The Carnivorous Plant Guild Welcomes a New Member

Photo by Michael Kauffmann (www.backcountrypress.com)

It is a rare but special day when we can add a new plant to the relatively small list of carnivorous plants. It is even more exciting when that plant has been “hiding” in plain sight all this time. Meet the western false asphodel (Triantha occidentalis), a lovely monocot native to nutrient-poor wetlands in western North America.

Triantha occidentalis may seem like an odd carnivorous plant. At first glance, it doesn’t have much in the way of carnivorous adaptations; there are not pitfall traps, no sticky leaves, no snap traps, and no bladders anywhere on the plant. However, if you were to examine this species during its flowering season, you would notice that a lot of small insects seem to get stuck to its flowering stem.

Indeed, the ability of this species to trap insects has been known for quite some time. Even old herbarium collections of T. occidentalis are chock full of insect remains stuck to the scape. Magnify the flowering stem and you will see that it is covered in sticky hairs or trichomes that look a lot like miniature versions of those covering the leaves of more obvious carnivores like sundews (Drosera spp.). Observations such as these led scientists to investigate whether this wonderful little wetland monocot actually benefits from trapping all those arthropods.

Via a series of experiments using isotopes of nitrogen, scientists have revealed that T. occidentalis really does obtain a nutritional boost from the insects it traps. This isn’t a passive process on the part of the plant either. It was also discovered that the plant also secrets the digestive enzyme phosphatase, which helps break down the trapped insects. When the team examined what was going on within the tissues of the plant, they found even more evidence of its carnivorous nature.

Look closely and you can see sticky glands and trapped insects just below the flowers! Photo by Michael Kauffmann (www.backcountrypress.com)

It turns out that 64% of the nitrogen within the plant is obtained via insect digestion, which is comparable to that of other known carnivorous plants such as the aforementioned sundews. Interestingly, it appears that the insect nitrogen the plant obtains is first stored in the flowering stem and fruits but is then transported down into the roots and rhizome underground to be utilized in the following growing season. Why exactly the plant does this requires further investigations. Perhaps by using its flowering stems to obtain nutrients that are in short supply in its wetland habitat, the plant is able to better offset the cost of flowering each year.

By far the most remarkable aspect of this discovery is where carnivory occurs on the plant. With few exceptions, the vast majority of carnivorous plants keep their feeding organs away from their flowers. The leading hypothesis on this suggests that separating feeding and reproduction in space (and sometimes time) helps carnivorous plants avoid catching and digesting their pollinators. However, T. occidentalis does the opposite. It produces all of its sticky hairs very close to its blooming flowers.

Large floral visitors like butterflies appear to be the main pollinators and are too large to get stuck, whereas smaller insects like midges do. Photo by Michael Kauffmann (www.backcountrypress.com)

The key to this apparent morphological contradiction may lie in the stickiness of those hairs. It has been observed that the vast majority of insects trapped on the flowering stems of T. occidentalis are mostly midges and other small insects that don’t function as pollinators for the plant. It is possible that the larger bees and butterflies that could function as true pollinators are simply too large and strong to be trapped. Again, more research is needed to say for sure.

All in all, T. occidentalis represents a unique carnivorous plant whose true nature required solid natural history knowledge and observation to reveal. The fact that we are just learning about its carnivorous habit after all this time suggests that many more potentially carnivorous plants may also be “hiding” in plain sight (I’m looking at you, Silene), waiting for curious minds to collect the necessary data. This is also an exciting discovery from a taxonomic perspective as well. Up until now, all of the known carnivorous monocots hail from the order Poales. Therefore, T. occidentalis represents the first non-Poalean carnivorous monocot! For all these reasons and more, I am excited about future research on this plant and others like it.

Further Reading: [1]

An Endemic Spurge in Florida

A pistillate cyathium of a Telephus spurge.

Endemism fascinates me. Why some organisms occur in certain restrict areas geographically and nowhere else is such a fun topic to ponder. On a recent trip to the Florida Panhandle, I was lucky enough to encounter a wonderful little plant endemic to pine flatwoods located at the very tip of the Apalachicola region. It is a type of spurge known as Telephus spurge (Euphorbia telephioides) whose natural history is captivating to say the least.

The Telephus spurge is a denizen of dry, sandy soils. Its fleshy leaves and deep, tuberous taproot not only allow it to handle drought via the storage of water and nutrients, its root system also allows it to live a long time. Though it is hard to say how long individuals can actually live, lifetimes measured in decades are well within the realm of possibility. Like many members of the spurge family (Euphorbiaceae), the Telephus spurge is also well defended by toxic, milky sap.

A staminate cyathium of a Telephus spurge.

The inflorescence of the Telephus spurge is defined as a cyathium. Plants can produce multiple cyathia per plant, and for the Telephus spurge, these can contain only male, only female, or both reproductive structures. Sex of individual Telephus spurge is an interesting topic unto itself and very important when it comes to conservation (more on that in a bit). Individual Telephus spurge can be fluid in their sexual expression from one year to the next. Individuals that produced only male cyathia one year can go on to produce only female or bisexual cyathia in subsequent years. No one can say for sure what triggers these changes among individuals, but disturbance and energy reserves likely play a considerable role.

One of the most important aspects of Telephus spurge ecology is fire. Without regular fires, the entire habitat of the Telephus spurge would gradually close in with woody shrubs and trees and disappear. Even though most of the top parts of these plants are killed by fires, their large tuberous root system allows them to readily regrow what was lost. That is not to say that individuals regularly regrow after fires. In fact, plants have been known to disappear for years at a time following top killing events, only to resprout at some point in the future when favorable conditions return.

Telephus spurge fruits are quite pretty!

At this point, it should be obvious that for this species to persist, its habitat needs to be maintain via fire. Management for this species is very important given its narrow distribution and sporadic occurrence on the landscape. However, there are still many hurdles in the way of effective Telephus spurge conservation. For starters, though it once likely enjoyed a more contiguous distribution throughout the Apalachicola region, habitat destruction from logging, ditching, and development have highly fragmented its populations into tiny clusters. The smaller these clusters become, the more vulnerable they are to extirpation.

Another factor complicating the conservation of this species is its aforementioned sexual fluidity. Because we still don’t know what triggers a change in sexual expression among individuals from one year to the next, populations can fluctuate greatly in terms of their reproductive capacity. For instance, if a population comprised of many individuals with bisexual cyathia one year suddenly switches to producing mostly male cyathia the following year, seed production can decrease greatly. Until we know more about the reproductive ecology of this species, maintaining populations with regular fire while limiting the amount of logging and development is the best chance we have at ensuring this extremely rare spurge has a future on this planet.

The one upside to this story is that, where properly managed, Telephus spurge can reach high abundances. With a little bit of effort, these populations are relatively easy to map and seed can be collected and maintained to preserve valuable genetic material. Still, without proper management and land conservation/restoration efforts, the future of this tiny spurge and many of its botanical neighbors hangs in the balance. Support your local land conservancy today, because stories like this are far more common than you think!

Further Reading: [1] [2]

Pitcher Plant Moths and their Pitcher Plant Homes

Discussions about pitcher plants usually revolve around the fact that they trap and eat insects and other animals. However, there are a handful of organisms out there that turn the table on pitcher plants, reminding us that these botanical carnivores can become food themselves. Spend any amount of time surveying pitcher plant populations in southeastern North America and you are likely to encounter at least one such species of pitcher plant eater.

There are three species of pitcher plant moths in the genus Exyra and all of them would not exist if it were not for pitcher plants in the genus Sarracenia. Whereas E. ridingsii and E. semicrocea are largely restricted to southeastern portions of North America, E. fax can be found as far north as Newfoundland. These three species also vary in their dietary specificity. As you can probably ascertain from its distribution, E. fax is a purple pitcher plant (S. purpurea) but will also feed on the southern pitcher plant (S. rosea) in the southern portions of its range. Exyra ridingsii is also a dietary specialist, feeding only on the pitchers of the yellow pitcher plant (Sarracenia flava). Alternatively, E. semicrocea is a generalist and can be found feeding on a variety of Sarracenia species.

An Exyra caterpillar busy feeding on a Sarracenia flava pitcher.

Both caterpillars and adult moths are physically adapted to living within the slippery interior of the pitcher walls. Microscopic analyses of their feet have revealed specialized morphological adaptations that allow them to cling to the waxy walls of the pitcher. The caterpillars may also benefit from their ability to spin silken lines. Interestingly, the moths are only ever found perched upright in the pitchers. Even when they mate (which also occurs within the pitcher), they do so at a 90 degree angle so that neither partner is facing downward. It is thought that they must remain mostly upright in order for their feet to properly cling to the waxy wall.

Regardless of which pitcher plant they are eating, these three moths all behave similarly throughout their lifecycle. The caterpillars are hatched within a pitcher. Immediately they begin feeding on the wall of the pitcher. They will only eat the interior cells of the pitcher wall, leaving a thin layer of tissue on the outside wall. This makes the pitcher look as if it is covered in translucent, brown windows. At some point in their development, the caterpillars will also spin a layer of silk over the mouth of the pitcher. This protects them from predators like lynx spiders and cuts off the pitchers ability to capture prey (more on this in a bit).

As the caterpillars grow, they will occasionally move to new pitchers. At larger sizes, their feeding damage can be quite extensive, damaging the walls of the pitcher to the point that it loses its structural integrity and folds over. This can also serve to protect the caterpillar from predators while similarly reducing the ability of the plant to capture food. After their fifth larval instar, the caterpillars will move to a new, usually undamaged pitcher. In many instances, they will crawl to the bottom and chew a small hole in the side, draining the pitcher of its digestive fluids. They will then pupate just above the drainage hole.

Signs of Exyra feeding damage.

After a period of time that varies between species, adult moths will emerge. The adults are adorable little critters dressed in shades of yellow and black. They are also very secretive and do not leave the pitchers until nightfall. Even then, they only do so to mate and lay eggs in new pitchers. After mating, the female will lay her eggs just below the mouth of a new pitcher and the cycle begins anew. Amazingly, it has been found that the only other stimulus besides the urge to mate that can coax the moths to leave their pitchers is smoke. This is especially true for the southern species as the bogs in which they live are subject to frequent fires. If they were to remain in the pitchers, it is likely that entire populations would be incinerated.

As terrifying as this sounds for the moths, fire is essential to their lifecycle. The pitcher plant bogs of southeastern North America could not persist without fire. When fires are suppressed, these bogs inevitably fill in with more aggressive vegetation such as swamp titi (Cyrilla racemiflora) or any of the myriad invasive species that grow in this region. As bogs become choked with woody shrubs and trees, pitcher plants and other bog species are choked out to the point that they can completely disappear. Fire in these habitats brings more life than it does death.

A population of Sarracenia flava var. rubricorpora showing signs of a thriving Exyra moth population in the form of damaged and bent over pitchers.

Given that the pitchers of pitcher plants function as both photosynthetic organs and a means to obtain nutrients like nitrogen and phosphorus, it stands to reason that damage from pitcher plant moths could harm the plants over the long term. Indeed, high densities of pitcher plant moths can exact quite a toll on pitcher plant individuals. Evidence from multiple sites has shown that heavily damaged pitcher plants can shrink in size over time, indicating loss of energy reserves. In support of this, some have also found that highly damaged pitcher plants go on to produce more pitchers, which indicates that such individuals are prioritizing more nutrient capture. In ecosystems already defined by nutrient scarcity, the effects of herbivory on these carnivorous plants are likely more severe than they are for plants growing in nutrient-rich environments. However, it should be noted that it is a rare case in which pitcher plant moths exact such a toll on plants as to completely kill the pitcher plants they rely on for survival.

That being said, there is plenty of room for concern over the future of both pitcher plants and moths. Only 3% of the bogs that once existed in southeastern North America remain today. Habitat loss means fewer populations of plants and thus less habitat for the moths (and myriad other lifeforms) that rely on them. For these reasons and more, habitat protection and restoration must be made a high priority moving into the future. Please consider supporting a land conservation/restoration organization in your area!

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

My Unforgettable Encounter with a Fevertree

When someone asks you if you would like to see a wild fever tree, you have to say yes. As a denizen of cold climates defined by months of freezing temperatures, I will never miss an opportunity to encounter any species in its native habitat that cannot survive frosts. This was the scenario I found myself in last week as friend and habitat restoration specialist for the Atlanta Botanical Garden, Jeff Talbert, was showing us around a wonderful chunk of Florida scrubland he has been managing over the last few years.

He drove our small group over to an area that, up until a year or two ago, was completely choked with swamp titi (Cyrilla racemiflora). Like many habitats throughout southeastern North America, this patch of Florida scrub is dependent on regular fires to maintain ecological function. Without it, aggressive shrubs like titi completely take over, choking out much of the amazing biodiversity that makes this region unique. Jeff and his team have been very busy restoring fire to this ecosystem and the results have been impressive to say the least.

We walked off the two-track, down into a wet depression and were greeted by an impressive population of spoon-leaf sundews (Drosera intermedia), which is a good sign that water quality on the site is improving. After a few minutes of sundew admiration, Jeff motioned for us to look upward towards the surrounding tree line. That’s when we saw it. Growing up out of the small seep that was feeding this wet depression was a spindly tree with bright pink splotches decorating its canopy. This was to be my first encounter with a fevertree (Pinckneya bracteata).

A few of us were willing to get our feet wet and were rewarded with a close look at the growth habit of this incredible tree. Clustered at the end of its spindly branches are dark green, ovate leaves that give the tree a tropical appearance. Erupting from the middle of some of those leafy branches were the inflorescences. These are what produce the pink splotches I could see in the canopy of larger individuals. They remind me a lot of a poinsettia and at first, I thought this tree might be a member of the genus Euphorbia. Indeed, the pink coloration comes from a handful of rather large, leaf-like sepals attached to the base of each inflorescence.

Upon seeing the flowers, I instantly knew this was not a member of Euphorbiaceae. Each flower was long and tubular ending in five reflexed lobes. They are colorful structures in and of themselves, adorned with splashes of pink and yellow. After a bit of scrutiny, our group was finally able to place this within its true taxonomic lineage, the coffee family (Rubiaceae).

Within the coffee family, fevertree is closely related to the genus Cinchona. Like Cinchona, the fevertree produces quinine and other alkaloids that are effective in treating malaria. Fevertree has been used for millennia to do just that, hence the common name. It also seems fitting that fevertrees tend to grow in wetland habitats where mosquitos can be abundant. However, this is by no means an obligate wetland species. Those who have grown fevertree frequently succeed in establishing plants in dry, upland habitats as well. Perhaps highly disturbed wetlands are some of the few places where this spindly tree can avoid intense competition from other forms of vegetation.

Fevertrees do need regular disturbance to persist. They are not a large, robust tree by any means and can easily get outcompeted by more aggressive vegetation. However, this species does have a trick that enables individuals to persist when disturbances don’t come frequent enough. Fevertree is highly clonal. Instead of producing a single trunk, it sends out numerous stems in all directions in search of a gap in the canopy. This clonal habit allows it to eek out an existence in the gaps between its more robust neighbors until disturbances return and clear things out.

This clonal habit is also very important when it comes to reproduction. Fevertree requires a decent amount of sunlight to successfully flower and set seed. By using its clonal stems to find light gaps, it can at least guarantee some level of reproduction until fires, floods, or some other form of canopy clearing disturbance frees up enough space for it to prosper and its seeds to germinate. However, its clonal habit can also hurt its reproductive capacity over the long term if recruitment of new individuals does not occur.

Fevertree is considered self-incompatible. In other words, its flowers cannot be pollinated via pollen from a genetically identical individual. As more and more clonal shoots are produced, the tree effectively increases the chances that its own pollen will end up on its own flowers. This is yet another important reason why regular disturbance favors fevertree reproduction. Fevertree seeds need light and bare ground to germinate, which is usually provided as fires and other disturbances clear the canopy and open up bare ground. Only then can enough unrelated individuals establish to ensure plenty of successful pollination opportunities.

With its long, tubular flowers and bright pink sepals, fevertrees don’t seem to have any trouble attracting pollinators, which mainly consist of ruby-throated hummingbirds and bumblebees. Only these organisms have what it takes to successfully access the pollen and nectar rewards of this plant and travel the distances necessary to ensure pollen ends up on unrelated individuals. The seeds that result from pollination are winged and can travel a decent distance with a decent wind. With any luck, a few seeds will end up in another disturbance-cleared wet area and usher in the next generation of fevertrees.

I am so happy that restoration activities at this site are making more suitable habitat for this unique tree. Looking around, we saw many more small individuals starting to emerge where there was once a dense canopy of titi. Hopefully with ongoing management, this population will continue to grow and spread, securing the a future for this species in a region with an ever-growing human presence. If you ever find the opportunity to see one of these trees in person, do yourself a favor and take it!

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

Bearcorn: A Mysterious Parasite from Eastern North America

Bearcorn (Conopholis americana) is one of those plants that really challenges mainstream assumptions of what a plant should look like. It produces no leaves, no chlorophyll, and all you ever see of it are its strange reproductive structures. One can easily be forgiven for thinking they had encountered some type of fungus.

Bearcorn is an obligate parasite on oak trees. It simply can’t exist without access to oak roots. From what I have been able to gather, the preferred hosts of bearcorn are the red oaks (section Lobatae). That is not to say the exceptions have not been documented. At least one author claims to have found bearcorn attached to the roots of a white oak (Quercus alba) and even earlier work suggests that American chestnut (Castanea dentata) may have served as an occasional host as well. Regardless, if you want to find bearcorn in the woods, you would do well to search out red oaks first.

According to those who have run germination trials, bearcorn seeds must be in close proximity to oak roots in order to germinate. Some sources say that direct contact is needed whereas others claim that seeds have to be close enough to detect root presence. It is likely that some sort of chemical cue is what initiates the process and this makes sense. For a plant that relies completely on another plant for its water and nutritional needs, it doesn’t make much sense for bearcorn seeds to germinate anywhere but near oak roots.

Upon germinating, the tiny seedling needs to act fast before its meager energy reserves are exhausted. If lucky, the growing seedling will come into contact with an oak root and begin developing a strange organ referred to as the nodule or tubercle. Thus begins its parasitic lifestyle. The tubercle continues to grow throughout the life of the plant, developing into an amorphous, woody blob that continues to envelope more and more oak roots. Its within the tubercle that all of the parasitism takes place.

Cells within the bearcorn tubercle penetrate into the vascular tissues of the oak root, stealing all the water and nutrients the plant will ever need. Over time, the bearcorn tubercle coaxes the roots of the oak to fan outward like the crown of a tiny tree. In doing so, bearcorn is effectively increasing the amount of surface area available to make more parasitic connections. Apparently this all comes at great cost to the oak roots. Over time, oak root size within the tubercle greatly diminishes until some completely perish. Considering the size of some bearcorn populations, one could expect the oak host to fight back.

Indeed, it would appear that oaks are not helpless against bearcorn infestations. Examination of the cells within bearcorn tubercles revealed that as the parasite grows, the oak will begin flooding the infected cells with tannin-rich compounds. Apparently this serves to slow the flow of water and nutrients into the tubercle. There is even evidence that some of those tannins are transferred into the bearcorn tubercle, leading some to suggest that the oak is literally poisoning its bearcorn parasites, albeit slowly.

There is a strong possibility that such oak defenses lend to the relatively short lifespan of bearcorn plants. In at least one study I read, no bearcorn individuals over 13 years of age were found and the average age is estimate to be about 10 years. Perhaps just over a decade is about all a bearcorn can hope for once the its oak host begins to fight back. Good thing bearcorn populations can be surprisingly fecund.

Bearcorn plants reach reproductive maturity at after about 3 years of growth. They flower in the spring and that is when they are at their most obvious. Numerous thick, finger-like stems emerge from the ground covered in whirls of cream-colored, tubular flowers. Though a dense population of flowering bearcorn may look like a bonanza for pollinators, they don’t seem to attract a lot of attention. From what I was able to find, bumblebees are pretty much the only insects to visit the flowers, and even then, visitation rates are low. Apparently bearcorn flowers do not produce any detectable scent nor are they full of nectar. I guess the only real reward is a meager helping of pollen.

Photo by Joshua Mayer licensed under CC BY-SA 2.0

No matter, bearcorn has a nice reproductive trick to ensure plenty of seeds are produced each year - it selfs. The anatomy of the flowers is such that, at maturity, the anthers are in direct contact with the stigma. Even if nothing visits a bloom, it will still go on to clone itself year after year. Once fertilized, each flower gives way to a large fruit chock full of seed. This is where the corn part of the name bearcorn comes from. A stem thick with fruits does resemble a strange, albeit juicy ear of corn sitting on the forest floor. The bear part of the name likely has to do with the fact that bear readily consume bearcorn fruits, stem and all. Working in the southern Appalachian Mountains, I can’t tell you how many times I came across bear scat absolutely loaded with bearcorn fruits and seeds. It’s not just bear either, deer are also very interested in bearcorn fruits.

Lucky for bearcorn, its seeds pass through the guts of these animals unharmed. Hopefully, with a bit of luck, at least one of these animals will make a deposit in an oak-rich region of the forest. With even more luck, some of those seeds might even find themselves nestled in near an oak root to begin the process anew.

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

The Future of New Zealand's Shrubby Tororaro Lies in Cultivation

Photo by Jon Sullivan licensed under CC BY-NC 2.0

I was watching a gardening show hosted by one of my favorite gardeners, Carol Klein, when she introduced viewers to a beautiful, divaricating shrub whose branching structure looked like a dense tracery of orange twigs. She referred to the shrub as a wiggy wig and remarked on its beauty and form before moving on to another wonderful plant. I was taken aback by the structure of the shrub and had to learn more. Certainly its form had to be the result of delicate pruning and selective breeding. Imagine my surprise when I found its growth habit was inherent to this wonderful and rare species.

The wiggy wig or shrubby tororaro is known to science as Muehlenbeckia astonii. It is a member of the buckwheat family (Polygonaceae) endemic to grey scrub habitats of eastern New Zealand. Though this species is widely cultivated for its unique appearance, the shrubby tororaro is not faring well in the wild. For reasons I will cover in a bit, this unique shrub is considered endangered. To understand some of these threats as well as what it will take to bring it back from the brink, we must first take a closer look at its ecology.

Photo by WJV&DB licensed under CC BY-SA 3.0

As mentioned, the shrubby tororaro is endemic to grey scrub habitats of eastern New Zealand. It is a long lived species, with individuals living upwards of 80 years inder the right conditions. Because its habitat is rather dry, the shrubby tororaro grows a deep taproot that allows it to access water deep within the soil. That is not to say that it doesn’t have to worry about drought. Indeed, the shrubby tororaro also has a deciduous habit, dropping most if not all of its tiny, heart-shaped leaves when conditions become too dry. During the wetter winter months, its divaricating twigs become bathed in tiny, cream colored flowers that are very reminiscent of the buckwheat family. From a reproductive standpoint, its flowers are quite interesting.

The shrubby tororaro is gynodioecious, which means individual shrubs produce either only female flowers or what is referred to as ‘inconstant male flowers.’ Essentially what this means is that certain individuals will produce some perfect flowers that have functional male and female parts. This reproductive strategy is thought to increase the chances of cross pollination among unrelated individuals when populations are large enough. Following successful pollination, the remaining tepals begin to swell and surround the hard nut at the center, forming a lovely translucent fruit-like structure that entices dispersal by birds. As interesting and effective as this reproductive strategy can be in healthy populations, the shrubby tororaro’s gynodioecious habit starts to break down as its numbers decrease in the wild.

Photo by Jon Sullivan licensed under CC BY-NC 2.0

As New Zealand was colonized, lowland habitats like the grey scrub were among the first to be converted to agriculture and that trend has not stopped. What grey scrub habitat remains today is highly degraded by intense grazing and invasive species. Habitat loss has been disastrous for the shrubby tororaro and its neighbors. Though this shrub was likely never common, today only a few widely scattered populations remain and most of these are located on private property, which make regular monitoring and protection difficult.

Observations made within remnant populations indicate that very little reproduction occurs anymore. Either populations are comprised of entirely female individuals or the few inconstant males that are produced are too widely spaced for pollination to occur. Even when a crop of viable seeds are produced, seedlings rarely find the proper conditions needed to germinate and grow. Invasive grasses and other plants shade them out and invasive insects and rodents consume the few that manage to make it to the seedling stage. Without intervention, this species will likely go extinct in the wild in the coming decades.

Photo by John Pons licensed under CC BY-SA 4.0

Luckily, conservation measures are well underway and they involve cultivation by scientists and gardeners alike. There is a reason this shrub has become very popular among gardeners - it is relatively easy to grow and propagate. From hardwood cuttings taken in winter, the shrubby tororaro will readily root and grow into a clone of the parent plant. Not only has this aided in spreading the plant among gardeners, it has also allowed conservationists to preserve and bolster much of the genetic diversity within remaining wild populations. By cloning, growing, and distributing individuals among various living collections, conservationists have at least safeguarded many of the remaining individuals.

Moreover, cultivation on this scale means dwindling wild populations can be supplemented with unrelated individuals that produce both kinds of flowers. By increasing the numbers within each population, conservationists are also decreasing the distances between female and inconstant male individuals, which means more chances for pollination and seed production. Though by no means out of the proverbial woods yet, the shrubby tororaro’s future in the wild is looking a bit brighter.

This is good news for biodiversity of the region as well. After all, the shrubby tororaro does not exist in a vacuum. Numerous other organisms rely on this shrub for their survival. Birds feed heavily on its fruits and disperse its seeds while the larvae of at least a handful of moths feed on its foliage. In fact, the larvae of a few moths utilize the shrubby tororaro as their sole food source. Without it, these moths would perish as well. Of course, those larvae also serve as food for birds and lizards. Needless to say, saving the shrubby tororaro benefits far more than just the plant itself. Certainly more work is needed to restore shrubby tororaro habitat but in the meantime, cultivation is ensuring this species will persist into the future.

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

Native Plants Make Every Day Earth Day

We get so much joy out of watching people take pictures of our gardens as they walk by our apartment.

Spring is here in the Northern Hemisphere which means gardening season is well underway. Having spent all winter thinking about what kinds of native plants we want to add to our gardens, my partner and I are always very excited to start germinating seeds and propagating plants. Though we always place the plants at the center of our focus, we would be lying if we said a big part of our gardening obsession wasn’t aimed at attracting wildlife to our property.

There is no denying that gardening, especially with native plants, is the best way to benefit local wildlife in your neighborhood. It doesn’t take much to succeed either. Our landlords are amazing people that allow us a certain degree of freedom to do what we wish with the yard, but they still want to ensure that we maintain something akin to a “traditional” suburban landscape. As such, most of our gardening efforts must be crammed into borders and other highly manicured areas surrounding the lawn. Even so, we are constantly amazed by how much life our plants attract.

I really wish we had the foresight to document insect diversity before we began planting so we could do a before and after comparison, but hindsight is always 20/20. From bees to mantis flies and a hefty population of fireflies, we spend hours each week pursuing the garden to see what kinds of interesting critters are hanging around the yard. The amount of insect life in our garden hasn’t gone unnoticed either.

Leafhoppers and treehoppers are among our favorite insects to see in our gardens.

I remember one afternoon a couple years back, our neighbor approached us to ask if we had seen any bees visiting our tomato plants. Our reply was a very enthusiastic “YES” followed by a rundown of our best estimates on how many different bee species we encountered each day. He seemed a bit bummed and replied that he had yet to see a single bee on his plants. This was a teaching moment that we needed to address as tactfully as possible.

You see, this neighbor is obsessed with mowing and spraying. Save for a few irises near his front porch and two raised beds chock full of tomatoes, no other plants beside grass are allowed to establish on his property. Though completely anecdotal, I can’t help but feel his lack of plants translates in a big way to his lack of bees. We mentioned that all of those “weeds” in our yard that he is always “jokingly” giving us a hard time about are the reason that we have so many bees. Tomato flowers are great but they aren’t around all the time and bees need other food to survive. They also need places to reproduce, which means leaving bare patches of soil around the property and allowing plenty of garden debris in the form of stems, twigs, and leaves to remain in place well into summer.

I am not sure we convinced him to completely change his ways with that conversation, but it definitely got him thinking. He asked if next time we have some spare plants if we wouldn’t mind donating a few so that he can plant them near his tomato beds. We enthusiastically agreed. Though a minor victory, we celebrated the fact that our garden had served as a mini catalyst for a tiny change in someone else’s life.

A firefly stopping for a sip of nectar on one of our common milkweeds (Asclepias syriaca).

With Earth Day coming up this week, the internet is full of quick tips on how to make your life more eco-friendly. There are endless articles available to those looking for advice on green living and sustainable gift ideas. I would like to argue that there is no greener gift than the gift of native plants. It doesn’t matter which species or why, just make sure you pick plants that are native to your region. By establishing native plants in your garden or even in pots on your patio or balcony, you are making a great step in celebrating Earth Day every day. Plants are truly the gift that keeps on giving and you can sleep better at night knowing that they are doing so much more than simply beautifying a space. They are providing food, shelter, and a place to breed for the countless organisms that allow ecosystems to function.

And, as we experienced with our neighbor, native plants can offer so many wonderful moments of inspiration and learning. As I discuss in my book, “In Defense of Plants: An Exploration into the Wonder of Plants,” realizing that native plants and the communities they comprise set the foundation for all other life on this planet set me on a path of wonder and discovery that I have never left. Plants changed my life for the better and by surrounding ourselves with them at all times, my partner and I know that we are doing our part to change the lives of the many organisms struggling to survive in this human-dominated world. So, if you want to live every day like it’s Earth Day, brighten up your life with a few native plants and enjoy all of the wonder and beauty they provide.

A Closer Look at Hyacinths

Photo by Radu Chibzii licensed under CC BY-SA 2.0

They say that our sense of smell is very closely tied with the formation of memories. It is around this time of year that I am strongly reminded of the power of that link. All I have to do is catch a whiff of a blooming hyacinth and I am immediately transported back to childhood where spring time gatherings with the family were always accompanied by mass quantities of these colorful bulbs. Indeed, the smell of hyacinths in bloom will forever hold a special place in my mind (and heart).

Because it is spring in my neck of the woods and because my partner recently came home with a wonderful potted hyacinth to add some springy joy our apartment, I decided to take a dive into the origins of these plants. Where do they come from and how do they live in the wild? Certainly they didn’t originate in our gardens.

To start with, there are surprisingly few true hyacinths in this world these days. Whereas many more spring flowering bulbs were once considered members, today the genus Hyacinthus is comprised of only three species, H. litwinovii, H. transcaspicus, and the most famous of them all, H. orientalis. All other “hyacinths” are hyacinths in name only. These plants were once considered members of the lily family (Liliaceae) but more recent genetic work places them in the asparagus family (Asparagaceae).

All three species of hyacinth are native to the eastern Mediterranean region, throughout the Middle East, and well into southwestern Asia. As you might imagine, there is a fair amount of geographical variation across populations of these plants. For instance, H. orientalis itself contains many putative subspecies and varieties. However, their long history of human cultivation has seen them introduced and naturalized over a much wider area of the globe. Generally speaking, these plants tend to prefer cool, higher elevation habitats and loose soils.

As many of you already know, hyacinths are bulbous plants. Throughout most of the year, they lie dormant beneath the soil waiting for warming spring weather to signal that it’s growing time. And grow they do! Because their leaves and inflorescence are already developed within the bulb, hyacinths can rapidly emerge, flower, and leaf out once snow thaws and releases water into the soil. And flower they do! Though selective breeding has resulted in myriad floral colors and strong, pleasant odors, the wild species are nonetheless put on quite a display.

The flowers of wild hyacinths are generally fewer in number and can range in color from almost white or light blue to nearly purple. Their wonderful floral scent is not a human-bred characteristic either, though we have certainly capitalized on it in the horticulture trade. In the wild, these scent compounds call in pollinators who are rewarded with tiny amounts of nectar. It is thought that bees are the primary pollinators of hyacinths both in their native and introduced habitats.

Of course, all of their floral beauty comes down to seed production. Upon ripening, each fruit (capsule) opens to reveal numerous seeds, each with a fleshy attachment called an elaiosome. The elaiosome is very attractive to resident ants that quickly go to work collecting seeds and bringing them back to their colony. However, it isn’t the seed itself the ants are interested in, but rather the elaiosome. Once it is removed and consumed, the seed is discarded, usually in a waste chamber within the colony where it is free to germinate far away from potential seed predators.

Once growth and reproduction are over, hyacinths once again retreat back underground into their bulb phase. Amazingly, these plants have a special adaptation to make sure that their bulbs are tucked safely underground, away from freezing winter temperatures. Throughout the growing season, hyacinths produce specialized roots that are able to contract. As they contract, they literally pull the base of the plant deeper into the soil. This is very advantageous for plants that enjoy growing in loose soils that are prone to freezing. Once underground and away from frost and snow, they lie dormant until spring returns.

I don’t know about you but getting to know how common garden plants like hyacinths make a living in the wild only makes me appreciate them more. I hope this brief introduction will have you looking at the hyacinths in your neighborhood in a whole new light.

Further Reading: [1] [2]

How Fungus Gnats Maintain Jack-in-the-pulpits

[SOURCE]

There are a variety of ways that the boundaries between species are maintained in nature. Among plants, some of the best studied examples include geographic distances, differences in flowering phenology, and pollinator specificity. The ability of pollinators to maintain species boundaries is of particular interest to scientists as it provides excellent examples of how multiple species can coexist in a given area without hybridizing. I recent study based out of Japan aimed to investigate pollinator specificity among fungus gnats and five species of Jack-in-the-pulpit (Arisaema spp.) and found that pollinator isolation is indeed a very strong force in maintaining species identity among these aroids, especially in the wake of forest disturbance.

Fungus gnats are the bane of many a houseplant grower. However, in nature, they play many important ecological roles. Pollination is one of the most underappreciated of these roles. Though woefully understudied compared to other pollination systems, scientific appreciation and understanding of fungus gnat pollination is growing. Studying such pollination systems is not an easy task. Fungus gnats are small and their behavior can be very difficult to observe in the wild. Luckily, Jack-in-the-pulpits often hold floral visitors captive for a period of time, allowing more opportunities for data collection.

By studying the number and identity of floral visitors among 5 species of Jack-in-the-pulpit native to Japan, researchers were able to paint a very interesting picture of pollinator specificity. It turns out, there is very little overlap among which fungus gnats visit which Jack-in-the-pulpit species. Though researchers did not analyze what exactly attracts a particular species of fungus gnat to a particular species of Jack-in-the-pulpit, evidence from other systems suggests it has something to do with scent.

Like many of their aroid cousins, Jack-in-the-pulpits produce complex scent cues that can mimicking everything from a potential food source to a nice place to mate and lay eggs. Fooled by these scents, pollinators investigate the blooms, picking up and (hopefully) depositing pollen in the process. One of the great benefits of pollinator specificity is that it greatly increases the chances that pollen will end up on a member of the same species, thus reducing the chances of wasted pollen or hybridization.

Still, this is not to say that fungus gnats are solely responsible for maintaining boundaries among these 5 Jack-in-the-pulpit species. Indeed, geography and flowering time also play a role. Under ideal conditions, each of the 5 Jack-in-the-pulpit species they studied tend to grow in different habitats. Some prefer lowland forests whereas others prefer growing at higher elevations. Similarly, each species tends to flower at different times, which means fungus gnats have few other options but to visit those blooms. However, such barriers quickly break down when these habitats are disturbed.

Forest degradation and logging can suddenly force many plant species with different habitat preferences into close proximity with one another. Moreover, some stressed plants will begin to flower at different times, increasing the overlap between blooming periods and potentially allowing more hybridization to occur if their pollinators begin visiting members of other species. This is where the strength of fungus gnat fidelity comes into play. By examining different Jack-in-the-pulpit species flowering in close proximity to one another, the team was able to show that fungus gnats that prefer or even specialize on one species of Jack-in-the-pulpit are not very likely to visit the inflorescence of a different species. Thanks to these preferences, it appears that, thanks to their fungus gnat partners, these Jack-in-the-pulpit species can continue to maintain species boundaries even in the face of disturbance.

All of this is not to say that disturbance can’t still affect species boundaries among these plants. The researchers were quick to note that forest disturbances affect more than just the plants. When a forest is logged or experiences too much pressure from over-abundant herbivores such as deer, the forest floor dries out a lot quicker. Because fungus gnats require high humidity and soil moisture to survive and reproduce, a drying forest can severely impact fungus gnat diversity. If the number of fungus gnat species declines, there is a strong change that these specific plant-pollinator interactions can begin to break down. It is hard to say what affect this could have on these Jack-in-the-pulpit species but a lack of pollinators is rarely a good thing. Certainly more research is needed.

Photo Credit: [1]

Further Reading: [1]

My New Book Has Arrived!

The time has finally come! In Defense of Plants: An Exploration into the Wonder of Plants is now in stores. I thank everyone who pre-ordered a copy of the book. They should be on their way! I still can’t believe this is a reality. I always knew I wanted to write a book and I am eternally grateful to Mango Publishing for giving me this opportunity.

In Defense of Plants is a celebration of plants for the sake of plants. There is no denying that plants are extremely useful to humanity in many ways, but that isn’t why this exist. Plants are living, breathing, self-replicating organisms that are fighting for survival just like the rest of life on Earth. And, thanks to their sessile habit, they are doing so in remarkable and sometimes alien ways.

One of the best illustrations of this can be found in Chapter 3 of my new book: “The Wild World of Plant Sex.” Whereas most of us will have a passing familiarity with the concept of pollination, we have only really scratched the surface of the myriad ways plants have figured out how to have sex. Some plants go the familiar rout, offering pollen and nectar to floral visitors in hopes that they will exchange their gametes with another flower of the same species.

Others have evolved trickier means to get the job done. Some fool their pollinators into thinking they are about to get a free meal using parts of their anatomy such as fake anthers or by offering nectar spurs that don’t actually produce nectar. Some plants even pretend to smell like dying bees to lure in scavenging flies. Still others bypass food stimuli altogether and instead smell like receptive female insects in hopes that sex-crazed males won’t know the difference.

Pollination isn’t just for flowering plants either. In In Defense of Plants I also discuss some of the novel ways that mosses have converged on a pollination-like strategy by co-opting tiny invertebrates that thrive in the humid microclimates produced by the dense, leafy stems of moss colonies.

This is just a taste of what is printed on the pages of my new book. I really hope you will consider picking up a copy. To those that already have, I hope you enjoy the read when it arrives! Thank you again for support In Defense of Plants. You are helping keep these operations up and running, allowing me to continue to bring quality, scientifically accurate botanical content to the world. Thank you from the bottom of my heart.

Click here if you would like to order a copy!

You can also purchase a copy directly from the publisher

A Rare Succulent Member of the Milkweed Family

Photo by: Gennaro Re

Across nearly every ecosystem on Earth, biodiversity tends to follow a pattern in which there are a small handful of very common species and many, many more rare species. It would seem our knowledge of plants follows a similar pattern; we know a lot about a small group of species and very little to nothing about most others. Take, for example, a succulent relative of the milkweeds known to science as Whitesloanea crassa. Despite its occurrence in specialist succulent plant collections, we know next to nothing about the natural history of this species or if it even still exists in the wild at all.

Without flowers, one would be hard pressed to place this odd succulent within a family. Even when in bloom, proper analysis of its taxonomic affinity requires a close inspection of the floral morphology. What W. crassa exhibits is a highly derived morphology well-adapted to its xeric environment. Native to Somalia, it was said to grow on bare ground and its appearance supposedly matches the rocks that dominate its desert habitat. Never producing leaves or branches, the main body of W. crassa consists of a succulent, quadrangular stem that slowly grows upwards as it ages.

Flowers are produced in a dense inflorescence, which is most often situated near the base of the plant. Each flower is very showy at maturity, consisting of a fleshy, fused, 5-lobed corolla decorated in shades of pink and red. As far as I can tell, this is not one of stinkier members of the family. Though I have found pictures of flowers crawling with maggots, most growers fail to comment on any strong odors. In fact, aside from limited care instructions, detailed descriptions of the plant represent the bulk of the scientific information available on this odd species.

Maggots crawling around inside the flowers indicates this species mimics carrion as its pollination mechanism. Photo by: Flavio Agrosi

As I mentioned, it is hard to say whether this species still exists in the wild or not. The original mention of this plant in the literature dates back to 1914. A small population of W. crassa was found in northern Somalia and a few individuals were shipped overseas where they didn’t really make much of an impact on botanists or growers at that time. It would be another 21 years before this plant would receive any additional scientific attention. Attempts to relocate that original population failed but thanks to a handful of cultivated specimens that had finally flowered, W. crassa was given a proper description in 1935. After that time, W. crassa once again slipped back into the world of horticultural obscurity.

A few decades later, two additional trips were made to try and locate additional W. crassa populations. Botanical expeditions to Somalia in 1957 and again in 1986 did manage to locate a few populations of this succulent and it is likely that most of the plants growing in cultivation today are descended from collections made during those periods. However, trying to find any current information on the status of this plant ends there. Some say it has gone extinct, yet another species lost to over-collection and agriculture. Others claim that populations still exist but their whereabouts are kept as a closely guarded secret by locals. Though such claims are largely unsubstantiated, I certainly hope the latter is true and the former is not.

Photo by: Flavio Agrosi

Our knowledge of W. crassa is thus restricted to what we can garner from cultivated specimens. It is interesting to think of how much about this species will remain a mystery simply because we have been unable to observe it in the wild. Despite these limitations, cultivation has nonetheless provided brief windows into it’s evolutionary history. Because of its rock-like appearance, it was assumed that W. crassa was related to the similar-looking members of the genus Pseudolithos. However, genetic analysis indicates that it is not all that closely related to this genus. Instead, W. crassa shares a much closer relationship to Huernia and Duvalia.

This is where the story ends unfortunately. Occasionally one can find cultivated individuals for sale and when you do, they are usually attached to a decent price tag. Those lucky enough to grow this species successfully seem to hold it in high esteem. If you are lucky enough to own one of these plants or to have at least laid eyes on one in person, cherish the experience. Also, consider sharing said experiences on the web. The more information we have on mysterious species like W. crassa, the better the future will be for species like this. With any luck, populations of this plant still exist in the wild, their locations known only to those who live nearby, and maybe one day a lucky scientist will finally get the chance to study its ecology a little bit better.

Photo Credits: [1] & Flavio Agrosi [2] [3] [4]

Further Reading: [1] [2]

Fraser Fir: A New Look at an Old Friend

Photo by James St. John licensed under CC BY 2.0

Growing up, Fraser fir (Abies fraseri) was a fairly common sight in our house. Each winter this species would usually win out over other options as the preferred tree for our living room during the holiday season. Indeed, its pleasing shape, lovely color, and soft needles have made it one of the most popular Christmas trees around the world. Amazingly, despite its popularity as a decoration, Fraser fir is so rare in the wild that it is considered an endangered species.

Fraser fir is native to only a handful of areas in the southern Appalachian Mountains. Together with red spruce (Picea rubens), this conifer makes up one of the rarest ecosystems on the continent - the southern Appalachian spruce-fir forest. Such forests only exist at elevations above 4,000 ft (1,200 m) from southwestern Virginia to western North Carolina and eastern Tennessee. The reason for this limited distribution is rooted in both modern day climate and North America’s glacial past.

USGS/Public Domain

Whereas anyone hiking through Appalachian spruce-fir forests could readily draw similarities to boreal forests found farther north, the Appalachian spruce-fir forests are nonetheless unique, hosting many species found nowhere else in the world. Indeed, these forests are holdovers from the Pleistocene when the southeast was much cooler than it is today. As glaciers retreated and the climate warmed, Appalachian spruce-fir forests “retreated” up the mountains, following their preferred climate zones until they hit the peaks of mountains and couldn’t go any further.

Indeed, Fraser fir is in large part limited in its distribution by temperature. This conifer does not perform well at high temperatures and is readily out-competed by other species under warmer conditions. Another factor that has maintained Appalachian spruce-fir forests at elevation is fog. The southern Appalachian Mountains host eastern North America’s only temperate rainforest and fog commonly blankets high elevation areas throughout the year. Research has shown that in addition to keeping these areas cool, fog also serves as an important source of water for Fraser fir and its neighbors. As fog condenses on its needles, these trees are able to absorb that water, keeping them hydrated even when rain is absent.

A view of an Appalachian spruce-fir forest from the Blue Ridge Parkway.

Due to its restricted habitat, Fraser fir has never been extremely common. However, things got even worse as Europeans colonized North America. Over the past two centuries, unsustainable logging and grazing practices have decimated southern Appalachian spruce-fir forests, fragmenting them into even smaller patches with no connectivity in between. In areas where thin, rocky soils were not completely washed away, Fraser fir seedlings did return, however, this was not always the case. In areas where soils were were lost, southern Appalachian spruce–fir forests were incapable of regenerating.

If the story ended there, Fraser fir and its habitat would still be in trouble but sadly, things only got worse with the introduction of the invasive balsam woolly adelgid (Adelges piceae) from Europe around 1900. Like the hemlock woolly adlegid, this invasive, sap-feeding insect has decimated Fraser fir populations throughout southern Appalachia. Having shared no evolutionary history with the adelgid, Fraser fir is essentially defenseless and estimates suggest that upwards of 90% of infect trees have been killed by the invasion. Although plenty of Fraser fir seedlings have sprung up in the wake of this destruction, experts fear that as soon as those trees grow large enough to start forming fissures in their bark, the balsam woolly adelgid will once again experience a massive population boom and repeat the process of destruction again.

Dead Fraser fir as seen from Clingman’s Dome. Photo by Brian Stansberry licensed under CC BY 3.0

The loss of Fraser fir from this imperiled ecosystem has had a ripple effect. Fraser fir is much sturdier than its red spruce neighbors and thus provides an important windbreak, protecting other trees from the powerful gusts that sweep over the mountain tops on a regular basis. With a decline in the Fraser fir canopy, red spruce and other trees are more susceptible to blowdowns. Also, the dense, evergreen canopy of these Appalachian spruce-fir forests produces a unique microclimate that fosters the growth of myriad mosses, liverworts, ferns, and herbs that in turn support species like the endangered endemic spruce-fir moss spider (Microhexura montivaga). As Fraser fir is lost from these areas, the species that it once supported decline as well, placing the whole ecosystem at risk of collapse.

The moss-dominated understory of an Appalachian spruce-fir forest supports species found nowhere else in the world. Photo by Miguel.v licensed under CC BY 3.0

Luckily, the plight of this tree and the habitat it supports has not gone unnoticed by conservationists. Numerous groups and agencies are working on conserving and restoring Fraser fir and southern Appalachian spruce-fir forests to at least a portion of their former glory. This is not an easy task by any means. Aside from lack of funding and human power, southern Appalachian spruce-fir forest conservation and restoration is hindered by the ever present threat of a changing climate. Fears that the life-giving fog that supports this ecosystem may be changing make it difficult to prioritize areas suitable for reforestation. Also, the continued threat from invasive species like the balsam woolly adelgid can hamper even the best restoration and conservation efforts. Still, this doesn’t mean we must give up hope. With continued collaboration and effort, we can still ensure that this unique ecosystem has a chance to persist.

Please visit the Central Appalachian Spruce Restoration Initiative (CASRI) website to learn more!

Photo Credits: [1] [2] [4] [5]

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

Dwarf Sumac: North America's Rarest Rhus

James Henderson, Golden Delight Honey, Bugwood.org.

In honor of my conversation with Anacardiaceae specialist, Dr. Susan Pell, I wanted to dedicate some time to looking at a member of this family that is in desperate need of more attention. I would like you to meet the dwarf sumac (Rhus michauxii). Found only in a few scattered locations throughout the Coastal Plain and Piedmont regions of southeastern North America, this small tree is growing increasingly rare.

Dwarf sumac is a small species, with most individuals maxing out around 1 - 3 feet (30.5 – 91 cm) in height. It produces compound fuzzy leaves with wonderfully serrated leaflets. It flowers throughout early and mid-summer, with individuals producing an upright inflorescence that is characteristic of what one might expect from the genus Rhus. Dwarf sumac is dioecious, meaning individual plants produce either male or female flowers. Also, like many of its cousins, dwarf sumac is highly clonal, sending out runners in all directions that grow into clones of the original. The end result of this habit is large populations comprised of a single genetic individual producing only one type of flower.

Current range of dwarf sumac (Rhus michauxii). Green indicates native presence in state, Yellow indicates present in county but rare, and Orange indicates historical occurrence that has since been extirpated. [SOURCE]

Research indicates that the pygmy sumac was likely never wide spread or common throughout its range. Its dependence on specific soil conditions (namely sandy or rocky, basic soils) and just the right amount of disturbance mean it is pretty picky as to where it can thrive. However, humans have pushed this species far beyond natural tolerances. A combination of agriculture, development, and fire sequestration have all but eliminated most of its historical occurrences.

Today, the remaining dwarf sumac populations are few and far between. Its habit of clonal spread complicates matters even more because remaining populations are largely comprised of clonal offshoots of single individuals that are either male or female, making sexual reproduction almost non-existent in most cases. Also, aside from outright destruction, a lack of fire has also been disastrous for the species. Dwarf sumac requires fairly open habitat to thrive and without regular fires, it is readily out-competed by surrounding vegetation.

A female infructescence. Photo by Alan Cressler

Luckily, dwarf sumac has gotten enough attention to earn it protected status as a federally listed endangered species. However, this doesn’t mean all is well in dwarf sumac land. Lack of funding and overall interest in this species means monitoring of existing populations is infrequent and often done on a volunteer basis. At least one study pointed out that some of the few remaining populations have only been monitored once, which means it is anyone’s guess as to their current status or whether they still exist at all. Some studies also indicate that dwarf sumac is capable of hybridizing with related species such as whinged sumac (Rhus copallinum).

Another complicating factor is that some populations occur in some surprisingly rundown places that can make conservation difficult. Because dwarf sumac relies on disturbance to keep competing vegetation at bay, some populations now exist along highway rights-of way, roadsides, and along the edges of artificially maintained clearings. While this is good news for current population numbers, ensuring that these populations are looked after and maintained is a difficult task when interests outside of conservation are involved.

Some of the best work being done to protect this species involves propagation and restoration. Though still limited in its scope and success, out-planting into new location in addition to augmenting existing populations offers hope of at least slowing dwarf sumac decline in the wild. Special attention has been given to planting genetically distinct male and female plants into existing clonal populations in hopes of increasing pollination and seed set. Though it is too early to count these few attempts as true successes, they do offer a glimmer of hope. Other conservation attempts involve protecting what little habitat remains for this species and encouraging better land management via prescribed burns and invasive species removal.

The future for dwarf sumac remains uncertain, but that doesn’t mean all hope is lost. With more attention and research, this species just may be saved from total destruction. The plight of species like the dwarf sumac serve as an important reminder of why both habitat conservation and restoration are so important for slowing biodiversity loss.

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

Further Reading: [1] [2] [3]James Henderson, Golden Delight Honey, Bugwood.org.

In Defense of Plants Book Coming February 2021!

I am extremely excited to announce that I have written a book! In Defense of Plants: An Exploration Into the Wonder of Plants is slated for release on February 16th, 2021 wherever books are sold.

“In Defense of Plants changes your relationship with the world from the comfort of your windowsill.

The ruthless, horny, and wonderful nature of plants. Understand how plants evolve and live on Earth with a never-before-seen look into their daily drama. Inside, Candeias explores the incredible ways plants live, fight, have sex, and conquer new territory. Whether a blossoming botanist or a professional plant scientist, In Defense of Plants is for anyone who sees plants as more than just static backdrops to more charismatic life forms.

In this easily accessible introduction to the incredible world of plants, you'll find:

• Fantastic botanical histories and plant symbolism

• Passionate stories of flora diversity and scientific names of plant organisms

• Personal tales of discovery through the study of plants

If you enjoyed books like The Botany of Desire, What a Plant Knows, or The Soul of an Octopus, then you'll love In Defense of Plants.”

You can pre-order In Defense of Plants here:

Amazon- https://amzn.to/3mBA1Ov

Bookshop- https://bit.ly/3lxih5B

Barnes and Noble- https://bit.ly/3qpE570

A Tree That Makes Poisonous Rats

For many organisms, poisons are an effective means to keep from being eaten. However, making poisons can be costly. Depending on the compounds involved, poison synthesis can require a lot of nutrients that could be directed elsewhere. This is why some animals acquire poisons through their diet. Take, for instance, the monarch butterfly. As its caterpillars feed on milkweed, they sequester the milkweed toxins in their tissues, which makes them unpalatable into adulthood. Cases like this abound in the invertebrate world, but recently scientists have confirmed that at least one mammal has evolved a similar strategy.

Meet the African crested rat (Lophiomys imhausi). Its large size and bold color patterns make it look like the result of a passionate encounter between a porcupine and a skunk. However, it is 100% rat and it has a fascinating defense strategy that begins with a tree native throughout parts of eastern Africa aptly referred to as the poison arrow tree (Acokanthera schimperi).

An African crested rat displaying its crest of toxic hairs and aposematic color pattern. [SOURCE]

The poison arrow tree is a member of the milkweed family (Apocynaceae), and like many of its relatives, this species produces potent toxins that can cause heart failure. The toxic nature of this tree has not been lost on humans. In fact, the particular strain of toxin it produces is referred to as ouabaïne or “arrow poison” as indigenous peoples have been coating their arrows with its sap for millennia. It turns out that humans aren’t the only mammals to find use for this sap either. The African crested rat uses it too.

The African crested rat grows highly specialized crest of hairs along its back. These hairs are thick and porous and when the rat feels threatened, it erects the crest and shows off its stark black and white coloring. It has been noted in the past that predators such as dogs that try to eat the rat run the risk of collapsing into convulsions and dying so the idea was put forth that that crest of hairs was toxic. Only recently has this been confirmed.

By studying a group of these rodents, scientists observed an interesting behavior. Many of the rats in their study would chew and lick twigs and branches of the poison arrow tree and then chew and lick their crest. What this behavior does is transfer the plant toxins onto those specialized hairs. The high surface area of each hair means they can soak up a lot of the toxins. Surprisingly, the rats appear to be resistant to the sap’s toxic effects. Perhaps they possess modified sodium pumps in their heart muscles that counter the effects of the toxin. Or, they may possess a highly specialized gut flora that breaks down the toxins. Either way, the rats do not show any signs of poisoning from this behavior.

A close-up view of the African crested rat’s poison anointed hairs. Photo by Sara B. Weinstein

The rats don’t have to do this very often to remain poisonous. By talking with locals that still use the poison arrow tree sap on their arrows, researchers learned that the compounds are extremely stable. Once coated, arrows will remain toxic for years. As such, the African crested rat likely doesn’t need constant application for this defense mechanism to remain effective.

As far as we know, this is the first example of a mammal sequestering plant toxins as a form of defense. It is amazing to think that a defense strategy evolved by a plant to avoid being eaten can be co-opted by a rat so that it too can avoid being eaten. Sadly, it is feared that this unique relationship between rat and tree is starting to disappear. Though more research is needed to accurately assess their numbers, there is growing evidence that African crested rats are on the decline. Hopefully with a bit more attention, these trends can be properly assessed and conservation measures can be put into place. In the meantime, please avoid putting any and all rats in your mouth.

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

Further Reading: [1]

A Remarkable Floral Radiation on Hawai'i

Ohaha (Brighamia rockii)

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

I am of course talking about the Hawaiian lobelioids (Campanulaceae). Many of you will be familiar with members of the genus Lobelia, which include the lovely cardinal flower (Lobelia cardinalis) and the great blue lobelia (Lobelia siphilitica), but the 6 genera that comprise the Hawaiian radiation are something quite different altogether.

'Oha Wai (Clermontia samuelii). Photo by Forest and Kim Starr licensed under CC BY 2.0

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

Delissea sp.

Sadly, like countless Hawaiian endemics, the invasion of the human species has spelled disaster. Hawaiian endemics are declining at an alarming rate due to threats like introduced pigs and rats that eat seeds, devour seedlings, and even go as far as to chew right through the stems of adult plants. To make matters worse, many species evolved to a specific suite of pollinators.

ʻŌlulu (Brighamia insignis)

Take, for instance, the case of the ʻŌlulu (Brighamia insignis). It is believed to have evolved a pollination syndrome with a species of sphinx moth known as the fabulous green sphinx moth (Tinostoma smaragditis), which is also believed to be extinct. Similarly, the ʻŌhā wai nui (Clermontia arborescens) evolved for pollination by the island's endemic honey creepers. Due to avian malaria and other human impacts, many honey creepers are endangered and some have already gone extinct. Without their pollinators, many of these lobelioids are doomed to slow extinction if they haven't disappeared already.

While it may be too late to bring back species that have likely gone extinct, that doesn’t mean conservation of these incredible plants is off the table. Indeed, many efforts are being put forth by institutions like the National Tropical Botanical Garden and the Chicago Botanic Gardens to help conserve and restore some of these species. Along the way, the Hawaiian lobelioids are teaching us important and timely lessons on the need for understanding and protecting all pieces of Earth’s ecosystems, rather than individual parts in isolation.

LISTEN TO EPISODE 291 OF THE IN DEFENSE OF PLANTS PODCAST TO LEARN MORE ABOUT LOBELIOID CONSERVATION IN HAWAI’I

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

Further Reading: [1] [2]

Why Plant Relationships Matter for Caterpillars

Photo by Judy Gallagher licensed under CC BY 2.0

When it comes to caterpillars, plant diversity matters. By studying nearly 30,000 plant-caterpillar interactions across three continents (Asia, North America, and Europe), scientists have uncovered important insights into lepidopteran biodiversity in temperate broadleaf forests.

Plants and the caterpillars they host are engaged in an evolutionary arms race. As plants evolve different defenses, caterpillars evolve new ways overcoming them. As you can imagine, studying these intricate relationships can be as fascinating as it is challenging. One could easily spend a lifetime trying to understand the relationships among only a handful of species. However, by taking a step back and asking bigger questions related to evolution and herbivory, scientists have found some interesting patterns than help describe the diversity of plant-caterpillar relationships.

As one might expect, they found that as plant diversity increases, so too does the diversity of caterpillars an ecosystem can support. Many caterpillars specialize on one or only a few different host plants and these are often (though not always) within the same plant family. The reason for this has to do with plant defenses. The more closely related plants are, the more likely they are to share similar defense strategies. For instance, most milkweeds (Asclepias spp.) produce toxic compounds called cardiac glycosides and many different members of the nightshade family (Solanaceae) produce similar suites of toxic alkaloids. As a result, insects that munch on their tissues have similar hurdles to overcome in an evolutionary sense.

The more closely related plants there are in an environment, the more likely it is that the caterpillars they host can jump from one plant species to another. As a result, ecosystems that boast relatively few plant lineages support relatively few caterpillar species in part because the caterpillars they do host can more easily jump from plant species to another. The same logic applies in the opposite direction as well. Ecosystems comprised of a diversity of plant lineages limit the likelihood that any given species of caterpillar can find multiple different hosts. Because each clade of plants produces their own brand of herbivore defenses, the caterpillars hosted by each are also more likely to be different. Thus, as plant diversity goes up, so too do the numbers of caterpillar species an ecosystem can support.

Though not tested by this research, this also provides yet another example of why invasive plants harm biodiversity. Plants from other areas of the world are more likely to present novel defenses to native herbivores. If the caterpillars do not have what it takes to overcome these defenses or simply don’t recognize the plant as food, the fewer caterpillars that ecosystem can support.

Of course, none of this should come as a surprise to those interesting in native plants and gardening. The more indigenous plants you grow in and around your landscape, the more insects you can support. I also firmly believe that the results of this research are not limited to caterpillars. The same pattern likely applies to any number of plant eaters, from microbes to mammals, no matter where you look. What this research gives us are some answers to questions like “why does biodiversity matter?”

Photo Credit: [1]

Further Reading: [1]

The Knife-Edge Economy of Panama's Trash-Basket Treelet

Trade-offs abound in nature. It would be impossible for any organism to evolve a combination of attributes that are ideal under all circumstances. This is especially true for plants. The botanical world’s need to obtain water and nutrients from roots while simultaneously maximizing photosynthetic area often means finding a balance between allocating resources to leaves and roots. This trade-off is made especially apparent in species like Panama’s basurera (Quadrella antonensis), whose name translates to trash basket.

The basurera is a rare treelet endemic to only a few highland locations in Panama where it grows in the dense shade of the rainforest canopy. It earned the name basurera because this tiny tree has adopted a litter trapping lifestyle. The few leaves it produces form a basket-like structure at the tip of its spindly stem. As debris falls from the canopy above, some of it is trapped by basurera’s leafy basket. The fact that basurera collects debris isn’t all that shocking. Many understory plants are saddled with a debris load to one degree or another. The most striking feature of its anatomy can be found by digging around in the litter trapped within its leafy basket.

Even “large” basurera are not that big. [SOURCE]

From its tiny stem and branches emerges numerous adventitious roots. These roots branch out into the humus as it builds up within the basket. Not only do the roots help the treelet to hold onto any litter that falls into the basket, they also function just like roots in the soil. As the roots branch and fork, they produce copious fine root hairs. These root hairs have even been found to associate with arbuscular mycorrhizal fungi! Indeed, the basurera is creating its own soil by trapping litter from above that it can use to obtain nutrients that it can’t get from the soil at its base. However, in using its leaves to do this, this treelet puts a damper on its potential photosynthetic capacity.

As humus develops within the basket, it blocks sunlight from hitting the leaves. As you can imagine, this creates a delicate knife-edge economy in this already shady habitat. By manipulating the amount of humus in the basket, scientists have shown that the basurera relies on that humus for sustenance. When the humus was selectively removed, basurera lack the nutrients needed to produce more leaves. However, as humus builds up, the plant photosynthesizes less and less. It would appear that this species has dealing with a trade-off in assimilating carbon and acquiring other forms of nutrients.

Adventitious roots emerging from the stem of a basurera. [SOURCE]

Research suggests that the shift towards litter trapping likely has to do with the nutrient-poor soils in which the basurera grows. Instead of relying on the ground to provide it with the nutrients it needs, the basurera simply produces its own supply of soil in its leaves. It seems that for this shade-tolerant treelet, obtaining nutrients is more pressing than maximizing photosynthesis. However, in doing so, it is sacrificing growth and reproduction. By studying 112 individuals over the course of a year, scientists found that only 30 basurera actually flowered and, out of those 30, only 10 fruits were produced. Such low reproductive output likely explains why this treelet can only be found in a few areas of Panama. It also makes the basurera extremely vulnerable to disturbance. With slow growth and even slower reproduction, the basurera is at high risk from anything that can reduce population numbers.

Despite its rarity in the highland forests of Panama, the basurera nonetheless offers a window into the economic balance plants must strike as they try to make a living. It just goes to show you that even small, obscure species have a lot to teach us about the evolution of life on our planet.

Photo Credits & Further Reading: [1]

The Overcup Oak

Photo by Bruce Kirchoff licensed under CC BY 2.0

I sure do love me a good oak. Moving to the Midwest of North America has given me the opportunity to meet many new oak species. One oak that has captured my attention in recent years is the overcup oak (Quercus lyrata) whose both common and scientific names first attracted me to this wonderful tree.

Let’s start by looking at the scientific name of this species. The specific epithet “lyrata” was given to this tree because its leaves are said to resemble a lyre. Having no familiarity with popular instruments of Ancient Greece, I had to look this one up. Personally, I have a hard time seeing the resemblance in most leaves. Perhaps this is because the leaves on any given tree can be highly variable in both shape and size depending on both where they are positioned in the canopy and where the tree itself is rooted.

Photo by Bruce Kirchoff licensed under CC BY 2.0

The name “overcup” comes from the fact that the caps of each acorn nearly encompass the entire seed. It is neat to see a mature acorn of this species as they appear to be immature at all stages of development. The odd morphology of these acorns has everything to do with where these trees grow in nature and the way in which they manage seed dispersal.

Photo by Bruce Kirchoff licensed under CC BY 2.0

Overcup oak is one of the most flood tolerant oaks in all of North America. In fact, it most often grows in around wetlands and in floodplains throughout south-central portions of the continent. As such, this species has evolved to tolerate and take advantage of periodic flooding from one year to the next. Not only can mature trees handle weeks of having their roots and trunks completely submerged, the overcup oak also utilizes flooding as a means of seed dispersal.

The cap that covers each seed is very corky, which causes the acorns to float. This is good news for the seeds as young trees have a hard time making a living in the shade of their parents. Historically, floods would pick up and move overcup acorn crops and, with any luck, deposit the acorns in a new floodplain where disturbance has cleared enough spots in the canopy for the acorns to germinate and grow into vigorous young saplings.

USGS/Public Domain

Speaking of germination, overcup oaks are unique among the white oak tribe in that their seeds exhibit a prolonged dormancy. Normally, acorns of the various white oaks germinate in the fall, not long after they were shed from the trees above. However, living in areas prone to flooding would make germinating at that time of year a risky endeavor. As such, overcup oak acorns lay dormant for months until some environmental cue(s) signals enough time has passed.

Overcup oak is also extremely intolerant of fires. Even modest sized burns can severely damage or kill all but the largest individuals. Normally, the forests in which these trees grow are too wet to produce large fires but prolonged droughts and altered flood regimes can change those dynamics to such a degree that large swaths of overcup oak can be killed.

In fact, altered flooding regimes are one of the biggest threats facing overcup oaks in their native range. Because we have dammed, diverted, and channeled so many waterways in North America, the floods that once maintained overcup oak habitats have changed in a big way. Without regular flooding to disperse their seeds and reduce competition from the canopy above, overcup oaks are having a much harder time regenerating. Saplings gradually dwindle in the shade of their parents and, where rivers do continue to flood, these events are often much more severe than they were in the past. Saplings that aren’t tall enough to rise above the floodwaters eventually drown. Overcup oak may be tolerant of flooding but it is by no means its preferred way to live.

Despite these challenges, overcup oak is still a prominent member of seasonally flooded forests throughout its range. It is a magnificent species well worth spending the time to become familiar. It can also make an excellent specimen tree in all but the driest of south-central North American soils. Also, because it is an oak, this incredible species is also chock full of wildlife value, making it an important component of the ecology wherever it is native.

Photo Credits: Bruce Kirchoff [1] [2] (Licensed under CC-BY), U.S. Geological Survey, Chhe, USDA

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

Learn to Love Bluevine

I will admit that it took me a bit to figure this plant out. At first I thought I was looking at a significant bindweed infestation. These heart shaped leaves were twinging all over our fence. Then it flowered and I realized that this was no bindweed. This mysterious vine was none other than bluevine (also commonly called honeyvine, Cynanchum laeve)

Believe it or not, this is a species of milkweed. Though not in the genus Asclepias, it nonetheless belongs within the same family (Apocynaceae) and is close enough in relation to function as a host for species such as the charismatic monarch butterfly.

Mention this in many of the native plant groups and you are bound to be met with resistance. Because this species can be weedy, many people seem to want to overlook its value as a food source for monarch caterpillars. There is even scientific evidence to suggest that there are no significant differences in fitness and survival among caterpillars raised on either common milkweed or bluevine. The authors of one study even make the conclusion that,

“Given the abundance of honeyvine milkweed in the east-central United States, this species may be a more important host plant for the monarch than has been generally recognized.”

The biggest problem people seem to have with bluevine is that it can be very aggressive in disturbed soils. In many places it is considered a serious agricultural pest. Like its milkweed cousins, its seeds erupt from pods and are born on light, feathery filaments. Because of this they can travel great distances on the slightest breeze. They germinate readily and, once established, the plant can regrow from rootstock.

Regardless of where you stand on bluevine, there is no denying that it is an interesting species. Its flowers are packed into clusters and smell heavily of honey. They are primarily visited by small solitary bees. As is typical of the family, bluevine produces some serious chemical defenses. As such, it is generally ignored by mammalian herbivores but is readily consumed by many of the other native milkweed specialists in North America. So, I urge you to consider giving bluevine a chance. You may grow to love its hardy disposition and its great ecological value.

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