A Case of Sexual Fluidity in the Plant World

In humans, sex is determined at fertilization. The embryo receives either an X or a Y chromosome. Many other organisms have their sex determined in a manner similar to this as well. The case with plants is not so rigid. Many plants produce both male and female parts on the same flower, others have flowers that are either male or female, while some can change their sex throughout their lifetime. The latter is quite interesting and offers an insight into the differences in maleness and femaleness. 

The green dragon (Arisaema dracontium) is an arum related to jack-in-the-pulpit. It is wide spread throughout the east but declining in much of its northern range. This species produces a single inflorescence that can be purely male, both male and female, or, in some rare cases, entirely female. The mechanism for this has been a subject of interest for many botanists as it does not seem to be dictated solely by genetics. It has been discovered that any given plant may switch up its flowering strategy from year to year.

What researchers have found is that male flowers are most often produced in younger plants as well as plants that are stressed. In years where environmental conditions are not as conducive to survival or if the plants have not had enough time to build up energy reserves, it is not uncommon to find only male plants. This is advantageous since male flowers and pollen are a lot less costly to produce than ovaries. Also, the plant does not have to allocate resources into developing seeds. In good years and also in older, larger plants, inflorescence are produced that are both male and female. If the plants are less stressed and large enough, more energy can be allocated to seed production. In some rare cases, very large plants have been known to produce only female flowers. This seems to be a strategy that is adopted only under the best of conditions. 

It should be noted that whereas there seems to be a threshold for environmental conditions as well as plant size in determining what kinds of flowers will be produced, each green dragon population seems to vary. In essence there is some genetic determination for how the plant will respond in any given year but this is where teasing the gene environment out of the actual environment gets tricky. Studying these plants is giving us more insight into the advantages and disadvantages of each sex as well as helping to inform how sensitive species like the green dragon will respond in a changing climate. 

Further Reading:

http://plants.usda.gov/core/profile?symbol=ardr3

http://www.jstor.org/stable/2656980

http://www.jstor.org/stable/2445597?seq=1

Flower Color Beyond What We Can See

Photo by Plantsurfer licensed under CC BY-SA 3.0

Despite their aesthetic appeal, flowers are not here to dazzle us. While they have enticed us to spread the offspring of many species around the globe, flowers have one purpose and one purpose only - sex. 

There are many different and even tricky ways flowers manage pollination. The most common and by far the most widely utilized is the use of insects. Though flowers look like they have done everything they can to attract pollinators, we can only see a narrow range of the electromagnetic spectrum. What we see as visible light is only a mere fraction of what is really out there. 

Many insects see well into the ultraviolet range and this has caused some very interesting evolutionary adaptations in flowers to attract insects to their business parts. When viewed with UV cameras, many species of plants have seemed to have drawn maps and arrows to their anthers and stigmas. It is amazing to witness a species of say Potentilla with, to us, solid yellow petals in this manner. The patterns that appear are striking! There are far too many examples to go into detail on this subject so instead, here is a great website to show you some examples 

http://www.naturfotograf.com/UV_flowers_list.html

The Evolution of a Helicopter

Stevenson, Robert A., Dennis Evangelista, and Cindy V. Looy. "When conifers took flight: a biomechanical evaluation of an imperfect evolutionary takeoff." Paleobiology 41.2 (2015): 205-225. [SOURCE]

The whirring helicopter seeds of modern day conifers (as well as a handful of other tree species) are truly marvels of evolution. We humans have yet to top the simple efficiency of this form of locomotion. It is easy to see how such seed anatomy benefits a tree. Instead of plummeting to the ground and struggling under the shade of its parents, winged seeds are often carried great distances by the breeze. Such a dispersal mechanism is so effective that multiple tree lineages have converged on a single asymmetrical wing design of their samaras.  

The key to this type of seed dispersal lies in the movement of the seed in the air. The whirring motion allows the seeds to stay airborne as they are carried away from their cones. It would be all too easy to argue that any intermediate must be doomed to failure. However, this is not the case. A rich collection of 270 million year old fossils discovered in Texas is shining light on how at least one lineage of conifers settled in on this wonderful adaptation for seed dispersal. 

Artists reconstruction of a seed-bearing shoot of Manifera talaris. Drawing by Ivo Duijnstee

Instead of producing one type of winged seed, an ancient species of conifer known scientifically as Manifera talaris produced multiple different samara designs. Some were symmetrical, others were double winged, and still others matched what we would readily recognize as a samara today. It would seem that early conifers were “trying out” many different forms of wind dispersed seed designs. Manifera talaris was alive during the early Permian. At that time, there were not many animals alive (that we are aware of) that could function as seed dispersers for conifers. Instead, these early trees relied on the wind to do the work for them. 

Though these fossils offer a unique window into the evolution of winged seeds, they do not give any indication as to how each seed designs would have performed. For paleobotanist Dr. Cindy Looy, this meant a chance to have a little fun with science. She and her colleagues built functional paper models of each of the samara types represented in the fossils. By attaching the paper wings to comparably sized seeds from an extant conifer, she was able to test the flight performance of each of these samara types. What she found was quite interesting. 

As it turns out, symmetric and asymmetric double-winged seeds performed quite poorly. They fluttered to the ground, barely achieving any rotation. Contrast this with the asymmetric single-winged seeds, which stayed airborne for twice as long as any other samara design. What this research shows is that early conifers were, in a sense, "experimenting" with different samara designs. Those designs that allowed for greater seed dispersal produced more trees that did the same. 

Photo Credit: Dr. Cindy Looy

Further Reading: [1]

The Arisaema Complex

If you live in the east, Jack-in-the-pulpit or Arisaema triphyllum, is most likely an unmistakable part of late spring. Being a member of the arum family, the bracts of the plant form a tube and hood over the spadix and flowers. This is a highly variable species, in fact, there are at least 4 recognized subspecies that make up the Arisaema complex, A. triphyllum ssp. pusillum, A. triphyllum ssp. quinatum, A. triphyllum ssp. stewardsonii, and A. triphyllum ssp. triphyllum.

Interestingly enough, each subspecies seems to be reproductively isolated from the others. Each also seems to prefer its own habitat. For instance, triphyllum, a denizen of rich woods, blooms after the last frosts while stewardsonii, a denizen of swamps and bogs, blooms a few weeks later. Another interesting aspect of this complex is that pusillum and stweardsonii are both diploid plants, having 28 sets of chromosomes each, whereas triphyllum, our most common subspecies, is believed to be a hybrid of the two and is tetraploid and thus has 56 sets of chromosomes. Some would argue that these plants should be treated as distinct species since the characteristics that designate each subspecies seem rather specific but all across their range, there are many plants that seem to blur the lines. This is a debate that is only going to be solved by more accurate DNA analysis. However, nature doesn't seem to be reading any science texts and therefore rarely falls into our neat, clear-cut mindsets.

Being an arum, this species does produce some heat as well as an odor. The flowers produce a smell reminiscent of mushrooms and indeed, this is to attract their main pollinators, fungus gnats. Next time you come across a blooming Jack-in-the-pulpit, get down and take a whiff. It isn't necessarily good or bad but either way it is an experience. This species is gaining some traction in the gardening community as well due to its ease of care and unique appearance. It is also easy to establish from seed, however, make sure to wear gloves and avoid any skin contact while de-fleshing the seeds because being that it is a member of the arum family, this species produces calcium oxalate crystals that can cause severe burning.

Further Reading:
http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=222000013

http://www.theprimrosepath.com/Featured_Plants/Arisaema_triphyllum/triphyllumcomplex.htm

http://plants.usda.gov/java/profile?symbol=ARTR

http://www.amjbot.org/content/90/12/1729.full.pdf+html?sid=5babeddb-908d-4782-a866-6e0938b93580

http://www.amjbot.org/content/91/6/881.full.pdf+html?sid=5babeddb-908d-4782-a866-6e0938b93580

Ancient Equisetum

Photo by Christian Ostrosky licensed under CC BY-NC-ND 2.0

Whenever you cross paths with an Equisetum, you are looking at a member of the sole surviving genus of a once great lineage. The horsetails, as they are commonly called, hit their peak during the Devonian Era, some 350 + million years ago. Back then, they comprised a considerable portion of those early forests. Much of the world's coal deposits are derived from these plants.

The horsetails once towered over the landscape, reaching heights of 30 meters or more. Today, however, they have been reduced to mostly small, lanky plants. The tallest of the extant horestails are the giant horsetail (Equisetum giganteum) and the Mexican giant horsetail (Equisetum myriochaetum) of Central and South America. These two species are known to reach heights of 16 ft. (4 m.) and 24 ft. (7 m.) respectively. Certainly an impressive site to see.

Equisetum giganteum (Chad Husby for scale.) Photo by Chad Husby licensed under CC BY-NC-ND 2.0

As a genus, Equisetum is composed of somewhere around 20 species, with many instances of hybridization known to occur. Most species tend to frequent wet areas, though dry, nutrient poor soils seem to suit some species just fine. The horsetails are known for their biomineralisation of silica, earning some the common name of "scouring rush." Settlers used to use these plants to clean their pots and pans. However, this is certainly not why this trait evolved. It is likely that the silicates have something to do with structural support as well as physical protection against pathogens. More work needs to be done looking at the benefits rather than the mechanisms involved.

Though they are not ferns, horsetails are frequently referred to as "fern allies." This is due to the fact that, like ferns, horsetails are not seed plants. Instead, they produce spores and exhibit a distinct alternation of generations between the small, gamete-producing gametophyte and the tall spore-producing sporophyte. Spores are produced from a cone-like structure at the top of the stem called a stobilus. This may be attached to the photosynthetic stem or it can arise as its own non-photosynthetic stem. Either way it is an interesting structure to encounter and well worth studying under some form of magnification.

Despite their diminutive appearance, many horsetails are quite hardy and thrive in human disturbance. For this reason, horsetails such as E. hyemale and E. arvense have come to be considered aggressive invasive species in many areas. They thrive in nutrient poor soils and their deep, wide-ranging rhizomes can make control difficult to impossible. There is something to be said for these little plants. Love them or hate them, they have stood the test of time. They were some of the first plants on land and it is likely that some will be here to stay, even if we go the way of the Devonian forests.

Photo by born1945 licensed under CC BY 2.0

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

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

An Endemic Houstonia

Photo by BlueRidgeKitties licensed under CC BY-NC-SA 2.0

The weathered peaks of the Southern Appalachians are home to a bewildering variety of plant life. This region is thought to have provided refuge for many different types of flora and fauna pushed south by repeated glaciation. High humidity and precipitation coupled with a variety of microclimates has allowed plants to flourish and evolve over the millennia. In fact, a handful of species are found nowhere else in the world. One of these montane endemics is none other than a species of Houstonia. 

Some feel it best designated as a subspecies, Houstonia purpurea var. montana, whereas others feel that both morphological and reproductive distinctions deserve it a status as its own species, Houstonia montana. I prefer to refer to it as the Roan Mountain bluet. Either way, this unique little plant can be found  growing among rocky summits and balds on only a handful of mountain tops between Tennessee and North Carolina.  

This species requires disturbance to survive. Without the constantly shifting landscape characteristic of high altitude regions, this little plant would quickly be overtopped and outcompeted by more aggressive vegetation. This is not a lifestyle unique to this little bluet. Many of the worlds rare plant species require some level of disturbance to release them from competition with other more common plant species. Aside from competition, one of the largest threats to the continued survival is trampling by hikers. It is always important to watch where we hike. A little bit of attention can go a long way for our botanical neighbors. 

Photo Credit: BlueRidgeKitties (http://bit.ly/1dJ7SkA)

Further Reading:

http://www.esajournals.org/doi/abs/10.1890/1051-0761(1998)008%5B0909:PORPOA%5D2.0.CO%3B2

http://www.bioone.org/doi/abs/10.3159/1095-5674(2007)134%5B177:GOTRSA%5D2.0.CO%3B2

http://link.springer.com/article/10.1007/s10682-011-9539-x#page-1

http://www.jstor.org/discover/10.2307/4032597?uid=2&uid=4&sid=21106703459663

Colorful Claytonia

If you live where spring beauty, specifically Claytonia virginica, is native, then you may have noticed great variations in flower color. We all know the influence pollinators can have on flower shape and color but how do we explain populations with such a spectrum?

Like me you might be thinking that it is related to its growing conditions. Well, researched based out of Indiana University would suggest otherwise. It turns out, the variety of flower color in Claytonia has to do with opposing natural selection from herbivores and pathogens.

In a 2 year study, researchers made some amazing discoveries about how herbivores, pollinators, and pathogens can interact to produce the variety of flower colors one can find in any given Claytonia population. First, they made sure that Claytonia flower color is not a result of soil pH or anything like that by growing a ton of them in different conditions. They were able to demonstrate that flower color is indeed genetic and is controlled by a couple different compounds. Crimson coloring comes from a compound called "cyanidin" and white colors comes from two flavonols, "guercetin" and "kaempferol". Researchers then used spectrometry to analyze flower colors throughout the population and found 4 distinct color morphs ranging from all white to mostly crimson.

As it turns out, the flavonol compounds have pleiotropic effects in Claytonia. While they do produce white pigments, they also help defend the plants against herbivory and pathogens. Researchers then used a multitude of different analytical methods to assess overall fitness of each color morph and the results are jaw-droppingly cool to say the least.

Fitness of Claytonia was measured as total fruit production and total seed set. Because Claytonia needs a pollinator to visit the plant in order to produce fruit and set seed, reproduction is directly linked to pollinator preference. This research showed that pollinators, which for Claytonia are solitary bees, do, in fact, prefer crimson color morphs. This helps to explain the greater number of crimson colored flowers in in many populations because the more pollinators that visit a flower, the higher overall fitness for that plant. What it does not explain though, is why white morphs exist in the population at all.

As stated above, the flavonols that produce white pigmentation also beef up the plants defenses. It was found that white colored flowers experienced significantly less predation than crimson flowers. This is big news because herbivory has serious consequences for Claytonia. Plants that receive high levels of herbivore damage are far more likely to die. Because of this, white morphs, even with significantly less reproductive fitness, are able to maintain themselves in any given population.

If you're at all like me then you may need to pick you jaw up off the ground at this point. But wait! It gets cooler.... In areas where other white flowering plants like Stellaria pubera abound, white Claytonia morphs are even more rare. Why is this exactly? Well, this is due to a push towards a more pollinator-mediated selective pressure. In areas where many plants share the same flower color, it pays to be different. This causes a selective pressure in these Claytonia populations to favor even more crimson color morphs.

Isn't evolution amazing?

Further Reading:

http://bit.ly/1QxVy5Q

http://plants.usda.gov/java/profile?symbol=clvi3

When One Becomes Two

One of the most stunning spring flowering plants in the eastern forests has to be blue cohosh (Caulophyllum spp.). Around this time of year they begin poking up through the leaf litter, their deep purple stems gradually giving way to shades of blue and green as the leaves and flowers expand into the springtime sun. They seem almost otherworldly and finding them among the speckled leaves of trout lily is a sight I will never tire of.

For as long as it has been known, North America's Caulophyllum has been considered a single species, Caulophyllum thalictroides. The specific epithet hints at how similar this species can look to the meadow rues (Thalictrum spp.). However, a keen observer could tell you that there are apparent differences between some blue cohosh populations, especially in the northeast. Some cohosh flower much earlier than others. Also, there are differences in flower color as well. Some plants sport flowers decked in deep maroon whereas others are pale green. These differences have led some authors to list the purple flowering variety as a subspecies, Caulophyllum thalictroides giganteum.

Caulophyllum thalictroides

Photo by Tom Potterfield licensed under CC BY-NC-SA 2.0

More recently, however, it has become apparent that these two varieties may actually be separate species. Though their ranges overlap, what is now being called Caulophyllum giganteum is distributed much farther north than C. thalictroides. The key differences between these two has to do with flowering time. If these two species become reproductively active at different times, then they are in fact reproductively isolated from one another. Though they can hybridize, the resulting seeds experience reduced viability and do not perform as well as either parent.

Photo Credit: Tom Potterfield (http://bit.ly/1E0JcQ5)

Further Reading: [1] [2]
 

The Badass Spring Ephemerals

Spring ephemerals and the word "badass" are probably not frequent associates but I am here to argue that they should be.

Spring ephemeral season is here for some and just around the corner for the rest of us. It's my favorite wildflower season and I often go missing in the woods for those first few weeks of spring. It is easy to look at their diminutive size and their ephemeral nature as signs of delicacy but these plants are anything but. In fact, when one examines the intricacies of their lifestyle, they can see that spring ephemerals make most other plants look like total softies.

Spring ephemerals, the designation of which gets blurred depending on who you ask, have to complete most of their life cycle in the early spring before the trees and understory shrubs leaf out and completely take over most of the available light. This is an incredibly tough time to be a plant. Soil temperatures are low, which makes nutrient and water uptake a difficult task, all but the most robust pollinators are still sound asleep, and there is the ever present danger of a hard frost or freak snow storm. These factors have led to some incredible adaptations in all of the species that emerge around this time. Whereas each species has its own methods, there are some generalities that are common throughout.

For the most part, spring ephemerals have two distinct growth phases; epigeous (above ground) and hypogeous (below ground). The hypogeous phase of growth takes place throughout fall and winter. Yes, winter. This is the phase in which the plants put out more roots and develop next season’s buds. This goes on at the expense of nutrients that were stored the previous spring. Once spring arrives and soils begin to warm, the plants enter the epigeous phase of growth where leaves and flowers are produced and reproduction occurs. This is an incredibly short period of time and spring ephemerals are well suited for the task.

Typical growth cycle of many spring ephemerals [Source}

For starters, photosynthetic activity for these species is at its best around 20 °C. Photosynthetic proteins activate very early on so that by the time the leaf is fully expanded, the plant is a powerhouse of carbohydrate production. Photosynthesizing in cool temperatures comes at a cost. Water stress in at this time of year is high. Low soil temperatures make uptake of water difficult and it is strange to note that many species of spring ephemeral have very little root surface area in the form of root hairs. These species, however, have extensive mycorrhizal associations which help assuage this issue.

Nutrient availability is also very limited by low soil temperatures. Chemical reactions that would unlock such nutrients are not efficient at low temperatures. Again, spring ephemerals get around this via their increased mycorrhizal associations. It should be noted that some species such as those belonging to the genus Dicentra, do not have these associations. In this situation, these species do in fact develop extensive root hairs as a coping mechanism. Despite specific adaptations for nutrient uptake, you will rarely find spring ephemerals not growing in deep, nutrient-rich soils.

Again, we must keep in mind that all of this is happening so that the plant can quickly complete what it needs to do in the few weeks before the canopy closes and things heat up. It has been observed that high temperatures are associated with slowed growth in most of these species. As temperatures increase, the plants begin to die back. Another adaptation to this ephemeral lifestyle is an increased ability to recycle nutrients in the leaves. As spring temperatures rise, the plants begin to pull in nutrients and store them in their perennial organs. They also show specific compartmentalization of energy stores. In many species, seed production is fueled solely by energy reserves in the stem. Some underground storage structures then receive nutrients to fuel autumn and winter growth while others receive nutrients to fuel leaf and stem growth in the early spring.

Despite all of these amazing adaptations, life is still no cake walk and growth is painstakingly slow. Many species, like trout lilies (Erythronium spp.), can take upwards of 8 years to flower! 8 years!! Think about that next time you are thinking of harvesting or picking some. Even worse in some areas are white tailed deer. East of the Mississippi their populations have grown to a point in which their foraging threatens the long term survival of many different plant species. Especially hard hit are spring ephemerals as they are the first plants to emerge after a long winter of near starvation. 

I hope this post wakes people up to how truly badass these species really are. As our climate warms, we can only speculate how things are going to change for many of them. Some research suggests that things may get easier whereas others suggest that conditions are going to get harsher. It's anyone's guess at this point. As populations are wiped out due to development or invasive species, we are losing much needed genetic diversity and corridors for gene transfer. This is yet another reason why land conservation efforts are so vital to resilient ecosystems. Support your local land conservancy today!

Spring is here and things are getting underway. Get out there and enjoy the heck out of the spring ephemerals! In a few short weeks they will be back underground, awaiting the next cold, damp spring.

Further Reading: [1] [2]

Bacterial Enduced Shield

Photo by Dick Culbert licensed under CC BY 2.0

Legumes are famous the world over for their nitrogen fixing capabilities. These hardy plants can live in soils that would otherwise not support much of anything. As such, nitrogen fixation is one reason that the legumes have found themselves as a focus of agriculture. However, this ability is not solely the plants doing nor has it evolved to benefit humans. Legumes owe their ability to turn a gas into food to a symbiotic relationship with special soil bacteria known collectively as "rhizobia." The legumes produce special root structures called "nodules" to house these bacteria. In return for nitrogen, the bacteria receive carbohydrates and other organic compounds. The nature of this relationship may seem pretty straight forward but, as with anything in nature, the closer we look the more interesting things get. As it turns out, rhizobia also play a role in plant defense.

When a team of researchers began raising Crotalaria, a genus of legume native to Africa, they noticed something strange. Plants that were not inoculated with rhizobia didn't produce nodules nor were they producing any of the alkaloid chemicals that defend them from herbivores. Even adding artificial nitrogen to the soil didn't stimulate the plants to produce their chemical cocktails. Something was going on here and it would seem that the missing bacteria were the key to the puzzle. 

Indeed, only after the plants were inoculated with their native rhizobia did they begin producing nodules and eventually the defensive alkaloid compounds. Could it be that the bacteria produce these chemicals for the plant? 

Not quite. As it turns out, the area of biosynthesis for these defense compounds happens to be in the root nodules that house the rhizobia. The rhizobia trigger the production of the nodules, which in turn triggers the production of the alkaloids. From there, the plant can export them to above-ground structures as a means of defense. The bacteria are simply a key that unlocks a genetic pathway for defense. Seeing as the alkaloids are, in part, made from nitrogenous molecules, this is not too surprising. There is no sense in trying to make these compounds if the chemical ingredients aren't there. This research serves as further evidence of how complex the microbiome can be. 

Photo Credit: Dick Culbert - Wikimedia Commons

Further Reading:

http://www.pnas.org/content/early/2015/03/13/1423457112

Moss Matriarchy

Photo by Wolfram Sondermann licensed under CC BY-ND 2.0

Mosses have been around for a long time. They also retain some interesting features of early land plants. Like their algal precursors, mosses have motile sperm that must literally swim their way to a female gamete. Of course, this process requires water. For some mosses, living on land makes reproduction difficult, even at the scale of a few centimeters. Distance is not the friend of diminutive, sexually reproducing mosses.

There are some groups of mosses that have evolved an interesting way around the issue of distance. Though it occurs in plenty of other genera, I would like to focus attention on one genus in particular, the Dicranum mosses. You can find these hairy-looking mosses growing in tufts or mats in forests throughout North America. Like all bryophytes, they exhibit an alternation of generations. The green gametophytes house the sexual organs and, after fertilization, give rise to the stalked sporophytes that produce and disseminate their spores. 

An inspection of Dicranum patches in the wild may reveal that all of the gametophytes seem to be female. Despite this observation, there would seem to be no shortage of sporophyte stalks poking above the mat. How is this possible? How does sperm make it from some undisclosed male population to fertilize the eggs of these entirely female mats? The answer is to be found only after you observe the females under a microscope. 

Dwarf males growing on the stem tomentum of Dicranum polysetum. Photos: L. Heden€ as [SOURCE]

Under magnification, you will notice that many of the female gametophytes appear to have hairy little outgrowths scattered around their tiny leaves. Under a higher powered lens you may then notice that these hairy outgrowths contain antheridia, the sperm producing organs of males. What is going on here? Are these mosses hermaphroditic? Nope! What you are seeing are indeed the males of this species. 

Spores of Dicranum don't start out as either sex. Instead, their fate in the environment determines what they eventually develop into. If a spore makes it to new terrain, it will become a female. Females are larger and can handle the rigors of establishing new territory. If a spore lands on another clump of moss, something different happens. The female gametophytes emit hormones which direct the development of that spore into one of these dwarfed males. Settled in among a forest of females, this tiny male individual is now primed and ready to release sperm. They are essentially live-in sperm donors.

For this genus, it doesn't make sense fore males to grow into full blown adults in such situations. The bigger a male gets, the more distance separates his sperm from the eggs of females. A reduction in size allows the males to insert themselves into colonies made entirely of females to serve as the reproductive agent for that grouping. Quite a fascinating life history trait if you ask me. Mosses have also been at the survival game much longer than pretty much all other forms of life we encounter on land. I think it goes without saying that they certainly deserve a greater recognition. 

Photo Credit: [1] [2]

Further Reading: [1] [2]

Unlikely Allies

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

On the Balearic Islands of Spain, an interesting relationship has developed between a plant and an animal. What's more, this relationship seems to have developed relatively recently in the history of these two species. The players in this story are the dead horse arum (Helicodiceros muscivorus) and an unsuspecting lizard known as Lilford’s wall lizard (Podarcis lilfordi).

Podarcis lilfordi is a lot like other fence lizards. They spend their days basking in the sun’s warmth and hunting for insect prey. They also have a tendency to feed on nectar and pollen, making them important pollinators of a handful of plant species around the island. For the dead horse arum, however, its not about pollination.

Like most members of its family, the dead horse arum relies on trickery for sex. As its common name suggests, the dead horse arum both looks and smells like rotting meat. Unsuspecting flies looking for a meal and a place to lay their eggs find the dead horse arum quite attractive in this regard. The plant even steps up its game a bit by producing its own heat. This helps volatilize its smell as well as to make it a cozy place worth investigating. Studies have found that during the peak flowering period, the inflorescence can be upwards of 24 °C (50 °F) warmer than its surroundings.

Photo by Marina Sanz Biendicho licensed under CC BY 2.0

As one would expect, this has caught the attention of the cold blooded lizards. Enticed by the heat source, lizards basking on the spathe quickly realize that the plant is also a great place to hunt. Flies attracted to and trapped by the flowers make an easy meal. On the surface this would seem counterproductive for the dead horse arum. What good is an animal hanging around that eats its pollinators?

The relationship doesn't end here though. At some point in recent history, a handful of lizards figured out that the seeds of the dead horse arum also make a great meal. This behavior quickly spread through the population to the point that Podarcis lilfordi regularly break open the seed heads and consume the fleshy berries within. Here's the catch, seeds that have passed through a lizards gut are twice as likely to germinate.

Researchers have been studying this interaction since 1999. Since then, the dead horse arum has gone from being relatively rare on the island (~5,000 individuals per hectare) to a density of roughly 30,000 individuals per hectare during the 6 year span of the study! Even though the lizards eat their pollinators, the dead horse arums of Aire Island have nonetheless benefited from interactions with their cold blooded companions.

Sadly, this novel relationship may not last too long. The introduction of cats and rats to the islands has drastically reduced the population of these lizards to the point that the IUCN has listed them as an endangered species. Research will be needed to see if the dead horse arum follows in their wake.

Photo Credit: [1] [2]

Further Reading: [1] [2]

The Largest Seed in the World

Photo by Reed Wiedower licensed under CC BY-SA 2.0

For Lodoicea maldivica, better known as coco de mer, producing the largest seeds in the world may seem like a cool fact for the record books but it certainly has its drawbacks. However, as with anything in nature, selection would not allow for wasteful traits to be passed on. Costs must be offset by a reproductive advantage on some level. A recent study looked at what these tradeoffs might be for L. maldivica and what they found is pretty incredible.

With seeds clocking in at upwards of 30 kg (66 lbs.) one has to wonder what L. maldivica is up to. It was long thought that, like the coconut, seeds of this palm must be dispersed by water. However, they are simply too dense to float. Instead, seed dispersal for this peculiar species of palm is actually quite limited. They simply fall from the tree and germinate below the canopy.

Photo by Wendy Cutler licensed under CC BY 2.0

This may explain why L. maldivica is endemic only to the islands of Praslin and Curieuse in the Seychelles. It's not just the seeds that are huge either. The female flowers, which are borne on separate trees than the males, are the largest female flowers of any species of palm. At 10 m (32 ft.) in diameter, the leaves are also massive, fanning outwards on petioles that can reach 2 m to 4 m (6.5 - 13 ft) in length. It goes without saying that L. maldivica is a palm full of superlatives.

Counterintuitively, the habitats in which they grow are notoriously low in nutrients. Why then would this palm invest so much energy into growing these gigantic structures? Because they tend to germinate and grow beneath their parents, the offspring of L. maldivica would appear to be at a disadvantage from the start. A recent study suggests that the answer lies in those massive leaves.

Researchers found that the areas directly beneath the adult trees were wetter and had more soil nutrients compared to the surroundings. As it turns out, L. maldivica modifies its own habitat. Those massive leaves do more than just collect sun, they also act as giant funnels. In fact, most of the water that rains down onto the canopy is collected by the leaves. In this way, everything from water, debris, and even excess pollen is funneled down to the base of each tree.

Photo by Ji-Elle licensed under CC BY-SA 3.0

Not only is this good for the parent tree, it is also a boon for the dispersal-limited offspring. Coupled with the considerable endosperm in those massive seeds, all of this additional water and fertilizer means that seedling L. maldivica enter into the world at a distinct advantage over many other plants on the islands. All of that endosperm serves to help fuel seedling growth while it is still shaded by its parent.

Sadly, over-harvesting of the seeds has crippled natural reproduction for L. maldivica. This coupled with habitat destruction paints a bleak picture for this record-holding palm. It has already been lost from three other Seychelles islands. Luckily there are many conservation efforts underway that are aimed at saving L. maldivica. The Seychelles are now considered a World Heritage Site and many of the wild populations of this palm lie within national parks.

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

Further Reading: [1] [2]

A New Look at a Common Bladderwort

Photo by Kevin Thiele licensed under CC BY 2.0

It is so often that common species are overshadowed by something more exotic. Indeed, we know more about some of the rarest plants on earth than we do about species growing in our own back yards. Every once in a while researchers break this pattern and sometimes this yields some amazing results. Nowhere has this been better illustrated in recent years than on the humped bladderwort, Utricularia gibba. 

This wonderful little carnivore can be found growing in shallow waters all over the world. Like all Utricularia, it uses tiny little bladders to capture its even tinier prey. Despite its diminutive size, U. gibba is nonetheless a very derived species. For all of its wonderful physical attributes, the real adventure begins at the microscopic level. As it turns out, U. gibba has some amazing genetic attributes that are shining light on some incredible evolutionary mechanisms. 

When researchers from the University at Buffalo, Universitat de Barcelona in Spain, and LANGEBIO in Mexico decided to sequence the genome of this plant, what they found was quite startling. For a rather complex little plant, the genome of U. gibba is incredibly small. What the researchers found is that U. gibba appears to be very efficient with its DNA. Let's back up for a moment and consider this fact. 

The genomes of most multicellular organisms contain both coding and non-coding DNA. For decades researchers have gone back and forth on how important non-coding DNA is. They do not code for any protein sequences but they may play a role in things like transcription and translation. For a long time this non-coding DNA has been referred to as junk DNA. 

This is where things get interesting. Sequencing of the U. gibba genome revealed that only 3% of its genome consisted of non-coding or junk DNA. For some reason the U. gibba lineage has managed to delete most of it. To put things in perspective, the human genome is comprised of roughly 98% non-coding or junk DNA. Despite its rather small and efficient genome, U. gibba nonetheless has more genes than plants with larger genomes. This may seem confusing but think of it this way, whereas U. gibba has a smaller overall genetic code, it is comprised of more genes that code for things like digestive enzymes (needed for digesting prey) and cell walls (needed to keep water out) than plants with more overall genetic code such as grapes or Arabidopsis. 

As one author put it, this tiny ubiquitous plant has revealed "a jewel box full of evolutionary treasures." It is a species many of us have encountered time and again at the local fishing hole or in your favorite swimming pond. Time and again we pass by the obvious. We overlook those organisms that are most familiar to us. We do so at the cost of so much knowledge. It would seem that the proverbial "Old Dog" has plenty of tricks to teach us. 

Photo Credit: Kevin Thiele (http://bit.ly/1Flouqd) and Reinaldo Aguilar (http://bit.ly/1B6mnHN)

Further Reading:

http://www.nature.com/nature/journal/v498/n7452/full/nature12132.html

http://mbe.oxfordjournals.org/content/early/2015/01/31/molbev.msv020

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

A Real Cliffhanger

Cliff faces are some of the most interesting habitat types on the planet. Few places in the world are as inhospitable. They are low in nutrient levels, they have limited space for root growth, and offer very little for recruitment. Cliffs do offer some benefits though. They are often sheltered from extremes in climate and can be inaccessible to large herbivores. With that in mind, it is understandable how they can be a haven for some very unique and equally extreme life forms.

One such life form that comes to mind is Borderea chouardii. This strange plant grows only on a couple cliff faces in the Pyrenees mountain range in Spain. It is critically endangered as it represents a relict population of a once tropical Tertiary environment. What makes it more interesting is the double mutualism it has formed with ants. As we have touched on a few times in the past, ants are often recruited as seed dispersers. Borderea chouardii does just that. In many of the observed cases of seed dispersal, researchers found that ants were the culprit. Interestingly enough, a majority of the remaining cases were due to the plant literally planting its own seeds. Known as "skototropism," the stems of the seed cases grow into dark crevices, which are perfect spots for seed to germinate and grow. Surprisingly, gravity plays a very small role in the reproduction of this species.

Let me back up for a bit here. I did mention this plant has a double mutualism with ant species after all. Based on years of observation, researchers found that ants actually served as the most efficient pollinator for Borderea chouardii. This is not a common thing. Generally speaking, ants do not make for effective pollinators. Most species have glands that secrete substances that destroy pollen. However, in a mountainous cliff setting, winged insects are relatively rare, so Borderea chouardii and ants have evolved together into this oddball double mutualism. To add an extra layer of complexity to the system, dare I mention that it isn't just one ant species that Borderea chouardii relies on, but rather 3. Two ant species serve as the pollinators while a a third ant species serves as a seed disperser. This is one risky plant species. The plant gets around the rarity of successful recruitment by living a long time. Individual plants can live upwards of 300 years, which is quite possibly the record for a non-clonal forb species.

Photo Credit: María B. García, Xavier Espadaler, Jens M. Olesen

Further Reading:

http://www.plosone.org/…/info%3Adoi%2F10.1371%2Fjournal.pon…

http://www.iucnredlist.org/details/162110/0

Fly Guild

Photo by Rictor Norton & David Allen licensed under CC BY 2.0

Lapeirousia oreogena grows in the western portion of South Africa. Though it may be difficult to tell by looking at it, this little plant is a member of the iris family. Decked out in its striking shade of purple, the white spots on its petals really stand out. Shaped like arrowheads, it would almost seem as if the plant was trying to advertise the perfect place to grab a sip of nectar. Indeed, that is exactly what they are doing. Those white arrows serve as guides for a rather peculiar pollinator.

Photo by Peter Goldblatt

Prosoeca peringueyi is a pretty incredible little fly. For starters, its proboscis is 2 inches in length! It looks rather awkward buzzing around a patch of these beautiful irises. Seeing it in action may change your mind though. It is truly an ariel acrobat as it maneuvers itself above a flower and expertly dips its long proboscis down the slightly longer nectar tube of the flowers. How is the fly so adept at hitting its target every time? The answer lies in those white arrows. 

A team of researchers performed a series of experiments in which they covered up the white arrows of some flowers. As it turned out, the flies still approached the flowers but, with no arrows visible, successful insertion of the proboscis was drastically reduced. The arrows serve as a guide for the flies to tell them exactly where they are going to be able to get an energy rich drink.

How exactly does a system like this evolve? A clue to the answer lies in the fertility of these irises. Plants that aren't visited sequentially by these long-tongued flies do not set seed. As it turns out, the plants need the flies to be just out of reach of the bottom of the nectar tube for efficient transfer of pollen. Over time, an evolutionary arms race developed in which the proboscis of the flies gradually got longer to get as much nectar as possible and thus selecting for irises with longer and longer flower tubes.

This system seems to have had an effect on other plant species growing in this region too. Lapeirousia oreogena is only in bloom for a small window of time during the growing season. What happens to these long tongued flies when this window is closed? Interestingly, other plant species form what is referred to as a guild with L. oreogena. They all cater to these flies with varying lengths of elongated nectar tubes. In total, at least 28 plant species in this region have seemed to have converged on this pollination syndrome. To see more of these plants, click here.

Photo Credits: Rictor Norton, David Allen (http://bit.ly/1jzvHeK) and Peter Goldblatt

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

Amber Fossils of Grain

In what may be one of the most interesting fossil discoveries in recent years, scientists from Oregon State University have described the earliest fossil evidence of grasses. Encased in 100 million year old amber this ancient grass spikelet suggests grasses were already around in the early to mid Cretaceous period. This is some 20 to 30 million years earlier than previous estimates for grass evolution. If that isn't cool enough, the grass appears to have been infected by a fungus related to ergot (the darker portion at the top), showing that this parasitism may be as old as grasses themselves. 

We humans have a long history with ergot's fondness for grasses. It is best known for producing the chemical precursors of LSD (as well as many other useful drugs) and has been implicated in some major historical events throughout our short time on this planet. However, suggesting that dinosaurs were getting high off the stuff is pushing it. Ergot likely evolved its chemical cocktail to deter herbivores from eating the grasses that it parasitizes. It has a bitter taste and cattle are said to avoid grasses that have been infected by it. It is quite possible that dinosaurs probably did the same thing. 

Either way, this finding represents a major milestone in the understanding of one of the most important plant families on the planet. Following the mass extinction at the end of the Cretaceous, grasses quickly rose to dominate roughly 20% of global vegetation. This little piece of amber now suggests that dinosaurs and their neighbors likely had a role in shaping this plant family. 

Photo Credit: Oregon State University

Further Reading: [1]

Stained Glass Leaves

Photo by Jardín Botánico Nacional, Viña del Mar, Chile licensed under CC BY-NC-SA 2.0

Producing flowers is a costly endeavor for plants. They require a lot of resources and give nothing back in the way of photosynthesis. The showier the flower, the greater the investment. It should be no shock then that some plants utilize more energy efficient strategies for attracting pollinators. One of the more interesting ways in which a plant has evolved to save energy on flowering comes from a rather surprising family. 

Gesneriads are known for their showy flowers. There are many variations on the theme but most are rather colorful and tubular. However, in the jungles of Central and South America grows two species of Columnea that make such generalizations a waste of time. The flowers of C. consanguinea and C. florida are small, drab affairs, especially for a Columnea. They arise from the stem at the base of the leaves and would largely go unnoticed without close inspection. It is amazing that anything could find them among the chaos of the jungle understory let alone pollinate them. That is where the leaves come in. 

Photo by alex monro licensed under CC BY-NC 2.0

Towards the tip of the long, blade-like leaves are heart shaped red spots. They are translucent and to stand below one conjures a mental image of stained glass windows. Against the background of greens, these spots really stand out. Their purpose is to attract pollinators, specifically the green-crowned brilliant hummingbird (Heliodoxa jacula), which can then locate the nectar-rich flowers, pollinating them as they feed. By producing these translucent red spots on their leaves, these plants are able to save a lot of energy. Leaves are retained for much longer than flowers are and, of course, they photosynthesize.

Photo Credit: Jardín Botánico Nacional, Viña del Mar, Chile (http://bit.ly/1CXtToh) and alex monro (http://bit.ly/1uVwf0x)

Further Reading:

http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2745.2008.01465.x/full

An Abominable Mystery

Photo by Shizhao licensed under CC BY-SA 2.5

We all love flowers but for all the attention we pay them, their origin remains elusive. Darwin called their sudden appearance in the fossil record an “abominable mystery.” Since Darwin's time, we have been able to clarify that picture a little bit. Even so, our understanding of the origin of the angiosperm lineage is dubious at best. When and why did flowers evolve?

For millions of years the land was dominated first by ferns and their allies and then by gymnosperms like cycads and gingkos. It was not until the Cretaceous that angiosperms began to rise to their current place as the dominant and most diverse group of plants. Their sudden appearance on the scene has been largely shrouded in mystery. There is scant fossil evidence to illustrate the early evolutionary steps in this development of flowers. Many paleobotanists believed that flowers had their origin in shrub-like ancestors of gymnosperms. Others felt that the origin of flowers belonged with the seed ferns (http://bit.ly/1zKfriM).

Around 2001 a fossil discovery from Yixian Formation, Liaoning, China was believed to have changed all of that. A researcher by the name of Ge Sun had stumbled upon a very primitive looking fossil plant. To his surprise, the reproductive structures seemed to show stamens in pairs below carpels and a lack of petals and sepals. The formation in which the fossil was found dated back to the Jurassic period. Could this represent the remains of the earliest flowers?

The fossil has been coined Archaefructus and since its discovery at least two species have been identified. Archaefructus was an aquatic plant, likely living on the edge of freshwater lakes. These fossils (as one would expect) are quite contentious. Some argue that it is more derived than would be expected from the first flower. Recently it has been suggested that Archaefructus is a sister lineage to early flowering plants, not unlike Nymphaeales or Amborella living today. 

What Archaefructus does suggest is that flowers had their origin much earlier than the Cretaceous. Other discoveries from the same formation (ie. Archaeamphora longicervia) suggest that flowering plants were already diversifying at this time. So, if this is the case, when did flowers appear on the scene? Far from the smoking gun that a fossilized flower would represent, researchers are nonetheless finding tantalizing fossil evidence that places the origin of flowering plants all the way back to the Triassic. 

By examining Triassic microfossils, some researchers believe they have found fossilized pollen grains that are distinctly angiosperm in origin. I won't go into it here but extant examples show a major distinction between pollen from gymnosperms and pollen from angiosperms. If this is true, flowers may be way older than ever expected. For now, the jury is still out on this one. 

Flowers evolved for sex. We associate animals like bees, bats, and birds with flowers today but most of these lineages came much later in the game. Exactly what was around pollinating early flowers remains a bit of a mystery as well. Were the earliest flowers wind pollinated or was there some insect or even reptile that served the selection pressure necessary for their evolution? Only time and more fossil discoveries will tell. 

Photo Credit: Shizhao (Wikimedia Commons)

Further Reading:

http://www.sciencemag.org/content/296/5569/899.abstract?ck=nck&siteid=sci&ijkey=8dZ6zTqF606ps&keytype=ref

http://faculty.frostburg.edu/biol/hli/research/Eoflora.pdf

http://www.ohio.edu/people/braselto/readings/angiosperms.html

http://journal.frontiersin.org/Journal/10.3389/fpls.2013.00344/full

http://www.amjbot.org/content/96/1/5.abstract

Cooksonia: A Step Into the Canopy

Photo by Steel Wool licensed under CC BY-NC-ND 2.0

For plants, the journey onto land did not happen over night. It began some 485.4–443.4 million years ago during the Ordovician. The best evidence we have for this comes in the form of fossilized spores. These spores resemble those of modern day liverworts. Under high powered microscopes, one can easily see that they were indeed adapted for life on land. These early plants were a lot like the hornworts, liverworts, and mosses we see today in having no vascular tissues for transporting water, an adaptation that would not come along for another few million years. 

Without vascular tissues, plants like liverworts and mosses cannot transport water very far. They instead rely on osmosis and diffusion to get water and nutrients to where they need to be, which severely limits the size of these types of plants to only a few centimeters. This growth pattern carried on well into the Silurian. Until then, the greening of our planet happened in miniature. 

Photo by Sabrina Setaro licensed under CC BY 2.0

Around 415 million years ago, however, plants became vascularized. This changed everything. It set the stage for the botanical world we know and love today. Paleobotanists place the fossil remains of these newly evolved vascular plants in the genus Cooksonia. Based on what we would call a plant today, Cooksonia probably pushes the limits. However, in some species the branching structure is full of dark stripes, which have been interpreted as vascular tissues. It still wasn't a very tall plant with the tallest specimen standing only a few centimeters but it was a major step towards a much taller green world. 

Cooksonia did not have any leaves that we are aware of but some species certainly had stomata (another major innovation for water regulation in plants). Each branched tip ended in a sporangium or spore-bearing capsule. It has been suggested that Cooksonia may not represent an individual photosynthetic plant but rather a highly adapted sporophyte that may have relied on a gametophyte for photosynthesis. This hypothesis is supported by the diminutive size of many Cooksonia fossils. They simply do not have enough room within their tissues to support photosynthetic machinery. Because of this, some botanists believe that vascularization sprang from a dependent sporophyte that gradually became more and more independent from its gametophyte over time. Until an associated gametophyte fossil is found, we simply don't know. 

Photo Credits: Steel Wool (http://bit.ly/1AjLYh8) and Sabrina Setaro (http://bit.ly/16mdyxw)

Further Reading: [1] [2] [3]