American Bittersweet

Photo by Peter Gorman licensed by CC BY-NC-SA 2.0

As the bright colors of fall start to give way to the dreary grays of winter, people often go looking for ways to bring a little bit of botanical color indoors to enjoy. It is around this time of year that one species in particular starts turning up in flower arrangements, however, it's not the flowers people are interested in but rather the seeds. This species is so popular in arrangements that its numbers in the wild are facing steep declines.

Meet Celastrus scandens, the American bittersweet vine. It hails from the family Celastraceae, which makes it a distant cousins of Euonymus. This lovely climbing vine is native to much to eastern North America and is most at home growing at the edge of woodlots, thickets, and along rocky bluffs and outcroppings. As mentioned, It isn't the flowers of this species that catch the eye but rather the showy seeds. Encased in bright orange capsules, the crimson berry-like fruits are toxic to us mammals but highly sought after by birds. Despite their toxicity, humans nonetheless covet these fruits. Entire vines are cut down and used in arrangements, especially during the months of fall. This has had detrimental effects on wild populations of American bittersweet.

To add insult to injury, its Asian cousin, Celastrus orbiculatus, has been introduced to this continent and is running amuck in the wild. Known commonly as Oriental bittersweet, this invasive is quickly outpacing its native cousin throughout much of North America. It would seem that Oriental bittersweet can adapt to a wider range of habitat types than American bittersweet and, where these species co-occur, hybridization has been reported. The hybrid offspring are not only fertile, they also have shorter seed dormancy and are much more vigorous growers than either of the parents.

Photo by MN Department of Agriculture

Unfortunately it can be hard to tell these species apart. However, with a little patience and a decent field guide, differences become apparent. The best diagnostic feature I have found is that American bittersweet carries its flowers and fruit on the terminal ends of the stems whereas Oriental bittersweet carries them in the axils of the leaves.

All in all, American bittersweet is a lovely native vine. Its beauty in our eyes has, like so many other plant species, created some serious survival issues. Coupled with the the threat of its highly aggressive Asian cousin, the future of this wonderful species remains uncertain. That being said, this doesn’t have to remain a trend. The good news is that it does quite well as a garden species and many nurseries are beginning to carry the native over the invasive. If you live in eastern North America, consider using this plant in your landscape. It would certainly help. And, if flower arrangements are something you enjoy, please give American bittersweet a break.

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

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

History of Grass Evolution Written in Dinosaur Poop

Photo by Sugeesh licensed by CC BY-SA 3.0

Grasses dominate our planet today but that has not always been the case. Because of both their ecological and cultural importance , the origin and diversification of grasses has long been a hot topic in biology. We know that grasses really hit their stride following the extinction of the dinosaurs, and that they changed herbivore anatomy in a big way, but their origins remain shrouded in mystery. Recently, a discovery made in fossilized dinosaur poop has shone a surprisingly bright light into the history of grasses on our planet.

Prior to this discovery, the earliest evidence of grasses came in the form of fossilized pollen and tiny pieces of silica called phytoliths. Phytoliths are essentially tiny pieces of glass that serve as a form of defense against herbivores. Because they are made of silica and fossilize well, phytoliths turn up frequently in the fossil record. This makes them extremely useful for finding evidence of grasses even where whole-plant fossilization is unlikely.

Illustration by Nobu Tamura (http://spinops.blogspot.com) licensed by CC BY-NC-ND 3.0

Whereas phytoliths are not unique to grasses, their form is often taxon-specific. With a good eye and a bit of training, one can look at a phytolith under a microscope and tell you what type of plant it came from. This is where the dinosaur poop comes into the picture. By examining fossilized dinosaur poop from India, paleontologists can get an idea of what dinosaurs were eating.

By examining the fossilized poop of a group of large herbivorous dinosaurs called Titanosaurs, paleontologists now have a better idea of grass diversity in the late Cretaceous. They have uncovered a surprising diversity of phytoliths, which demonstrate that at least 5 distinct grass taxa that we would recognize today were alive and well some 100.5 to 66 million years ago. These include extant groups like Oryzoideae (think rice and bamboo), Puelioideae, and Pooideae (think wheat, barley, oat, rye, and many lawn and pasture grasses). There were other lesser known lineages mixed in there as well.

Fossilized dinosaur poop or “coprolite.” USGS Public Domain

These findings are exciting for a variety of reasons. For one, it tells us that despite lacking teeth specialized for eating grasses, large herbivorous dinosaurs like the Titanosaurs were nonetheless incorporating these plants into their diet. It also tells us that grasses were already quite diverse by the late Cretaceous. The fact that modern clades of grass were around back then sets back grass evolution many millions of years. It also tells us something about grass biogeography. It suggests that grasses were already wide spread across the supercontinent of Gondwana long before India broke away. Finally, it tells us that grasses evolved silicate phytoliths long before more recognizable grass-eating herbivores came onto the scene.

I am always blown away by the details paleontologists are able to extract from such tiny fossils. Who knew dinosaur poop could tell us so much?

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

Further Reading: [1]

Twinflower

Here is a short story about my first encounter with twinflower (Linnaea borealis) back in fall of 2014.

"Summer and occasionally fall" is all I needed to read. So, I had a chance after all. After a few days of sitting in a kayak, musing over various wetland plants, I was excited to get my feet back on solid ground. The Adirondack Mountains offer seemingly endless opportunities for botanizers (and all nature nuts really) to meet new and exciting species that aren't often seen. For me, Linnaea borealis is such a species.

Commonly referred to as twinflower, this small plant is technically a dwarf shrub. In fact, it is a member of the honeysuckle family, Caprifoliaceae. Unlike its larger, more aggressive cousins, twinflower would be an easy plant to miss for most. It behaves much like partridge berry as it ambles over rocks and logs, never leaving the damp forest floor. Out of those who would pay it any mind, even fewer would consider this nondescript plant much to fuss about but those people have never seen this plant in flower.

During the warmer summer months, L. borealis puts on an unbelievable display. Each sprig of stem and leaves throws up a pair of bell-like flowers that will knock your socks off. Each flower is permanently aimed at the ground like tiny lampshades. The flowers are small and dressed in a mixture of white and pink but a large population in full bloom would be impossible to miss. There is something to be said about the beauty of small plants like this. Unlike larger, gaudy flowers, L. borealis forces its admirers to get down on its level to enjoy its full beauty. I like that in a plant.

Twinflower ambling over a rock in the company of some Cladonia lichen.

The genus name "Linnaea" was given to this species in honor of the Swedish botanist, physician, and zoologist, Carl Linnaeus, who invented the binomial nomenclature naming scheme that we still use today. L. borealis has been said to be his favorite plant. As the specific epithet suggests, this species is circumboreal in its distribution. It is found in the northern forested regions of every continent in the northern hemisphere. It can also be found farther south but only at high elevation. These southern populations are disjunct relicts of the Pleistocene Epoch.

Pushed south by advancing ice sheets, boreal species like L. borealis took refuge at high elevation where climates were more similar to the far north. After the glaciers retreated, these populations were able to hang on in small pockets atop mountains. The most interesting thing about this is that L. borealis is not self compatible. It needs genetically different individuals to successfully set seed. In areas where only a small group of individuals represent an entire population, L. borealis has a hard time reproducing sexually. Such populations populations only persist via vegetative cloning. In places like Scotland, this has lead to some concern over genetic stagnation. Throughout the world, at the edges of its range, L. borealis has taken a hit from this genetic stagnation and its range is shrinking. As favorable climates continue to change, the relict populations atop mountains have nowhere to go and thus risk extirpation.

Despite all of this, L. borealis is one tough cookie. If you live where this plant is native, make sure to keep a watchful eye out for it when you are hiking. All too often it is trampled over by unwary hikers. If you are lucky enough to find a patch in bloom, get down on your hands and knees and really get to know this species. You will certainly be happy that you did.

Further Reading: [1] [2]

The Role of Leaf Shape on Insect Herbivory

Plants can defend themselves from herbivores in a variety of ways - thorns, spines, hairs, toxins, etc. - but have you ever considered the role of leaf shape in preventing herbivory? It’s okay if you haven’t because leaf shape rarely, if ever, makes it into conversations of plants defense. A recent experiment from Japan has changed that by demonstrating that leaf shape can actually deter a specialist leaf-rolling weevil.

Meet Apoderus praecellens, a leaf rolling weevil that specializes on a genus of mints called Isodon. To successfully reproduce, female leaf rolling weevils must roll up an Isodon leaf while laying eggs as she goes. The end result is a tiny cigar-shaped, edible nursery chamber in which her larvae will develop. The act of processing a leaf is a complex process.

Isodon trichocarpus Photo by Qwert1234 licensed by CC BY-SA 3.0

The female weevil begins by walking along the margin of the leaf until she reaches the apex. At that point she walks sideways towards the interior of the leaf until she finds the midrib. She then turns around and walks back toward the leaf base again. She repeats these steps several times on both sides of the leaf until she is satisfied. At that point, she will take several bites out of the midrib, which causes the leaf to wilt. The wilted leaf is then much easier to manipulate and thus the rolling process begins.

In the wild, female weevils are well documented on the leaves of I. trichocarpus but not on the leaves of I. umbrosus. This is strange because not only are these plants closely related, they frequently grow in close proximity to one another. Why would the female weevils prefer one over the other? The answer appears to lie in the shape of their leaves.

Isodon trichocarpus produces non-lobed leaves whereas the leaves of I. umbrosus are deeply lobed. When presented with a choice, female weevils did indeed choose to roll I. trichocarpus leaves over those of I. umbrosus. These plants do not differ in their chemical makeup and larvae raised on both species did not differ in their health or development time. Thus, nutritional value or defense compounds don’t explain weevil preference.

Even more amazing is that the preferences seemed to change when I. trichocarpus leaves were cut to resemble the lobed I. umbrosus leaves. It seems that the presence of leaf lobes is the key to whether a weevil decides to lay her eggs or not. The reason for this seems to be the complex leaf inspection behavior outlined above. The deep lobes of I. umbrosus leaves disrupt the female weevils as they carry out their complex inspection process. If the females are interrupted, they rarely progress to the leaf rolling stage.

The researchers are quick to point out that leaf shape in this instance probably didn’t evolve in response to herbivory. Leaf shape is the result of a multitude of selection pressures like light availability, heat, and drought. Still, the fact that leaf shape can also influence herbivore pressure is an interesting piece to add to the puzzle. It is a great reminder that an organism’s niche comprises so much more than simply the abiotic conditions in which it lives. The niche is also the myriad biological interactions each organism undertakes.

Photo Credits: [1] [2]

Further Reading: [1]

Mutant Orchids Have a lot to Teach Us About Parasitic Plants

A) Albino and (B) green individual of Goodyera velutina.

The botanical world is synonymous with the idea of photosynthesis. Plants take in carbon dioxide and water and utilize light to make their own food. However, not all plants make a living this way. There are many different species of plants that have evolved a parasitic lifestyle to one degree or another. Some of my favorites are those that parasitize mycorrhizal fungi. We call these plants “mycoheterotrophs” and they are fascinating to say the least. Orchids are especially prone to this strategy, with over 1% of all known species having completely lost the ability to photosynthesize.

Our knowledge of the mycoheterotrophic strategy is fragmentary at best. We still don’t fully understand things like how the plants obtain what they need from the fungus nor how they are able to maintain their parasitic lifestyle without the fungus catching on and rejecting the one-sided partnership. This is not to say we know nothing. In fact, as technologies advance, we are unlocking at least some of the mysteries of mycoheterotrophic plants. Some of the best advances come from studying mutant, albino orchids. To understand how, we have to take a closer look at the “average” orchid lifestyle.

Orchids in general make great candidates for understanding the evolution of mycoheterotrophy because all of them start their lives as parasites. Orchids produce some of the smallest seeds in the plant kingdom and without the help of mycorrhizal fungi, they would never be able to germinate. For much of their early life, orchids rely on fungi to provide them with both their mineral and carbohydrate needs. Only after the orchids are large enough to grow leaves will most of them start to give back to their fungal partners in the form of carbohydrates generated from photosynthesis.

Still, many orchids never fully let go of this parasitic lifestyle. This is especially true for orchids living under dense forest canopies. With light in limited supply, many orchids adopt a mixotrophic lifestyle. Essentially this means that although they actively photosynthesize, they nonetheless rely on fungi to provide them with both carbohydrates and minerals. Mixotrphy is likely the most wide-spread orchid strategy and it has been hypothesized that it is also the first step along the path to becoming fully parasitic. This is where the mutant orchids enter the equation.

(A) Albino and (B) green individuals of Epipactis helleborine

Every once in a while, some orchids will germinate and grow into albino versions of their species. Without the ability to produce chlorophyll, these mutants should be destined for a quick death. Such is not the case for many of these orchids. Albino orchids often go on to live full lives, growing and flowering just like their photosynthetic progenitors. Although they do exhibit signs of reduced fitness, the fact that they are able to live at all brings up a lot of questions ready for science to tackle.

Recent investigations into the lives of these albino mutants has revealed some interesting insights into how mycoheterotrophy may have evolved in the first place. By studying the fungal partners of both healthy plants and the albinos, researchers have been able to demonstrate that albinos are doing things a bit differently than their photosynthetic parents. Using isotopes of carbon and nitrogen, scientists are discovering that the albinos have switched their interaction with the fungi in such a way that they more resemble fully mycoheterotrophic orchid species. This is done despite the fact that both albinos and their fully functional parents associate with the same guild of mycorrhizal fungi.

Another interesting difference between albinos and their photosynthetic parents is the fact that the genes involved both antioxidant metabolism and metabolite transfer (mainly carbon in this case) were more active in the albinos than they were in functioning plants. The uptick in gene functioning related to antioxidant metabolism suggests that the mutant plants are undergoing greater oxidative stress than their functional parents. This may have something to do with how the albinos are able to obtain nutrients from their fungal partners. It is thought that mycoheterotrophs actively digest parts of the fungi, which allows them to access the carbon and minerals they need to survive. This process exposes their cells to reactive oxygen compounds that can be very damaging. Antioxidants would help to reduce such damage.

The uptick in genes associated with metabolite transfer was more surprising because it suggests that despite being parasites, the plants are actively transferring substances back to the fungi. It has long been assumed that mycoheterotrophy was a one way street, with fungi transferring nutrients to plants only. These genes now suggest that, at least in some species, such transfer is a two-way street. The exact nature of this two-way transfer remains a mystery and certainly brings up many more questions that must be asked before we can better understand this relationship.

All of this is not to say that such albino mutants are fruitful “next steps” in the evolution of these species. Far from it, in fact. Two things that most albino orchid variants have in common is the fact that they are rare and, of those that have been studied, produce far fewer seeds. There are a lot of anatomical and physiological differences between true mycoheterotrophic species and albino variants and it appears that without those anatomical adaptations, the albinos are a lot less fit than their photosynthetic parents. As authors Selosse and Roy put it:

“non-chlorophyllous variants are likely to represent unique snapshots of failed transitions from mixotrophy to mycoheterotrophy. They are ecological equivalents to mutants in genetics, that is, their dysfunctions might suggest what makes mycoheterotrophy successful. Although their determinism remains unknown, they offer fascinating models for comparing the physiology of mixo- and mycoheterotrophs within similar genetic backgrounds.”

Mutants are strange indeed but with the right kinds of questions and approaches, they have a lot to teach us about ecology, evolution, and life at large.

Photo Credits: [1] [2]

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

Mysterious Franklinia

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

In 1765, a pair of botanists, John and William Bartram, observed "several very curious shrubs" growing in one small area along the banks of the Altamaha River in what is now Georgia. Again in 1773, William Bartram returned to this same area. He reported that he "was greatly delighted at the appearance of two beautiful shrubs in all their blooming graces. One of them appeared to be a species of Gordonia, but the flowers are larger, and more fragrant than those of the Gordonia lasianthus.” The species Bartram was referring to was not a Gordonia, but rather a unique species in a genus all of its own. After years of study, Bartram would name the plant in honor of a close family friend, Benjamin Franklin.

This tree is none other than the Franklin tree - Franklinia alatamaha. This beautiful member of the tea family (Theaceae) is unique in that it no longer exists outside of cultivation. It is completely extinct in the wild. However, this is not a recent extinction brought on by the industrialization of North America. IT would seem that Franklinia was nearing extinction before Europeans ever made it to North America. As Bartram first noted "We never saw it grow in any other place, nor have I ever since seen it growing wild, in all my travels, from Pennsylvania to Point Coupe, on the banks of the Mississippi, which must be allowed a very singular and unaccountable circumstance; at this place there are two or 3 acres of ground where it grows plentifully." Indeed, no reports of this species came from anywhere other than that two to three acre section of land on he banks of the Altamaha River. The last confirmed sighting of Franklinia in the wild was in 1790.

Photo by Krzysztof Ziarnek, Kenraiz licensed by CC BY-SA 4.0

What happened to Franklinia? The truth is, no one really knows. Many theories have been put forth to try to explain the disappearance of this unique shrub. What can be agreed on at this point is that Franklinia was probably mostly extinct by the time Europeans arrived. One thought is that it was a northern species that "escaped" glaciation thanks to a few scattered populations in southeastern North America. Indeed, it has been well documented that plants grown in the northern US fare a lot better than those grown in the south. It is thought that perhaps Franklinia was not well adapted to the hot southern climate and slowly dwindled in numbers before it had a chance to expand its range back north after the glaciers retreated.

Others blame early botanists for collecting this already rare species out of existence. What few trees may have remained could easily have been whipped out by a stochastic event like a flood or fire. Another possibility is that habitat loss from Indigenous and subsequent European settlement coupled with disease introduced via cotton farming proved too much for a small, genetically shallow population to handle. In my opinion, it was probably the combination of all of these factors that lead to the extinction of Franklinia in the wild.

Photo by Tony Rodd licensed by CC BY-NC-SA 2.0

Anyone growing this tree may notice some funny aspects of its ecology. For instance, it blooms in September, which is a lot later than most North American flowering tree species. Also, the fruits take a long time to mature, needing 13 - 15 months on the tree to be viable. The combination of these strange quirks of Franklinia biology as well as its inability to handle drought (a condition quite common in its only known natural range in Georgia), lends credence to the glacial retreat theory.

We do owe Bartram though. Without him, this species may have disappeared entirely. During his expeditions to Georgia, he collected a few seeds from that Franklinia population. Any Franklinia trees growing in gardens today are direct descendants of those original collections. Franklinia is yet another plant species kept alive by cultivation. Without its addition to gardens all over the country, this species would have been lost forever, living on in our minds as illustrations and herbarium specimens.

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

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

Emus + Ants = One Heck of a Seed Dispersal Strategy

A guest post by Dr. Scott Zona

The emu is a large, flightless bird, a cousin of kiwis and cassowaries. They range throughout much of Australia, favoring savannah woodlands and sclerophyll forests, where they are generalist feeders, consuming a variety of plants and arthropods. A favorite food of the emu is Petalostigma pubescens, a tree variously known as quinine tree, bitter bark or quinine berry. Petalostigma is in the Picrodendraceae, a family formerly included in the Euphorbiaceae. Quinine trees grow in the same open woodlands favored by emus.

The quinine tree bears yellow fruits, 2.0-2.5 cm in diameter, with a thin layer of flesh. The fruits are divided into six to eight segmented, like a tangerine, and each segment contains a hard endocarp or stone (technically, a pyrene). Each endocarp contains a single seed, 6-8 mm long. Left on the tree, the fruits will eventually dry up and open to release their seeds, but if ripe fruits are discovered by a hungry emu, the feasting begins.

A quinine tree (Petalostigma pubescens) in bloom. Photo by Ethel Aardvark licensed by CC BY 3.0

An emu may eat dozens of fruits in one meal. It swallows fruits whole, digesting the soft, fleshy part and defecating the hard, indigestible endocarps. On an average day, an emu can range over a large territory, spreading endocarps as it goes. In one of science's least glamorous moments, Australian biologists counted by hand as many as 142 endocarps in one emu dropping. If the story ended with Quinine Tree seeds in a pile of emu dung, we would say that the emu provided excellent seed dispersal services for the quinine tree, but the dispersal story is not over.

Quinine tree (Petalostigma pubescens) fruits. Photo by Robert Whyte licensed by CC BY-NC-ND 2.0

The emu dung and endocarps begin to bake in the hot, outback sun. As the endocarps dry, they explode. Just like the pod of a legume, the endocarp has fibers in its tissues oriented in opposing directions.  As the fibers dry, they contract and pull the endocarp apart. The dehiscence is sudden and explosive, sending seeds up to 2.5 m from the point of origin. Launching seeds away from the dung pile is beneficial to seeds: the special separation means that seedlings well be less likely to compete with one another.

But that is not the final disposition of Quinine Tree seeds. Each Petalostigma seed bears a small, oily food body, called an elaiosome, that is attractive to ants. Ants pick up the seed with its attached elaisome and carry it back to their nest. Once at the nest, the ants will remove and consume the elaisome and deposit the inedible seed in midden outside the nest. It is the ants that disperse the seeds to their ultimate site.

The association between emus, exploding endocarps, ants and Petalostigma pubescens probably represents one of the most complicated dispersal scenarios in the Plant Kingdom.

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

Further Reading: [1]

NOTE: Guest posts are invite only

A Sundew with Catapults

Photo by Mike Bayly licensed by CC BY-NC-SA 2.0

The pimpernel sundew (Drosera glanduligera) is a very special sundew. It is native to parts of southern Australia as well as Tasmania. With a rosette diameter of only 2.5–6 cm (1–2 in), it is a tiny plant. It is also very short lived, living out its entire lifecycle within the span of winter. However, these facts are not what make this species so interesting. This little sundew grows its own catapults that help it capture prey.

Sundews are incredible carnivores. Each of their leaves are decked out in “tentacles” whose tips secrete sticky mucilage. Whether attracted to the leaves on purpose or simply brushing by them on accident, insects find themselves mired down by the mucilage. To make matters worse, the leaves of many sundew species are capable of movement. As the insects struggle, the tentacles bend inwards and the leaves begin to roll up, thus securing the fate of the hapless victim.

Photo by Peterbest1954 licensed by CC BY-SA 4.0

For small sundews, prey capture is a bit tricky. Whereas smaller arthropods like springtails and isopods are easily captured, larger arthropods are often able to wriggle their way free of the leaves of all but the largest species of sundew. Drosera glanduligera is by no means large and that may be why it utilizes a unique method of trapping larger prey.

Along the outside of each leaf are tentacles that are much longer than the rest. They also differ from the typical sundew tentacle in that they are not tipped with sticky mucilage. However, they are more deadly than they look. Each of these long tentacles is essentially a mini catapult lying in wait. Anything unfortunate enough to brush across one of those tentacles is in for a rude awakening.

(A) Each step between 1 and 10 depicts a 5 ms time interval. (B) Speed (blue) and acceleration (red) of the tentacle head during the bending motion.

Withing only a few miliseconds, the tentacle bends upward, catapulting the prey towards the center of the leaf. Each leaf on D. glanduligera is shaped like a spoon with the highest concentration of sticky hairs at the center. By catapulting arthropods into the center of the leaf, they are far less likely to escape. Once immobilized, the plant can go about the digestion process.

It is amazing just how fast these tentacles can move. To see this happen in any detail, one needs a high speed camera. The amazing thing is that experts still aren’t 100% certain how such rapid movement is possible. The leading hypothesis involves a change in water pressure within specific cells at the base of the tentacles. When triggered, water is rapidly transported out of the cells on the surface of the tentacle base. With stress coming from water-filled cells underneath, the base of the tentacle bends quickly.

Amazingly, the cells often rupture after the tentacle is triggered. What’s more, they do not reset. Each tentacle is only good for one catapult. This may seem wasteful for such a short-lived species but D. glanduligera produces leaves throughout the entirety of its short life. Therefore, there are always new traps waiting to be triggered. Also, provided arthropods are caught with enough frequency, the plant is sure to obtain enough nutrients from each meal to fuel flowering and seed set. Pretty remarkable for such a tiny carnivore!

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

Further Reading: [1]

An Intriguing Way of Presenting One's Pollen

Photo by Monteregina (Nicole) licensed by CC BY-NC-SA 2.0

Getting pollen from one flower to another is the main reason why flowers exist in the first place. It makes sense then why pollen is often made readily available to pollinators. For many flowering plants, this means directing the pollen-filled anthers outward where they are ready to take advantage of floral visitors. The sunflower family (Asteraceae) does this a bit differently than most. They utilize a technique called secondary pollen presentation.

Though secondary pollen presentation is not unique to the sunflower family, their abundance on the landscape makes it super easy to observe. For the sunflower family, what looks like a single flower is actually an inflorescence made up of dense clusters of individual flowers. Each individual flower is roughly tubular in shape and, oddly enough, the anthers are tucked inside the tube facing the interior of the flower. It may seem odd to hide the anthers and their pollen inside of a tube until you see the blooming process sped up.

Photo by László Németh licensed by CC BY-SA 3.0

The sunflower family actually relies on the female parts of the flower to bring the pollen out from the floral tube and into the environment where pollinators can access it. Members of the sunflower family are protandrous, meaning the male parts mature before the female parts. What this means is that the style of the flower can be involved in presenting pollen before it becomes receptive to pollen. This allows enough time for pollen presentation and reduces the likelihood of self pollination.

As the style elongates within the floral tube, one of two things can happen with the pollen inside. In some cases, the style acts like a tiny piston, literally pushing the pollen out into the world. In other cases, the style is covered in tiny, brush-like hairs that rake the pollen from the sides of the floral tube and carry it out as it emerges. In both cases, the style remains closed until enough time has passed for pollen to be taken away from the inflorescence.

Watch _asteraceae GIF on Gfycat. Discover more Timelapse, aster, awesome, back, background, bloom, cool, flower, ground, grow, lapse, out, relax, slender, slow, time, visuals, white, wood, zone GIFs on Gfycat

After a period of time (which varies from species to species), the style splits at the tip and each side curls back on itself to reveal the stigmatic surface. Only at this point in time is are the female parts of the flower mature and ready to receive pollen. With any luck, much of the flowers own pollen would have been collected and taken away to other plants.

The combination of sequential blooming of individual flowers and protandry mean that members of the sunflower family both maximize their chances of pollination and reduce the likelihood of inbreeding. Add to that their ability to disperse their seeds great distances and myriad defense strategies and it should come as no surprise that this family is so darn successful. Get outside and try to witness secondary pollen presentation for yourself. Armed with a hand lens, you will unlock a world of evolutionary wonders!

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

Further Reading: [1] [2]

Peculiar Pillworts

Photo by Christian Fischer licensed by CC BY-SA 3.0

As far as ferns are concerned, the pillworts are pretty unusual. Belonging to the genus Pilularia, there are something like 3 to 6 species depending who you ask. To find them, you need to have an eye for detail and be looking in the right kind of habitats. Pillworts won’t grow just anywhere, which is of growing concern for one species. Today I would like to give you a brief introduction to these peculiar semi-aquatic ferns.

Pillworts really challenge the notion of what a fern should look like. Instead of feathery fronds, pillworts produce narrow, grass-like leaves. Look closely and you will see that these leaves do in fact unfurl in fiddlehead fashion from a long stolon. Situated at the base of the leaves are small, hairy capsules called sporocarps, which house the spores. When presented with favorable growing conditions, pillworts can form large, creeping mats that resemble a shaggy lawn.

No matter where you find them, pillworts largely require the same types of habitats to prosper. These tiny ferns are specialists on muddy banks of seasonal ponds. You see, pillworts simply cannot compete with more aggressive vegetation. For them to thrive, pond conditions must be maintained in an early successional state. The ideal pond for a pillwort fills with water during the winter and largely dries down to mud in the summer. Such fluctuations in water levels keeps competing vegetation at bay. Fully aquatic plants quickly dry out in the summer whereas more terrestrial species drown in the winter. In places like Europe, where Pilularia globulifera is native, grazing by large herbivores such as cattle play a big role as well. As cattle eat up and trample the vegetation around seasonal ponds, they create bare ground where pillworts can thrive.

One of the biggest threats to pillworts is pollution. As runoff from farms and residential areas dump massive quantities of nitrogen and phosphorus into the water, more aggressive plants start to take hold. As this happens, pillworts simply can’t keep up. The degradation and loss of seasonal ponds is causing severe declines in pillwort populations in Europe. Though Pilularia globulifera is still listed as a species of least concern, the rate at which it is being lost from its historical range is enough to place it on the watch list of many conservation organizations.

Photo by Sam Thomas licensed by CC BY-NC-SA 2.0

Outside of the UK, pillworts are receiving much less attention. Little information exists on pillworts growing in Australia and New Zealand, and there is ongoing debate as to whether North American populations represent a single species or two distinct, albeit cryptic species. Such lack of attention and confusion coupled with its inconspicuous appearance could be bad news for this tiny plant. Without proper assessments of what species occur where and their relative abundance, few conservation measures can be put into place. What we can say for sure is that to protect pillworts, we must protect their habitat.

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

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

Encounters With a Rare White-Topped Carnivore

I am not a list maker. Never have been and never will be. That being said, there are always going to be certain plants that I feel I need to see in the wild before I die. The white-topped pitcher plant (Sarracenia leucophylla) was one such plant.

I will never forget the first time I laid eyes on one of these plants. It was at a carnivorous plant club meeting in which the theme had been “show and tell.” Local growers were proudly showcasing select plants from their collections and it was a great introduction to many groups which, at the time, I was unfamiliar with. Such was the case for the taller pitcher plants in the genus Sarracenia. Up until that point, I had only ever encountered the squat purple pitcher plant (S. purpurea).

I rounded the corner to a row of display tables and was greeted with a line of stunning botanical pitfall traps. Nestled in among the greens, reds, and yellows was a single pot full of tremendously white, green, and red pitcher plants. I picked my jaw up off the floor and inquired. This was the first time I had seen Sarracenia leucophylla. At that point I knew I had to see such a beauty in the wild.

More like white and red top…

It would be nearly a decade before that dream came true. On my recent trip to the Florida panhandle, I learned that there may be a chance to see this species in situ. Needless to say, this plant nerd was feeling pretty ecstatic. Between survey sites, we pulled down a long road and parked our vehicle. I could tell that there was a large clearing just beyond the ditch, on the other side of the trees.

The clearing turned out to be an old logging site. Apparently the site was not damaged too severely during the process as the plant diversity was pretty impressive. We put on our boots and slogged our way down an old two track nearly knee deep in dark, tanic water. All around us we could see amazing species of Sabatia, Lycopodiella, Drosera, and so much more. We didn’t walk far before something white caught my eye.

There to the left of me was a small patch of S. leucophylla. I had a hard time keeping it together. I wanted to jump up and down, run around, and let off all of the excited energy that had built up that morning. I decided to reign it in, however, as I had to be extra careful not to trample any of the other incredible plants growing near by. It is always sad to see the complete disregard even seasoned botanists have for plants that are unlucky enough to be growing next door to a species deemed “more exciting,” but I digress.

Sarracenia leucophylla flower. Photo by Noah Elhardt licensed by GNU Free Documentation License [SOURCE]

This was truly a moment I needed to savor. I took a few pictures and then put my camera away to simply enjoyed being in the presence of such an evolutionary marvel. If you know how pitcher plants work then you will be familiar with S. leucophylla. Its brightly colored pitchers are pitfall traps. Insects lured in by the bright colors, sweet smell, and tasty extrafloral nectar eventually lose their footing and fall down into the mouth of the pitcher. Once they have passed the rim, escape is unlikely. Downward pointing hairs and slippery walls ensure that few, if any, insects can crawl back out.

What makes this species so precious (other than its amazing appearance) is just how rare it has become. Sarracenia leucophylla is a poster child for the impact humans are having on this entire ecosystem. It can only be found in a few scattered locations along the Gulf Coast of North America. The main threat to this species is, of course, loss of habitat.

A large conservation population growing ex situ at the Atlanta Botanical Garden.

Southeastern North America has seen an explosion in its human population over the last few decades and that has come at great cost to wild spaces. Destruction from human development, agriculture, and timber production have seen much of its wetland habitats disappear. What is left has been severely degraded by a loss of fire. Fires act as a sort of reset button on the vegetation dynamics of fire-prone habitats by clearing the area of vegetation. Without fires, species like S. leucophylla are quickly out-competed by more aggressive plants, especially woody shrubs like titi (Cyrilla racemiflora).

Another major threat to this species is poaching, though the main reasons may surprise you. Though S. leucophylla is a highly sought-after species by carnivorous plant growers, its ease of propagation means seed grown plants are usually readily available. That is not to say poaching for the plant trade doesn’t happen. It does and the locations of wild populations are best kept secret.

Sarracenia leucophylla habitat. Photo by Brad Adler licensed by CC BY-SA 2.5 [SOURCE]

The main issue with poaching involves the cut flower trade. Florists looking to add something exotic to their floral displays have taken to using the brightly colored pitchers of various Sarracenia species. One or two pitchers from a population probably doesn’t hurt the plants very much but reports of entire populations having their pitchers removed are not uncommon to hear about. It is important to realize that not only do the pitchers provide these plants with much-needed nutrients, they are also the main photosynthetic organs. Without them, plants will starve and die.

I think at this point my reasons for excitement are pretty obvious. Wandering around we found a handful more plants and a few even had ripening seed pods. By far the coolest part of the encounter came when I noticed a couple damaged pitchers. I bent down and noticed that they had holes chewed out of the pitcher walls and all were positioned about half way up the pitcher.

I peered down into one of these damaged pitchers and was greeted by two tiny moths. Each moth was yellow with a black head and thick black bands on each wing. A quick internet search revealed that these were very special moths indeed. What we had found was a species of moth called the pitcher plant mining moth (Exyra semicrocea).

An adult pitcher plant mining moth (Exyra semicrocea) sitting within a pitcher!

Amazingly, the lives of these moths are completely tied to the lives of the pitcher plants. Their larvae feed on nothing else. As if seeing this rare plant wasn’t incredible enough, I was witnessing such a wonderfully specific symbiotic relationship right before my very eyes.

Fortunately, the plight of S. leucophylla has not gone unnoticed by conservationists. Lots of attention is being paid to protecting remaining populations, collecting seeds, and reintroducing plants to part of their former range. For instance, it has been estimated that efforts to protect this species by the Atlanta Botanical Garden have safeguarded most of the genetic diversity that remains for S. leucophylla. Outside of direct conservation efforts, many agencies both public and private are bringing fire back into the ecology of these systems. Fires benefit so much more than S. leucophylla. They are restoring the integrity and resiliency of these biodiverse wetland habitats.

LEARN MORE ABOUT WHAT PLACES LIKE THE ATLANTA BOTANICAL GARDEN ARE DOING TO PROTECT IMPORTANT PLANT HABITATS THROUGHOUT THE SOUTHEAST AND MORE.

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

Sea Oats: Builder of Dunes & Guardian of the Coast

Photo by Sara Johnson

Coastal habitats can be really unforgiving to life. Anything that makes a living along the coast has to be tough and they don’t come much tougher than sea oats (Uniola paniculata). This stately grass can be found growing along much of the Atlantic coast of North America as well as along the Gulf of Mexico. What’s more, its range is expanding. Not only is this grass extremely good at living on the coast, it is a major reason coastal habitats like sand dunes exist in the first place. Its presence also serves to protect coastlines from the damaging effects of storm surges. What follows is a celebration of this amazing ecosystem engineer.

Sea oats is a dominant player in coastal plant communities. Few other species can hold a candle to its ability to survive and thrive in conditions that are lethal to most other plants. The ever-present winds that blow off the ocean bring with them plenty of sand and salt spray. Sea oats takes this in strides. Not only are its tissues extremely tough, they also help prevent too much water loss in a system defined by desiccation.

Photo © Don Henise licensed by CC BY 2.0

The life cycle of sea oats begins with seeds. Its all about numbers for this species and seat oats certainly produces a lot of seed. Surprisingly, many of the seeds produced are not viable. What’s more, most will never make it past the seedling stage. You see, sea oat seeds require just the right amount of burial in sand to germinate and establish successfully. Too shallow and they are either picked off by seed predators or the resulting seedlings quickly dry up. Too deep and the limited reserves within mean the seedling exhausts itself before it can ever reach the surface.

Still, enough seeds germinate from year to year that new colonies of sea oats are frequently established. Given the right amount of burial, seedlings focus much of their first few months on developing a complex, albeit shallow root system. Within two months of germination, a single sea oat can grow a root system that is as much as 10 times the size of the rest of the plant. This is because sand is not a forgiving growing medium. Sand is constantly shifting, it does not hold on to water very long, and it is usually extremely low in nutrients. By growing a large, shallow root system, sea oats are able to not only anchor themselves in place, they are also able to take advantage of what limited water and nutrients are available.

It is also this intense root growth that makes sea oats such an important ecosystem engineer in coastal habitats. All of those roots hold on to sand extremely well. Add to that some vast mychorrhizal fungi partnerships and you have yourself a recipe for serious erosion control. The interesting thing is that as sea oats grow larger, they trap more sand. As more sand builds up around the plants, they grow even larger to avoid burial. This process snowballs until an entire dune complex develops. As the dunes stabilize, more plants are able to establish, which in turn attracts more organisms into the community. A literal ecosystem is built from sand thanks to the establishment of a single species of grass.

Photo © Hans Hillewaert / CC BY-SA 4.0

As sea oats mature, they will begin to produce flowers, and the process repeats itself over and over again. As mentioned above, the sea oats seeds are subject to a lot of seed predation. This means that as sea oat populations grow, more and more animals can find food in and among the dunes. So, not only do sea oats build the habitat, they also supply it with plenty of resources for organisms to utilize.

The power of sea oats does not end there. Because they are so good at controlling erosion, they help stabilize the shoreline from the punishing blow of storm surges. Dune systems, especially those of barrier islands, help reduce the amount of erosion and the momentum of wave action reaching coastal communities. Many states here in North America are starting to realize this and are now protecting sea oat populations as a result.

Sea oats, though tough, are not indestructible. We humans can do a lot of damage to these plants and the communities they create simply by walking or driving on them. Pathways from foot and vehicle traffic kill off the dune vegetation and create a path of least resistance for wind, which quickly erodes the dunes. Apart from that, development and resulting runoff also destroy sensitive dune communities, making our coastlines that much more vulnerable to the inevitable storms that threaten their very existence.

As our climate continues to change at an unprecedented rate and storms grow ever stronger, it is very important that we recognize the role important species like sea oats play in not only providing habitat, but also protecting our coastlines. Dune stabilization and restoration projects are growing in popularity as a cost effective solution to some of the threats facing coastal communities. Among the many techniques for restoring dunes is the planting of native dune building species like sea oats. If you live near or simply like to enjoy the coast, please stay off the dunes. Foot and vehicle traffic make quick work of these habitats and we simply cannot afford less of them.

Watch our short film DUNES to learn more about these incredible ecosystems.

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

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

Eelgrass Sex is Strange

Photo by Fredlyfish4 licensed by CC BY-SA 4.0

Pollination may seem like a strange thing to us humans. Whereas we only require two of us to accomplish reproduction, plants have to utilize a third party. The most familiar cases include insects like bees and butterflies. Unique examples include birds, bats, and even lizards. Many plants forego the need of an animal and instead rely on wind to broadcast copious amounts of pollen into the air in hopes that it will randomly bump into a receptive female organ.

This has worked very well for terrestrial plants but what about their aquatic relatives? Water proves to be quite an obstacle for the methods mentioned above. Some species get around this by thrusting their flowers above the surface but others don't bother. One genus in particular has evolved a truly novel way of achieving sexual reproduction without having to leave its aquatic environment in any way.

Photo by eyeweed licensed by CC BY-NC-ND 2.0

Meet the Vallisnerias. Commonly referred to as tape or eelgrasses, this genus of aquatic plants has been made famous the world over by their use in the aquarium trade. In the wild they grow submerged with their long, grass-like leaves dancing up into the water column. Where they are native, eelgrasses function as an important component of aquatic ecology. Everything from fish and crustaceans all the way up to manatees utilize tape grass beds for both food and shelter. Eelgrasses stabilize stream beds and shorelines and even act as water filters.

All this is quite nice but, to me, the most interesting aspect of Vallisneria ecology is their reproductive strategy. Whereas they will reproduce vegetatively by throwing out runners, it is their method of sexual reproduction that boggles the mind. Vallisneria are dioecious, meaning individual plants produce either male or female flowers. The female flowers are borne on long stalks that reach up to the water surface. Once there they stop growing and start waiting. Because of their positioning, water tension causes a slight depression around the flowers at the surface. The depression resembles a little dimple with a tiny white flower in the center.

A female Vallisneria flower. Photo by eyeweed licensed by CC BY-NC-ND 2.0

Male Vallisneria flowers floating on the water surface. Photo by eyeweed licensed by CC BY-NC-ND 2.0

Male flowers are very different. Much smaller than the female flowers, a single inflorescence can contain thousands of individual male organs. As they mature underwater, the male flowers break off from the inflorescence and float to the surface. Similar to wind pollinated terrestrial plants, Vallisneria use water currents to disperse their pollen. Once at the surface, the tiny male flowers float around like little pollen-filled rafts.

If a male flower floats near the dimple created by a female flower, it will slide down into the funnel-like depression where it will contact with the female flowers. This is how pollination is achieved. Once pollinated, hormonal changes signal the stem of the female flower to begin to coil up like a spring, drawing the developing seeds safely underwater where they will mature. Eventually hundreds of seeds are released into the water currents.

After pollination, the stem of the female flower coils up, drawing the ripening ovaries safely underwater. Photo by Peter M. Dziuk [source]

The Vallisneria are incredible aquatic plants. Their bizarre reproductive strategy has ensured that these plants never really have to leave the water. The fact that they can also reproduce vegetatively means that many species are very successful plants. In fact, some species have become noxious invasive weeds where they have been introduced far outside of their native range. If you own these plants in any way, do take the necessary measures to ensure that they never have the chance to become invasive.

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

Further Reading: [1]

Path Rush

Photo by Matt Lavin licensed by CC BY-SA 2.0

Path rush (Juncus tenuis) is one of those plants that has really benefited from human expansion. Originally native to North America, it can now be found in numerous countries around the globe. It owes much of its success to both its ability to tolerate lots of disturbance as well as an ingenious seed dispersal mechanism. If you like to hike, there is a good chance you have encountered path rush somewhere along the way. There is also a strong chance that you have dispersed its seeds.

Path rush is a relatively small species, topping out around 60 cm in height. Because it frequently grows where foot traffic is heavy, plants don’t always reach such stature. Like most rushes, it has round stems and surprisingly attractive flowers, though one would need a hand lens to fully appreciate their beauty. Flowering for path rush occurs during the summer and it is thought that wind is the main pollination mechanism for this species.

The darker vegetation running along the path is all path rush! Photo by Tom Potterfield licensed by CC BY-NC-SA 2.0

Following pollination, each flower is replaced by a tiny capsule filled with tiny seeds. Each seed is covered in a substance that turns into a sticky mucilage when wet. This mucilage is how path rush manages to move around the landscape so easily. The sticky seeds glom onto pretty much everything from fur to feathers, boots to car tires. This is why you most often find path rush on, well, paths! Its sticky seeds are carried far and wide by foot traffic. It is also why you can now find path rush growing well outside of North America.

Path rush enjoying a crack in the sidewalk.

Path rush frequents more habitats than simply paths too. The key to its success is soil disturbance. Anywhere the soil has been compacted and disturbed, path rush can find its niche. With little competition from surrounding vegetation, this tiny rush can grow into impressive colonies. Even cracks in asphalt can harbor a plant or two. Aside from its ability to tolerate soil disturbance, its tough, stringy foliage is not fed on by a lot of herbivores, which gives it yet another leg up on potential competitors. All in all, this is one tough little plant.

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

Further Reading: [1] [2]

Meeting the Elusive Three Birds Orchid

Rare but locally abundant has to be the only proper way of describing the distribution of this peculiar little orchid. I have known about the three birds orchid (Triphora trianthophoros) for some time now. I'm generally not a jealous person but I did find myself quite envious of those who have encountered it. Even with ample herbarium records I simply could not seem to locate any individuals of this species.

The best advice for finding it that I was ever given was to not go looking for it. This secretive little plant is something you almost have to stumble upon. And stumble I did. While surveying some vegetation plots that I had combed over all summer back in 2016 I noticed something new poking up. The slender red stalks had tiny green leaves and elongated flower buds at the top. I knew instantly that this could only mean one thing - I had finally found some three birds.

Both the common and scientific name hint at the fact that these plants are often seen with three flowers. This is not a rule by any means as plants can be found with as few as one flower or as many as 10. Regardless of the amount, finding them is only part of the battle. The other challenge is to catch them in bloom.

The secretive nature of this orchid has led to some interesting tips on how to get your timing right. Some say to check a known population after the first big rain of August. Another more pervasive tip claims that one must take to the forest after nighttime temperatures take a sudden dip. Despite this entertaining advice, it would seem that you just have to be in the right place at the right time.

What is known about the flowering habits of the three birds orchid is that populations tend to flower in unison. The buds all develop to a certain point and stop. They will sit and wait for the right conditions (whatever they might be) to arise. Once that crucial condition is hit, they rapidly bloom en masse. This is a wonderful strategy for a flowering plant that lives tucked away on the shady forest floor.

Concealed among the forest debris, one or two flowers wouldn't get much attention. Hundreds of bright white and pink flowers, however, certainly do! Juxtaposed against the shade of the forest, these little orchids almost glow like little neon signs. Despite this mass effort, it has been found that pollination rates are usually very low. Instead, this orchid most often reproduces vegetatively by budding off tiny plantlets from the main root stock. Because of this, it is not uncommon to find literally hundreds of plants of various sizes clustered together within inches of each other. This is an impressive sight to behold.... again, if you are lucky enough to find it.

Like many of its orchid cousins, this species is no stranger to the disappearing act. Because they rely so heavily on mycorrhizal fungi for their nutrient needs, exhausted plants will often go dormant under the soil for years until they gain enough energy to produce stems, leaves, and flowers again. If you come across the three birds orchid during your travels, do yourself a favor and take some time to relish the moment. It may be a long time before you ever see them again.

Further Reading: [1] [2]

A Tiny Passionflower with a Hardy Disposition

Passionflowers barely need an introduction. Who hasn't marveled at the beautiful splendor of their intricate blossoms. Thought largely tropical in their distribution, there are a couple members of the genus Passiflora that have tackled temperate North America. My favorite of these is small and not nearly as gaudy as its cousins but that is kind of what makes me like it so much. Today, I would like to introduce you to the yellow passionflower (Passiflora lutea).

Did I mention this was a small plant? Whereas it can vine itself over surrounding vegetation very effectively, it is by no means a bulky plant. Even more incredible are its flowers. Anyone familiar with the anatomy of Passiflora flowers will be shocked to see all of that detail miniaturized into a yellow-green bloom about the size of your thumbnail. You must be quick to catch these in flower as they themselves are only open for about a day.

As I mentioned above, Passiflora don't come any hardier than the yellow passionflower (except maybe P. incarnata). With a range that extends as far north as Pennsylvania, this lovely little vine can handle winter temperatures as low as −30 °C (-22 °F)! This has earned it the designation of the northernmost species of Passiflora. Even then, I have heard reports of people growing this hardy little plant farther north in Canada.

Pollination for this species works in much the same way as it does for the genus as a whole. The flowers require an insect large enough to contact the peculiar arrangement of anthers and stigmas. The strange yet beautiful filaments that ring the center of the bloom are collectively referred to as the corona and it is believed that these guide insects to the nectar and thus into perfect position for pollination.

By far the most peculiar aspect of this plant is the relationship it has formed in part of its range with a tiny bee aptly named the passionflower bee (Anthemurgus passiflorae). Native from central Texas to North Carolina and north to Illinois, this tiny black bee is the only member of its genus. What's more, it absolutely requires the yellow passionflower for its reproduction. It feeds its larvae solely on pollen from the yellow passionflower. If that wasn't strange enough, despite its highly specific foraging habits, the diminutive size of the bee has led experts to believe that the passionflower bee contributes very little in the way of pollination for the plant.

Further Reading: [1] [2]

The Pine Lily

The pine lily (Lilium catesbaei) is one of North America’s finest species of lily. It produces the largest flowers of the genus on this continent and to see one in person is a breathtaking experience. The pine lily is endemic to the Southeastern Coastal Plain where it prefers to grow in mesic to wet flatwoods, wet prairies, and savannas. Though it enjoys a relatively wide distribution, today it rarely occurs in any abundance.

The pine lily’s rarity may be a relatively recent status change for this wonderful plant. Historical records indicate that it was once quite abundant in states like Florida. Today it occurs in scattered localities and predicting its presence from year to year has been a bit tricky. Indeed, the pine lily appears to be very picky when it comes to growing and flowering.

One aspect of its biology that might lend to its limited appearance is the fact that it can remain underground in a dormant state for years. Like other members of this genus, the pine lily emerges from a bulb. This underground storage structure is small by lily standards, which means that most pine lilies are operating on marginal stores of energy in any given year.

Some have estimated that individual bulbs can remain dormant for upwards of 5 years before the right conditions for growth flowering present themselves. Of course, such dormancy can be a nightmare for proper conservation of such a unique plant. Aside from the individual flower borne at the tip of a long, slender stem, the rest of the plant is very dainty. In fact, its flowers can be so heavy compared to the rest of the plant that some stems simply topple to the ground before they can set seed. The slender stem, small leaves, and tiny bulb equate to a small operating budget in terms of energy stores. That being said, we are starting to get a clearer picture of what pine lilies need to thrive and it all comes down to fire.

Photo by Eleanor licensed by CC BY-NC 2.0

The key to acquiring enough energy for growth and reproduction appears to be a proper amount of sunlight. Without it, plants languish. This is where fire comes in. The pine lily lives in a region of North America that historically would have burned with some frequency. Wildfires sweep through an area, burning away competing vegetation like saw palmetto (Serenoa repens) and clearing the ground of accumulated debris like sticks and leaves. By burning away the competition, fire creates open areas where delicate plants like the pine lily can eke out an existence. Indeed, research has shown that pine lilies produce more flowers and seed immediately following ground-clearing burn followed by a subsequent decline in flowering and seed set as the surrounding vegetation begins to grow back.

If a pine lily does have enough energy to flower, then one of the most stunning flowers in all of North America is presented with its face towards the sky. Its 6 large petals are brightly colored and taper down into what looks like tiny tubes. Nectar is produced within these tubes and, coupled with the bright coloration, attract numerous insect visitors.

Not all insects are capable of successfully pollinating such a large flower. In fact, it would appear that only a couple of species take up the bulk of the pollination of this incredible plant. As far as we know, the Palamede swallowtail butterfly (Papilio palamedes) and perhaps the spicebush swallowtail (P. troilus) are the only species large enough to properly contact both anthers and stigma while feeding at the flowers. The large wingspan of these butterflies do all of the work in picking up and depositing pollen. All other insects are simply too small to adequately achieve such feats.

Though we still have a lot more to learn about the pine lily, what we do know tells us a story that is repeated for fire-dependent ecosystems throughout the world. Without regular disturbance from fire, biodiversity drops. The pine lily is not alone in this either. Its fate is intertwined with countless other unique plant species that call the coastal plains their home.

Photo Credits: [2]

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

Surprising Genetic Diversity in Old Growth Trees

Photo by S. Rae licensed by CC BY 2.0

Long-lived trees face a lot of challenges throughout their lives. Many trees can live for centuries, which can be a problem because plants cannot get up and move when conditions become unfavorable. This should equate to a slower rates of adaptation and evolution for long lived trees but that isn’t always the case. Many trees are often superbly capable of adapting to local conditions. Recently, a team of researchers from the University of British Columbia have provided some insights into the genetic mechanisms that may underpin such adaptive potential.

Genetic insights came from a species of conifer many will be familiar with - the Sitka spruce (Picea sitchensis). Researchers were interested in these trees because they live for a long time (upwards of 500 years or more) and can grow to heights of over 70 meters (230 ft.). They wanted to understand how genetic mutations work in trees like the Sitka spruce because plants are doing things a bit different than animals in that department.

Plants are modular organisms, meaning they grow by producing multiple copies of discrete units. This equates to a branching structure whose overall shape is in large part determined by environmental influences. It also means that when genetic mutations occur in one branch, they can be carried on throughout the growth of those tissues independent of what is going on throughout the rest of the plant. This means that older trees can often accumulate a surprising amount of genetic diversity throughout the entire body of the plant.

Photo by Brandon Kuschel licensed by Creative Commons Attribution 3.0 Unported

When researchers sampled the DNA of tissues from the trunks and the needles of tall, old growth Sitka spruce, they were shocked by what they had found. From the base of the tree to the needles in the canopy, an old growth Sitka spruce can show as much as 100,000 genetic differences. That is a lot of genetic diversity for a single organism. Though plenty of other trees have been found to exhibit varying levels of genetic differences within individuals, this is one of the highest mutation rates ever found in a single eukaryotic organism. This could also explain why such long-lived organisms can survive in a changing world for their entire lives.

Now, it is important to note that many mutations are likely either neutral or potentially harmful. Also, the rates of mutation may differ depending on where you look on this tree. For instance, needles at the top of a Sitka spruce are going to be exposed to far more gene-altering UV radiation than bark tissues near the base. Still, over the lifetime of a single tree, rare beneficial mutations can and do accumulate. Imagine a scenario in which one branch mutation results in needles that are more resistant to say an insect pest. Those needles could hypothetically receive less damage than needles elsewhere on the tree. This odd form of selection is occurring within the lifetime of that tree and may even have implications for the future offspring of that tree thanks again to the quirks of how tree reproductive cells develop.

Many trees also do not have segregated germlines. What this means is that unlike animals whose reproductive cells develop from separate cell lineages than the rest of their body cells, the reproductive cells of trees develop from somatic cells, which are the same cells that form stems, leaves, and branches. This means that if a mutation occurs on the germline of a branch that eventually goes on to produce cones, these mutations can be passed on in the seeds of those cones. This obviously needs a lot of evidence to substantiate but now that a mechanism is in place, we know where and what to look for.

Photo Credits: [1] [2]

Further Reading: [1] [2]

Let's Talk About Recruitment

Photo by --Tico-- licensed by CC BY-NC-ND 2.0

For any species to be considered successful, it must replace itself generation after generation. We call this process recruitment and it is very important. After all, reproduction is arguably the most fundamental aspect of life in a Darwinian sense. For plants, this can be done either vegetatively or sexually via seeds and spores. Though vegetative reproduction is a fundamental process for many plants around the globe, seed or spore germination is arguably the most important. To truly understand what a plant needs, we have to understand its germination requirements.

Recruitment is a considerable limiting factor for plant populations. In fact, it is the first major bottleneck plants must pass through. It is estimated that a majority of plant mortality occurs during the germination and seedling stages. However, not all plants are equal in this way. Some plants are considered seed or propagule limited whereas others are habitat limited.

If a plant is seed limited, it means that its ability to expand its population or colonize new habitats its limited by the ability of seeds (or spores) to make it to a new location. Once there, nature takes its course and germination occurs with little impediment. If a plant is habitat limited, however, things get a bit more tricky. For habitat limited plants, simply getting seeds to a new location is not enough. Some other aspect of the environment (soil moisture, texture, temperature, disturbance, etc.) limit successful germination. Only when the right conditions are present can habitat limited plants germinate and begin to grow.

Habitat limitation is probably the most common limit to plant establishment. Simply put, not all plants will be successful everywhere. Even the successful growth and persistence of adult plants can be poor predictors of seedling success. Many plants can live for decades or even centuries and the conditions that were present when they germinated may have long since changed. Even the presence of the adults themselves can make a site unsuitable for germination. Think of all of those fire adapted species out there that require the entire community to burn before their seeds will ever germinate.

In reality, it is likely that most plants are habitat limited to some degree. These are not binary categories after all, rather they are aligned along a spectrum of possibilities. The fact that most plants don’t completely take over an area once seeds or spores arrive is proof of the myriad limits to plant establishment. As such, recruitment limitation is extremely important to study. It can make a huge difference in the context of conservation and restoration. Even the successful establishment of adult plants is no guarantee that seedlings stand a chance. Without successful recruitment, all you have left is a nice garden that is doomed to run its course. By understanding the limits to plant recruitment, we can do much more than just improve on our ability to protect and bolster plant populations, we can also gain insights into why so many plants remain rare on the landscape and so few ever rise to dominance.

Photo Credits: [1]

Further Reading: [1] [2]

The Round Leaved Orchid

In the northern temperate regions of North America, late June marks the beginning of what I like to call orchid season. If you're lucky you may stumble across one of these rare beauties in full bloom. Their diversity in shape and size are mainly a result of the intricate evolutionary relationships they have formed with their pollinators. I spend much of my time botanizing trying to locate and photograph these botanical curiosities and any time I get to meet a new species is a very special time indeed. 

Take the round leaved orchid (Platanthera orbiculata) for example. For years I have only known this species as two round leaves that are slightly reminiscent of the phaleanopsis orchids you see for sale in nurseries and grocery stores. The leaves can be quite large too. With their glossy appearance, they are the easiest way to locate this plant.

When conditions are right and the plants have enough stored energy they will begin to flower. Rising from the middle of the pair of leaves is a decent sized inflorescence loaded with greenish white flowers. The flowers are interesting structures. Not particularly colorful, they have a long white lip and considerable green nectar spurs. There are said to be two varieties of this species, each being characterized by the length of the nectar spur. Unlike many orchids that offer no reward to pollinators, P. orbiculata produces nectar. The flowers are pollinated by noctuid moths, which is probably why they are white in color. Whereas most lepidopteran pollinated orchid attach their pollinia to the proboscis of the butterfly or moth, P. orbiculata attaches its pollinia to the eyes of visiting moths. 

If this isn't strange enough, the pollinia themselves have some of their own intriguing adaptations. Visiting moths take a certain amount of time to successfully access the nectar from the nectar spur. If the plant is to avoid wasting precious pollen on itself, then it must find a way to delay this process. The pollinia are the solution to this. When first attached to the eyes, the pollinia stick straight up. This keeps them away from the female parts of the plant as the moth feeds. Only after enough time has elapsed will the stalks of the pollinia begin to bend forward. At this point the moth will hopefully have moved on to the flowers of an unrelated individual. Pointing straight forward, they are now perfectly positioned to transfer pollen. 

Like all orchids, P. orbiculata relies on specialized mycorrhizal fungi for germination and survival. At the beginning of its life, P. orbiculata relies solely on the fungi for sustenance. Once it has enough energy to produce leaves it will repay the fungi by providing carbohydrates. However, the relationship is not over at this point. Every spring, P. orbiculata produces a new set of leaves as well as a whole new root system. The fungi supply a lot of energy for this process and if the plant is disturbed (ie. dug up by greedy poachers) or browsed upon, it is likely that it will not recover from the stress and it will die. The mycorrhizal fungi it relies on live on rotting wood so finding well rotted logs is a good place to start searching for this species. With declining populations throughout much of its range, it is important to remember to enjoy it where it grows. Leave wild orchids in the wild!

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