A Beautiful and Bizarre Gentian

There is something about gentians that I am drawn to. I can't quite put my finger on it but it definitely has something to do with their interesting pollination strategies. One of the coolest gentian species I have ever met grows in the mountainous regions of western North America.

Meet Frasera speciosa a.k.a. the monument plant (a.k.a. elkweed). It is only one of 14 species in the genus. This fascinating species (as well as its relatives) lives out most of its life as a rosette of large, floppy leaves. The monument plant is what is known as a "monocarpic perennial", meaning it lives for many years as a rosette before flowering once and dying. It has been recorded that some individuals can be upwards of 30 years old by the time they flower!

This reproductive strategy brings with it a specific set of challenges but yet, if balanced correctly, offers many advantages. For starters, if you only flower once in a life time, you best make it count. The good news is, if flowering events are rare and widely spaced, this is a good strategy for avoiding herbivores. Such an irregular reproductive lifestyle means that the likelihood of a flowering population getting munched on is greatly reduced.

The same goes for seeds. If setting seed is a rare and widely spaced event, the likelihood of seed predation is also reduced. This is what is known as predator avoidance behavior. While it is not quite understood how plants synchronize flowering (though environmental conditions do play a role), it has been found that, for at least some populations, it alternates in intervals of 3 and 7 years. In essence, each flowering event can be seen as mast event. This keeps the overall impact of any potential herbivores and seed predators to a minimum.

This synchronous flowering strategy can also be beneficial for insuring cross pollination. The flowers are large and seemingly quite attractive to many different species of pollinators. By flowering all at once, a population is offering a tempting bonanza for pollinators that ensures many visits to each flower, thus increasing the chances of reproductive success. Since each individual plant invests all of its collective energy into a single flowering event, more energy is allocated to producing flowers and seed than if it flowered year after year.

The interesting habits of this plant's lifestyle don't end there. Each plant is essentially a pretty awesome parent! It has been found that seeds that are buried under the decomposing remains of a parent plant not only germinate better but the resulting seedlings also have a much higher rate of survival. This is good news for two big reasons.

For one, the decomposing remains enrich the surrounding soil while also creating a humid micro climate that is very conducive to growth. Second, the fact that they all germinate and grow relatively close to the parent plant, means that the density of young plants closely mimics that of the parental population. If the seeds were to be dispersed great distances from each other, it would be much more difficult to synchronize a flowering event and to ensure sufficient pollination. This way, entire populations grow up together in this nursery made from the remains of their parents. This is such a cool genus and I hope you get the chance to meet one for yourself.

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

Not All Pitchers Are Equal: How Prey Capture Has Driven Speciation in the genus Nepenthes

Source

Species of the genus Nepenthes are as bizarre as they are beautiful. Known the world around for their carnivorous lifestyle, these plants looks like something out of a macabre art exhibit. It is easy to get caught up in this beauty. I often find myself lost in thought while staring at full grown specimen. How did this genus come to be? Why are they so diverse? What is going on with the morphology of these plants?

Nepenthes hail from nutrient poor habitats, which has driven them to supplement their growth with nutrients gained via the breakdown of a variety of organisms. The business ends of a Nepenthes are their pitchers. We get so caught up in the bewildering diversity of shapes, colors, and sizes that we often overlook them as the anatomical marvels of evolution that they truly are. Whereas the main body of these plants often look quite similar among different species, it's the pitchers that really allow us to separate them out as distinct species. Pitcher morphology not only gives us a convenient means to identify these plants, research is now showing that the structure of these pitchers is likely to be the driving force in their evolution. 

Source

Let's back up for a second. Before we get to the subject of adaptive radiation, we should take a closer look at the anatomy of these plants. To put it simply, the pitchers of Nepenthes are actually leaves, albeit highly modified versions. What we readily recognize as the photosynthetic leaves of a Nepenthes plant are actually modified leaf bases or petioles. Over evolutionary time, these bases have flattened to increase the amount of surface area available for photosynthesis.

From the tip of each of these "leaves" is produced a tendril. Gradually this tendril will elongate and the tip starts to swell. This tip will eventually become the pitcher. The pitchers themselves are highly modified leaves. They are some of the most specialized leaves in all of the plant kingdom. As the tip grows larger, it becomes clear that there is a distinctive lid apparatus. Once the pitcher is fully mature, this lid pops open revealing the death trap filled with digestive fluids.

Source

As if producing pitchers wasn't cool enough, each species of Nepenthes produces two distinct forms - lower pitchers, which are produced by young plants as well as on mature plants near the ground, and upper pitchers, which are produced up on the climbing stems as they vine through the canopy. The upper and lower pitchers look radically different from one another to the point that one may easily confuse them for different species. The reason for such stark differences has to do with the type of prey captured. Lower pitchers are generally larger and can capture prey that crawls along the forest floor. Upper pitchers tend to be more slender and most often capture flying insects as well as other creepy crawlies hanging out in the forest canopy.

The key to the success of these traps seems pretty straight forward - insects attracted by bright colors and sweet nectar land on the traps and fall to their death. Certainly this holds true throughout the genus, however, there are at least two major variations on this theme and a handful of bizarre mishmashes. As the lid of a Nepenthes pitcher starts to open, a ring of tissue called the peristome unfurls. The shape and color varies wildly between species and this has to do with the methods in which they capture their prey. These variations are the key to the amazing diversity of Nepenthes we see throughout the range of this genus.

Nepenthes vogelii

The first of the three strategies is referred to as the 'insect aquaplaning' strategy. Insects walking around on the peristome of the pitcher find it hard to get a foothold. These are species such as N. raja, N. ampullaria, and N. bicalcarata (just to name a few). The slipperiness of the peristome of these species is further enhanced when humidity is high. Considering how much it rains in these habitats, it is no wonder why capture efficiency is often as high as 80%. Although there is some variation on this theme, pitchers that utilize the insect aquaplaning strategy often lack waxy cells on the interior of the pitcher walls.

Slippery pitcher walls are the second strategy that Nepenthes have converged upon. These are species such as N. diatas, N. mirabilis, and N. alata (again, just to name a few) Insects attracted to the pitchers are often lured in by sweet nectar. Once they cross the lip of the pitcher, prey find it hard to hang on and inevitably fall inside. Once this happens, waxy cells lining the interior walls make it impossible for anything to climb back out. It should be mentioned that a slippery peristome and waxy pitcher walls are not mutually exclusive. That being said, there are clear trends among species that show a reduction in waxy cells as peristome size and slope increases.

This brings us to the oddballs. There are species like N. lowii, whose pitchers function as a toilet bowl for shrews, and N. aristolochioides, whose pitchers seemed to have abandonded both strategies and now function as light traps similar to what we see in Darlingtonia. Regardless of their strategy, the diversity in trapping mechanisms appear to be the driving force behind the bewildering diversity of Nepenthes. 

Nepenthes aristolochioides

All of the evidence taken together shows that prey capture is at the core of this radiation. There seems to be incredibly strong selective pressures that result in strong divergence in pitcher morphology. The disruptive selection that seems to be driving a wedge between the insect aquaplaning strategy and the waxy wall strategy may have its roots in reducing competition. Nutrients are low and competition for food is high. Different Nepenthes species could be evolving to capture different kinds of prey. Even closely related species such as N. ampullaria, N. rafflesiana, N. mirabilis, N. albomarginata, and N. gracilis all seem to occupy their own unique spot on the spectrum of prey capture strategy.

It could also be that Nepenthes are responding to the specific characteristics of the habitats in which they are found. Those inhabiting drier sites may favor the waxy wall strategy whereas those living in wetter habitats tend to favor the slippery peristome. More work needs to be done to investigate where and how these different strategies are maximized. Until then, I think it is safe to say that the diversity of this incredible genus has a lot to do with obtaining food. 

Photo Credits: [1] 

Further Reading:

[1] [2] [3]

Meet the Fringe Tree

The fringe tree (Chionanthus virginicus) Photo by Arthur T. LaBar licensed under CC BY-NC 2.0

Coming across a fringe tree in full bloom is a spectacular experience. Known scientifically as Chionanthus virginicus, some may surprised to realize that this is a native tree to eastern North America. Though it has found its way into the horticultural trade, it is still not terribly common. Today I would like to celebrate this interesting tree as well as bring to your attention some alarming facts that might threaten its existence in the wild. 

Fringe tree can be found growing wild in the understories and edges of forests throughout eastern North America. It tends to be quite a rarity on the edges of its range, hitting its densest distribution in a handful of the southeastern states. Individual trees are either male or female but both produce quite a floral display. They produce dense clusters of wispy white flowers, which do give off a slight fragrance but one has to get up close and personal with the branches to really appreciate it. 

The fringe tree hails from the same family as the ash trees - Oleaceae. Unfortunately, this taxonomic relationship may be bad news for the fringe tree in the long run. At least one study has shown that fringe trees can serve as hosts for the emerald ashborer. The sample size on this study was quite low, only 4 of 20 adult trees showed signs of completed larval development and adult emergence holes. Subsequent observations suggest that fringe trees are in fact viable hosts for this invasive pest, which is certainly cause for concern. Perhaps the one thing fringe tree has going for it are its sparse populations, making it harder to detect by these wood boring beetles. Only time and a lot of attention will tell. 

Regardless, I think this is a wonderfully underrated tree for a native eastern North America landscape. It is rather hardy and puts on quite a show every spring. As the Grumpy Gardener so eloquently put it, "It’s tougher than dogwood, more dependable than saucer magnolia, longer-lived than cherry, and smells better than stinky Bradford. And it’s beautiful." I couldn't agree more. Just make sure that if you know of wild fringe tree populations or have some growing on your property that you regularly monitor them for signs of emerald ashborer infestation.

Photo Credits: [1] [2] 

Further Reading: [1] [2]

Invasion of the Earthworms

Photo by Rob Hille licensed under CC BY-SA 3.0

As an avid gardener, amateur fisherman, and a descendant of a long line of farmers, I have always held earthworms in high regard. These little ecosystem engineers are great for all of the above, right?

Not so fast! Things in life are never that simple! Let's start at the beginning. If you live in an area of North America where the glaciers once rested, there are no native terrestrial worms in your region. All of North America's native worm populations reside in the southeast and the Pacific northwest. All other worms species were wiped out by the glaciers. This means that, for millennia, northern North America's native ecosystems have evolved without the influence of any type of worms in the soil.

When Europeans settled the continent, they brought with them earthworms, specifically those known as night crawlers and red wigglers, in the ballasts of their ships. Since then, these worms have been spread all over the continent by a wide range of human activities like farming, composting, and fishing. Since their introduction, many forests have been invaded by these annelids and are now suffering heavily from earthworm activities.

As I said above, any areas that experienced glaciation have evolved without the influence of worms. Because of this, forests in these regions have built up a large, nutrient-rich, layer of decomposing organic material commonly referred to as "duff" or "humus." Native trees, shrubs, and forbs rely on this slowly decomposing organic material to grow. It is high in nutrients and holds onto moisture extremely well. When earthworms invade an area of a forest, they disrupt this rich, organic layer in very serious ways.

Worms break through the duff and and distribute it deeper into the soil where tree and forb species can no longer access it. Worms also pull down and speed up the decomposition of leaves and other plant materials that normally build up and slowly create this rich organic soil. Finally, earthworm castings or poop actually speed up runoff and soil erosion.

All of this leads to seriously negative impacts on native ecosystems. As leaves and other organic materials disappear into the soil at an alarming rate via earthworms, important habitat and food is lost for myriad forest floor organisms. In areas with high earthworm infestations, there is a significant lack of small invertebrates like copepods. The loss of these organisms has rippling effects throughout the ecosystem as well. It has been shown that, through these activities, earthworms are causing declines in salamander populations.

It gets worse too. As earthworms speed up the breakdown of the duff or humus, our native plant species are suffering. They have evolved to germinate and grow in these rich, organic soils. They rely on these soils for survival. As the nutrient rich layers get redistributed by earthworms, native plant and tree populations take a hit. Spring ephemerals have been hit the hardest by earthworm invasions for these reasons and more. There is very little recruitment and, in time, many species are lost. For small seeded species like orchids, earthworms can even consume seeds, which either destroys them outright or drags them down deeper into the soil where they cannot germinate. Earthworms have also been shown to upset the mycorrhizal fungi networks which most plant species cannot live without.

Top Left: Forest soil horizons without earthworms; Top Right: Forest soil mixed due to earthworms; Bottom Left: Forest understory diversity without earthworms; Bottom Right: Forest understory diversity with earthworms. Credits: [1]

So, what can we do about this? Well, for starters, avoid introducing new populations of earthworms to your neighborhood. If you are using earthworms as bait, do not dump them out onto land when you're done. If you must get rid of them, dump them into the water. Also, if you are using worm castings in your garden, it has been recommended that you freeze them for about a week to assure that no eggs or small worms survive the ride. If you are bringing new plants onto your property, make sure to check their root masses for any worm travelers. Remember, no worms are native if you live in a once glaciated region.

Sadly, there is not much we have come up with at this point for dealing with the current earthworm invasion. What few control methods have been developed are not practical on a large scale and can also be as upsetting to the native ecology as the earthworms. The best bet we have is to minimize the cases of new introductions. Earthworms are slow critters. They do not colonize new areas swiftly. In fact, studies have shown that it takes upwards of 100 years for earthworm populations to migrate 1/2 mile! Armed with new knowledge and a little attention to detail, we can at least slow their rampage.

Further Reading: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]

How Spiders Increase Plant Diversity

If healthy ecosystems are what we desire, we must embrace predators. There is no way around it. Because of their meat-based diets, predators can have serious effects on plant diversity. Generally speaking, as plant diversity increases, so does the biodiversity of that region. It's not just large predators like wolves and bears either. Even predators as small as spiders can have considerable impacts on not only plant diversity, but ecosystem processes as well. Before we get to that, however, we should take a moment to review some of the background on this subject.

The way in which predators mediate plant diversity falls under a realm of an ecological science called top-down ecosystem controls. In a top-down system, predators mediate the populations of herbivores, which takes pressure off of the plant community. It makes a lot of sense as a numbers game. The fewer herbivores there are, the better the plants perform overall. However, ecology is never that simple. More and more we are realizing that top-down controls have less to do with fewer herbivores than they do with herbivore behavior.

Herbivores, like any organism on this planet, respond to changes in their environment. When predators are present, herbivores often become more cautious and change up their behavior as a result. Such is the case of grasshoppers living in fields. Grasshoppers are incredibly numerous and can do considerable amounts of damage to plant communities as they feed. Picture swarms of locusts and you kind of get the idea.

Photo by Andrew Cannizzaro licensed under CC BY 2.0

Given the choice, grasshoppers will preferentially feed on some plants more than others. Such was the case when researchers began observing grasshopper behavior in some old fields in Connecticut. The grasshoppers in this study really seemed to prefer grasses to all other plants. That is unless spiders were present. In this particular system lives a spider known as the nursery web spider (Pisaurina mira). The nursery web spider is an effective hunter and the fact does not seem to be lost on the grasshoppers.

In the presence of spiders, grasshoppers change up their feeding behavior quite a bit. Instead of feeding on grasses, they switch over to feeding on goldenrod (Solidago rugosa). Although the researchers are not entirely sure why they make this shift, they came up with three possible explanations. First is that the goldenrod is much more structurally complex than the grass and thus offers more places for the grasshopper to hide. Second is that goldenrod fills the grasshoppers stomach in less time thanks to the higher water content of the leaves. This would mean that grasshoppers had more time to watch for predators than they would if they were eating grass. Third is that the feeding behaviors of both arthropods allows the grasshopper to better keep track of where spiders might be lurking. It is very likely that all three hypotheses play a role in this shift.

Photo by Tibor Nagy licensed under CC BY-NC 2.0

It's the shift in diet itself that has ramifications throughout the entire ecosystem in question. Many goldenrod species are highly competitive when left to their own devices. If left untouched, abandoned fields can quickly become a monoculture of goldenrod. That is where the spiders come in. By causing a behavioral shift in their grasshopper prey, the spiders are having indirect effects on plant diversity in these habitats. Because grasshoppers spend more time feeding on goldenrods in the presence of spiders, they knock back some of the competitive advantages of these plants.

The researchers found that when spiders were present, overall plant diversity increased. This is not because the spiders ate more grasshoppers. Instead, it's because the grasshoppers shifted to a diet of goldenrod, which knocked the goldenrod back just enough to allow other plants to establish. It's not just plant diversity that changed either. Spiders also caused an increase in both solar radiation and nitrogen reaching the soils!

In knocking back the goldenrod, the habitat became slightly more open and patchy as various plant species of different shapes and sizes gradually established. This allowed more light to reach the soil, thus changing the environment for new seeds to germinate. Also, because goldenrod leaves tend to break down more slowly, they can have significant influences on nutrient cycles within the soil. As a more diverse set of plants establish in these field habitats, the type of leaf litter that falls to the ground changes as well. This resulted in an overall increase in the nitrogen supply to the soil, which also influences plant diversity.

In total, the mere presence of spiders was enough to set in motion these top-down ecosystem effects. It's not that spiders eat more grasshoppers, it's that they are changing the behavior of grasshoppers in a way that results in a more diverse plant community overall. This is a radically different narrative than what has been observed with examples such as the reintroduction of wolves to the greater Yellowstone ecosystem yet the conclusions are very much the same. Predators have innumerable ecosystem benefits that we simply can't afford to ignore. 

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

Further Reading: [1] [2]

Broomrape: What's in a Name?

Dr. Reuven Jacobsohn, Agricultural Research Organization, Bugwood.org
licensed under a Creative Commons Attribution-Noncommercial 3.0 License.

One can turn a lot of heads by speaking publicly of the plants in the family Orobanchaceae. This interesting and often beautiful parasitic plant family is collectively referred to as the broomrape family. Species with common names like “naked broomrape” and “spiked broomrape” can really make a casual plant conversation turn sour in no time.

Despite how heinous the name sounds, its origin is a bit more innocent. I have really grown to appreciate etymology. Learning the hidden meaning behind the words we utilize for taxonomy can be a lot of fun. It can also teach you a little bit more about the species itself. 

In this context, rape stems from the Latin word “rapum,” which roughly translates to “tuber” or “turnip.” Broom is an English word that, in this context, refers to a shrubby plant related to vetch, which is often parasitized by broomrapes. So, the literal meaning of broomrape is something akin to “broom tuber.” In other words, they are plants growing on the roots of vetch. So, yea, the more you know…

Further Reading: [1]

Photo by Ian Boyd licensed under CC BY-NC 2.0

Photo by Martin Heigan licensed under CC BY-NC-ND 2.0

Photo by Park Ranger licensed under CC BY-NC-SA 2.0

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

On Soil and Speciation

Lord Howe Island. Photo by John Game licensed under CC BY 2.0

Many of you will undoubtedly be familiar with some variation of this evolutionary story: A population of one species becomes geographically isolated from another population of the same species. Over time, these two separate populations gradually evolve in response to environmental pressures in their respective habitats. After enough time has elapsed, gradual genetic changes result in reproductive isolation and eventually the formation of two new species. This is called allopatric speciation and countless examples of this exist in the real world.

At the opposite end of this speciation spectrum is sympatric speciation. Under this scenario, physical isolation does not occur. Instead, through some other form of isolation, perhaps reproductive or phenological, a species gives rise to two new species despite still having contact. Examples of this in nature are far less common but various investigations have shown it is indeed possible. Despite its rarity, examples of sympatric speciation have nonetheless been found and one incredible example has occurred on a small oceanic island off the coast of Australia called Lord Howe Island.

Howea belmoreana and Howea forsteriana [SOURCE]

Lord Howe Island is relatively small, volcanic island that formed approximately 6.4–6.9 million years ago. It is home to four distinct species of palm trees from three different genera, all of which are endemic. Of these four different palms, two species, Howea belmoreana and Howea forsteriana, are quite common. Interestingly enough, H. forsteriana, commonly known as the kentia palm, is one of the most commonly grown houseplants in the entire world. However, their horticultural value is not the most interesting thing about these palms. What is most remarkable is how these two species arose. 

Multiple genetic analyses have reveled that both species originated on Lord Howe Island. This is kind of odd considering how small the island actually is. Both palms can regularly be found growing in the vicinity of one another so the big question here is what exactly drove the evolution of their common ancestor? How does a single species growing on a small, isolated island become two? The answer is quite surprising.

Howea belmoreana Photo by John Game licensed under CC BY 2.0

When researchers took a closer look at the natural histories of these two species, they found that they were in a sense isolated from one another. The isolation is due to major phenological or timing differences in their reproductive efforts. H. forsteriana flowers roughly six weeks before H. belmoreana. Flowering time is certainly enough to drive a wedge between populations but the question that still needed answering was how do such phenological asynchronies occur, especially on an island with a land area less than 12 square kilometers? 

As it turns out, the answer all comes down to soil. Individuals of H. belmoreana are restricted to growing in neutral to acidic soils whereas H. forsteriana seems to prefer to grow in soils rich in calcarenite. These soils have a more basic pH and dominate the low lying areas of the island. Growing in calcarenite soils is stressful as they are poor in nutrients. This physiological stress has caused a shift in the way in which the flowers of H. forsteriana mature. When found growing on richer volcanic soils, the researchers noted that the flowers mature in a way that is more synchronous, not unlike the flowers of H. belmoreana.

Thanks to their attention to detailed life history events and conditions, researchers were able to show that soil preferences caused a phenological shift in the flowering of these two related species. Because they flower at completely different times when growing on their respective soil types, enough reproductive isolation was introduced to disrupt the random mating process of these wind pollinated palms. As soon as such reproductive biases are introduced, speciation can and will occur.

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

Further Reading: [1]

A Peculiar Parasite at Berkeley

Parasitic plants are fascinating. I never pass up an opportunity to meet them. On a recent trip to California, my host for the day mentioned that something funny was growing in a patch of ivy on the Berkeley Campus. I had to know what it was. We took a detour from our intended rout and there, growing underneath a pine tree in a dense patch of ivy were these odd purple and brown stalks. This was definitely a parasitic plant.

The plant in question was the ivy broomrape (Orobanche hederae). As both its common and scientific name suggests, it is a parasite on ivy (Hedera spp.). As you can probably guess based on the identity of its host, ivy broomrape is not native to North America. In fact, the population we were looking at is the only known population of this plant you will find in the Americas. How it came to be in that specific location is a bit of a mystery but the proximity to the life sciences building suggests that this introduction might have been intentional. Personally I am quite alright with this introduction as it is parasitizing one of the nastier invasive species on this continent.

The ivy broomrape starts its life as a tiny seed. Upon germination, the tiny embryo sends out a thin thread-like filament that spirals out away from the embryo into the surrounding soils. The filament is looking for the roots of its host. Upon contact with ivy roots, the filament penetrates xylem tissues. The ivy broomrape is now plugged in, receiving all of its water, nutrient, and carbohydrate needs from the ivy. At this point the embryo begins to grow larger, throwing out more and more parasitic roots in the process. These locate more and more ivy roots until the needs of the ivy broomrape are met. Of course, all of this is going on underground.

Only when the ivy broomrape has garnered enough energy to flower will you see this plant. A stalk full of purple tinged, tubular flowers emerges from the ground. At this point its membership in the family Orobanchaceae is readily apparent. Like all members of this family, its parasitic lifestyle is so complete that it is beginning to lose genes for the production of chlorophyll and Rubisco, all things we generally associate with plants. This is why I love parasites so much. Not only are their ecological impacts bewilderingly complex, their evolutionary histories are such a departure from the norm. I will never tire of appreciating such species and I am happy to have met yet another awesome member of this group.

Further Reading:
http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.1925.tb06671.x/pdf

http://cat.inist.fr/?aModele=afficheN&cpsidt=4107447

The Shrubs of Iridaceae

Nivenia corymbosa

Did you know there are shrubs in the iris family? I didn't either until quite recently. I had the distinct honor of getting to tour the collections of Martin Grantham, a resident of the Bay Area and quite possibly the most talented horticulturist I have ever met. Martin has had quite a bit of luck with these plants and because of this, I was able to meet a handful of them growing quite happily in large containers. There are some things in life that your brain just simply isn't prepared to take in. The shrubby iriads are one of them.

The true shrubby species all hail from a subfamily of Iridaceae coined Nivenioideae. This is not a single grouping of all shrubby genera. It contains other genera that look a lot more like what we would consider an iris. Nivenioideae as a whole is considered to be pretty derived for the iris family, with the shrubby species serving as an excellent example of how bizarrely unique the subfamily really is. In total, there are three genera of shrubby iriads - Klattia, Nivenia, and Witsenia, all of which are native to South Africa. Klattia and Nivenia contain a small handful of species whereas Witsenia has only a single representative.

Once you get past the initial shock and awe of what you have just laid eyes on, their membership in the iris family becomes a bit more apparent. Though there is great variation in size, the species I encountered all looked roughly like long, slender sticks with multiple iris-like fans of leaves jutting out. Like most members of the family, the flowers of this group are spectacular. In the wild they are visited by long tongue bees and flies.

Overall this group is poorly understood. Some molecular phylogenetic work has been performed but it is by no means concrete. More attention may result in either the addition or subtraction of species. The most thorough treatment on the shrubby iriads comes from a monograph written by Dr. Peter Goldblatt as well as a handful of horticultural articles written by those lucky enough to have had some success in growing these plants (see Martin's essay on his experiences - http://bit.ly/2pStMZ4).

Like most of South Africa's unique flora, these plants are at threatened by habitat destruction, invasive species, and climate change. Luckily many of these species have caught the attention of folks like Martin who have put in the time and dedication into understanding their germination and growth requirements.

Seeing these plants in person was breathtaking. Not only was I completely flabbergasted at their appearance, the fact that plants like this exist is a testament to the wild diversity of life this planet supports. I never tire of meeting new plant species and this is one encounter I won't soon forget. Just when you think you are starting to understand plant diversity, plants like these show up to remind you that you have just barely scratched the surface.

Further Reading: [1] [2]

The Power of Leaves

Photo by Bourassamr licensed under CC BY-SA 3.0

When we think of the dominance of flowering plants on the landscape, we usually invoke the evolution of flowers and seed characteristics like endosperm and fruit. However, evolutionary adaptations in the structure of the angiosperm leaf may have been one of the most critical factors in the massive diversification that elevated them to their dominant position on the landscape today. 

Leaves are the primary organs used in water and gas exchange. They are the centers of photosynthesis, allowing plants to take energy from our closest star and turn it into food. To optimize this system, plants must balance water loss with transpiration in order to maximize their energy gain. This requires a complex plumbing system that can deliver water where it needs to be. It makes sense that plant physiology should maximize vein production, however, there are tradeoffs in doing so. Veins are not only costly to construct, they also displace valuable photosynthetic machinery. 

It appears that this is something that flowering plants do quite well. Because leaves fossilize with magnificent detail, researchers are able to look back in time through 400 million years of leaf evolution. What they found is quite incredible. There appears to be a consistent pattern in the vein densities between flowering and non-flowering plants. The densities found in angiosperm leaves both past and present are orders of magnitude higher than all non-flowering plants. These high densities are unique to flowering plants alone. 

This innovation in leaf physiology allowed flowering plants to maintain transpiration and carbon assimilation rates that are three and four times higher than those of non-flowering plants. This gives them a competitive edge across a multitude of different environments. The evolution of such dense vein structure also had major ramifications on the environment. 

The massive change in transpiration rates among the angiosperm lineage is likely to have completely changed the way water moved through the environment. These effects would be most extreme in tropical regions. Today, transpiration from tropical forests account for 30-50% of precipitation. A lot of this has to do with patterns in the intertropical convergence zone, which ensures that such humid conditions can be maintained. However, in areas outside of this zone such as in the Amazon, a high abundance of flowering plants with their increased rates of transpiration enhances the amount of rainfall and thus forms a sort of positive feedback.

Because precipitation is the single greatest factor in maintaining plant diversity in these regions, increases in rainfall due to angiosperm transpiration effectively helps to maintain such diversity. As angiosperms rose to dominance, this effect would have propagated throughout the ecosystems of the world. Plants really are the ultimate ecosystem engineers. 

Photo Credit: Bourassamr (Wikimedia Commons)

Further Reading: [1]

Purple Mouse Ears

Mimulus douglasii photo by Oregon Caves licensed under CC BY 2.0

The success of some plant species comes from the simple fact that they can grow where other plants can't. Such is the case for the purple mouse ear (Mimulus/Diplacus douglasii). Native to northern California and Oregon, this tiny plant can most often be found growing in serpentine soils. Finding it can get tricky as it is quite diminutive in size and doesn't always produce its outlandishly showy flowers. 

Mature plants stand roughly 4 cm in height. When produced, the flowers are rather large and showy, often much larger than the rest of the plant. Unlike other members of the genus, the bottom lip of the tubular flowers has been reduced so much that it might as well not exist. Instead, the two top petals dominate the display, giving this plant a cartoonish outline of a mouse. As you can see, they are incredibly showy. 

This plant has to do what it can to ensure that it sets seed in any given growing season. Purple mouse ears are annual plants, so they only get one shot at reproduction. To make matters more difficult, they frequently grow in serpentine soils, which are low in essential nutrients and high in toxic metals like nickel, cobalt, and chromium. Despite these difficult conditions, purple mouse ears seem to benefit from the lack of competition on these traditionally toxic substrates. 

Cleistogamous flowers

Plants don't always produce their showy floral displays. When times are tough, they opt for asexual reproduction. Instead of the big, showy flowers, plants will produce tiny flower buds that never open. These are called cleistogamous flowers. Instead, they simply self-pollinate, which ensures that the genes that allowed the parent to survive environmental hardships are guaranteed to make it into the next generation. For annuals whose entire life is wrapped up in a single season, sometimes its not worth taking any chances. 

Photo Credit: [1] 

Further Reading: [1] [2] 

Meet the Redbuds

I look forward to the blooming of the redbuds (Cercis spp.) every spring. They paint entire swaths of forest and roadside with a gentle pink haze. It’s this beauty that has led to their popularity as an ornamental tree in many temperate landscapes. Aside from their appeal as a specimen tree, their evolutionary history and ecology is quite fascinating. What follows is a brief introduction to this wonderful genus.

The redbuds belong to the genus Cercis, which resides in the legume family (Fabaceae). In total, there are about 10 species disjunctly distributed between eastern and western North America, southern Europe, and eastern Asia. The present day distribution of this genus is the result of vicariance or the geographic separation of a once continuous distribution. At one point in Earth’s history, the genus Cercis ranged from Eurasia to North America thanks to land bridges that once connected these continents. At some point during the Miocene, this continuous distribution began to break apart. As the climate changed, various Cercis began to diverge from one another, resulting in the range of species we know and love today.

All of them are relatively small trees with beautiful pink flowers. Interestingly enough, unlike the vast majority of leguminous species, redbuds are not known to form root nodules and therefore do not form symbiotic relationships with nitrogen-fixing bacteria called rhizobia. This might have something to do with their preference for rich, forest soils. With plenty of nitrogen available, why waste energy growing nodules? Until more work is done on the subject, its hard to say for sure why they don’t bother with nitrogen fixers.

One of the most interesting aspects of the redbuds are their flowers. We have already established that they are very beautiful but their development makes them even more interesting. You have probably noticed that they are not borne on the tips of branches as is the case in many flowering tree species. Instead, they arise directly from the trunks and branches. This is called "cauliflory," which literally translates to "stem-flower." In older specimens, the trunks and branches become riddled with bumps from years of flower and seed production.

It's difficult to make generalizations about this flowering strategy. What we do know is that it is most common in dense tropical forests. Some have suggests that producing flowers on trunks and stems makes them more available to small insects or other pollinators that are more common in forest understories. Others have suggested that it may have more to do with seed dispersal than pollination. Regardless of any potential fitness advantages cauliflory may incur, the appearance of a redbud covered in clusters of bright pink flowers is truly a sight to behold.

Further Reading: [1] [2] [3] [4] [5] [6] [7]

Mighty Magnolias

Magnolias are one of those trees that even the non-botanically minded among us will easily recognize. They are one of the more popular plant groups grown as ornamentals and their symbolism throughout human history is quite interesting. But, for all this attention, few may realize how special magnolias really are. Did you know they they are one of the most ancient flowering plant lineages in existence?

Magnolias first came on to the scene somewhere around 95 million years ago. Although they are not representative of what the earliest flowering plants may have looked like, they do offer us some interesting insights into the evolution of flowers. To start with, the flower bud is enclosed in bracts (modified leaves) instead of more differentiated sepals. The "petals" themselves are not actually petals but tepals, which are also undifferentiated. The most striking aspect of magnolia flower morphology is in the actual reproductive structures themselves.

Magnolias evolved before there were bees. Because of this, the basic structure that makes them unique was in place long before bees could work as a selective pressure in pollination. Beetles are the real pollinators of magnolia flowers. The flowers have a hardened carpel to avoid damage by their gnawing mandibles as the feed. The beetles are after the protein-rich pollen. Because the beetles are interesting in pollen and pollen alone, the flowers mature in a way that ensures cross pollination. The male parts mature first and offer said pollen. The female parts of the flower are second to mature. They produce no reward for the beetles but are instead believed to mimic the male parts, ensuring that the beetles will spend some time exploring and thus effectively pollinating the flowers.

It is pretty neat to think that you don't necessarily have to track down a dawn redwood or a gingko to see a plant that has survived major extinction events. You can find magnolias very close to home with a keen eye. Looking at one, knowing that this is a piece of biology that has worked for millennia, is quite astounding in my opinion.

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

Meet Snorkelwort

Photo by James Henderson, Golden Delight Honey, Bugwood.org
licensed under a Creative Commons Attribution 3.0 License.

If vernal pools are considered ephemeral then granite pools are downright fleeting. Any organism that specializes in such a habitat must be ready to deal with extremes. That is what makes a little plant known scientifically as Gratiola amphiantha so darn cool. It's what also makes it so darn threatened. 

This tiny member of the Plantaginaceae family is native to the Piedmont province of southeastern North America. It lives out its entire life in shallow pools that form in weathered granitic outcrops. One must really think about the specificity of this sort of habitat to truly appreciate what this little aquatic herb is up against. Pools must be deep enough to hold water just long enough but not too deep to allow normal plant succession. They must have just enough soil to allow these plants to take root but the soil must be thin enough to prevent other vegetation from taking over. They must also be low in nutrients to limit the growth of algae that would otherwise cloud the water. Needless to say, this makes suitable habitat for snorkelwort hard to come by. 

Photo by Keith Bradley kab_g_amphiantha_1012 March
Forty Acre Rock Heritage Preserve Lancaster County SC [SOURCE]

When such conditions are met, however, snorkelwort can be quite prolific. Seeds of this species germinate in late fall and early winter when only a thing veneer of water covers the equally thin soils. Individual plants form a small rosette that sits in wait until rains fill the tiny pools. Once submerged, the rosettes send up thin stem-like structures called scapes. These scapes terminate in two tiny bracts that float at the waters surface. Between the two bracts emerges tiny, white, five petaled flowers. Submerged flowers are also produced but these are cleistogamous flowers that never open and only self-pollinate. This ensures that at least some seeds are produced every growing season. 

Photo by Philip Bouchard licensed under CC BY-NC-ND 2.0

When you consider all aspects of its ecology, it is no wonder that snorkelwort is teetering on the edge of extinction. The granitic pools in which it lives are very sensitive to change. It doesn't take much to make them totally unsuitable places to live. Protecting them alone is hard enough. Mining, pollution, littering, and even casual hikers can wipe out entire populations in an instant. Even populations living within the boarders of protected parks have been extirpated by hiking and littering. When you live on the edge, it doesn't take much to fall off. In total, only about 31 populations scattered through Alabama, Georgia, and South Carolina are all that remains of this overlooked little plant. 

The upside to all of this is that numerous stake holders, both public and private, are invested in the ongoing success of this species. Private land owners whose land supports snorkelwort populations are cooperating with botanists to ensure that this species continues to find what it needs to survive. Luckily a sizable chunk of the remaining populations are large enough to support ample genetic diversity and, at this point in time, don't seem to be at any risk of destruction. For a little plant like snorkelwort, a little attention can go a long way. If you know a spot where this interesting little plant grows, tread lightly and appreciate it from a safe distance. 

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

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

In Search of Spring Wildflowers

In this episode we are exploring a small park located in central Illinois in hopes of finding spring wildflowers. Will we find any? Watch a find out ;)

Producer, Editor, Camera:
Grant Czadzeck (www.grantczadzeck.com)

The World's Only (Known) Photosynthetic Vertebrate

You may be asking yourself right now why I have posted a picture of a salamander this morning. This is a plant blog after all! Well, what I am about to tell you may seem a bit crazy, but I assure you this discovery has opened up some doors that science never really considered a possibility before. The yellow spotted salamander (Ambystoma maculatum) is the first and only (known) photosynthetic vertebrate ever discovered!

That's right. You heard me. A photosynthetic animal. More accurately speaking, it is the embryos of this species that undergo photosynthesis. To understand why this happens we must back up a little bit. Yellow spotted salamanders are a species of mole salamander that can be found in wet areas of eastern North America. They spend most of their adult lives underground, hiding beneath logs and rocks in the forest, feeding on any manner of invertebrates. Once a year (around this time) adult yellow spotted salamanders undertake a massive migration down to the pools where they mate. On the first few warm, rainy nights, thousands of salamanders can be seen trucking their way to vernal pools and ponds to breed. It is an amazing sight to behold.

The thing about yellow spotted salamanders is they will only breed in fishless ponds. Their larvae would be an easy meal for many predatory fish species. The problem that arises out of this breeding strategy is that fishless ponds tend to be very low in oxygen. It has long been known that the eggs of this species form a symbiotic relationship with an algae. The algae produce oxygen for the developing embryo and the embryo feeds the algae via its nitrogen rich waste and CO2. This relationship was always thought to be external, that is until Ryan Kerney of Dalhousie University in Halifax, Nova Scotia discovered that embryos of a certain age actually had algae living within their cells.

They algae don't seem to start off inside the cells though. This may be why this relationship wasn't discovered earlier. Roger Hangarter at Indiana University found that it isn't until parts of the salamander's nervous system begin to develop that the algae move into the embryo and set up shop. The algae then reside near the salamander's mitochondria, which are the powerhouses of the cell. So where are the algae coming from? While more research needs to be done, Karney also discovered the presence of algae in the oviducts of adult female spotted salamanders. It is looking like mother salamanders are actually passing the algae on to their offspring. 

Though this is the first and only instance we know of this sort of photosynthetic relationship in vertebrate animals, this discovery has opened the door for exploring the possibility of other photosynthetic symbionts. It has also allowed scientists a different avenue to explore just how cells recognize and deal with foreign bodies. We live in such an amazing world!

Further Reading: [1] [2] [3]

 

The Fetid Adderstongue

Photo by Ken-ichi Ueda licensed under CC BY-NC 2.0

"Fetid adderstongue" seems like a pretty ominous name for such a small and beautiful plant. Hailing from coastal North America, the genus Scoliopus is most at home in the deep shaded forests of California and Oregon. Spring is the best time to see these little lilies and once you know a little bit about their ecology, such encounters are made all the more interesting.

There are two species nestled within this genus - S. bigelovii and S. hallii. Both are similar in that they are plants of deep shaded environments, however, you are more likely to find S. hallii growing along the banks of wooded streams. As is typical of many members of the lily family, their flowers are quite beautiful in appearance. The trick is finding them. Though showy, they are rather small and their dark coloration causes them to blend in well in their shaded environments. That is all fine and dandy for a species that relies more on smell rather than looks to attract pollinators.

As the common name suggests, the flowers of the fetid adderstongues give off a bit of an odor. I have heard it best described as "musty." The flowers of these two species attract a lot of fungus gnats. Although these tiny flies are generally viewed as sub par pollinators for most flowering plants, the fetid adderstongues seem to do well with them. What they lack in robust pollination behavior, they make up for in sheer numbers. There are a lot of fungus gnats hanging around wet, shaded forests.

Photo by Eric in SF licensed under CC BY-SA 3.0

The flowers themselves are borne on tall stalks. Though they look separate, they are actually an extension of a large, underground umbel. Once pollination has been achieved, the flower stalks begin to bend over, putting the developing ovaries much closer to the ground. Each seed comes equip with a fleshy little attachment called an eliasome. These are essentially ant bait. Once mature, the seeds are released near the base of the parent. Hungry ants that are out foraging find the fleshy attachment much to their liking.

They bring the seeds back to the nest, remove the eliasomes, and discard the seed into a trash midden. Inside the ant nest, seeds are well protected, surrounded by nutrient-rich compost, and as some evidence is starting to suggest, guarded against damaging fungal invaders. In other words, the plants have tricked ants into planting their seeds for them. This is a very successful strategy that is adopted by many different plant species the world over.

Though small, the fetid adderstongues are two plants with a lot of character. They are definitely a group that you want to keep an eye out for the next time you find yourself in the forests of western North America. If you do end up finding some, just take some time to think of all the interesting ecological interactions these small lilies maintain.

Photo Credits: [1] [2]

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

Cedar-Apple Rust

Photo by Rocky Houghtby licensed under CC BY 2.0

I have had my eye on these strange brown golf ball shaped growths growing on the twigs of a cedar in my neighborhood for about a year now. I first took notice of them late last spring. They looked pretty nasty but I knew they had to be something interesting. Indeed, “interesting” doesn't even come close to describing their true nature. 

These odd little growths are actually a single stage in the complex life cycle of a group of fungi in the genus Gymnosporangium. Collectively they are referred to as cedar-apple galls. Its a group of fungi whose hosts include junipers and relatives of the apple. Wherever these two lineages coexist you are bound to find this fungus. 

Gymnosporangium exhibit a fascinating life cycle that includes multiple hosts. The golf ball shaped galls will appear on the twigs of a juniper nearly a year after being infected with spores. They grow in size until they reach a point in which they will barely fit in the palm of your hand, though not all reach such proportions. The gall itself is covered in a series of uniform depressions, making it look a little out of place in a natural setting. After a year on a juniper tree, the galls enter into their next stage of development. 

Photo by klm185 licensed under CC BY 2.0

Usually triggered by the first warm rains of spring, strange gelatinous protrusions start to poke out of each depression on the gall's surface. These protrusions continue to swell until the entire gall is covered in bright orange, finger-like masses. These are where the spores are produced. The spores, however, cannot infect another juniper. Instead, they need to land on the next host to complete their life cycle. 

If the spores land on a member of the family Rosaceae (species within the genus Malus are preferred), then the second stage of the life cycle begins. Spores can germinate on both the leaves and the fruit but instead of turning into a large brown gall, they take on a different appearance. This is what makes this fungus readily apparent as a type of rust. A patch of orange will begin to grow. Upon closer inspection one can see that the orange patch is actually a series of small cup-like structures full of spores. 

Come fall, the spores are ready to be dispersed by wind. With any luck, they will land back on a juniper tree and the cycle will start anew. Because of its propensity for apple crops, cedar-apple rust fungi are considered to be a serious pest in apple orchards. In a more natural setting, however, it is a bizarrely unique fungus worth looking for.

Photo Credits: [1] [2]

Further Reading: [1] [2]

Seed Anchor

[SOURCE]

Epiphytic plants live out their entire lives on the trunks or branches of trees. Using their roots, they attach themselves tightly to the bark. Spend any amount of time in the tropics and it will become quite clear that such a lifestyle has been very successful for a plethora of different plant families. Still, living on a tree isn't easy. Epiphytic plants must overcome harsh conditions among or near the canopy.

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

One of the biggest challenges these plants face starts before they even germinate. This is especially true for orchids. Orchid seeds are more like spores than they are seeds. They are so small that thousands could fit inside of a thimble. Upon ripening, the dust-like seeds waft away on the slightest breeze. In order for epiphytic species to germinate and grow, their seeds must somehow anchor themselves in place on a trunk or branch. Inevitably most seeds are doomed to fail. They simply will not land in a suitable location. It stands to reason then that any adaptation that increases their chances of finding the right kind of habitat will be favored. That's where the strange coils on the tip of Chiloschista seeds, a genus of leafless orchids native to southeast Asia, New Guinea, and Australia, come in. For these orchids, this process is aided by some truly unique seed morphology.

Unlike most orchid seeds that are nothing more than a thin sheath surrounding a tiny embryo, the seeds of Chiloschista have additional parts. These "appendages," which are specialized seed coat cells, are tightly wound into coils. Upon contact with water, these coils shoot out like tiny grappling hooks that grab on to moss and bark alike. In doing so, they anchor the seed in place. By securing their hold on the trunk or branch of a tree, the seeds are much more likely to germinate and grow. This is one of the most extreme examples of seed specialization in the orchid family.

Photo Credit: [1] [2]

Further Reading: [1]

A Brief Primer on the Vernal Dam Hypothesis