Paleo Pinus

Photo Credit: Howard Falcon-Lang, Royal Holloway University of London

What you are looking at here is the oldest fossil evidence of the genus Pinus. Now, conifers have been around a long time. I mean really long. Recognizable members of this group first came onto the scene sometime during the late Triassic, some 235 million years ago. Today, one of the most species-rich genera of conifers are those in the genus Pinus. They dominate northern hemisphere forests and can be found growing in dry soils throughout the globe. For such a commonly encountered group, their origins have remained a bit of a mystery. 

The fossil was discovered in Nova Scotia, Canada. Unlike the rocky fossils we normally think of, this fossil was preserved as charcoal, undoubtedly thanks to a forest fire. The degree of preservation in this charcoal specimen is astounding and provides ample opportunity for close investigation. 

I mentioned that this fossil is old. Indeed it is. It dates back roughly 133 –140 million years, which places it in the lower Cretaceous. What is remarkable is that it predates the previous record holder by something like 11 million years. Even more remarkable, however, is what this tiny fossil can tell us about the ecology of Pinus at that time. 

Firstly, the leaf scars indicate that this tree had two needles per fascicle. This implies that the genus Pinus had already undergone quite the adaptive radiation by this time. If this is the case, it pushes back the clock on pine evolution even earlier. Another interesting feature are the presence of resin ducts. In extant species, these ducts secrete highly flammable terpenes, which would have potentially promoted fire. 

Species that exhibit this morphology today often utilize an ecology that promotes devastating crown fires that clear the land of competition for their seedlings. Although more evidence is needed to confirm this, it nonetheless suggests that such fire adaptations in pines were already shaping the landscape of the Cretaceous period. All in all, this fossil is a reminder that big things often come in small packages. 

Photo Credit: Howard Falcon-Lang, Royal Holloway University of London

Further Reading:

http://bit.ly/1QP85zm

Sand Armor

Photo by Franco Folini licensed under CC BY-SA 2.0

Plants go through a lot to protect themselves from the hungry jaws of herbivores. They have evolved a multitude of ways in which to do this - toxins, stinging hairs, thorns, and even camouflage. And now, thanks to research by a team from UC Davis, we can add sand to this list. 

At this point you may be asking "sand?!" Stick with me here. Undoubtedly you have noticed that sticky plants often have bits of whatever substrate they are growing in stuck to their stems and leaves. You wouldn't be the first to notice this. Back in 1996 a term was coined for this very phenomenon. It has been called “psammophory,” which translates to "sand-carrying."

Over 200 species of plants hailing from 88 genera in 34 families have been identified as psammorphorous. The nature of this habit has been an object of inquiry for at least a handful of researchers over the last few decades. Hypotheses have ranged from protection from physical abrasion, reduction of water loss, reduced surface temperature, reduced solar radiation, and protection from herbivory. 

It was this last hypothesis that seemed to stick. Indeed, many plants produce crystalline structures in their tissues (phytoliths, raphides, etc., which are often silica or calcium based) to deter herbivores. Sand, being silica based, is known to cause tooth wear in humans, ungulates, and rodents. Perhaps a coating of sand is enough to drive away insects and other hungry critters looking to snack on a plant. 

By controlling the amount and color of the sand stuck to plants, the researchers were able to demonstrate that plants covered in sand were less palatable to both mammalian and insect herbivores. In total, sand-covered individuals received significantly less damage to their leaves than individuals that had their sand coat removed. By altering the color of the sand, the researchers were able to demonstrate that this was not a function of camouflage. In total, the presence of sand led to an overall increase in fitness due to a decrease in damage over time. These results are the first conclusive evidence in support of psammophory as yet another fantastic plant defense mechanism. 

Photo Credit: Franco Folini (bit.ly/1RApG1R) and Wolfram Burner (http://bit.ly/1RMNR9V)

Further Reading:
http://onlinelibrary.wiley.com/wol1/doi/10.1890/15-1696/abstract

Photo by Wolfram Burner licensed under CC BY-NC 2.0

Finding The Lobed Spleenwort

This is the story of my first encounter with a hybrid fern back in the spring of 2016.

I love exploring geologically diverse areas. The more rock outcroppings the better. You never know what you are going to find in the numerous nooks and crannies, each with their own unique microclimate. This weekend a few of us decided to get out of town for a bit and explore southern Illinois. You can imagine my excitement then when I laid eyes on a rugged terrain filled with ridges and rock outcrops. With only a few days to botanize, I didn't waste any time. 

The woods were alive with early spring ephemerals. Trilliums, Phacelias, Claytonias, and Dicentras filled the forest with a soft pallet of colors. Along the numerous cliff faces I was finding lots of walking ferns already awaking from the mild winter. At one point I found myself following the meandering path of a small stream. Along each side were small cliffs that were carved out of the surrounding bedrock over eons. Their appearance was softened by the myriad species of lichen and moss that carpeted their surfaces. Upon this moss, small ferns and plants are able to take root. My eye kept leaving the creek bed, finding its way along the rocks, looking for anything peculiar that might catch my eye. That's when I saw it. 

Sticking out of a small hole in the rock was an interesting looking fern. At first glance I thought it was another walking fern. Something was off though. It's outline didn't look right and I had to investigate. Its fronds looked lobed. Indeed they were. This was no walking fern but I wasn't ready to jump to conclusions just yet. I pulled out my fern guide in order to confirm my suspicions. 

What I was looking at was a hybrid. Not just any hybrid either. This unique looking little plant is known scientifically as Asplenium pinnatifidum - the lobed spleenwort. I was just lucky enough to be botanizing on the far western portion of its range. Although it is far more prevalent in the Appalachian Mountains, this hybrid is by no means common. I was very lucky to have spotted it.

It is the result of a chance mix between the walking fern (Asplenium rhizophyllum) and the mountain spleenwort (Asplenium montanum). My original inclination towards walking fern wasn't far off. One interesting aspect of this particular hybrids biology is that it is an allotetraploid. Instead of getting one set of chromosomes from each parent (diploid), this little fern gets a full compliment of chromosomes from each, giving it 4 copies total. 

Because it has a lot of functional chromosomes to work with, the lobed spleenwort is fertile. As such, experts have given it the designation of a true species. It can even go on to produce subsequent hybrids. It has been reported to hybridize with other members of the genus Asplenium, however, the offspring produced from these crosses are usually sterile. 

I looked around the area to see if I could find more. In total I only saw two. That's not to say more aren't out there. There are plenty of rock ledges and cliffs that make this region so uniquely beautiful. It is likely that this hybrid fern has unknown populations growing out of reach of watchful eyes. Long may it be that way. 

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

An Underground Orchid

Photo by Jean and Fred licensed under CC BY 2.0

Are you ready to have your mind blown away? What you are looking at here is not some strange kind of mushroom, though fungus is involved. What you are seeing is actually the inflorescence of a parasitic orchid from Australia that lives and blooms underground!

Meet Rhizanthella gardneri. This strange little orchid is endemic to Western Australia and it lives, blooms, and sets seed entirely underground. It is extremely rare, with only 6 known populations. Fewer than 50 mature plants are known to exist. This is another one of those tricky orchids that does not photosynthesize but, instead, parasitizes a fungus that is mycorrhizal with the broom honey myrtle (Melaleuca uncinata). To date, the orchid has only been found under that specific species of shrub. Because of its incredibly unique requirements, its limited range, and habitat destruction, R. gardneri is critically endangered.

The flowers open up a few centimeters under the soil. They are quite fragrant and it is believed that ants, termites, and beetles are the main pollinators. The resulting seeds take up to 6 months to mature and are quite fleshy. It is hypothesized that some sort of small marsupial eats them and consequently distributes them in its droppings. Either way, the chances of successful sexual reproduction for this species are quite low. Because of this, R. gardneri also reproduces asexually by budding off daughter plants.

Despite not photosynthesizing, this orchid is quite unique in that it still retains chloroplasts in its cells. They are a very stripped down form of chloroplast though, containing about half of the genes a normal chloroplast would. It is the smallest known chloroplast genome on the planet. This offers researchers a unique opportunity to look deeper into how these intracellular relationships function. The remaining chloroplast genes code for 4 essential plant proteins, meaning chloroplasts offer functions beyond just photosynthesis.

I am so amazed by this species. I'm having a hard time keeping my jaw off the ground. What an amazing world we live in. If you would like to see more pictures of R. gardneri, please make sure to check out the following website:
http://www.arkive.org/underground-orchid/rhizanthella-gardneri/

Photo Credit: Jean and Fred Hort

Further Reading:
http://www.sciencedaily.com/releases/2011/02/110208101337.htm

http://www.eurekalert.org/pub_releases/2011-02/uowa-wai020711.php

http://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=20109

Studying Mimicry in Orchids Using 3D Printing

Photo by Luis Baquero licensed under CC BY-NC-ND 2.0

Just when I thought I could stop acting surprised by the myriad applications of 3D printing, a recent study published in the journal New Phytologist has me pulling my jaw up off the floor. Using a 3D printer, researchers from the University of Oregon have unlocked the mystery surrounding one of the more peculiar forms of mimicry in the botanical world. 

The genus Dracula is probably most famous for containing the monkey face orchids (Dracula simia). Thanks to our predisposition for pareidolia, we look at these flowers and see a simian face staring back at us. Less obvious, however, is the intricate detail of the labellum, which superficially resembles the monkey's mouth. A close inspection of this highly modified petal would reveal a striking resemblance to some sort of gilled mushroom. 

Indeed, a mushroom is exactly what the Dracula orchids are actually trying to mimic. The main pollinators of this genus are tiny fruit flies that are mushroom specialists. They can be seen in the wild crawling all over Dracula flowers looking for a fungal meal and a place to mate. Some of the flies inevitably come away from the Dracula flower with a wad of pollen stuck to their backs. With any luck they will fall for the ruse of another Dracula flower and thus pollination is achieved. 

Despite being well aware of this mimicry, scientists didn't quite know what specifically attracted the flies to the flower. This is where the 3D printer came in. The research team made exact replicas of the flowers of Dracula lafleurii out of odorless silicone. They also printed individual flower parts. In doing so, the researchers were able to vary the color patterns as well as the scent of each flower. Using the parts, they were also able to construct chimeras, which allowed them disentangle which parts contribute most to the mimicry. 

What they discovered is that the key to Dracula's mushroom mimicry lies in its gilled labellum. This petal not only looks like a mushroom, it smells like one too. The result is a rather ingenious ruse that its tiny fly pollinators simply can't resist. What's more, this approach offers an ingenious way of investigating the evolution of mimicry throughout the botanical kingdom. 

Photo Credit: Luis Baquero (http://bit.ly/21GhYGJ)

Further Reading:
http://onlinelibrary.wiley.com/doi/10.1111/nph.13855/abstract

Plant Plasticity

One of the central tenets of evolutionary science is that individuals within a species vary, however slightly, in their form, physiology, and behavior. Without variability, life would languish, remaining static in a soupy ooze somewhere in the oceans. Perhaps it may not have evolved in the first place. Regardless, observation and experimentation has taught us a lot about how variation among individuals or populations can drive evolution. Today I would like to introduce you to a tiny plant native to northern and western North America that is teaching us a lot about how mating systems develop in plants.

Meet Collinsia parviflora, the maiden blue eyed Mary. Few plants are as iconic to my time living out west than this wonderful little plant. Indeed, C. parviflora is highly variable. It ranges in size from 5 for 40 centimeters in height and produces lovely little flowers that range from 4 to 7 millimeters in length. The size range of these flowers is key to investigating variations in pollination strategies. 

C. parviflora has evolved what researchers refer to as a mixed mating strategy. Populations differ in that some plants self pollinate whereas others fully outcross with the help of a variety of bees. Exactly why these plants would maintain both strategies can tell us a lot about how mating systems develop in plants. What researchers have found is that there seems to be a tradeoff. 

Populations that frequently self are often located in the harshest environments. Cold temperatures and a short growing season make investing in complex floral development a risky strategy. Indeed, plants growing where environmental conditions are harshest produce smaller flowers. These small flowers pack all of their reproductive bits close together, thus increasing the chances of self fertilization. It has been found that despite the risk of inbreeding, these plants produce far more seeds than plants that produce larger flowers and experience high rates of insect pollination. 

The reasons for this are quite complex and more work is needed to be certain but it would seem that this is all an evolutionary adaptation to dealing with varied climates. With wide ranging species like C. parviflora, populations can experience highly varied environmental conditions. It would seem maladaptive to focus in on one particular reproductive strategy. As such, C. parviflora has evolved a range of possible anatomies as a way of adapting to many unique local conditions. If times are good and pollinators are abundant, it makes more sense to hedge bets on sexual reproduction whereas when conditions are poor and pollinators are scarce, it makes sense to produce offspring with a genome identical to that of the parents. If they can exist in a harsh location then so can the cloned offspring. 

Investigations into the mating system of this tiny plant has revealed that big things can really come in small packages. I miss seeing this species. Its amazing how these tiny little flowers can be so numerous as to turn wide swaths of its habitat a pleasing shade of blue. 

Further Reading:
http://www.amjbot.org/content/90/6/888.full

http://plants.usda.gov/core/profile?symbol=COPA3

Rhizanthes lowii

Photo Credit: Ch'ien C. Lee - www.wildborneo.com.my/photo.php?f=cld1500900.jpg

Imagine hiking through the forests of Borneo and coming across this strange object. It's hairy, it's fleshy, and it smells awful. With no vegetative bits lying around, you may jump to the conclusion that this was some sort of fungus. You would be wrong. What you are looking at is the flower of a strange parasitic plant known as Rhizanthes lowii.

Rhizanthes lowii is a holoparasite. It produces no photosynthetic tissues whatsoever. In fact, aside from its bizarre flowers, its doesn't produce anything that would readily characterize it as a plant. In lieu of stems, leaves, and roots, this species lives as a network of mycelium-like cells inside the roots of their vine hosts. Only when it comes time to flower will you ever encounter this species (or any of its relatives for that matter).

The flowers are interesting structures. Their sole function, of course, is to attract their pollinators, which in this case are carrion flies. As one would imagine, the flowers add to their already meaty appearance a smell that has been likened to that of a rotting corpse. Even more peculiar, however, is the fact that these flowers produce their own heat. Using a unique metabolic pathway, the flower temperature can rise as much as 7 degrees above ambient. Even more strange is the fact that the flowers seem to be able to regulate this temperature. Instead of a dramatic spike followed by a gradual decrease in temperature, the flowers of R. lowii are able to maintain this temperature gradient throughout the flowering period.

Photo Credit: Ch'ien C. Lee - www.wildborneo.com.my/photo.php?f=cld1500900.jpg

There could be many reasons for doing this. Heat could enhance the rate of floral development. This is a likely possibility as temperature increases have been recorded during bud development. It could also be used as a way of enticing pollinators, which can use the flower to warm up. This seems unlikely given its tropical habitat. Another possibility is that it helps disperse its odor by volatilizing the smelly compounds. In a similar vein, it may improve the carrion mimicry. Certainly this may play a role, however, flies don't seem to have an issue finding carrion that has cooled to ambient temperature. Finally, it has also been suggested that the heat may improve fertilization rates. This also seems quite likely as thermoregulation has been shown to continue after the flowers have withered away.

Regardless of its true purpose, the combination of lifestyle, appearance, and heat producing properties of this species makes for a bizarrely spectacular floral encounter. To see this plant in the wild would be a truly special event.

Photo Credit: Ch'ien C. Lee - www.wildborneo.com.my/photo.php?f=cld1500900.jpg

Further Reading: [1] [2]

A Litter Trapping Orchid From Borneo

Ch'ien C. Lee - http://www.wildborneo.com.my/

Epiphytes live a unique lifestyle that can be quite challenging. Sure, they have a relatively sturdy place on a limb or a trunk, however, blistering sun, intense heat, and plenty of wind can create hostile conditions for life. One of the hardest things to come by in the canopy is a steady source of nutrients. Whereas plants growing in the ground have soil, epiphytes must make do with whatever falls their way. Some plants have evolve a morphology that traps falling litter. There are seemingly endless litter trapping plants out there but today I want to highlight one in particular.

Meet Bulbophyllum beccarii. This beautiful orchid is endemic to lowland areas of Sarawak, Borneo. What is most interesting about this species is how it grows. Instead of forming a clump of pseudobulbs on a branch or trunk, this orchid grows upwards, wrapping around the trunk like a leafy green snake. At regular intervals it produces tiny egg-shapes pseudobulbs which give rise to rather large, cup-shaped leaves. These leaves are the secret to this orchids success.

The cup-like appearance of the leaves is indeed functional. Each one acts like, well, a cup. As leaves and other debris fall from the canopy above, the orchid is able to capture them. Over time, a community of fungi and microbes decompose the debris, turning it into a nutrient-rich humus. Instead of having to compete for soil nutrients like terrestrial species, this orchid makes its own soil buffet!

If that wasn't strange enough, the flowers of this species are another story entirely. Every so often when conditions are just right, the plant produces an inflorescence packed full of hundreds of tiny flowers. The flowers dangle down below the leaves and emit an odor that has been compared to that of rotting fish. Though certainly disdainful to our sensibilities, it is not us this plant is trying to attract. Carrion flies are the main pollinators of this orchid and the scent coupled with their carrion-like crimson color attracts them in swarms.

The flies are looking for food and a place to lay their eggs. This is all a ruse, of course. Instead, they end up visiting a flower with no rewards whatsoever. Regardless, some of these flies will end up picking up and dropping off pollinia, thus helping this orchid achieve pollination.

Epiphyte diversity is incredible and makes up a sizable chunk of overall biodiversity in tropical forests. The myriad ways that epiphytic plants have adapted to life in the canopy is staggering. Bulbophyllum beccarii is but one player in this fascinating niche.

Photo Credits:
Ch'ien C. Lee - http://www.wildborneo.com.my/

Further Reading:
http://www.orchidspecies.com/bulbbeccarrii.htm

Bowerbirds - Accidental Gardeners

To look upon the bower of a male bowerbird is to see something bizarrely familiar. These are not elaborate nests but rather architectural monuments whose sole purpose is to serve as a staging ground for mating displays. Males build and adorn these structures with precision and a sense of aesthetics. Because of this behavior, at least one species of bowerbird, the spotted bowerbird, can add another occupation to its resume - accidental gardener.

Photo by Jess Isden via University of Exeter

When a male finds a certain color he likes, he scours the landscape in search of these treasures. For many male bowerbirds, fruits offer a wide array of colors and textures of which they can add to their menagerie. Male spotted bowerbirds seem to have a fondness for the fruits of the potato bush (Solanum ellipticum). Their stark green hue contrasts nicely with the bower architecture.

When the fruits start to decompose, they no longer serve any purpose for the male bowerbird and he tosses them aside. Seeds begin to accumulate around the bower and after some time they will germinate. Researchers decided to investigate this relationship a bit further. What they found was pretty astounding.

They discovered that bush potato plants grew in higher numbers around bowers than they do at random locations throughout the forest. What's more, the fruits produced by bush potatoes growing near bowers were much greener than those of plants elsewhere. In effect, male spotted bowerbirds are not only cultivating the bush potato, they are also artificially selecting for improved coloration of its fruits.

To date, this is the only example of something other than a human cultivating a plant for reasons other than food. The similarities between human cultivation and bowerbird cultivation are mind blowing. Similar to human farmers, male bowerbirds clear the site of competing vegetation and remove the fuel load so as to minimize the risk of fire, all of which provides ideal habitat for germination. Though the male bowerbirds are not intentionally cultivating the bush potato, they have nonetheless entered into a mutualistic relationship in which the males get ready access to beautiful fruits and in return, the bush potato gets a nice, safe place to grow.

Photo Credit: University of Exeter

Further Reading:

http://www.sciencedirect.com/science/article/pii/S0960982212002084

Anise: An Angiosperm Success Story

Illicium floridanum Photo by Scott Zona licensed under CC BY-NC 2.0

I must admit there are few flavors I loath more than anise (and consequently licorice and fennel). Regardless of the flavor, I nonetheless find myself enamored by their whorled seed capsules of star anise. In an attempt to reconcile my feelings towards anise in a culinary sense, I decided to get to know the plants that are responsible for it and I am so glad that I did. As it turns out, this group of small trees and shrubs offer us a glimpse at some of the earliest branchings on the angiosperm family tree.

We get star anise from the genus Illicium. Native to humid tropical understories, there are roughly 40 species scattered around southeast Asia, southeastern North America, the Caribbean, and parts of Mexico. Molecular as well as fossil evidence suggests this group diverged during the mid to late Cretaceous, not long after flowering plants came onto the scene. Indeed, along with Amborella and Nymphaeales, Illicium represent the three lineages that are sister to all other flowering plants alive today.

Illicium henryi Photo by Scott Zona licensed under CC BY-NC 2.0

To call them primitive, however, would be a serious misnomer. Because they diverged so early on, these lineages represent serious success stories in flowering plant evolution. Instead, think of them as fruitful early experiments in angiosperm evolution. Illicium has characteristics that set it out as being sister to all other flowering plants. For instance, the vascular tissues more closely resemble those of gymnosperms than they do angiosperms. Also, like the other sister angiosperms, Illicium blur the line between the long standing categories of monocot and eudicot. As such, they are sometimes referred to as "paleoherbs." Another key diagnostic feature lies in their floral morphology.

They don't have what could be considered true petals or sepals. Instead, they have whorls of tepals, which start off sepal-like and gradually become more petal-like as you near the center of the flower. The stamens, which are laminar or leaf-like, are also arranged in a dense whorl surrounding a yet another whorl of fused carpels. Once fertilized, each carpel gives rise to a hard, glossy seed. As the carpels mature and begin to dry, the individual capsules get tighter and tighter until at some point the seed is pinched so hard that it is ejected from a slit in the fruit in projectile fashion.

Illicium verum. Photo by Tim Waters licensed under CC BY-NC-ND 2.0

Although this research will never rectify the taste of this spice, it nonetheless has given me a new found respect and sense of awe for this genus. To look upon the fruit of Illicium is to look at a biological structure that has stood the test of time. These plants are evolutionary successes that should be admired for their unique place in the story of flowering plant evolution.

Photo Credits: Scott Zona and Tim Waters

Further Reading: [1]

The Evolution of Bulbs

Photo by Ewan Bellamy licensed under CC BY-NC-ND 2.0

Spring time is bulb time. As the winter gives way to warmer, longer days, bulbs are among the first of our beloved botanical neighbors to begin their race for the sun. Functionally speaking, bulbs are storage organs. They are made up of a short stem surrounded by layers of fleshy leaves, which contain plenty of energy to fuel rapid growth. Their ability to maintain dormancy is something most of us will be familiar with.

As you might expect, bulbs are an adaptation for short growing seasons. Their ability to rapidly grow shoots gives them an advantage during short periods of time when favorable growing conditions arrive. Despite the energetic costs associated with supplying and maintaining such a relatively large storage organ, the ability to rapidly deploy leaves when conditions become favorable is very advantageous.

Contrast this with rhizomatous species, which are often associated with a life in the understory (though not exclusively) or in crowded habitats like grasslands where competition for light and space can be fierce. Their ambling subterranean habit allows them to vegetatively "explore" for light and nutrients. What's more, the connected rhizomes allow the parent plant to provide nutrients to the developing clones until they grow large enough to support themselves. Under such conditions, bulbs would be at a disadvantage.

Bulbs have evolved independently throughout the angiosperm tree. Many instances of a switch from rhizomatous to bulbous growth habit occurred during the Miocene (23.03 to 5.332 million years ago) and has been associated with a global decrease in temperature and an increase in seasonality at higher latitudes. The decrease in growing season may have favored the evolution of bulbous plants such as those in the lily family. Today, we take advantage of this hardy habit, making bulbous species some of the most common plants used in gardens.


Further Reading: [1]
 

Screw Pines, Volcanism, and Diamonds

Photo by Jakob Fahr/iNaturalist (CC BY-NC)

The association between geology and botany has always fascinated me. The closer you look, the more you can't separate the two. Rocks and minerals influence soil characteristics, which in turn influences which plant species will grow and where, which in turn influences soil properties. Take for instance the case of kimberlite.

Kimberlite is a volcanic rock whose origin is quite intense. Kimberlite is found in the form of large vertical columns, often referred to as pipes. They are the result of some seriously explosive volcanism. Intense heat and pressure builds deep within the mantle until it explodes upward, forming a column of this igneous rock. 

Over long spans of time, these pipes begin to weather and erode. This results in soil that is rich in minerals like magnesium, potassium, and phosphorous. As anyone who gardens can tell you, these are the ingredients of many fertilizers. In Africa where these sorts of pipes are well known, there is a species of plant that seems to take advantage of these conditions. 

It has been coined Pandanus candelabrum and it belongs to a group of plants called the screw pines. They aren't true pines but are instead a type of angiosperm. Now, the taxonomy of the genus Pandanus is a bit shaky. Systematics within the family as a whole has largely been based on fragmentary materials such as fruits and flowers. What's more, for much of its taxonomic history, each new collection was largely regarded as a new species. You might be asking why this is important. The answer has something to do with the kimberlite P. candelabrum grows upon. 

There is something other than explosive volcanic activity that makes kimberlite famous. It is mostly known for containing diamonds. In a 2015 paper, geologist Stephen E. Haggerty made this connection between P. candelabrum and kimberlite. As far as anyone can tell, the plant is a specialist on this soil type. As such, prospectors are now using the presence of this plant as a sort of litmus test for finding diamond deposits. This is why I think taxonomy becomes important. 

If P. candelabrum turns out not to be a unique species but rather a variation then perhaps this discovery doesn't mean much for the genus as a whole. However, if it turns out that P. candelabrum is a truly unique species then this new-found association with diamond-rich rocks may spell disaster. Mining for diamonds is a destructive process and if every population of P. candelabrum signals the potential for diamonds, then the future of this species lies in the balance of how much our species loves clear, shiny chunks of carbon. A bit unsettling if you ask me. 


Further Reading:
http://econgeol.geoscienceworld.org/content/110/4/851.full

Dung Seeds

Midgley, J., White, J., Johnson, S. et al. Faecal mimicry by seeds ensures dispersal by dung beetles. Nature Plants 1, 15141 (2015). https://doi.org/10.1038/nplants.2015.141

Photo by Nicola van Berkel (Nicky vB)

There are a lot of interesting seed dispersal mechanisms out there. It makes sense too because effective seed dispersal is one of the most important factors in a plant's life cycle. It is no wonder then that plants have evolved myriad ways to achieve this. Everything from wind to birds to mammals and even ants have been recruited for this task. Now, thanks to a group of researchers in South Africa, we can add dung beetles to this list.

That's right, dung beetles. These little insects are famous the world over for their dung rolling lifestyle. These industrious beetles are quite numerous and play an important role in the decomposition of feces on the landscape. Without them, the world would be a gross place. They don't do this for us, of course. Instead, dung beetles both consume the dung and lay their eggs on the balls. They are often seen rolling these balls across the landscape until they find the perfect spot to bury it where other dung-feeding animals won't find it. It is this habit that a plant known scientifically as Ceratocaryum argenteum has honed in on.

The seeds of this grass relative are hard and pungent. Researchers questioned why the plant would produce such smelly seeds. After all, the scent would hypothetically make it easier for seed predators to find them. However, the typical seed predators of this region such as birds and rodents show no real interest in them. What's more, when offered seeds directly, rodents only ate seeds in which the tough, smelly coat had been removed. Using cameras, the researchers studied the behavior of these animals time and time again. It was only after viewing hours of video that they made their discovery.

Although they weren't big enough to trip the cameras themselves, incidental footage caught dung beetles checking out the seeds and rolling them away. As it turns out, the scent and appearance (which closely mimics that of antelope dung) tricks the dung beetles into thinking they found the perfect meal. As such, the dung beetles do exactly what the plant needs - they bury the seeds. This is a dead end for the dung beetle. Only after a seed has been buried do they realize that it is both inedible and an unsuitable nursery. Nonetheless, the drive for reproduction is so strong that the plant is able to successfully trick the dung beetles into dispersing their seeds.

Photo Credit: Nicky vB (bit.ly/1WVgs0G) and Nature Plants

Further Reading:
http://www.nature.com/articles/nplants2015141

The Accidental Grain - How Rye Evolved Its Way Into Our Diet

Photo by Lotte Grønkjær licensed under CC BY-NC-SA 2.0

Humans have been altering the genomes of plants for a very long time. Nowhere is this more apparent than in the crops we grow. These botanical mutants are pampered beasts compared to their wild congeners. It is easy to see why some traits have been selected over others, whether it be larger leaves or fruit to munch on, smaller seeds to keep them out of our way, or tough rinds to make shipping easier. However, not all of our crops have been consciously bred for our consumption. Just as many weed species are adapting to herbicides today, some species of plant were able to adapt to the more archaic methods of early farming, which allowed them to avoid the ever watchful eye of the farmer.

This concept is known as Vavilovian mimicry (sometimes referred to as crop mimicry) and it is named after the Soviet botanist and geneticist Nikolai Vavilov (who was later imprisoned and starved to death by Stalin because of his firm stance on basic genetic principles). The idea is rather simple. At its core it involves artificial selection, albeit unintentional. A wild plant species finds certain forms of agriculture appealing. It becomes an apparent weed and the farmer begins to deal with it. Perhaps this plant is a close relative and thus looks quite similar to the crop in question. As the farmer weeds out plants that look different from the crop, they may be unintentionally selecting for individual weeds that more closely resemble the crop species. Over enough seasons, only those weeds that look enough like the crop survive and reproduce, sometimes to the point in which the two are almost indistinguishable.

Rye is an interesting example of this idea. Wild rye (Secale montanum) was not intentionally grown for food. It was a weed in the fields of other crops like wheat and barley. Both wheat and barley are annual plants, producing their edible seeds at the end of their first growing season. Wild rye, however, is a perennial and does not produce seed until at least its second season. Therefore, most wild rye plants growing in wheat or barely fields are killed at the end of the season when the field gets tilled. However, there are some mutant rye plants that occasionally pop up and produce seeds in their first year.

It is believed that these mutant annual rye were harvested unintentionally and reseeded season after season. Over time, other traits likely developed to help push rye into the spotlight for these early farmers. Like many wild grasses, wild rye has weak spindles (the part that holds the seed to the plant). In the wild, this allows for efficient seed dispersal. On the farm, this is not a desirable trait as you end up quickly losing the seeds you want to harvest. Again, by accidentally selecting for mutants that also had thicker spindles and thus held on to their seeds, farmers were unintentionally domesticating rye to parallel other cereal crops. It is believed that oats (Avena sterilis) also originated in this manner.

Photo Credit: Lotte Grønkjær (http://bit.ly/1xMEfVw)

Further Reading: [1] [2]

Bark!

Photos by SNappa2006 (CC BY 2.0), nutmeg66 (CC BY-NC-ND 2.0), Eli Sagor (CC BY-NC 2.0), and Randy McRoberts (CC BY 2.0)

Say "tree bark" and everyone knows what you're talking about. We learn at an early age that bark is something trees have. But what is bark? What is its purpose and why are there so many different kinds? Indeed, there would seem to be as many different types of bark as there are trees. It can even be used as a diagnostic feature, allowing tree enthusiasts to tease apart what kind of tree they are looking at. Bark is not only fascinating, it serves a serious adaptive purpose as well. To begin to understand bark, we must first look at how it is formed.

To start out, bark isn't a very technical term. Bark isn't even a single type of tissue. Instead, bark encompasses several different kinds of tissues. If you remember back to Plant Growth 101, you may have heard the word "cambium" get thrown around. Cambium is a layer of actively dividing tissue sandwiched between the xylem and the phloem in the stems and roots of plants. As this layer grows and divides, the inside cells become the xylem whereas the outside cells become the phloem. 

Successive divisions produce what is known as secondary phloem. This is where the bark begins. On the outside of this secondary phloem are three rings of tissues collectively referred to as the "periderm." It is the periderm which is responsible for the distinctive bark patterns we see. As a layer of cells called the "cork cambium" divides, the outer layer becomes cork. These cells die as soon as they are fully developed. This layer is most obvious in smooth bark species such as beech. 

Similar to insect growth, however, the growth of the insides of a tree will eventually outpace the bark. When this happens, the periderm begins to split and cracks will begin to appear in the bark. This phenomenon is most readily visible in trees like red oaks. When this starts to happen, cells within the secondary phloem begin to divide. This forms a new periderm underneath the old one. The cumulative result of this results in alternating layers of old periderm tissue referred to as "rhytidome." 

This gives trees like black cherry their scaly appearance or, if the rhytidome consists of tight layers, the characteristic ridges of white ash and white oak. Essentially, the distribution and growth pattern of the periderm gives the tree its bark characteristics. But why do trees do this? Why is bark there in the first place?

The dominant role of bark is protection. Without it, vital vascular tissues risk being damaged and the tree would rapidly loose water. It also protects the tree from pests and pathogens. The cell walls of cork contain high amounts of suberin, a waxy substance that protects against desiccation, insect attack, as well as fungal and bacterial infection. Thick bark can also insulate trees from fire. 

Countless aspects of the environment have influenced the evolution of tree bark. In some species such as aspen or sycamore, the trunk and stems function as additional photosynthetic organs. In these species, cork layers are thin and often flaky. Shedding these thin layers of bark ensures that buildup of mosses, lichens, and other epiphytes doesn't interfere with photosynthesis. The white substance on paper birch bark not only inhibits fungal growth, it also helps prevent desiccation while at the same time making it distasteful for browsing insects and mammals alike.

When you consider all the different roles that bark can play, it is no wonder then that there are so many different kinds. This is only the tip of the ice berg. Entire scientific careers have been devoted to understanding this group of tissues. For now, winter is an excellent time to start noticing bark. Take some time and get to know the trees around you for their bark rather than their leaves.

Photo Credits: Eli Sagor (bit.ly/1OTnA8H), Randy McRoberts (bit.ly/1PgzH35), Lotus Johnson (bit.ly/1JyVt1E), SNappa2006 (bit.ly/1TkjHil), and nutmeg66 (bit.ly/1QwyZQ8)

Further Reading:
http://www.botgard.ucla.edu/

html/botanytextbooks/generalbotany

/barkfeatures/typesofbark.html

http://dendro.cnre.vt.edu/forestbiolog

y/cambium2_no_scene_1.swf

http://life9e.sinauer.com/life9e/pages

/34/342001.html

http://www.botgard.ucla.edu/html/bo

tanytextbooks/generalbotany/barkfe

atures/

Zoophagous Liverworts?

Photo by Matt von Konrat Ph.D - Biblioteca Digital Mundial (eol.org) licensed under CC BY 3.0

Mention the word "liverwort" to most folks and you are going to get some funny looks. However, mention it to the right person and you will inevitably be drawn into a world of deep appreciation for this overlooked branch of the plant kingdom. The world of liverworts is best appreciated with a hand lens or microscope.

A complete lack of vascular tissue means this ancient lineage is often consigned to humid nooks and crannies. Look closely, however, and you are in for lots of surprises. For instance, did you know that there are liverworts that may be utilizing animal traps?

Right out of the gates I need to say that the most current research does not have this labelled as carnivorous behavior. Nonetheless, the presence of such derived morphological features in liverworts is quite sensational. These "traps" have been identified in at least two species of liverwort, Colura zoophaga, which is native to the highlands of Africa, and Pleurozia purpurea, which has a much wider distribution throughout the peatlands of the world.

A liverwort “trap” showing the lid (L), water sac (wl). {SOURCE]

The traps are incredibly small and likely derived from water storage organs. What is different about these traps is that they have a moveable lid that only opens inward. In the wild it is not uncommon to find these traps full of protozoans as well as other small microfauna. Researchers aimed to find out whether or not this is due to chance or if there is some active capture going on.

[SOURCE]

Using feeding experiments it was found that some protozoans are actually attracted to these plants. What's more these traps do indeed function in a similar way to the bladders of the known carnivorous genus Utricularia. Despite these observations, no digestive enzymes have been detected to date. For now researchers are suggesting that this is a form of "zoophagy" in which animals lured inside the traps die and are broken down by bacterial communities. In this way, these liverworts may be indirectly benefiting from the work of the bacteria.

This is not unheard of in the plant world. In fact, there are many species of pitcher plants that utilize similar methods of obtaining valuable nutrients. Certainly the lack of nutrients in the preferred habitats of these liverworts mean any supplement would be beneficial.

Photo Credits: Matt von Konrat Ph.D - Biblioteca Digital Mundial (eol.org), HESS ET AL. 2005 (http://www.bioone.org/doi/abs/10.1639/6), and Sebastian Hess (http://virtuelle.gefil.de/s-hess/forsch.html)

Further Reading: [1]

The Curly-Whirly Plants of South Africa

Gethyllis villosa. Photo by Capetown Botanist: www.capetownbotanist.com

In a region of South Africa traditionally referred to as Namaqualand there exists a guild of plants that exhibit a strange pattern in their growth habits. These plants hail from at least eight different monocot families as well as the family Oxalidaceae. They are all geophytes, meaning they live out the driest months of the year as dormant, bulb-like structure underground. However, this is not the only feature that unites them.

A walk through this region during the growing season would reveal that members of this guild all produce leaves that at least one author has described as "curly-whirly." To the casual observer it would seem that they had left the natural expanse of the desert flora and entered into the garden of someone with very particular tastes.

What these plants have managed to do is to converge on a morphological strategy that allows them to take full advantage of their unique geographical location. The region along the coastal belt of Namibia is famous for being a "fog desert." Despite receiving very little rain, humid air blowing in from the southwestern Atlantic runs into colder air blowing down from the north and condenses, carrying fog inland. This produces copious amounts of dew.

Normally dew would be unavailable to most plants. It simply doesn't penetrate the soil enough to be useful for roots. This is where those curly-whirly leaves come in. Researchers have discovered that this leaf anatomy is specifically adapted for capturing and concentrating fog and dew. This has the effect of significantly improving their water budget in this otherwise arid region. What's more, the advantages are additive.

The most obvious advantage has to do with surface area. Curled leaves increase the amount of edge a leaf has. This provides ample area for capturing fog and dew. Also, by curling up, the leaves are able to reduce the overall size of the leaf exposed to the air, which reduces the amount of transpiration stress these plants encounter in their hot desert environment. Another advantage is direct absorption. Although no specific organs exist for absorbing water, the leaves of most of these species are nonetheless capable of absorbing considerable amounts.

Dipcadi crispum By roncorylus

Finally, each curled leaf acts like a mini gutter, channeling water to the base of the plant. Many of these plants have surprisingly shallow root zones. The lack of a deep taproot may seem odd until one considers the fact that dew dripping down from the leaves above doesn't penetrate too deeply into the soil. These roots are sometimes referred to as "dew roots."

I don't know about you but this may be one of the coolest plant guilds I have ever heard about. This is such a wonderfully clear example of just how strong of a selective pressure the combination of geography and climate can be. What's more, this is not the only region in the world where drought-tolerant plants have converged on this curly strategy. Similar guilds exist in other arid regions of Africa, as well as in Turkey, Australia, and Asia.

Albuca spiralis. Photo by Wolf G. licensed under CC BY-NC-ND 2.0

Photo Credits: Cape Town Botanist (http://bit.ly/1PzPkP7), www.ispotnature.org, roncorylus (http://bit.ly/1PzPoi6), and Wolf G. (http://bit.ly/1n4Mo6b)

Further Reading: [1]

Cretaceous Seeds Shine Light on the Evolution of Flowering Plants

What you are looking at here are some of the earliest fossil remains of flowering plants. These seeds were preserved in Cretaceous sediments dating back some 125–110 million years ago. Fossil evidence dating to the early days of the angiosperm lineage is scant, which makes these fossils all the more spectacular. Thanks to a large collaborative effort, Dr. Else Marie Friis is shining light on the evolution of seeds.

Finding these fossils is not a matter of seeing them with the naked eye. These seeds are tiny, ranging from half a millimeter up to 2 millimeters in length. They were discovered using an advanced form of X-ray microscopy. The advantage of this technique is not only that it is nondestructive but it also allows researchers to investigate the internal structures of the seeds that would otherwise be impossible to see. Their preservation is mind blowingly delicate, allowing researchers to see minute details of the embryo and even subcellular structures like nuclei. 

Dr. Friis' team was able to look at over 250 fossil seeds from 75 different taxa. They were able to make 3D models of the embryos, allowing for more detailed studies than ever before. For some of the fossils, the detail was such that they were able to match them to extant lineages of flowering plants. For others, this technique is allowing for better reclassification of now extinct species. 

By far the most exciting part about these fossils are what they can tell us about the ecology of early flowering plants. In all instances, the embryos within the seeds were small, immature, and dormant. This suggests that seed dormancy is a fundamental trait of flowering plants. What's more, this lends support to the hypothesis that angiosperms first evolved as opportunistic, early successional colonizers. Seed dormancy allows flowering plants to wait out the bad times until favorable environmental conditions allowed for germination and seedling establishment. 

Photo Credit: Dr. Else Marie Friis

Further Reading:
http://www.nature.com/nature/journal/v528/n7583/full/nature16441.html

The Dawn Redwood

The dawn redwood (Metasequoia glyptostroboides) is one of the first trees that I learned to identify as a young child. My grandfather had one growing in his backyard. I always thought it was a strange looking tree but its low slung branches made for some great climbing. I was really into paleontology back then so when he told me this tree was a "living fossil" I loved it even more. It would be many years before I would learn the story behind this interesting conifer.

Photo by Ruth Hartnup licensed under CC BY 2.0

Along with the coast redwood (Sequoia sempervirens) and giant sequoia (Sequoiadendron giganteum), the dawn redwood makes up the subfamily Sequoioideae. Compared to its cousins, the dawn redwood is the runt, however, with a max height of around 200 feet (60 meters), a mature dawn redwood is still an impressive sight.

Until 1944 the genus Metasequoia was only known from fossil evidence. As with the other redwood species, the dawn redwood once realized quite a wide distribution. It could be found throughout the northern regions of Asia and North America. In fact, the fossilized remains of these trees make up a significant proportion of the fossils found in the Badlands of North Dakota.

Fossil evidence dates from the late Cretaceous into the Miocene. The genus hit its widest distribution during a time when most of the world was warm and tropical. Evidence would suggest that the dawn redwood and its relatives were already deciduous by this time. Why would a tree living in tropical climates drop its leaves? Sun.

Regardless of climate, axial tilt nonetheless made it so that the northern hemisphere did not see much sun during the winter months. It is hypothesized that the genus Metasequoia evolved its deciduous nature to cope with the darkness. Despite its success, fossil evidence of this genus disappears after the Miocene. For this reason, Metasequoia was thought to be an extinct lineage.

Photo by Georgialh licensed under CC BY-SA 4.0

All of this changed in 1943 when a Chinese forestry official collected samples from a strange tree growing in Moudao, Hubei. Though the samples were quite peculiar, World War II restricted further investigations. In 1946, two professors looked over the samples and determined them to be quite unique indeed. They realized that these were from a living member of the genus Metasequoia.

Thanks to a collecting trip in 1948, seeds of this species were distributed to arboretums around the world. The dawn redwood would become quite the sensation. Everyone wanted to own this living fossil. Today we now know of a few more populations. However, most of these are quite small, consisting of around 30 trees. The largest population of this species can be found growing in Xiaohe Valley and consists of around 5,000 individuals. Despite its success as a landscape tree, the dawn redwood is still considered endangered in the wild. Demand for seeds has led to very little recruitment in the remaining populations.

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

Further Reading: [1] [2]
 

An Orchid With Body Odor

Photo by Ryan LeBlanc licensed under CC BY-NC-SA 2.0

Aside from ourselves, mosquitoes may be humanity's largest threat. For many species of mosquito, females require blood to produce eggs. As such, they voraciously seek out animals and in doing so can spread deadly diseases. They do this by homing in on the chemicals such as CO2 and other compounds given off by animals. What is less commonly known about mosquitoes is that blood isn't their only food source. Males and females alike seek out nectar as source of carbohydrates.

Though mosquitoes visit flowers on a regular basis, they are pretty poor pollinators. However, some plants have managed to hone in on the mosquito as a pollinator. It should be no surprise that some orchids utilize this strategy. Despite knowledge of this relationship, it has been largely unknown exactly how these plants lure mosquitoes to their flowers. Recent work on one orchid, Platanthera obtusata, has revealed a very intriguing strategy to attract their mosquito pollinators.

This orchid produces human body odor. Though it is undetectable to the human nose, it seems to work for mosquitoes. Researchers at the University of Washington were able to isolate the scent compounds and found that they elicited electrical activity in the mosquitoes antennae. Though more work needs to be done to verify that these compounds do indeed attract mosquitoes in the wild, it nonetheless hints at one of the most unique ruses in the floral world.

Photo Credit: Kiley Riffell and Jacob W. Frank

Further Reading:

http://bit.ly/1JXP2jk