs.

A female  Rediviva longimanus  with its long forelegs.

A female Rediviva longimanus with its long forelegs.

If you look closely at each front leg, you will notice that they are covered in specialized hairs. Those hairs mop up the oily secretions from within each spur and the bee then transfers the oils to sacs on their hind legs. What is even more amazing is that each flower seems to have entered into a relationship with either a small handful or even a single species of Rediviva bee. That is why the spur lengths differ from species to species - each one caters to the front leg length of each species of Rediviva bee. It is worth noting that at least a few species of Diascia are generalists and are visited by at least a couple different bees. Still, the specificity of this relationship appears to have led to reproductive isolation among many populations of these plants, no doubt lending to the diversity of Diascia species we see today.

Diascia  'Coral Belle'

Diascia 'Coral Belle'

The female bees do not eat the oils they collect. Instead, they take them back to their brood chambers, feed them to their developing offspring, and use what remains to line their nests. At this point it goes without saying that if Diascia were to disappear, so too would these bees. It is incredible to think of the myriad ways that plants have tricked their pollinators into giving up most, if not all of their attention to a single type of flower. Also, I love the fact that a simple trip to a garden center unlocked a whole new world of appreciation for a group of pretty, little bedding plants. It just goes to show you that plants have so much more to offer than just their beauty.

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

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