The Gas Plant

Photo by Jörg Hempel licensed under CC BY-SA 3.0 de

Meet the gas plant, Dictamnus albus. This lovely herbaceous species is native to southern Europe, north Africa, and Asia. The gas plant is a member of the citrus family, Rutaceae, and like many members of this group, it has very showy blossoms. Its affiliation with the citrus fruits on your counter isn't the only interesting thing about this species. As the common name might suggest, this plant does something quite strange. 

During the heat of summer, parts of the gas plant exude an oily substance that smells much like the fruits of its cousin, the lemon. These oils have been known to cause contact dermatitis not unlike the sap of giant hogweed. However, this is not the strangest aspect of the gas plants oily nature. One of the properties of these oils is that they are highly volatile. So volatile in fact that they can ignite. 

Another common name for this species is burning bush (though not the one of biblical lore). If air temperatures get high enough or if someone takes a match to this plant on a hot day, the oils covering its tissues will ignite in a flash. The oils burn off so quickly that it is of no consequence to the plant. It goes on growing like nothing ever happened. If you're like me then you have one burning question after reading this - why?!

Despite how incredible this phenomenon may seem, it doesn't appear that too many people have looked into its function. Research has identified a highly flammable organic compound within the oils called isoprene. In plants, isoprenes are thought to protect against heat stress. This is bolstered by the fact that the gas plant produces these compounds during the heat of summer. 

Another possibility is that spontaneous ignition of these compounds could create small wildfires that clear the surrounding area of competition. I have not seen any evidence suggesting this. Yet another possibility is that this is simply an unrelated side effect of oil production. Since the plant is not hurt by the quick burst of flames, it simply hasn't had any reason to evolve a less flammable alternative. Evolution is funny like that. 

Still don't believe what you are reading? Check out this video:

Photo Credit: Jörg Hempel (Wikimedia Commons)

Further Reading: [1]

Lizard Helpers

Photo by Tatters ✾ licensed under CC BY-NC-ND 2.0

The beauty of Tasmania's honeybush, Richea scoparia, is equally matched by its hardiness. At home across alpine areas of this island, this stout Ericaceous shrub has to contend with cold temperatures and turbulent winds. The honeybush is superbly adapted to these conditions with its compact growth, and tough, pointy leaves. Even its flowers are primed for its environment. They emerge in dense spikes and are covered by a protective casing comprised of fused petals called a "calyptra." Such adaptations are great for protecting the plant and its valuable flowers from such brutal conditions but how does this plant manage pollination if its flowers are closed off to the rest of the world? The answer lies in a wonderful little lizard known as the snow skink (Niveoscincus microlepidotus).

The snow skink is not a pollinator. Far from it. All the snow skink wants is access to the energy rich nectar contained within the calyptra. In reality, the snow skink is a facilitator. You see, the calyptra may be very good at shielding the developing flower parts from harsh conditions, but it tends to get in the way of pollination. That is where the snow skink comes in. Attracted by the bright coloration and the nectar inside, the snow skink climbs up to the flower spike and starts eating the calyptra. In doing so, the plants reproductive structures are liberated from their protective sheath. 

Photo by Tindo2 - Tim Rudman licensed under CC BY-NC 2.0

Once removed, the flowers are visited by a wide array of insect pollinators. In fact, research shows that this is the only mechanism by which these plants can successfully outcross with their neighbors. Not only does the removal of the calyptra increase pollination for the honeybush, it also aids in seed dispersal. Experiments have shown that leaving the calyptra on resulted in no seed dispersal. The dried covering kept the seed capsules from opening. When calyptras are removed, upwards of 87% of seeds were released successfully. 

Although several lizard species have been identified as pollinators and seed dispersers, this is some of the first evidence of a reptilian pollination syndrome that doesn't actually involve a lizard in the act of pollination. It is kind of bizarre when you think about it. As if pollination wasn't strange enough in requiring a third party for sexual reproduction to occur, here is evidence of a fourth party required to facilitate the action in the first place. It may not be just snow skinks that are involved either. Evidence of birds removing the calyptra have also been documented. Whether its bird or lizard, this is nonetheless a fascinating coevolutionary relationship in response to cold alpine conditions. 

Photo Credits: [1] [2]

Further Reading: [1]

Shade Gives This Begonia the Iridescent Blues

Believe it or not, the blue iridescence of Begonia pavonina is an evolutionary adaptation to extracting the most amount of energy out of the dim light that makes it through the thick rainforest canopy above. Even more bizarre, it works thanks to an interesting property of quantum mechanics. 

Native to Malaysia, B. pavonina lives out its life in deep shade. Most of the sunlight that hits this region is absorbed by the thick canopy of trees above. As such, eking out an existence is a challenge for these understory herbs. That is where this fantastic blue iridescence comes in. To understand it better, researchers had to take a closer look at its cause. 

Inside any photosynthetic leaves resides the chloroplasts. Chloroplasts are filled with tiny stacks of membranous compartments called "thylakoids." This is where the light reactions of photosynthesis take place. Now, in most plants, these thylakoids are haphazardly distributed throughout the chloroplast. This is not the case for B. pavonina. For this species, the thylakoids are arranged in a very precise way.

It is this precision that gives the leaves their iridescent color. Their placement causes blue wavelengths of light to be reflected. This isn't a big loss for the plant as most of the blue light is absorbed by the canopy above anyway. What it does instead is quite fascinating. The stacked thylakoids act like a dense crystal. When light enters the chloroplasts of B. pavonina it is physically slowed down.

This effect is known to quantum physicists as "slow light." Whereas light traveling through a vacuum maintains a constant speed, light passing through different types of matter can actually be slowed down. By slowing light as it passes through the chloroplasts, the thylakoids are able to take advantage of what little light the leaves are able to intercept. For B. pavonina, this equates to a 10% increase in photosynthetic rates. Coupled with an increase in the absorbance of red-green light, one can understand why this is such an advantage. 

Another interesting aspect of its physiology is the fact that B. pavonina produces both "normal" and iridescent chloroplasts. It is thought that this is a form of backup for the plant. In instances where enough light actually does make it through to the forest floor, B. pavonina can use its normal chloroplasts instead. It should be noted that this is not the only case of blue iridescent leaves in the plant kingdom. Many other species including spike mosses, ferns, and even orchids exhibit this trait. Even leaves that don't appear iridescent to our eyes may be utilizing nanostructures such as those seen in B. pavonina to increase their photosynthetic efficiency in low light conditions. It is very likely that many different kinds of plants are physically manipulating light to their benefit.

Photo Credit: Michael Perry

Further Reading:

[1]

Evolving For City Life

Photo by Stefan.lefnaer licensed under CC BY-SA 4.0

Urban environments pose unique challenges to any plant. Cities are generally warmer, have significantly higher CO2 levels, and experience altered levels of disturbance and precipitation patterns than do rural areas nearby. Still, many plants have taken to these concrete jungles, popping up wherever they can eke out an existence. Although we are not reinventing ecological principals in urban areas, they nonetheless present distinct selective pressures on every living thing within their jurisdiction. Evidence now suggests that urban environments are actually shaping the evolution of at least some plant species. 

Motivated by a desire to better understand how urban conditions are influencing evolution, a team of researchers based out of the University of Minnesota decided to take a closer look at a common mustard called Virginia pepperweed (Lepidium virginicum). This hardy little annual is at home wherever disturbance occurs. As such, it can be found throughout most of North America and beyond. Because it self pollinates readily, researchers were able to quantify phenotypic differences between populations growing in dense urban centers and compare them to those growing in more rural areas.

Photo by Stefan.lefnaer licensed under CC BY-SA 4.0

They collected seeds from numerous urban and rural populations and grew them together in a greenhouse experiment. By exposing each population to the same conditions in the greenhouse, the team were able to tease out the true phenotypic differences between these populations. 

What their data revealed were distinct differences between urban and rural populations. For starters, urban plants had larger rosettes but fewer leaves. They also bolted sooner than rural plants but then exhibited a much longer period of time between bolting and flowers. Previous studies have shown that the inflorescence of related species "accounted for 55% of a plants photosynthetic activity but only 25% of water loss." Coupled with the reduction in the number of leaves, these results suggest that urban plants are maximizing photosynthesis under drier conditions. 

Another interesting difference is that urban plants produced far more seed than their rural counterparts. This very well may be due to the fact that urban plants tended to be larger. This could also be due to reduced herbivory in urban environments, though such pressures may vary from city to city. Due to the urban heat island effect, it is likely that this could be a result of more stable temperature conditions than those experienced by their rural counterparts. Taken together, these results show that there is indeed selection for traits that allow plants to not only survive but thrive in urban environments.

Photo Credit: Wikimedia Commons

Further Reading: [1]

Live-In Mites

Photo by Scott Zona licensed under CC BY-NC 2.0

Hearing the word "mite" as a gardener instantly makes me think of pests such as spider mites. This is not fair. The family to which mites belong (Acari) is highly varied and contains many beneficial species. Many mites are important predators at the micro scale. Some are fungivorous, eating potentially harmful species of fungi. Whereas this may be lost on the majority of us humans, it is certainly not lost on many species of plants. In fact, the relationship between some plants and mites is so strong that these plants go as far as to provide them with a sort of home.

Photo by Jsarratt licensed under CC BY-SA 3.0

Domatia are specialized structures that are produced by plants to house arthropods. A lot of different plant species produce domatia but not all of them are readily apparent to us. For instance, many trees and vines such as red oak (Quercus rubra), sugar maples (Acer saccharum), black cherries (Prunus serotina), and many species of grape (Vitis spp.) produce tiny domatia specifically for mites. The domatia are often small, hairy, and function as shelter for both the mites and their eggs.

By housing certain species of mites, these plants are ensuring that they have a steady supply of hunters and cleaners living on their leaves. Predatory mites are voracious hunters, keeping valuable leaves free of microscopic herbivores while frugivorous mites clean the leaves of detrimental fungi that are known to cause infections such as powdery mildew. The exchange is pretty straight forward. Mites get a home and a place to breed and the plants get some protection. Still, some plants seem to want to sweeten the relationship in a literal sense.

Some plants, specifically grape vines in the genus Vitis, also produce extrafloral nectaries on their leaves. These tiny glands secrete sugary nectar. In a paper recently published in the Annals of Botany, it was found that extrafloral nectaries enhances the efficacy of these mite domatia by enticing more mites to stick around. By adding nectar to domatia-producing leaves that did not secrete it, the researchers found that nectar increases beneficial mite densities on these leaves by 60 - 80%. This translates to an increase in fitness for these plants in the long run.

I love research like this. I had no idea that so many of my favorite and most familiar tree and vine species had entered into an evolutionary relationship with beneficial mites. This adds a whole new layer of complexity to the interactions within any given environment. It just goes to show you how much is left to be discovered in our own back yards.

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

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

On Crickets and Seed Dispersal

Photo by Vojtěch Zavadil licensed under CC BY-SA 4.0

The world of seed dispersal strategies is fascinating. Since the survival of any plant species requires that its seed find a suitable place to germinate, it is no wonder then that there are myriad ways in which plants disseminate their propagules. Probably my favorite strategies to ponder are those involving diplochory. Diplochory is a fancy way of saying that seed dispersal involves two or more dispersal agents. Probably the most obvious to us are those that utilize fruit. For example, any time a bird eats a fruit and poops out the seeds elsewhere, diplochory has happened.

Less familiar but equally as cool forms of diplochory involve insect vectors. We have discussed myrmecochory (ant dispersal) in the past as well as a unique form of dispersal in which seeds mimic animal dung and are dispersed by dung beetles. But what about other insects? Are there more forms of insect seed dispersal out there? Yes there are. In fact, a 2016 paper offers evidence of a completely overlooked form of insect seed dispersal in the rainforests of Brazil. The seed dispersers in this case are crickets.

Yes, you read that correctly - crickets. Crickets have been largely ignored as potential seed dispersers. Most are omnivores that eat everything from leaves to seeds and even other insects. One report from New Zealand showed that a large species of cricket known as the King weta can disperse viable seeds in its poop after consuming fruits. However, this is largely thought to be incidental. Despite this, few plant folk have ever considered looking at this melodic group of insects... until now. 

The team who published the paper noticed some interesting behavior between crickets and seeds of plants in the family Marantaceae. Plants in this group attach a fleshy structure to their seeds called an aril. The function of this aril is to attract potential seed dispersers. By offering up seeds from various members of the family, the research team were able to demonstrate that seed dispersal by crickets in this region is quite common. Even more astounding, they found that at least six different species of cricket were involved in removing seeds from the study area. What's more, these crickets only ate the aril, leaving the seed behind.

[SOURCE]

The question of whether this constitutes effective seed dispersal remains to be seen. Still, this research suggests some very interesting things regarding crickets as seed dispersal agents. Not only did the crickets in this study remove the same amount of seeds as ants, they also removed larger seeds and took them farther than any ant species. Since only the aril is consumed, such behavior can seriously benefit large-seeded plants. Also, whereas ant seed dispersal occurs largely during daylight hours, cricket dispersal occurs mostly at night, thus adding more resolution to the story of seed dispersal in these habitats. I am very interested to see if this sort of cricket/seed interaction happens elsewhere in the world.

Photo Credits: [1] [2]

Further Reading: [1]

Color Changing Asters

Fall is here and the asters are out in force. Their floral displays are some of the last we will see before the first fall frost takes its toll. Their beauty is something of legend and I could sit in a field and stare at them for hours. In doing so, an interesting pattern becomes apparent. Have you ever noticed that the disc flowers of the many aster species gradually turn from yellow to red? Whereas this certainly correlates with age, there must be some sort of evolutionary reason for this.

Indeed, there is. If you sat and watched as bees hurriedly dashed from plant to plant, you may notice that they seem to prefer flowers with yellow discs over those with red. The plot thickens. What about these different colored discs makes them more or less appealing to bees desperately in need of fuel? The answer is pollen.

A closer observation would reveal that yellow disks contain more pollen than those with red discs. Of course, this does relate to age. Flowers with red discs are older and have already had most of their pollen removed. In this way, the color change seems to be signaling that the older flowers are not worth visiting. Certainly the bees notice this. But why go through the trouble of keeping spent flowers? Why not speed up senescence and pour that extra energy into seed production?

Well, its all about cues. Bees being the epitome of search image foragers are more likely to visit plants with larger floral displays. By retaining these old, spent flowers, the asters are maintaining a larger sign post that ensures continued pollinator visitation and thus increases their chances of cross pollination. The bees simply learn over time to ignore the red disc flowers once they have landed. In this way, they maximize their benefit as well.

Further Reading: [1]

The Colorful Megaherbs of Sub-Antarctic New Zealand

Photo by twiddleblat licensed under CC BY-SA 2.0

There is a common morphological thread among herbaceous plants growing in the colder regions of the world. Most grow small and take on a cushion-like habit. For these species, it is all about getting sensitive tissues out of the chilling winds and into an insulated microclimate. This convergent morphology seems to have been entirely lost on a cohort of plants native to the sub-Antarctic islands of New Zealand. The aptly named "megaherbs" are characterized by their large size an the often gaudy dark coloration of their blooms. Why would an entire guild of plants growing in such cold, dreary, harsh conditions converge on a strategy that, for most plants of their size, spell certain death? 

The answer to this mystery is heat. In such a harsh environment any advantage, no matter how slight, can make a huge difference. What's more, whereas smaller neighboring species largely reproduce asexually, these bizarre behemoths seem to have sexual reproduction all to themselves. The key lies in their large size and extravagant coloration. A team of researchers looking at six different species of megaherb found that the thick, hairy leaves and dark colored flowers were able to take advantage of the rare occasions when the sun poked through the thick, grey, sub-Antarctic clouds. 

Photo by twiddleblat licensed under CC BY-SA 2.0

On average, leaf and inflorescence temperatures of these megaherbs were significantly higher than the ambient conditions. For instance, in the Campbell Island daisy (Pleurophyllum speciosum), leaf and flower temperatures were consistently 9 and 11 degrees Celsius warmer than their surroundings during periods of sunshine. Because of their large size (think surface area to volume ratio), they were able to hold on to this heat much longer than smaller plant species in the same habitat. In essence, they are creating a glasshouse effect. 

This means more than just a warm microclimate for these plants. Insects in this environment seek out these plants for warmth and shelter. In a region with such a sparse insect community, concentrating pollinators in and around your leaves means a higher chance of pollination, a win-win for both sides. As if this wasn't enough, higher temperatures can also facilitate seed production, adding yet another layer of benefit to growing large and darkly colored.  

Photo Credits: [1] [2]

Further Reading: [1]

A Digestive "On" Switch

Photo by Luiz licensed under CC BY-NC-ND 2.0

A common thread throughout the world of carnivorous plants is that all hail from nutrient poor environments. That is why they evolved carnivory in the first place, as a way of supplementing their nitrogen and phosphorous needs. For as amazing as their various adaptations are, the evolutionary histories of the world's carnivorous plants are still largely shrouded in mystery. A recent paper published in the Annals of Botany takes a closer look at what goes on inside the pitchers of the tropical pitcher plant Nepenthes alata. What they found is quite amazing.

As it turns out, N. alata seems to be able to regulate the amount of digestive enzymes within its pitchers based on prey availability. This makes a lot of sense. Since these species live in nutrient poor conditions, it would be very wasteful to continuously produce digestive fluids. Instead, the research team found that the genes responsible for the productive of digestive enzymes turn on in response to certain cues. In this case, its the presence of insect tissues, specifically chitin. The addition of insect prey coincided with a 24 to 48 hour burst in digestive enzyme production followed by a gradual decrease as the insects were digested. As interesting as this is, these were not the only findings to come out of this research.

When the researchers looked closely at what kinds of enzymes N. alata were producing, they discovered evidence in support of a long-held hypothesis regarding the evolution of carnivory in plants. The genetic pathways induced by the addition of insect chitin are nearly identical to those seen in plant defense pathways. These pathways also induced the production of a series of proteins known to play a role in plant defense reactions against microbial pathogens. What's more, many of the enzymes N. alata were producing inside their pitchers are classified as defense-related proteins. Taken together, this is strong evidence in support of the hypothesis that carnivory in plants evolved from defense reactions already in place.

This finding comes in the wake of an earlier discovery that showed similar pathways in the traps of the Venus fly trap. This is yet more evidence for the fact that evolution does not always occur via novel pathways. Instead, systems that are already in place are retooled to fit a new set of challenges.

Photo Credit: [1]

Further Reading: [1]

Cycads & Kin Selection

What is not to like about cycads? They are beautiful, they are ancient, and they have a bizarre reproductive biology. Well, we can now add kin recognition to that list. That's right, cycads can somehow discern when they are growing next to a relative and when they are growing next to a stranger. This discovery means that not only has kin selection been a feature of plants for a long time, it is probably more wide spread than we ever thought. 

Kin selection and cycads starts at the roots. Although it isn't easy to see, competition for root space is critical for most plant species. Roots are how plants obtain water and nutrients so maximizing root growth is of paramount importance for a plant. This often means taking up space before their neighbors can. That is, unless that neighbor is your sibling. Researchers set about testing this phenomenon in the lab. By using specialized growth chambers, they were able to compare how plants "behaved" when grown next to their siblings vs. unrelated individuals. What they found was quite astounding. 

Cycads growing next to their half siblings allocated significantly less energy to root growth than when they were growing next to unrelated plants. This had implications for their overall size as well. Plants growing next to siblings were significantly smaller at the end of the experiment. This may seem like a disadvantage until you consider it from the perspective of their genes. Siblings share 50% of their DNA. Since life is all about getting as many copies of your genes into out into the environment as possible, it stands to reason that competing with copies of yourself is often counter productive. That is not the case when fewer genes are shared. Plants growing next to unrelated individuals responded with increased root mass and thus increased growth. In other words, they were more competitive. 

Examples of kin selection abound in the animal kingdom. Currently, the same is not true for plants (click here for another example). What this research does is show us that we probably haven't been looking hard enough. If such cases of kin selection occur in cycads, then it stands to reason that this is an ancient phenomenon. 

Further Reading: [1] [2]

The Orchid Mantis Might Not be so Orchid After All

Here we see a juvenile orchid mantis perched atop a man-made orchid cultivar that would not be found in the wild. Photo by N. A. licensed under CC BY-NC-SA 2.0

The orchid mantis is a very popular critter these days, and rightly so. Native to southeast Asia, they are beautiful examples of how intricately the forces of natural selection can operate on a genome. The reasoning behind such mimicry is pretty apparent, right? The mantis mimics an orchid flower and thus, has easy access to unsuspecting prey.

Not so fast...

Despite its popularity as an orchid mimic, there is no evidence that this species is mimicking a specific flower. Most of the pictures you see on the internet are actually showing orchid mantids sitting atop cultivated Phalaenopsis or Dendrobium orchids that simply do not occur in the wild. Observations from the field have shown that the orchid mantis is frequently found on the flowers of Straits meadowbeauty (Melastoma polyanthum). A study done in 2013 looked at whether or not the mantids disguise offers an attractive stimulus to potential prey. Indeed, there is some evidence for UV absorption as well as convincing bilateral symmetry that is very flower-like. They also exhibit the ability to change their color to some degree depending on the background.

Orchid mantis nymphs are more brightly colored than adults. Photo by Frupus licensed under CC BY-NC 2.0

Despite our predilection for finding patterns (even when there are none) it is far more likely that this species has evolved to present a "generalized flower-like stimulus." In other words, they may simply succeed in tapping into pollinators' bias towards bright, colorful objects. We see similar strategies in non-rewarding flowering plants that simply offer a large enough stimulus that pollinators can't ignore them. The use of colored mantis models has provided some support for this idea. Manipulating the overall shape and color of these models had no effect on the number of pollinators attracted to them.

The most interesting aspect of all of this is that the most convincing (and most popular) mimicking the orchid mantis displays is during the juvenile phase. Indeed, most pictures circulating around the web of these insects are those of immature mantids. The adults tend to look rather drab, with long, brownish wing covers. However, they still maintain some aspects of the juvenile traits.

Adult orchid mantids take on a relatively drab appearance compared to their juvenile form. Photo by Philipp Psurek licensed under CC BY-SA 3.0 DE

The fact of the matter is, we still don't know very much about this species. It is speculated that the mimicry is both for protection and for hunting. As O'Hanlon (2016) put it, "The orchid mantis' predatory strategy can be interpreted as a form of 'generalized food deception' rather than 'floral mimicry'." It just goes to show you how easily popular misconceptions can spread. Until more studies are performed, the orchid mantis will continue to remain a beautiful mystery.

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

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

The Tallest Moss

Photo by Doug Beckers licensed under CC BY-SA 2.0

For all the attributes we apply to the world of bryophytes, height is usually not one of them. That is, unless you are talking about the genus Dawsonia. Within this taxonomic grouping exists the tallest mosses in the world. Topping out around 60 cm (24 inches),  Dawsonia superba enjoys heights normally reserved for vascular plants. Although this may not seem like much to those who are more familiar with robust forbs and towering trees, height is not a trait that comes easy to mosses. To find out why, we must take a look at the interior workings of bryophytes. 

Mosses as a whole are considered non-vasular. In other words, they do not have the internal plumbing that can carry water to various tissues. Coupled with the lack of a cuticle, this means that mosses can be sensitive to water loss. For many mosses, this anatomical feature relegates them to humid environments and/or a small stature. This is not the situation for the genus Dawsonia. Thanks to a curious case of convergent evolution, this genus breaks the physiological glass ceiling and reaches for the sky. 

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Photo by Salsero35 licensed under CC BY-SA 4.0

Unlike other mosses, Dawsonia have a conduction system analogous to xylem and phloem. Being convergent, however, it isn't the same thing. Instead, the xylem-like tissue of these mosses is called the "hydrome" and is made up of cells called "hydroids." The phloem-like tissue is called the "leptome" and is made up of cells called "leptoids." These structures differ from xylem and phloem in that they are not lignified. Mosses never evolved the ability to produce this organic polymer. Regardless of their chemical makeup, Dawsonia vascular tissue allows water to move greater distances within the plant.

Another major adaption found in Dawsonia has to do with the structure of the leaves. Whereas the leaves of most mosses are only a few cells thick, the leaves of Dawsonia produce special cells on their surface called "lamella." These cells are analogous to the mesophyll cells in the leaves of vascular plants. They not only function to increase surface area and CO2 uptake, they also serve to maintain a humid layer of air within the leaf, further reducing water loss. 

All of this equates to a genus of moss that has reached considerable proportions. Sure, they are easily over-topped by most vascular plant species but that is missing the point. Through convergent evolution, mosses in the genus Dawsonia have independently evolved an anatomical strategy that has allowed them to do what no other extant groups of moss have done - grow tall.

Photo by Jon Sullivan licensed under CC BY-NC 2.0

Photo Credits: Wikimedia Commons, Doug Beckers, and Jon Sullivan

Further Reading: [1]

Yeast in Lichens

Quite possibly one of the oldest symbiotic relationships on Earth has been hiding in plain sight all this time. Lichens have long been regarded as the poster child for symbiotic relationships. Certain species of fungi team up with specific algae and/or cyanobacteria in a sort of "you scratch my back and I'll scratch yours" type of relationship. In return for room and board the photosynthetic partner feeds the fungus. There are many variations on this theme which translates into the myriad shapes and colors of lichen species around the globe. For 150 years we have been operating under the assumption that there is only ever one species of fungus (in the phylum Ascomycota) for any given lichen. We were wrong. 

Originally thought to be contamination, researchers at the University of Montana and Perdue found gene expression belonging to the other major fungal phyla, Basidiomycota. The research team soon realized that they had uncovered something quite monumental. Lichens were harboring a partner we never knew existed. These newly discovered fungi are an entirely new lineage of yeast. What's more, this relationship has been documented in upwards of 52 other lichen genera worldwide! 

This discovery has led to another major breakthrough in lichen biology, their bizarre variety. The exact same species of fungus and alga can produce completely different lichens with wildly different attributes. Take the example of Bryoria torturosa and B. fremontii. They were thought to share the same partners and yet one is yellow and toxic whereas the other is brown and innocuous. Knowing what to look for, however, has revealed that their yeast partners are entirely different. The yeast is thought to be a sort of shield for the lichen, producing noxious acids that deter infections and predation. 

Almost overnight a new light has been shown on our lichen neighbors. These newly discovered partners aren't a recent evolutionary development. This trifecta likely stems back to the early days when little else lived on land. It just goes to show you how much we still do not know about our planet. It's nice to be reminded of this. 

Further Reading:

http://bit.ly/29WWZ2z 

Meeting Amborella trichopoda

When I found out I would be seeing a living Amborella, a lump formed in my throat. There I was standing in one of the tropical houses at the Atlanta Botanical Garden trying to keep my cool. No amount of patience was ample enough to quell my excitement. How was I going to react? How big were these plants? Would I see flowers? Could I touch them? What were they growing in? My curiosity was through the roof.

Naturally this sort of excitement is reserved for those of us familiar with Amborella trichopoda. This strange shrub is not something that would readily stand out against a backdrop of tropical flora. However, if life history and ecology were to be translated into outward appearances, Amborella would likely be one of the most gaudy plants on this planet. What I was about the lay eyes on is the only member of the sole genus belonging to the family Amborellaceae, which is the sole member of the order Amborellales.

Even more exciting is its position on the angiosperm family tree. As flowering plants go, Amborella is thought to be the oldest alive today. Okay, so maybe this shrub isn't the oldest flowering plant in the world. It is likely that at one time, many millions of years ago, there were more representatives of Amborellaceae growing on this planet. Until we turn up more fossil evidence it is nearly impossible to say. Still, Amborella's place in the story of flowering plant evolution is consistently located at the base.

That is not to say that this shrub is by any means primitive. I think the first thing that shocked me about these plants is just how "normal" they appear. Sans flowers, I didn't see much out of the ordinary about them. They certainly look like they belong on our timeline. Without proper training in plant anatomy and physiology, there is little one could deduce about their evolutionary position. Regardless of my ignorance on plant morphology, there is plenty to look at on Amborella.

For starters, Amborella has tracheids but no vessel elements, making its vascular system more like that of a gymnosperm than an angiosperm. Its small flowers are borne in the axils of the evergreen leaves. It has no petals, only bracts arranged into a spiral of tepals. The female flowers consist of 4 to 8 free carpels and do not produce a style. Male flowers look like nothing more than a spiral cluster of stamens borne on short filaments.

If plant anatomy isn't enough to convince you, then the genetic analyses tell a much more compelling story. DNA sequencing consistently places Amborella at the base of the flowering plant family tree. Again, this is not to say that this shrub is by any means "primitive" but rather its lineage diverged long before what we would readily recognize as a flowering plant evolved. As such, Amborella offers us a window into the early days of flowering plants. By comparing traits present in more derived angiosperms to those of Amborella, researchers are able to better understand how the most dominant group of plants found their place in this world.

Another interesting thing happened when researchers looked at the DNA of Amborella. What they found was more than just Amborella genes. Inside the mitochondrial DNA are an unprecedented amount of foreign DNA from algae, lichens and mosses. In fact, an entire chunk of DNA corresponded to an entire mitochondrial genome of a moss! Researchers now believe that this is a case of extreme horizontal gene transfer between Amborella and its neighbors both growing on and around it. Both in the wild and in cultivation, Amborella is covered in a sort of "biofilm." Whether or not such gene transfer has assisted in the conservatism of this lineage over time remains to be seen.

At this point you may be asking how this lineage has persisted for over 130 million years. For the most part, it is probably due to chance. However, there is one aspect of its ecology that really stands out in this debate and that is its geographic distribution. Amborella is endemic to Grande Terre, the main island of New Caledonia. This is a very special place for biodiversity.

New Caledonia is a small fragment of the once great super-continent Gondwana. New Caledonia, which was part of Australia at that time, broke away from Gondwana when the super-continent began to break up some 200-180 million years ago. New Caledonia then broke away from Australia some 66 million years ago and has not been connected to another land mass since. A warm, stable climate has allowed some of the most unique flora and fauna to persist for all that time. Amborella is but one of the myriad endemic plants that call New Caledonia home. For instance, 43 species of tropical conifers that grow on these small islands are found nowhere else in the world. The whole region is a refugia of a long lost world.

Being a biodiversity hot spot has not spared New Caledonia from the threats of modern man. Mining, agriculture, urbanization, and climate change are all threatening to undo much of what makes this place so unique. The loss of a species like Amborella would be a serious blow to biodiversity, conservation, and the world as whole. We cannot allow this species to exist only in cultivation. New Caledonia is one place we must desperately try to conserve. Meeting this species has left a mark on me. Being able to observe living Amborella up close and personal is something I will never forget as my chances of seeing this species in the wild are quite slim. I am so happy to know that places like the Atlanta Botanical Garden are committed to understanding and conserving this species both in the wild and in cultivation. For now Amborella is here to stay. Long may it be that way.

Further Reading:

http://bit.ly/29MuMuw

http://bit.ly/29MuML0

http://bit.ly/29ZKNJS

The Endangered Running Buffalo Clover

Endangered species come in all different shapes and sizes. Though the average person on the street can readily cite charismatic animals species such as the giant panda or the white rhino, few folks ever realize that many of the world's plants are at risk of extinction. In fact, the latest reports show that one in five plant species are in danger of disappearing forever. They aren't all charismatic species like orchids either, some of the most endangered plants are often the most ignored. They simply don't find their way into conversations about conservation. 

One prime example of such an imperiled plant is the running buffalo clover (Trifolium stoloniferum). This lovely little clover once ranged from Arkansas, through Illinois and Indiana, all the way to Ohio and West Virginia. It was a species of open disturbed areas in prairies and forests. It enjoyed rich soils and probably followed in the wake of the large herds of bison and regular fires that once shaped the countryside. Another interesting aspect of this clover's ecology is that it apparently does not fix nitrogen. It lacks the rhizobial associates that make legumes famous. 

The loss of the bison from most of its range coupled with rampant habitat destruction spelled disaster for the running buffalo clover. It was thought to be extinct for nearly a century until 1983 when a single population was discovered in West Virginia. Since then scattered populations have been found, however, these are few and far between. As such, it is now considered a federally endangered species. 

The continued survival of the running buffalo clover is completely tied to proper land management. Without a natural disturbance regime, this lovely little plant is quickly overtaken by more aggressive vegetation. Gone are the days of the roaming buffalo and natural fire regimes. 

Luckily this species was able to garnish enough attention to earn it some protection. However, for far too many plant species this is simply not the case. Until we change the kinds of conversations we are having about plants and habitat in general, we stand to lose more plant species than I care to imagine. This in turn will have rippling effects through the entire ecosystem. So, today I want you to think about the running buffalo clover as a stark reminder of just how important conservation can be. 

Photo Credit: Andrew Lane Gibson (http://bit.ly/25Sb6f1)

Further Reading:
http://1.usa.gov/1sB7oo9

Buffalonut - A Parasitic Shrub From Appalachia

I have a hard time with shrubby species. They just don't stand out to me like herbaceous plants or giant trees. As such, my identification skills for this group of medium-sized woody plants are subpar. However, every once in a while I find something that I can't let go. Usually its a species with a trait that really stands out. This is how I came to know buffalo nut (Pyrularia pubera). Its unique inflorescence was like nothing I had ever encountered before. 

There is good reason for my unfamiliarity with this species. It is largely restricted to the core of the Appalachian Mountains, although there are records of it growing on Long Island as well. Regardless, it is not a species I grew up around. The first time I saw its flowers I was stumped. I simply couldn't place it. Luckily its unique appearance made it easy to track down. I was happy with buffalo nut for the time being but I was surprised yet again when I sat down for a chat with someone who knows woody species much better than I do. 

As it turns out, buffalo nut belongs to the sandalwood family, Santalaceae. This makes it a distant cousin of the mistletoes. Like most members of this family, buffalo nut lives a parasitic lifestyle. Although it is fully capable of photosynthesis and "normal" root behavior, under natural conditions, it parasitizes the roots of other tree species. It doesn't really seem to have a preference either. Over 60 different species hailing from 31 different families have been recorded as hosts. 

When a buffalo nut seed germinates, it starts by throwing down a taproot. Once the taproot reaches a certain depth, lateral roots are sent out in search of a host. These roots "sniff out" the roots of other species by honing in on root exudates. When a suitable root is found, the buffalo nut root will tap into its host using specialized cells called haustoria. Once connected, it begins stealing water and nutrients. Buffalo nut roots have been known to travel distances of 40 feet in search of a host, which is pretty incredible if you ask me. 

It is easy to look down on parasites. Heck, they are largely maligned as free loaders. This could not be farther from the truth. Parasites are a healthy component of every ecosystem on the planet. They are a yet another player in a system that is constantly changing. What's more, the presence of parasites can actually increase biodiversity in a system by keeping certain species from becoming too dominant. Buffalo nut should not be persecuted. Instead it should be celebrated. It is yet another species that makes the Appalachian Mountain flora so unique. 

Further Reading: [1] [2]

Fern Ant Farm

Photo by Ch'ien C. Lee (www.wildborneo.com.my/photo.php?f=cld1505721.jpg)

An epiphytic lifestyle is no walk in the park. Baking sun, drying winds, and a lack of soil are the norm. As a result, epiphytic plants exhibit numerous adaptations for retaining water and obtaining nutrients. One of the most interesting adaptations to this lifestyle can be seen in plants that have struck up a relationship with ants.

An amazing example of one such relationship can be seen in a genus of epiphytic ferns called Lecanopteris. Native to Southeast Asia and New Guinea, their unique look is equally matched by their unique ecology. Using a highly modified rhizome, they are able to latch on to the branch of a tree. In species such as Lecanopteris mirabilis (pictured above), it's as if the fronds are emerging from a strange green amoeba.

However, it's whats going on underneath their strange rhizomes that makes this group so fascinating. These ferns literally grow ant farms. Chambers and middens within the amorphous rhizome entice colonies of ants to set up shop. In return for lodging, the ants provide protection. Anything looking to take a bite out of a frond must contend with an army of angry ants. Moreover, the ants provide valuable nutrients in the form of waste and other detritus.

These are by no means the only plants to have evolved a relationship of this sort. Myriad plant species utilize ants for protection, nutrient acquisition, and seed dispersal. It has even been suggested that the unique morphology of Lecanopteris spores is an adaptation for ant dispersal. Certainly one can imagine how that would come into play. Interestingly enough, this group of ferns has attracted the attention of plant enthusiasts looking for a unique plant to grow in their home. As such, you can now find many different species of Lecanopteris being cultivated for the horticultural trade.

Photo Credit: Ch'ien C. Lee (www.wildborneo.com.my/photo.php?f=cld1505721.jpg)

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

The Aposematic Gall Hypothesis

Maple eyespot gall (left) and the grape tumid gall (right)

If you spend any time around plants you will have undoubtedly come across a gall. In fact, once you know what to look for you quickly realize that galls are everywhere. They come in many different shapes and sizes and they vary as much as the species you will find them on. Galls are abnormal growths on plant tissues and their causes range from bacteria, fungi, and nematodes to insects and mites. Most of the galls we regularly encounter are caused by insects. 

You can think of galls as a type of edible nursery chamber. A female insect will lay her eggs in the tissue of the plant and chemicals released by the eggs and subsequently the developing larvae trigger abnormal tissue growth in the plant. Every detail of each gall you see is the result of the insect housed inside, which has led some authors to consider gall formation a literal extension of the insect phenotype. Without the chemicals released by the developing insects, the plant would not form such elaborate growths.

Lime nail gall (Eriophyes tiliae). Public Domain.

As mentioned, galls act as an edible nursery chamber. Not only does the developing larvae gain physical protection, they also consume the swollen plant tissues on the inside of the gall. Despite the attention galls have received in the literature, very few studies have touched on one fact of gall ecology that becomes quite obvious to the casual observer - most of them are very conspicuous.

Oak apple gall (Cynipidae). Public domain.

The shape and coloration of different kinds of gall causes them to really stand out against the background vegetation. Why would a structure meant to protect the developing insect inside be so easy to spot? A handful of interesting hypotheses have been put forth to explain this phenomenon. For starters, the chemical compounds that give many galls their distinctive coloration are the result of hijacked plant pigments such as carotenoids, anthocyanins, as well as tannins and other phenolic compounds. These are thought to protect the insect inside. This certainly plays a role, but we will come back to that in a minute.

Cynipid gall (Diplolepis polita). Photo by Dean Morley licensed under CC BY-ND 2.0

Still, one would think being so strikingly obvious would have some serious drawbacks. Predators and parasitoids alike could easily hunt down a bright red gall. Even if potential predators can't see color, the outlandish shape of many galls certainly makes them stand out. There is another hypothesis that gets right to the core of this. Simply put, it is thought that the conspicuousness of galls serves as a warning to potential predators that eating them would be a mistake. In other words, galls very well may be aposematic. 

You will be most familiar with aposematic coloring in bees and wasps. Bright colors such as red or yellow contrasted against a strikingly different colored background serve as a warning to anything that might be thinking of taking a bite. "Stay away, I will hurt you" is the gist of the message. The bright coloration and often outlandish shape of galls coupled with the defensive compounds mentioned above may be sending a signal to herbivores, predators, and parasites to stay away or risk injury or illness. Being easy to find also makes galls easier to remember and a bad experience with one gall may make a bird think twice before messing with one again. In this way, the insects inside can go unmolested until it matures. 

Obviously there are many caveats to this idea. Certainly not all galls fall under this umbrella. The researchers behind this hypothesis have outlined a series of predictions that are thought to promote the evolution of aposematism as a strategy. What's more, this hypothesis will need to be tested on many different types of galls in many different habitats with many different potential predators if it is to hold up. Still, it is an interesting idea worth investigating. One can see the potential here. 
 

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

Further Reading: [1]

The Anachronistic Kentucky Coffee Tree

Photo by Flora Urbana

To see a Kentucky coffee tree (Gymnocladus dioicus) in the wild is a rare event. Each year your chances of doing so are diminishing. This interesting and beautiful legume is quite rare, growing in small scattered populations throughout eastern and Midwestern North America. Presettlement records hint that its rarity in nature is not necessarily a recent phenomenon either. It seems that, at least since humans have been paying attention, this tree has always been scarce. 

Despite its rarity in the wild, the Kentucky coffee tree has gained a lot of popularity as a landscape tree. It is an attractive species with contorted branching and large, airy leaves. It's about this time of year when folks start wondering if they have killed the new tree they planted last fall. I often hear complaints from folks new to this species that their trees must have lost their buds over the winter. The reason for this lies in its generic name. "Gymnocladus" is Greek for "naked branch." The leaf buds are not exposed like they are in other tree species. Instead, they are imbedded within the twigs, hidden under a hairy ring of bark. Kentucky coffee tree does not leaf out until late spring, well after most other trees have broken dormancy.

In the wild, Kentucky coffee tree can be found growing on floodplains and, very occasionally, scattered through upland habitats. As such, water has been invoked as the only known dispersal agent. This is a strange mechanism to call on as nothing about this tree (other than its current habitat) suggests adaptations for water dispersal. Its seed pods are quite heavy, chock full sweet pulp, and don't float very well. What's more, the pods often remain on the tree all winter and the large seeds within require ample scarification before they will germinate. They are toxic to boot. 

Even more perplexing is just how well this species does when planted outside of floodplains. It seems equally at home growing in a yard or along the sidewalk as it does on a floodplain. Taken together, all of these clues seem to suggest that the Kentucky coffee tree is missing something. Perhaps it is missing a preferred seed disperser? 

The megafaunal dispersal syndrome has become a sexy topic in ecology. Essentially it posits that North America was once home to a bewildering array of large mammals that flourished leading up to the end of the Pleistocene. With that many large animals haunting this once wild continent, many have suggested that North American vegetation evolved to cope with and even exploit their presence. Certainly we see this happen on a smaller scale with things like birds and small mammals. We see it on a much larger scale with animals like elephants and rhinos in Africa and Asia. Could it be that when the Pleistocene megafuna went extinct in North America, the plant species they dispersed suffered a huge ecological blow? 

The limited range of species like the Kentucky coffee tree would certainly seem to suggest so. Though it is a hard theory to test, the fruits of this tree seem adapted to something much more specific than running water. The large pod, the sweet pulp, and the hard seeds would suggest that the Kentucky coffee tree requires a larger mammalian herbivore to eat, scarify, and pass its seeds. No animal native to this continent today does the trick effectively. Most animals avoid the seeds entirely, which is likely due to their toxicity. Sure, the occasional seed germinates successfully, however, based on its limited natural range, the fecundity of the Kentucky coffee tree has been diminished. 

Photo Credit: Roger Latourwww.floraurbana.blogspot.ca

Further Reading:

http://1.usa.gov/1WUB4YX

http://bit.ly/239BSbW

Three Cheers for Fungus Gnats!

Photo by Canyon Country Discovery Center licensed under CC BY-ND 2.0

Bees, butterflies, bats, and birds... Most of us are all too familiar (and thankful) for their roles as plant pollinators. However, there are some unsung heroes of this niche and one of them are the often overlooked fungus gnats.

Pollinators, for good reason, are one of the largest selective pressures on flower evolution. As flowers evolve to cater to a specific kind of pollinator, be it a bird, a bee, or even fungus gnats, we refer to it as a pollinator syndrome. I have been enchanted by the flowers of the genus Mitella ever since I stumbled across them. As you can see in the picture, they are generally saucer shaped and have snowflake-like appendages protruding from their rim. I wondered, what kind of pollinator syndrome would produce such delicate beauty?

A quick search in the literature turned up a paper from a team of botanists based out of the University of Idaho. The paper outlines work done across a wide range of genera in the Saxifragaceae family. They looked at flower morphology and, through hours of field observation, found a common theme in many species. Those with small, white, saucer-shaped flowers, such as those of Mitella pentandra, all seem to be pollinated by fungus gnats. Fungus gnats are themselves quite small and their larvae live in moist soils, feeding on fungi. As it turns out, the adults are avid pollinators of many plant species and because of this, some species, like M. pentandra, have evolved a pollinator syndrome with them.

The research team also found a strong correlation between fungus gnat flowers and habitat type. They all seemed to be tied to moist forest habitats. This is because moist forests are the only place fungus gnats can live. Plants in drier habitats rarely come into contact with fungus gnats and therefore have no selective pressures to cater to these insects.

I love it when general observations based on aesthetics lead to a deeper understanding of what is going on outside.

Photo Credit: Four Corners School of Outdoor Education (http://bit.ly/1jmNLDR)

Further Reading:
http://bit.ly/1VFiHY4