Grass Defenses

Cut grass, sword grass, ripgut? All of these names have been applied to grasses. It may seem strange to attach such sharp adjectives to grasses but run through a prairie full of Leersia oryzoides or Spartina pectinata with shorts on and you will quickly learn why. As innocuous as they may look, grasses are well defended.

What looks like the mouth of a shark is actually a blade of grass. As you can see, it is covered in microscopic, razor sharp daggers. The daggers themselves are specialized structures called "phytoliths." Grasses manufacture phytoliths from silica that they absorb from the soil. Not all species produce these daggers. Some distribute phytoliths throughout their leaves, essentially packing themselves with tiny granules of glass. Their presence is an adaptation against herbivory. 

It's not hard to imagine how effective silica daggers can be. Run your finger along the stem or leaves of one of these grasses and you are likely to draw blood. Early settlers coined the term "ripgut grass" because the bellies of horses and other livestock would get seriously lacerated from running through it. Whereas this defense is rather straight forward, the other types of phytoliths are a little more subtle in their effectiveness. 

Silica is tough and chewing on leaves chock full of it can do a real number on your teeth. That is the main reason why the teeth of many grass grazers alive today grow continuously. If their teeth were like ours, the phytoliths within the blades of grass would wear them down to useless nubs. In fact, the evolution of phytoliths in grass is thought to have ushered in a new age of grazing mammals via the extinction of those that could not cope with these microscopic defenses. 

It's not just about teeth either. Insects feeding on blades of grass may be able to get past the phytoliths without an issue but the story changes once it makes it to the gut. Silica particles have been shown to interfere with digestion. Caterpillars feeding on grasses containing high amounts of silica in their leaves had decreased levels of digestion efficiency, which resulted in reduced growth rates. Unlike other plants, grasses can handle certain amounts of grazing because their growth tips are located beneath the soil rather than near the tips. As such, they can afford to gradually weaken the effectiveness of their predators. 

I have gained a new appreciation for grasses since moving to the prairies. This diverse order of plants has shaped the world we see today in a very big way. Because they don't have showy flowers, grasses are often overlooked as nothing more than turf. In reality, they are fascinating organisms supremely adapted to what the environment throws at them. One could only wish to be as hardy as a grass. 

Photo Credits: [1] [2]

Further Reading: [1] [2] 

A Recently Discovered Species From Brazil Plants Its Own Seeds

Life on the ground is tough in the rainforest. There is ample competition and extremely fast rates of decomposition. Anything that can give a plant an advantage, however slight, can mean the difference between death and survival. For a recently discovered plant, this means planting its own seeds.

Spigelia genuflexa was first described in 2011. It was found in northeastern Brazil in an area known as Bahia. It is a small plant, maxing out around 20 cm in height. In actuality, two growth forms have been recognized, a tall form, which produces flowers at heights of 10-20 cm, and a short form that produces flowers at heights of about 1 cm. It has been placed in the family Loganiaceae, making it a distant cousin of the North American Indian pink. It blooms during the rainy season, throwing up a couple of small white and pink flowers. At this point, no pollinators have been identified and morphological evidence would suggest it most often self fertilizes. Overall it is an adorable little plant.

The coolest aspect of this new species is how it manages seed dispersal. S. genuflexa exhibits an interesting form of reproduction called "geocarpy." In other words, this diminutive species plants its own seeds. After fertilization, the flowering stems start to bend towards the ground. In the tall form, the ripe fruits are deposited on the soil surface. The small form does something a bit different. It doesn't stop once it touches the ground. The stem continues to push the fruits down into the soil. This behavior was only discovered after the plant had been collected. Back in the lab, the researchers noticed the flowering stems ducking down under the moss they were growing in. By doing this, the parent plants are helping their precious seeds avoid predation and the myriad other threats to seed survival, thus giving them a head start on germination.

Photo Credit: Alex Popovkin

Further Reading: [1]

 

A Carnivorous Plant and its Bug

Carnivory and symbiosis are two topics within the field of botany that are endlessly fascinating. Because they are static entities, plant evolution has gone through some very interesting pathways for survival. Recently, a group of plants found only on the southern tip of Africa have shone a light on yet another interesting plant/insect relationship that is unlike any other yet known to science.

The genus Roridula contains two species that, for all intents and purposes, look like carnivorous plants. They closely resemble sundews in having leaves packed full of sticky hairs that ensnare hapless insects. However, they are neither closely related to sundews nor do they have any sort of digestive enzyme for breaking down their insect victims. Why then would these plants go through the trouble of producing glandular traps? There must be some adaptive benefit to make up for the cost of production. A closer look at these plants revealed that indeed there is.

Living on Roridula plants are tiny capsid bugs that are covered in a special waxy substance that keeps them from getting stuck in the sticky traps. The bugs move about the sticky leaves, looking for trapped insects. When the insects are found, the capsid bugs impale them with their proboscis and suck them dry. As the capsid bugs feed, their droppings end up littering the Roridula leaves. This is how Roridula gets the added nutrients it needs to survive. Although the plants are not capable of actively digesting the full insects, they are capable of absorbing the components of the capsid bug feces. They are literally getting a little bit of fertilizer every time a capsid bug goes to the bathroom. By offering the capsid bugs a place to live and plenty of free, immobilized prey, the plant is able to get nitrogen-rich meals in return!

Photo Credit: Alex Lomas, CARNIVORASLAND, and Darwiniana

Further Reading:
http://aob.oxfordjournals.org/content/95/5/757

Rediscovery Brings a Small Plant Back from Extinction

De-extinction is an exciting premise. Whereas the topic largely rests in the minds of hopeful scientists and Jurassic Park dreamers, occasionally a species is brought out of the extinction bin and ushered back into reality. This is a rare occurrence indeed but one worth celebrating. We don't get many second chances after all. The recent rediscovery of a small species of buckwheat affectionately called the Mount Diablo buckwheat (Eriogonum truncatum), offers us one such second chance. 

Discovered in 1862 on Mount Diablo, a rugged peak located just east of San Francisco, this tiny annual wouldn't readily catch the eye of most passers by. Despite its size, the Mount Diablo buckwheat is quite unique as it is endemic to this single mountain. Despite its special status, this tiny little plant was declared extinct in 1936. The cause of this extinction was the introduction of non-native grasses that now carpet the open areas that once fostered this delicate little plant. 

Everything changed for the Mount Diablo buckwheat in 2005. A graduate student working on a floristic survey of this region found something suspicious. He didn't believe it at first but further investigation revealed that he had rediscovered the Mount Diablo buckwheat. It was a small population, numbering only about 20 plants. Seeds were collected and cultivated from this single remaining population. Attempts to restore viable populations of the Mount Diablo buckwheat were meager at best. Only a small handful of plants established themselves. Still, at that time it seemed that this species was saved from extinction, albeit only marginally.

The situation drastically changed for the Mount Diablo buckwheat in May of 2016. Two botanists spotted a patch of plants giving off a pink hue. Closer inspection and lots of deliberation revealed this to be the largest population of Mount Diablo buckwheat in existence. Estimated at nearly 1.8 million individuals, this population spans nearly half an acre. Somehow they managed to escape being choked out by invasive grasses. This find is an astronomical boost for a species thought to be extinct for nearly 70 years. Again, floral surveys were to thank.

So, the question remains, how did this plant go undetected for all those years? I don't think there is a simple answer to this but a lot of it probably has to do with its lifestyle. Annuals can be tricky. We often think of them as hardy plants that boom and bust in a single season. In reality, annuals can be quite sensitive. Instead of toughing out harsh years like perennials do, annuals sit in wait as seeds until more favorable conditions come along. They can wait months, years, or even decades. It could be that the Mount Diablo buckwheat existed as a dormant seed bank for much of that time. Another factor could be its appearance. It is not a large plant by any means. Also, by the standards of your average botanizer, its definite not "knock your socks off showy." Unless you knew what you were looking for you might easily pass it over. 

Regardless of what it has been doing all this time, it is a wonderful thing that more plants have been found. It is by no means out of the woods as far as extinctions go but this is a major step forward in assuring that this species will be around for our children's children to enjoy. Threats still loom. Invasive plants are always a concern and the very fact that it is extremely rare opens it up to a lot of unwanted attention by hikers and botanizers alike. It would be all too easy to love this species to death. 

The story of the Mount Diablo buckwheat does something else for conservation. It highlights the importance of continued floristic surveys. Often scoffed at by academics and scientific journals alike, floristic surveys are far from the antiquated exercises some folks make them out to be. They serve a very important purpose. Without floristic surveys, this little buckwheat may have teetered off into oblivion without anyone ever noticing. 

Photo Credit: Holly Forbes   

Further Reading:

[1] [2]

Cycads and 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 an unrelated individual. What's more, this discovery means that kin selection in plants is not only ancient, 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. Half 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 no 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. The same is not true for plants (click here for another example). What this research does, however, is show us that we probably haven't been looking hard enough. Although extant cycad species are not those that once shared the environment with dinosaurs, the lineage to which they belong is nonetheless quite old. If such cases of kin selection occur in cycads, then it stands to reason that this is an ancient phenomenon. 

Further Reading:

http://bit.ly/2cmxp4i

http://bit.ly/2cA8jSL

The Largest Single Flower in the World

To find some of the largest flowers in the world, one must find themselves hiking through the the humid jungles of southeast Asia. From there you must be lucky enough to stumble across the flowers of a genus known scientifically as Rafflesia. It contains roughly 28 species spattered about various tropical islands. If you are very lucky, you might even find Rafflesia arnoldii. Producing flowers that are over 3 feet (1 m) in diameter and weighing as much as 24 pounds (11 kg), it produces the largest individual flower on the planet. 

Even more bizarre, these plants are entirely parasitic. They belong to a specialized group called holoparasites. These plants produce no stems, no leaves, nor any true roots. Their entire existence depends on a group of vines related to North America's grapes. Except for flowering, individual Rafflesia exist entirely as a network of mycelium-like cells inside the tissues of their vine hosts.


For a long time, the taxonomic status of this plant was highly debated but recent DNA evidence puts it in the order Malpighiales. From there, things get a little funny. One recent analysis suggested that Rafflesia belonged in the family Euphorbiaceae, however, it most likely warrants its own family - Rafflesiaceae.

So, why produce such large flowers? Well, existing solely within a vine makes it hard to establish a large population in any given area. This makes for a difficult situation in the pollinator department. Somehow plants must increase the odds that any given pollinator will visit multiple unrelated individuals of that particular species. By growing very large and and producing a lot of "stink" (this plant is also referred to as the corpse plant), Rafflesia make sure that pollinators will come from far and wide to investigate, thus increasing their chances of cross pollinating. How this plant goes about seed dispersal, however, remains a mystery.

Most interesting of all, it has been discovered that there is some amount of horizontal gene transfer going on between Rafflesia and its host. Basically, Rafflesia obtains strands of DNA from the vine and uses them in its own genetic code. It is believed this incurs some fitness benefit to Rafflesia but more research is needed to figure out why this may be happening. 

Sadly, many species within this family may be lost before we ever get a chance to get to know them. Forests throughout this region are disappearing rapidly to make room for expanding populations and agriculture. What makes matters worse for Rafflesia is that their lifestyle makes them very hard to study. It is especially difficult to obtain accurate population estimates. As more and more forests are cleared, we could be losing countless populations of these wonderful and intriguing plants. As with large mammals, it would seem that the world's largest flower is falling victim to the unending tide of human development. 

Photo Credit: Tamara van Molken


Further Reading:

http://bit.ly/2c2ALHl

http://bit.ly/2cPMP51

http://bit.ly/2cwP7ny

On Lynx Spiders and Pitcher Plants

On the coastal plains of southeastern North America, there exists a wide variety of pitcher plant species in the genus Sarracenia. These plants are the objects of desire for photographers, botanists, ecologists, gardeners, and unfortunately poachers. Far from simply being beautiful, these carnivores are marvels of evolution, each with their own unique ecology.

Pitcher plants are most famous for capturing and digesting insect prey but their interactions with arthropods aren't always in their favor. Browse the internet long enough and you will inevitably find photographs like this one above in which a green lynx spider (Peucetia viridans) can be seen haunting the traps of a pitcher plant. Instead of becoming prey, this is a spider that uses the pitchers to hunt.

I should start by saying this is not an obligate relationship. Lynx spiders can be found hunting on a variety of plant species. Instead, they are more accurately opportunistic robbers, stealing potential meals from the pitcher plants they hunt upon. However, what this relationship lacks in specificity, it makes up for in being really interesting. Sarracenia are not passive hunters. They do not sit and wait for insects to blindly stumble into their traps. Instead, they utilize bright colors and tasty nectar to lure insects to their demise. This is exactly what the lynx spider is using to its benefit. 

The green lynx spider does not spin a web like an orb weaver. It is an ambush predator. They have keen eyesight and will quickly pounce on any insect unfortunate enough to get too close. The reason the spider itself does not become yet another meal for the pitcher plant is because they utilize their silk as an anchor. By attaching one end to the outside of the pitcher, the can safely hunt on the trap without the risk of become prey themselves. In fact, spiders hunting on traps even go as far as to retreat down into the trap if threatened.

Photo Credit: Zachary Ambrose - nccarnivores

Further Reading:

http://bit.ly/2cyXlvS

http://bit.ly/2cyWTxT

The Orchid Mantis Might Not be so Orchid After All

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. Observations from the field have shown that the orchid mantis is frequently found on the flowers of Straits rhododendron (Melastoma polyanthum). A study done in 2013 looked at whether or not the mantis' 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.

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 simply 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 mantises. The adults tend to look rather drab, with long, brownish wing covers. However, they still maintain some aspects of the juvenile traits.

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: Frupus (http://bit.ly/1dRP2Va)

Further Reading:

http://bit.ly/2c2c6EW

http://bit.ly/2bRQEFu

http://bit.ly/2c5rsqS

http://bit.ly/2cEt00r

The World's Only Parasitic Gymnosperm

When we talk about parasitic plants, 99.9% of the time we are talking about angiosperms. However, deep in the mysterious forests of New Caledonia grows the single exception to the rule. Parasitaxus usta is the only parasitic gymnosperm known to exist. The sole member of its genus, P. usta is as strange and beautiful as it is mysterious.

P. usta hails from a strange family of gymnosperms known scientifically as Podocarpaceae. Its purple coloration is absolutely stunning. A high concentration of anthocyanin pigments in the vacuoles of its cells is responsible for the purple coloration. Although this strange gymnosperm does in fact produce chloroplasts, they are quite small and the electron transport mechanisms that make photosynthesis possible no longer function.

The true nature of its parasitic lifestyle has remained quite a mystery over the last few decades. A handful of investigations have shown it to be rather unlike any other type of parasitic plant currently known. One of the most bizarre aspects of its morphology is that P. usta does not form any roots. This provided botanists the first clues that it may be a parasite. Further investigation has suggested that, similar to parasitic ericads and orchids, P. usta utilized a fungal intermediary to parasitize the roots of its only known host, another member of the Podocarpaceae family, Falcatifolium taxoides.

Transfer of carbohydrates has been shown to occur through this fungal connection, however, P. usta also seems to obtain nitrogen and water via a direct connection to its host's xylem tissues. In this way it is similar to some mistletoes. As such, it not only can maintain a very high rate of stomatal conductance and a very low water potential, it can also produce cone crops year round. To the best of my knowledge, no other parasitic plant on Earth adopts such a strange combination of strategies.

Despite its unique status, much of the ecology of P. usta remains a complete mystery. For instance, despite being a root parasite, stems of P. usta have been found sprouting from its host tree over 3 feet above the ground. This suggests that P. usta may actually be a strange type of holoparasite. Also, it is entirely unknown how this parasitic gymnosperm becomes established on its host. To date no seed dispersal mechanisms have been described, nor are the seeds sticky. Perhaps its all a matter of chance, which would explain why so few individuals have been found. At the end of the day, the fact that it occurs on a remote island in very few locations means that this bizarrely unique gymnosperm will hold on to its mysteries for many years to come.

Photo Credit: Tim Waters

Further Reading:

http://www.conifers.org/po/Parasitaxus.php

http://bit.ly/2cBUwvj

Why We Shouldn't Rag on Ragweed

Common ragweed (Ambrosia artemisiifolia), the bane of hay fever sufferers. This could quite possibly be one of the most despised plants whether people realize it or not. It is ragweed, not goldenrod, that is responsible for causing hay fever. All this is thanks to the copious amounts of pollen it wafts into the breeze. With all that being said, I could not call this In Defense of Plants if I did not come to the defense of ragweed.

Despite all the suffering it causes, ragweeds are enormously important plants ecologically. We already know they produce a lot of pollen, but that pollen is doing more than just making you stuffy and fertilizing other ragweeds. It is also feeding bees. Because it flowers so late into the season, ragweed offers up a prodigious source of protein-rich pollen for bees gearing up for fall and winter. Even before they flower, ragweed is a valuable food source for the caterpillars of many butterflies and moths including species like the wavy-lined emerald and various bird dropping moths. It's not just insects either. The seeds of ragweed are rich in fatty oils. Birds and small mammals readily consume ragweed seeds to help fatten up for the lean months to come.

Ragweed also offers us some cultural significance too. Before European settlement, ragweed is believed to have had a much narrower distribution. Palynologists use pollen taken from lake and bog sediment cores to track ancient climates and plant communities. Because ragweed produces so much pollen, it is a useful species to look for when studying core sediments. As pollen falls out of the air and settles on lakes or bogs, it eventually sinks to the bottom where it can remain buried in a rather pristine state for millennia. Palynologists have actually been able to use ragweed pollen as a way of tracking the settlement history of North America. As colonies advanced further and further, they opened up huge chunks of land, inadvertently creating ample opportunities for ragweed to expand its range. As such, ragweed pollen taken from lake cores has proven to be a pretty precise clue for studying our own history.

For as much as we despise it, ragweed thrives on the kind of disturbance that we humans are so good at creating. We are the ones to blame for our own suffering when it comes to hay fever, not the plants.

Photo Credit: Frank Mayfield

Further Reading:

http://bit.ly/2c2HpOG

http://bit.ly/2c7hx6X

http://bit.ly/2c6mtsh

http://bit.ly/2bRPf2T

http://bit.ly/2c7hrwi

The Tiniest Flowers

It is easy to get caught up in grandeur. Finding the largest of something is always fun but what about the smallest? I have talked about the largest flowers in the world (http://on.fb.me/1bnfEbk) but how small can a flower get? The answer lies in one of the most common plants on earth, duckweed.

There are roughly 38 species of duckweed out there and all of them represent pretty much the epitome of flowering plant reductionism. They are little more than a pair or so of leaf-like structures that float at or near the waters surface and the occasional taproot. What is even more striking are the flowers. Whereas most duckweed will reproduce clonally, every once in a while a flower will be produced. One genus, Wolffia, produces the smallest flowers of any duckweed. They are also the smallest flowers known to science. As you can see from the picture, they are nothing more than a couple anthers (A1 and A2) and a pistil (Pi). What's more, the male parts mature and die before the female parts, thus limiting the chances of self fertilization. As one would expect, the fruits produced are also the smallest fruits in the world.

This is all quite interesting considering the fact that DNA analysis places duckweeds in the Araceae family, which is home to the largest single inflorescence in the world (http://on.fb.me/19i6XNX)! That's right, the arum family produces one of the largest groups of flowers in the world as well as the smallest flower and fruit in the world. Another cool fact about duckweed, specifically Wolffia, is that, gram for gram, it produces the same amount of protein as soy beans. Because of this, it is used as a food plant in many places around the world and more countries are waking up to its potential as both a food plant and a phytoremediation species. Pretty neat for such a small plant.

Photo Credit: Patrick Denny

Further Reading:

http://bit.ly/2c9smn9

http://bit.ly/2bPOMgX

http://bit.ly/2bPQw9A

http://bit.ly/2bzTL4I

Floating Ferns

Not every tiny plant you see growing on the surface of ponds are duckweeds. Sometimes they are Azolla. Believe it or not, these are tiny, floating ferns! The genus Azolla is comprised of about 7 to 11 different species, all of which are aquatic. Despite being quite small they nonetheless exert a massive influence wherever they grow. 

Like all ferns, Azolla reproduce via spores. Unlike more familiar ferns, however, sexual reproduction in Azolla consists of two markedly different types of spores. When conditions are right, little structures called "sporocarps" are formed underneath the branches. These produce one of two types of sporangia. Male sporangia are small and are often referred to as microspores whereas female sporangia are, relatively speaking, quite large and are referred to as megaspores. The resulting gametophytes develop within and never truly leave their respective spores. Instead, male gameotphytes release motile sperm into the water column and female gametophytes peak out of the megaspore to intercept them. Thus, fertilization is achieved. 

Azolla are fast growing plants. Via asexual reproduction, these little floating ferns can double their biomass every 3 to 10 days. That is a lot of plant matter in a short amount of time. As such, entire water bodies quickly become smothered by a fuzzy-looking carpet. Depending on the species and the environmental conditions, the color of this carpet can range from deep green to nearly burgundy. They are able to float because of their overlapping scale-like leaves, which trap air. Below each plant hangs a set of roots. The roots themselves form a symbiotic relationship with a type of cyanobacterium, which fixes atmospheric nitrogen. Couple with their astronomic growth rate, this means that colonies of Azolla quickly reach epic proportions.

They can grow so fast that Azolla may have played a serious role in a massive global cooling event that occurred some 50 million years ago. During that time, Earth was much warmer than it is now. In fact, global temperatures were so warm that tropical species such as palms grew all the way into the Arctic. There is fossil evidence that massive blooms of Azolla mau have occurred in the Arctic Ocean during this time, which was a lot less saline than it is now. Though plenty of other factors undoubtedly played a role, it is believed that Azolla blooms would have been so large that they would have drawn down CO2 levels considerably over thousands of years. As these blooms died they sank to the sea floor, bringing with them all of the carbon they had locked up in their cells. In part, this may have led to a massive drop in atmospheric CO2 levels and a subsequent cooling period. Evidence for this is tantalizing, so much so that some researchers have taken to calling this "The Azolla Event." However, this is far from a smoking gun. Regardless, it is an important reminder than really big things often come in very small packages.

Further Reading:

http://bit.ly/2c5c5zE

http://bit.ly/2c0DGD1

 

On the Wood Rose and its Bats

New Zealand has some weird nature. It is amazing to see what an island free of any major terrestrial predators can produce. Unfortunately, ever since humans found their way to this unique island, the ecology has suffered. One of the most unique plant and animal interactions in the world can be found on this archipelago but for how much longer is the question.

The story starts with a species of bat. In fact, this bat is New Zealand's only native terrestrial mammal. That's right, I said terrestrial. The New Zealand lesser short-tailed bat spends roughly 40% of its time foraging for insects on the ground. It has lots of specialized adaptations that I won't go into here but the cool part is they forage in packs, stirring up insects from the leaf litter until they reach a level of feeding frenzy that I thought was only reserved for sharks or piranhas. Along with using echo location, they also have a highly developed sense of smell. This is important for our second player in this forest floor drama.

Enter Dactylanthus taylorii, the wood rose. This plant is not a rose at all but rather a member of the tropical family Balanophoraceae. More importantly, it is parasitic. It produces no chlorophyll and lives most of its life wrapped around the roots of its host tree underground. Every once in a while a small patch of flowers break through the dirt and just barely peak above the leaf litter. This give this species it's Māori name of "pua o te reinga" or "pua reinga", which translates to "flower of the underworld." The flowers emit a musky, sweet smell that attracts these ground foraging bats. The bats are one of the only pollinators left on the island. They sniff out the flowers and dine on the nectar, all the while being dusted with pollen. Recently, it has been found that New Zealand's giant ground parrot, the kakapo, is also believed to have been a pollinator of this plant. Sadly, today the kakapo exists solely on one small island of the New Zealand archipelago.

Both the wood rose and the New Zealand lesser short-tailed bat are considered at risk for extinction. When modern man came to these islands they brought with them the general suite of mammalian invasives like rats, mongoose, cats, and pigs, which are exacting a major toll on the local ecology. The plants and animals native to New Zealand have not shared an evolutionary history with such aggressive mammalian invaders and thus have no adaptations for coping with their sudden presence. The future of the wood rose, the New Zealand lesser short-tailed bat, and the kakapo, along with many other uniquely New Zealand species are for now uncertain.

Photo Credits: Joseph Dalton Hooker (1859) and Nga Manu Nature Reserve (http://www.ngamanu.co.nz/)

Further Reading:

http://bit.ly/2bBw8FT

http://bit.ly/2bKRY90

http://bit.ly/2bKpxfE

The Devil's Walking Stick

The name "Devil's walking stick" just sounds cool. You can imagine my excitement then when I first laid eyes on the species it refers to. Aralia spinosa is no ordinary tree. It is a hardy species ready to take advantage of disturbance. Armed with spikes and a canopy that looks like it belongs in some far off tropical jungle, the Devil's walking stick is a tree species worth knowing. 

I used to think that spikenard (Aralia racemosa) was the most robust member of the aralia family found in North America. Not so. The Devil's walking stick is a medium sized tree capable of reaching heights of over 30 feet (10 m). Most interesting of all, its triply compound leaves are the largest leaves of any temperate tree in the continental United States. It can be found growing in disturbed areas and along forest edges throughout a large swatch of eastern North America. When young it is a rather spiny lot. These are not true spines, which are modified parts of leaves, but rather prickles, which arise from extensions of the cortex or epidermis. 

As it grows, however, it loses a lot of its prickliness. Such armaments are costly to produce after all. It is believed that younger plants develop these structures while they are still at convenient nibbling height only to lose them once they grow big enough to avoid hungry herbivores. Research has shown that most herbivorous mammals alive today do not bother much with the Devil's walking stick, which has led some to suggest that these defenses evolved back when this side of the continent was brimming with much larger herbivores such as elk and bison. 

Photo Credit: Celerylady - Wikimedia Commons

Photo Credit: Celerylady - Wikimedia Commons

As if the giant compound leaves of this tree were not stunning enough, the rather large inflorescence is sure to blow you away. Typical of the family, it consists of hundreds of tiny green flowers. Despite their size, they are a boon for pollinators. A tree in full bloom comes alive with bees and butterflies alike. Flowers soon give way to clusters of berries, which are a favorite food among birds. All in all this is one cool tree.

Further Reading:

http://bit.ly/2bjflW1

http://bit.ly/2bxgeye

Alien Plants

Confession: I am a huuuge science fiction nerd. That's right, when I am not reading and writing about botany or ecology, I like to unwind with the works of authors such as Arthur C. Clarke, Robert Heinlein, and David Gerrold. By and large my favorite sci fi topics are those dealing with aliens. Pondering alien ecology and culture is one of the best thought experiments. This obsession definitely bleeds into my day to day life. I have to admit that one of my greatest hopes is that we will discover life elsewhere in the universe. I'm not alone in this either. Many have devoted their careers to the search for extraterrestrial life. 

As any good scientist knows, we have to temper our expectations to the realm of reality. That being said, we have a very small sample size to base our expectations on. We only know of the carbon based life that we are part of. As such, this colors the way in which we think and search. Our search for habitable planets for instance takes into account all of the parameters that make Earth special. By looking for planets like ours, we are at least narrowing the possibilities to conditions we know can support life (as we know it). However, we can't let Earth be the only lens to color our search. That is where researchers such as Nancy Kiang come in. 

Nancy's work finds her modeling the conditions, both solar and atmospheric, of other planets in order to see which of them may be suitable for photosynthetic life. Certainly photosynthetic life isn't the only possibility out there but it sure is a good place to start. As on our planet, photosynthetic organisms are able to harness energy from the giant nuclear fusion reaction we call the Sun and turn that into food. However, not all suns are like ours. Alien "plants" may have to take advantage of stars very different from our own. 

This is where Nancy comes in. By modeling the conditions on the surface of hypothetical planets, she is able to identify the various wavelengths of energy that would be available to any organism primed to take advantage. For instance, the radiation given off by red dwarf stars would only provide a mere fraction of the visible light given off by our sun. "Plants" on a planet orbiting a red dwarf would need to absorb as much light as possible in order to photosynthesize properly. As such, these alien "plants" would likely appear black. 

Absorption is the key to this concept. The reason plants on Earth appear green is because that is the wavelength they do not absorb. Despite the fact that green light is the most abundant on our planet, it is quite weak in comparison to wavelengths of red and blue. Terrestrial plants absorb reds and blues and reflect green, which gives them their characteristic color. Because of this, Nancy and her team feel that it would be highly unlikely to find blue photosynthetic organisms elsewhere in the universe. Its simply too powerful a wavelength to not be utilized.

Still, until we find evidence of life on other planets, this is all a fun thought experiment. However, before you go writing off the work of researchers like Nancy Kiang as mere entertainment, remember that without such scientific speculation, we are left in the dark on exactly where and how to search for life elsewhere in the universe. By working out the possibilities of life on other planets, researchers like Nancy are helping to focus the search for extraterrestrial life. 

Photo Credit: Richard Mosse

Further Reading:

http://bit.ly/2bkQYbX

The Tallest Moss

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 these lowly plants. 

Mosses as a whole lack the vascularization of more derived plants. 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 are quite sensitive to water loss. For most mosses, this anatomical feature relegates them to humid environments and/or a small stature. This is not the case for Dawsonia. Thanks to a curious case of convergent evolution, this genus breaks this physiological glass ceiling and reaches for the sky. 

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 overtopped 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 it to do what no other extant groups of moss have done - grow tall. 

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

Why Trees?

Walking through the forest is my favorite activity in the world. It is where I feel truly myself. There is something about towering trees that calms me. The thought of why forests are even there often jumps to mind during my strolls. Plenty of plants seem to do just fine hanging out closer to the ground. Why have trees (and some forbs) taken to this vertical realm. Why do forests exist?

In essence, forests are a prime example of an evolutionary arms race. It is one that these organisms have been fighting since the Devonian, roughly 385 million years ago. As plants left the water and began covering the land, some inevitably grew taller than others. There are pros and cons to growing tall. Competition is likely the prime driver for most tree species. Getting above your neighbors means more sunlight. Not every plant is as content as a fern to live out its life in the understory.

Height also means better pollinator visibility and seed dispersal for many tree species. Out in the open, gametes and propagules can be carried great distances by the wind. Eventually colorful blooms would prove to be more exposed and easier for pollinators to locate. Growing tall can also get you out of harms way, removing sensitive growing parts from many different kinds of hungry herbivores and all but the worst forest fires.

There are many downsides to growing tall as well. For one, trees are exposed to the elements and are often victims of strong winds or lightening strikes. What's more, all of that wood takes a lot of energy to produce and, at least for most species, gives nothing back in the way of photosynthesis. It is a rather hefty investment. However, the cost of getting shaded out by your neighbors is definitely not worth the risk of staying small for sun-loving species. Pumping water is another serious issue. The laws of physics suggest that redwoods are pushing the limits for how tall a tree can grow and still be able to lift water to leaves way up in the canopy. Of course, humidity can assist with such issues but for a majority of the water needs of a tree, water must be able to travel against gravity via weak hydrogen bonds. Water forms an unbroken chain within the vascular tissues of plants. As it evaporates from the leaves, it pulls more water up to fill in the void. It is possible that in today's world, a tree would not physically be able to grow much over 400 feet.

Despite the seemingly lavish waste of limited resources that a forest of trees would suggest, they are nonetheless a common occurrence all over the globe and have been for millions of years. The pros must certainly outweigh the cons or else tallness in trees would never have evolved. The next time you find yourself hiking through a forest, think of how the struggle for survival has led these towering organisms from lowly green stains on rocks to hulking behemoths racing towards the sky.

Further Reading:

http://bit.ly/2aXwNSB

http://go.nature.com/1Mrnh65

http://bit.ly/1xn7Qng

Freshwater Sponges

The first true love of my life was the underwater world. I was obsessed with everything aquatic, especially fish. My obsession with fish gave way to a collection of home aquaria that tested the limits of my parents patience. Most of my aquariums were landscaped with a variety of aquatic plants whose variety boggled the mind. The underwater world is full of incredibly varied habitats that are home to a myriad of different organisms. Entire ecological communities exist, often unnoticed, just under the waters surface. This fact was not lost on me this past week as I was paddling my way around the Bog River in the Adirondacks. One group of organisms that I became especially enamored with were the river's freshwater sponges.

Though it is not readily apparent, sponges are animals. They aren't a single animal either. What functions as a single unit is actually a collection of individual organisms working in unison. The entire body of the sponge consists of these microscopic individuals connected by living tissue and held rigid by tiny rods made out of silica. I know what you're thinking, this is not a plant, why am I writing about it? The answer lies in the green color of this sponge.

There are many species of freshwater sponge throughout the world. Here in North America we have somewhere around 30. They are an indicator of clean, clear water. If you see sponges then you know it must be a healthy ecosystem. The freshwater sponges come in many different shapes, colors and sizes. Even within a species there can be a lot of variety between each colony. Pictured here is a species of Spongilla. Not all Spongilla are green though. Many are brown. The green coloration comes from algae living symbiotically within the tissue of the sponge. Similar to lichens, the algae photosynthesize and provide food to the sponge in return for a safe place to grow.

Though not technically a plant, the need to photosynthesize has pushed these sponges to grow into shapes not unlike what is seen in the plant kingdom. Depending on water clarity, temperature, and light levels, sponge shapes range from prostrate, creeping forms to upright branching structures. Also similar to plants, sponges can reproduce both sexually and asexually. As the water begins to cool in the fall, the sponges produce what are known as gemmules. These little packets of dormant cells are quite hardy, resisting pretty much anything the environment can throw at them. When the water begins to warm in the spring, the gemmules will grow into new sponge colonies. During the warm summer months, sponges reproduce sexually. Males release sperm into the water in hopes that it will come into contact with receptive females. This is similar to what we see many wind pollinated tree species do in the spring.

The idea that two completely different branches on the tree of life have converged onto similar biological strategies is a very exciting idea. Indeed, the similarities are striking. I went a long time before I knew that these freshwater sponges even existed. The fact that I live in the Great Lakes region and never encountered them tells me just how poorly we have treated our local waterways.

Further Reading:

http://bit.ly/2aK2rSM

http://bit.ly/2b4jhOg

http://bit.ly/2aDHVle

http://bit.ly/2b6fGAt

The Amazing Radiation of Hawaii's Lobeliads

Hawai'i is home to so many interesting species of plants, many of which are found nowhere else in the world. One group, however, stands out among the rest in that it represents the largest plant radiation not just in Hawai'i but on any island archipelago in the world!

I am of course talking about the Hawaiian lobelioids. We are familiar with species found on North America, which include the lovely cardinal flower (Lobelia cardinalis) and the great blue lobelia (Lobelia siphilitica), but the 6 genera that comprise the Hawaiian radiation are something quite different altogether.

Numbering roughly 125 species in total (and many extinct species as well), it was long thought that they were the result of at least 3 separate invasions. Thanks to recent DNA analysis, it is now believed that all 6 genera are the result of one single invasion by a lobelia-like ancestor. This may seem ridiculous but, when you consider the fact that this invasion happened back when Gardner Pinnacles and French Frigate Shoals were actual islands and none of the extant islands were even in existence, then you can kind of grasp the time scales involved that produced such a drastic and varied radiation.

Sadly, like countless Hawaiian endemics, the invasion of the human species has spelled disaster. Hawaiian endemics are declining at an alarming rate. Introduced pigs and rats eat seeds, devour seedlings, and even go as far as to chew right through the stems of adult plants. To make matters worse, many species evolved to a specific suite of pollinators. Take the genus Clermontia for example. The flowers of these species are evolved for pollination by the island's endemic honey creepers. Due to avian malaria and other human impacts, many honey creepers are endangered and some have already gone extinct. Without their pollinators, many of these lobelioids are doomed to slow extinction if they haven't disappeared already. For some, what few populations remain are now fenced off and have to be hand pollinated. As I have said all too often, the future of this great radiation of plants is uncertain.

Photo Credits: Oakapples (http://bit.ly/OjOqhU), Forest and Kim Starr (http://bit.ly/1miCAA5), Dave Janas

Further Reading:

http://bit.ly/2aIviF5

http://bit.ly/2bh9Dpv

http://bit.ly/2b4i5dV

Albino Redwoods

If you are a very lucky person hiking in the redwood forests of California you may just be able to see a ghost. Not a "real" ghost of course, but pretty darn close. Scattered about these ancient forests are rare and peculiar albino redwood trees! Seeing one is seeing something very special indeed.

Redwoods (Sequoia sempervirens) are some of the largest and oldest organisms on the planet. They are famous worldwide for their grandeur. Aside from their obvious charismatic physical traits, redwoods are quite interesting genetically. These giant gymnosperms are genetically hexaploid, meaning they have 6 copies of their genetic code. What this means for redwoods is the ability to experiment with a wider array of mutations than a diploid organism like you and I. A mutation in one set of chromosomes still leaves 5 other copies to maintain normal genetic function. Whereas this can translate into massive benefits in defenses against pathogens, it also means there is a lot of room for error as well. 

The albino redwoods are an example of a seemingly dead end mutation. For a plant that relies of photosynthesis to survive, the loss of photosynthetic pigments should spell disaster. So then why do albino redwoods exist at all? The answer lies in the their ability to graft their roots with neighboring trees. The albinos become parasites on their normal photosynthetic neighbors. Researchers have found that the leaves of albino redwoods have twice the amount of stomata than do normal redwood leaves. This makes them quite susceptible to drought. During dry years, the trees quickly dehydrate and their host trees withdraw all support. The albinos will often die off but then re-sprout when conditions improve. This disappearing and reappearing act further lends to their mythos. 

There doesn't seem to be a solid consensus on how many albinos exist in the wild. I have seen numbers as low as 25 and as high as 100. Either way, they are a rare element of the coastal redwood community. With thousands of acres still to be explored, it is likely that more will turn up. While some exist in protected parks, many are under threat with increasing fragmentation of these ancient forests. Very little of the coastal redwood forests are under protection and we may be losing more than we will ever know. 

Photo Credit: Cole Shatto and George Bruder

Further Reading:

http://bit.ly/1kBglE8

http://reut.rs/2aSFaz3