Meet the Crypts

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If you have ever spent time in an aquarium store, you have undoubtedly come across a Cryptocoryne or two. Indeed, these plants are most famous for their indispensable role in aquascaping freshwater aquaria. As organisms, however, crypts receive considerably less attention. Nonetheless, a handful of dedicated botanists have devoted time and effort to understanding this wonderful genus of tropical Aroids. What follows is a brief introduction to the world of Cryptocoryne plants. 

Cryptocoryne is a genus that currently consists of around 60 - 65 species, all of which are native to tropical regions of Asia and New Guinea. Every few years it seems at least one or two new species are added to this list and without a doubt, more species await discovery. All crypts are considered aquatic to one degree or another. Ecologically speaking, however, species fall into four broad categories based on the types of habitats they prefer.

  Cryptocoryne cognata in situ .

Cryptocoryne cognata in situ.

The most familiar crypts grow along the banks of slow-moving rivers and streams and find themselves submerged for a large portion of their life. Others grow in seasonally flooded habitats and experience a pronounced dry season. These species usually go dormant until flood waters return. Still others can be found growing in swampy forested habitats, often in acidic peat swamps. Finally, a few crypts have adapted to living in tidal zones in both fresh and brackish waters.

Like all aquatic plants, crypts face a lot of challenges living in water. One of the biggest challenges is reproduction. Despite their aquatic nature, crypts will not flower successfully underwater. If growing submerged, most crypt species reproduce vegetatively via a creeping rhizome. As such, crypts often form large, clonal colonies in both the wild and in aquaria, a fact that has made a few crypts aggressive invaders in places like Florida.

  Cryptocoryne wendtii  is one of the most common species in the aquarium trade. Its textured leaves are thought to have a higher surface area, allowing this plant to thrive in shaded aquatic habitats.

Cryptocoryne wendtii is one of the most common species in the aquarium trade. Its textured leaves are thought to have a higher surface area, allowing this plant to thrive in shaded aquatic habitats.

Given proper hydrologic cycles, however, crypts will flower and when they do, it is truly a sight to behold. As is typical of aroids, crypts produce an inflorescence comprised of a spadix with whirls of male and female flowers covered by a decorative sheath called a spathe. This spathe is the key to successful flowering among the various crypt species.

 Species like  C. becketti  have become invasive in places like Florida, no doubt thanks to aquarium hobbyists.

Species like C. becketti have become invasive in places like Florida, no doubt thanks to aquarium hobbyists.

If the spathe were to open underwater, the inflorescence would quickly rot. Instead, most crypts seem to have an uncanny ability to sense water levels. At early stages of development, the spathe completely encloses the developing spadix in a water tight package. The tubular spathe continues to grow upward until the top has breached the surface. Consequently, the overall length of a crypt inflorescence is highly variable depending on the water level of its habitat. Crypts living in tidal zones take this a step further. Somehow they are able to time their flowering events to the ebb and flow of the tides, only producing flowers during periods of the month when tides are at their lowest.

  Cryptocoryne ligua

Cryptocoryne ligua

With the tip of the inflorescence safely above water, the spathe will finally open revealing their surprisingly complex anatomy and coloration. It is a shame that most crypt growers never get to see such floral splendor in person. The spathe of many crypt species emit a faint but unpleasant odor. Additionally, some species adorn the spathe with fringes that, coupled with stark coloration, is thought to improve the chances of pollinator visitation.

Pollinators are poorly studied among crypts, however, it is thought that small flies take up the bulk of the work. Lured in by the promise of a rotting meal on which they can feed and lay their eggs, the flies become trapped inside the long tube of the spathe. Like the pitfall traps of a pitcher plant, the inner walls of the spathe are coated in a waxy substance that keeps the insects from crawling out before they do their job.

In general, the female flowers mature first. If the insect inside has visited a crypt of the same species the day before, it is likely carrying pollen and thus deposits said pollen onto the stigmas of the current crypt. After the female flowers have had a chance at being fertilized, the male flowers then mature. The insects inside are then dusted with new pollen, the walls of the spathe lose their slippery properties, and the insects are released in hopes of repeated the process again.

 The fruit of a  Cryptocoryne  is called a syncarp.

The fruit of a Cryptocoryne is called a syncarp.

To the best of my knowledge, most crypts are not self-compatible. Instead, plants must receive pollen from unrelated individuals to set seed. Because large crypt colonies are often made up of clones of a single mother plant, sexual reproduction can be rather infrequent among the various species. Nonetheless sexual reproduction does occur and the seeds are produced in a different way than most other aroids. Instead of berries, crypts produce their seeds in a aggregated collection of fruits called a syncarp. When ripe, the syncarp opens like a little star and the seeds float away on the current.

One species, Cryptocoryne ciliata, takes seed production to a whole different level by producing viviparous seeds. Before the syncarp even opens, the seeds actually germinate on the mother plant. In this way, tiny seedlings complete with roots and leaves are released instead of seeds. Seedlings have a much greater surface area than seeds and readily get stuck in mud as well as other aquatic vegetation. In this way, C. ciliata offspring get a jump start on the establishment process. It is no wonder then that C. ciliata has one of the widest distributions of any of the crypt species.

  Cryptocoryne ciliata

Cryptocoryne ciliata

Despite plenty of overlap among the ranges of various crypt species, the genus displays an amazing array of variation. Some have likened crypts to Araceae's version of Darwin's finches in that the unique ecology of each species appears to have created barriers to species introgression. Though hybrids do occur, each crypt seems to maintain its own niche via a unique habitat requirement, differing flower phenology, or a specific set of pollinators. It would appear that much can be learned about the mechanics of speciation by studying the various Cryptocoryne and their habits.

Unfortunately, the limited geographic distribution and specific habitat requirements of crypt species is cause for concern. Many are growing more and more rare as human settlements expand and destroy valuable crypt habitat. As popular as some crypts may be in cultivation, many others have proven too idiosyncratic to grow on a commercial level. More work is certainly needed to properly assess populations and bring plants into cultivation as a form of ex situ conservation.

  Cryptocoryne cordata  Var. Siamensis 'Rosanervig' is a contoversial variety names recognized by the stark patterns of venation on its leaves.

Cryptocoryne cordata Var. Siamensis 'Rosanervig' is a contoversial variety names recognized by the stark patterns of venation on its leaves.

Proper study is further complicated by the fact that many crypt species are highly plastic. They have to be in order to survive the rigors of their aquatic environment. True species identification can really only be assessed when flowers are present and some populations seem to prefer vegetative over sexual reproduction a majority of the time. A multitude of subspecies exist, though the degree to which they should be formally recognized is up for debate.

I think it is safe to say that Cryptocoryne is a genus worth far more attention than it currently receives. They are without a doubt important components of the ecology of their native habitats and humans would do well to understand them a bit better. With a bit more attention from botanical gardens and other conservation organizations, perhaps the future for many crypts does not have to be so bleak.

Photo Credits: [1] [2] [3] [4] [5]

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

 

Trout Lily Appreciation

This video is a celebration of the white trout lily (Erythronium albidum) and its various spring ephemeral neighbors. We even talk about the threat that invasive species like garlic mustard (Alliara petiolata).

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

Music by
Artist: Botanist
Track:
https://verdant-realm-botanist.bandcamp.com/

California Bumblebee Decline Linked to Feral Honeybees

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Worldwide, pollinators are having a rough go of it. Humans have altered the landscape to such a degree that many species simply can't keep up. The proverbial poster child for pollinator issues is the honeybee (Apis mellifera). As a result, countless native pollinators get the short shrift when it comes to media attention. This isn't good because outside of intense industrial agriculture, native pollinators make up the bulk of pollination services. Similarly, honeybee fandom often overshadows any potential negative effects these introduced insects might be having on native pollinators.

Long term scientific investigations are starting to paint a more nuanced picture of the impact introduced honeybees are having on native ecosystems. For instance, research based out of California is finding that honeybees are playing a big role in the decline of native bumblebee populations. What's more, these negative impacts are only made worse in the light of climate change.

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For over 15 years, ecologist Dr. Diane Thompson has been studying bumblebee populations in central California. At no point during those early years did any of the bumblebee species she focuses on show signs of decline. In fact, they were quite common. Then, around the year 2000, feral honeybees started to establish themselves in the area. Honeybee colonies were becoming more and more numerous each and every year and that is when she started noticing changes in bumblebee behavior and numbers.

You see, honeybees are extremely successful foragers. They are generalists, which means they can visit a wide variety of flower types. As a result, they are extremely good at competing for floral resources compared to native bumblebees. Her results show that increases in the number of honeybee colonies caused not only a reduction in foraging among the native bumblebees, they also caused a reduction in bumblebee colony success. The native bumblebees simply weren't raising as many young as they were before honeybees entered the system.

 Decreased rainfall cause a decline in flower densities of  Scrophularia californica , a key resource for native bumblebees in this system.

Decreased rainfall cause a decline in flower densities of Scrophularia californica, a key resource for native bumblebees in this system.

Climate change is only making things worse. As drought years become not only more severe but also more intense, the amount of flowers available during the growing season also declines. With fewer flowers on the landscape, bumblebees and honeybees are forced into closer proximity for foraging and the clear winner in most foraging disputes are the tenacious honeybees. As such, bumblebees are chased off the already diminishing floral displays. By 2014, Dr. Thompson had quantified a significant decline in native bumblebee populations as a result.

It would be all too convenient to say that this research represents an isolated case. It does not. More and more research is finding that honeybees frequently out-compete native pollinators for resources such as food and nesting sites. Such effects are especially pronounced in rapidly changing ecosystems. Although honeybees are here to stay, it is important that we realize the impacts that these feral insects are having on our native ecosystems and begin to better appreciate and facilitate the services provided by our native pollinators. 

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

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

Ferns Afloat

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My introduction to the genus Salvinia was as an oddball aquarium plant floating in a display tank at the local pet store. I knew nothing about plants at the time but I found it to be rather charming nonetheless. Every time the green raft of leaves floated under the filter outlet, water droplets would bead off them like water off of a ducks back. Even more attractive were the upside down forest of "roots" which were actively sheltering a bunch of baby guppies. 

I grew some Salvinia for a few years before my interest in maintaining aquariums faded. I had forgotten about them for quite some time. Much later as I was diving into the wild world of botany, I started revisiting some of the plants that I had grown in various aquariums to learn more about them. It wasn't long before the memory of Salvinia returned. A quick search revealed something quite astonishing. Salvinia are not flowering plants. They are ferns! 

The genus Salvinia is quite wide spread. They can be found growing naturally throughout North, Central, and South America, the West Indies, Europe, Africa, and Madagascar. Sadly, because of their popularity as aquarium and pond plants, a few species have become extremely aggressive invaders in many water ways. More on that in a bit. 

Salvinia is comprised of roughly 12 different species. Of these, at least 4 are suspected to be naturally occurring hybrids. As you have probably already gathered, these ferns live out their entire lives as floating aquatic plants. Their most obvious feature are the pairs of fuzzy green leaves borne on tiny branching stems. These leaves are covered in trichomes that repel water, thus keeping them dry despite their aquatic habit. 

 These are not roots!

These are not roots!

Less obvious are the other types of leaves these ferns produce. What looks like roots dangling below the water's surface are actually highly specialized, finely dissected leaves! I was quite shocked to learn this and to be honest, it makes me appreciate these odd little ferns even more. Its on these underwater leaves that the spores are produced. Specialized structures called sporocarps form like tiny nodules on the tips of the leaf hairs.

Sporocarps come in two sizes, each producing its own kind of spore. Large sporocarps produce megaspores while the smaller sporocarps produce microspores. This reproductive strategy is called heterospory. Microspores germinate into gametophytes containing male sex organs or "antheridia" whereas the megaspores develop into gametophytes containing female sex organs or "archegonia." 

As I mentioned above, some species of Salvinia have become aggressive invaders, especially in tropical and sub-tropical water ways. Original introductions were likely via plants released from aquariums and ponds but their small spores and vegetative growth habit means new introductions occur all too easily. Left unchecked, invasive Salvinia can form impenetrable mats that completely cover entire bodies of water and can be upwards of 2 feet thick!

 Sporocarps galore! 

Sporocarps galore! 

Lots of work has been done to find a cost effective way to control invasive Salvinia populations. A tiny weevil known scientifically as Cyrtobagous singularis has been used with great success in places like Australia. Still, the best way to fight invasive species is to prevent them from spreading into new areas. Check your boots, check your boats, and never ever dump your aquarium or pond plants into local water ways. Provided you pay attention, Salvinia are rather fascinating plants that really break the mold as far as most ferns are concerned. 

Photo Credits: [1] [2] [3]

Further Reading: [1] [2] [3]

 

This Isn't Even My Final Form! A Pothos Story

Pothos might be one of the most widely cultivated plants in modern history. These vining aroids are so common that I don't think I can name a single person in my life that hasn't had one in their house at some point or another. Renowned for their hardy disposition and ability to handle extremely low light conditions, they have become famous the world over. They are so common that it is all too easy to forget that they have a wild origin. What's more, few of us ever get to see a mature specimen. The plants living in our homes and offices are mere juveniles, struggling to hang on as they search for a canopy that isn't there.

Trying to find information on the progenitors of these ubiquitous houseplants can be a bit confusing. To do so, one must figure out which species they are talking about. Without a proper scientific name, it is nearly impossible to know which plant to refer to. Common names aside, pothos have also undergone a lot of taxonomic revisions since their introduction to the scientific community. Also, what was thought to be a single species is actually a couple.

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To start with, the plants you have growing in your home are no longer considered Pothos. The genus Pothos seemed to be a dumping ground for a lot of nondescript aroid vines throughout the last century. Many species were placed there until proper materials were thoroughly scrutinized. Today, what we know as a "Pothos" has been moved into the genus Epipremnum. This revision did not put all controversies to rest, however, as the morphological changes these plants go through as they age can make things quite tricky.

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As I mentioned, the plants we keep in our homes are still in their juvenile form. Like all plants, these vines start out small. When they find a solid structure in a decent location, they make their bid for the canopy. Up in a tree in reach of life giving sunlight, these vines really hit their stride. They quickly grow their own version of a canopy that consists of massive leaves nearing 2 feet in length! This is when these plants begin to flower. 

As is typical for the family, the inflorescence consists of a spadix covered by a leafy spathe. The spadix itself is covered in minute flowers and these are the key to properly identifying species. When pothos first made its way into the hands of botanists, all they had to go on were the small, juvenile leaves. This is why their taxonomy had been such a mess for so long. Materials obtained in 1880 were originally named Pothos aureus. It was then moved into the genus Scindapsus in 1908.

Controversy surrounding a proper generic placement continued throughout the 1900's. Then, in the early 1960's, an aroid expert was finally able to get their hands on an inflorescence. By 1964, it was established that these plants did indeed belong in the genus Epipremnum. Sadly, confusion did not end there. The plasticity in forms and colors these vines exhibit left many confusing a handful of species within the group. At various times since the late 1960's, E. aureum and E. pinnatum have been considered two forms of the same species as well as two distinct species. The latest evidence I am aware of is that these two vines are in fact distinct enough to warrant species status. 

The plant we most often encounter is E. aureum. Its long history of following humans wherever they go has led to it becoming an aggressive invader throughout many regions of the world. It is considered a noxious weed in places like Australia, Southeast Asia, India, Pakistan, and Hawai'i (just to name a few). It does so well in these places that it has been a little difficult to figure out where these plants originated. Thanks to some solid detective work, E. aureum is now believed to be native to Mo'orea Island off the west coast of French Polynesia. 

  Epipremnum pinnatum  is similar until you see an adult plant

Epipremnum pinnatum is similar until you see an adult plant

It is unlikely that most folks have what it takes to grow this species to its full potential in their home. They are simply too large and require ample sunlight, nutrients, and humidity to hit their stride. Nonetheless there is something to be said for the familiarity we have with these plants. They have managed to enthrall us just enough to be a fixture in so many homes, offices, and shopping centers. It has also helped them conquer far more than the tiny Pacific island on which they evolved. Becoming an invasive species always seems to have a strong human element and this aroid is the perfect example.

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

Further Reading: [1] [2] [3] 

 

Getting to Know Elodea

When I think back on it, one of the first plants I ever actively tried growing was waterweed (Elodea canadensis). My 4th grade teacher had invested in a unit on the ecosystem concept. We all brought in 2 liter soda bottles that we craftily turned into mini terrariums. The top half of the terrarium was filled with soil and planted with some grass seed. The bottom half was filled with water and some gravel. In that portion we placed a single guppy and a few sprigs of Elodea

The idea was to teach us about water and nutrient cycles. It didn't work out too well as most of my classmates abandoned theirs not long after the unit was over. Being the avid little nerd that I was, I fell deeply in love with my new miniature ecosystem. The grass didn't last long but the guppy and the Elodea did. Since then, I have kept Elodea in various aquariums throughout the years but never gave it much thought. It is easy enough to grow but it never did much. Today I would like to make up for my lack of concern for this plant by taking a closer look at Elodea

 An example of the soda bottle terrariums

An example of the soda bottle terrariums

The genus Elodea is one of 16 genera that make up the family Hydrocharitaceae and is comprised of 6 species. All 6 of these plants are native to either North or South America, with Elodea canadensis preferring the cooler regions of northern North America. They are adaptable plants and can grow both rooted or floating in a variety of aquatic conditions. It is this adaptability that has made them so popular in the aquarium trade. It is also the reason why the genus is considered a nasty aquatic invasive throughout the globe. For this reason, I do not recommend growing this plant outdoors in any way, shape, or form unless that species is native to your region. 

Believe it or not, Elodea are indeed flowering plants. Small white to pink flowers are borne on delicate stalks at the water's surface. They are attractive structures that aren't frequently observed. In fact, it is such a rare occurrence that trying to figure out what exactly pollinates them proved to be quite difficult. What we do know is that sexual reproduction and seed set is not the main way in which these plants reproduce. 

Anyone who has grown them in an aquarium knows that it doesn't take much to propagate an Elodea plant. They have a remarkable ability for cloning themselves from mere fragments of the stem. This is yet another reason why they can become so invasive. Plants growing in temperate waterways produce a thick bud at the tips of their stems come fall. This is how they overwinter. Once favorable temperatures return, this bud "germinates" and grows into a new plant. In more mild climates, these plants are evergreen. 

One of the most interesting aspects of Elodea ecology is that at least two species, E canadensis and E. nuttallii, are considered allelopathic. In other words, these plants produce secondary chemicals in their tissues that inhibit the growth of other photosynthetic organisms. In this case, their allelopathic nature is believed to be a response to epiphytic algae and cyanobacteria.

Slow growing aquatic plants must contend with films of algae and cyanobacteria building up on their leaves. Under certain conditions, this buildup can outpace the plants' ability to deal with it and ends up completely blocking all sunlight reaching the leaves. Researchers found that chemicals produced by these two species of Elodea actually inhibited the growth of algae and cyanobacteria on their leaves, thus reducing the competition for light in their aquatic environments. 

Elodea make for a wonderful introduction to the world of aquatic plants. They are easy to grow and, if cared for properly, look really cool. Just remember that their hardy nature also makes them an aggressive invader where they are not native. Never ever dump the contents of an aquarium into local water ways. Provided you keep that in mind, Elodea can be a wonderful introduction to the home aquarium. If you are lucky enough to see them in flower in the wild, take the time to enjoy it. Who knows when you will see it again. 

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

Further Reading: [1] [2] 

Bird Pollination Of The Bird Of Paradise

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Who hasn't stared in wonderment at the inflorescence of a bird of paradise? One doesn't need too much of an imagination to understand how these plants got this common name. Flowers, however, did not evolve in response to our aesthetic tastes. They are solely for sex and in the case of bird of paradise, Strelitzia reginae, pollination involves birds.

In its native range in South Africa, S. reginae is pollinated by sunbirds, primarily the Cape weaver (Ploceus capensis). That alluring floral morphology is wonderfully adapted to maximize the chances of successful cross-pollination by their avian visitors. Cape weavers are looking for a sip of energy rich nectar. To get at said nectar, the birds must perch on the inflorescence. Not any position will do either.

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To get their reward, the birds must perch so that their beaks are at just the right angle to reach down into the floral tubes. The plant ensures this by providing a convenient perch. Those fused blue petals are structurally reinforced and actually serve as a convenient perch! Upon alighting on the perch, the hidden anthers are thrust outward from their resting chamber, brushing up against the bird's feet in the process. The Cape weaver doesn't move around much once on the flower so self pollination is minimized.

When the bird visits another plant, the process is repeated and pollination is achieved. Seed set is severely pollen limited. This is a good thing considering how popular they are in cultivation. Plants growing outside of South Africa rarely set seed without a helping hand. However, here in North America, some birds seemed to have figured out how to get at bird of paradise nectar.

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Observations made in southern California found that at least one species of warbler, the common yellowthroat (Geothlypis trichas), not only made regular visits to a stand of S. reginae, it also seemed to figure out the proper way to do so. Individuals were seen perching on the floral perch and drinking the nectar. They were pretty effective visitors at that. Of the 14,400 inflorescence found within the study area, 88% of them produced viable seed! It seems that far from its native range, S. reginae has a friend in at least one New World warbler. Armed with this knowledge, land owners should be vigilant to ensure this plant doesn't become a problem in climates suitable for its growth.

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

Further Reading: [1]

 

Evidence Of Carnivory In Teasel

As far as carnivorous plants are concerned, the common teasel (Dipsacus fullonum) seems like a strange fit. Observe this plant up close, however, and you might notice something interesting. Its leaves are perfoliate and form a cup-like depression where they attach to the main stem. Not only does this cup regularly fill with water, it also frequently traps small insects.

Many have speculated over the function of this anatomical trap. Much of this speculation has centered around the idea that it may serve as a form of protection for the flowers located above. Insect herbivores climbing up the stem in search of food instead find a moat of water. Some inevitably fall in and drown in the process. Other hypotheses have been put forward as well including the possibility of something approaching carnivory. 

The idea that common teasel could be, to some degree, carnivorous never really went away. For most of this time it has remained entirely theoretical. There simply was no empirical evidence available to say otherwise. All of that changed with a 2011 study published in PLOS. A research duo finally put this theory to the test in the first ever experiment to see if teasel gains any sort of nutrient benefit from its insect victims.

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By systematically supplying teasel plants with insect prey, the team was able to look at how plants responded to the addition of a potential meal. They added various levels of insect larvae to some plants and removed them from others. For their study, evidence would come in the form of some sort of physiological response to the feeding treatments. If teasel really is obtaining nutrients from its insect victims, it stands to reason that those nutrients would be allocated to either growth or reproduction.

The resulting data offers the first evidence that teasel may in fact be benefiting from the insect carcasses. Although the team found no evidence that plants supplemented with insects were increasing in overall biomass, they did see a positive effect on not only the number of seeds produced but also their size. In other words, when fed a diet of insects, the plants weren't growing any larger but they were producing larger amounts of heavier seeds. This is a real boon for a plant with a biennial life cycle like teasel. The more healthy seeds they can produce, the better.

As exciting as these finds are, one must temper their expectations. As the authors themselves state in their paper, these findings must be replicated in order to say for certain that the effects they measured were due to the addition of insect prey. Second, no chemical analyses were made to determine if the plants are actively digesting these insects or even how available nutrients may be absorbed. Simply put, more work is needed. Perhaps teasel is a species that, evolutionary speaking, is on its way to becoming a true carnivore. We still can't say for sure. Nonetheless, they have given us the first evidence in support of a theory that went more than a century without testing. It is interesting to think that there is a strong possibility that if someone wants to see a carnivorous plant, they need go no further than a fallow field.

Photo Credits: [1] [2]

Further Reading: [1]

Understanding the Cocklebur

Spend enough time in disturbed areas and you will certainly cross paths with a cocklebur (Xanthium strumarium). As anyone with a dog can tell you, this plant has no problems getting around. It is such a common occurrence in my life that I honestly never stopped long enough to think about its place on the taxonomic tree. I always assumed it was some sort of Amaranth relative. You can imagine my surprise then when I recently learned that this hardy species is actually a member of the family Asteraceae. 

Cocklebur doesn't seem to fit with most of its composite relatives. For starters, its flowers are not all clustered together into a single flower head. Instead, male and female flowers are borne separately on the same plant. Male flower clusters are produced at the top of the flowering stem. Being wind pollinated, they quickly dump mass quantities of pollen into the air and wither away. The female flowers are clustered lower on the stem and consist of two pistillate florets situated atop a cluster of spiny bracts. 

After fertilization, these bracts swell to form the burs that so many of us have had to dig out of the fur of our loved ones. Inside that bur resides the seeds. Cocklebur is a bit strange in the seed department as well. Instead of producing multiple seeds complete with hairy parachutes, the cocklebur produces two relatively large seeds within each bur. There is a "top" seed, which sits along the curved, convex side of the bur, and a "bottom" seed that sits along the inner flat surface of the bur. Studies performed over a century ago demonstrated that these two seeds are quite important in maintaining cocklebur on the landscape. 

You see, cocklebur is an annual. It only has one season to germinate, grow, flower, and produce the next generation. We often think of annual plants as being quite hardy but in reality, they can sometimes be a bit picky about when and where they will grow. For that reason, seed banking is super important. Not every year will produce favorable conditions so dormant seeds lying in the soil act as an insurance policy. 

Whereas the bottom seed germinates within a year and maintains the plants presence when times are good, the top seed appears to have a much longer dormancy period. These long-lived seeds can sit in the soil for decades before they decide to germinate. Before humans, when disturbance regimes were a lot less hectic, this strategy likely assured that cocklebur would manage to stick around in any given area for the long term. Whereas fast germinating seeds might have been killed off, the seeds within the seed bank could pop up whenever favorable conditions finally presented themselves. 

Today cocklebur seems to be over-insured. It is a common weed anywhere soil disturbance produces bare soils with poor drainage. The plant seems equally at home growing along scoured stream banks as it does roadsides and farm fields. It is an incredibly plastic species, tuning its growth habit to best fit whatever conditions come its way. As a result, numerous subspecies, varieties, and types have been described over the years but most are not recognized in any serious fashion. 

Sadly, cocklebur can become the villain as its burs get hopelessly tangled in hair and fur. Also, every part of the plant is extremely toxic to mammals. This plant has caused many a death in both livestock and humans. It is an ironic situation to consider that we are so good at creating the exact kind of conditions needed for this species to thrive. Love it or hate it, it is a plant worth some respect. 

Photo Credits: [1] [2] 

Further Reading: [1] [2]

The Flowering Rush

Say the words "flowering rush" and many will picture some grass-like, pond vegetation. However, the plant I am talking about today is not a rush at all. Known scientifically as Butomus umbellatus, the flowering rush superficially resembles a patch of true rushes, especially when not in flower. However, it is actually quite a unique species and the sole member of the family Butomaceae. Native to parts of Europe and Asia, this beautiful aquatic plant can now be found invading wetlands throughout northern North America.

Growing quite tall and producing an umbel of beautiful pink flowers, it is no wonder that this plant came to North America as a horticultural curiosity. Its overall appearance suggests a relationship with the genus Allium but genetic analysis puts it somewhere near the water plantains - Alismataceae. The interesting thing about this plant is that here in North America, individual populations exhibit either diploid or triploid chromosome counts.

This is most likely a function of its horticultural past. Many commonly grown garden species have been selected for polyploidy in their chromosomes. Polyploid plants are often larger and more hardy than their diploid relatives, mostly due to the extra genetic material they harbor. It has been noted that there seems to be some reproductive differences between diploid and triploid flowering rush populations as a result. Diploids are more likely to reproduce sexually via seeds whereas triploids are usually sterile and reproduce vegetatively. Triploids are also less commonly found as escapees but they are more widely distributed than diploids. This is likely due to the fact that triploids are more commonly planted in gardens.

Whereas it seems that there is plenty of areas where people disagree on the invasive species issue, one thing we must keep in mind is that, no matter where you stand, biological invasions are one of the largest natural experiments this world has ever seen. We mustn't waste any opportunity to learn from these invasions and to gather as much data as we possibly can. Species like flowering rush offer us insights into how and why some species become invasive while others do not. The more we know, the better we can learn from the mistakes of the past.

Photo Credit: [1] [2]

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

The White Walnut

I must admit, I am not very savvy when it comes to trees. I love and appreciate them all the same, however, my attention is often paid to the species growing beneath their canopy. last summer changed a lot of that. I was very lucky to be surrounded by people that know trees quite well. Needless to say I picked up a lot of great skills from them. Despite all of this new information knocking around in my brain, there was one tree that seemed to stand out from the rest and that species is Juglans cinerea.

Afternoons and evenings at the research station were a time for sharing. We would all come out of the field each day tired but excited. The days finds were recounted to eager ears. Often these stories segued into our goals for the coming days. That is how I first heard of the elusive "white walnut." I had to admit, it sounded made up. Its as if I was being told a folktale of a tree that lived in the imagination of anyone who spent too much time in the forest. 

Only a handful of people knew what it was. I listened intently for a bit, hoping to pick up some sort of clue as to what exactly this tree was. Finally I couldn't take it any longer so I chimed in and asked. As it turns out, the white walnut is a tree I was already familiar with, though not personally. Another common name for this mysterious tree is the butternut. Ah, common names. 

I instantly recalled a memory from a few years back. A friend of mine was quite excited about finding a handful of these trees. He was very hesitant to reveal the location but as proof of his discovery he produced a handful of nuts that sort of resembled those of a black walnut. These nuts were more egg shaped and not nearly as large. Refocusing on the conversation at hand, I now had a new set of questions. Why was this tree so special? Moreover, why was it so hard to find?

The white walnut has quite a large distribution in relation to all the excitement. Preferring to grow along stream banks in well-drained soils, this tree is native from New Brunswick to northern Arkansas. Its leaflets are downy, its bark is light gray to almost silver, and it has a band of fuzzy hairs along the upper margins of the leaf scars. Its a stunning tree to say the least. 

Sadly, it is a species in decline. As it turns out, the excitement surrounding this tree is due to the fact that finding large, robust adults has become a somewhat rare occurrence. Yet another casualty of the global movement of species from continent to continent, the white walnut is falling victim to an invasive species of fungus known scientifically as Sirococcus clavigignenti-juglandacearum

The fungus enters the tree through wounds in the bark and, through a complex life cycle, causes cankers to form. These cankers open the tree up to subsequent infections and eventually girdle it. The fungus was first discovered in Wisconsin but has now spread throughout the entire range of the tree. The losses in Wisconsin alone are staggering with an estimated 90% infection rate. Farther south in the white walnuts range, it is even worse. Some believe it is only a matter of time before white walnut becomes functionally extinct in areas such as the Carolinas. No one knows for sure where this fungus came from but Asia is a likely candidate.

A sad and all too common story to say the least. It was starting to look like I was not going to get a chance to meet this tree in person... ever. My luck changed a few weeks later. My friend Mark took us on a walk near a creek and forced us to keep our eyes on the canopy. We walked under a tree and he made sure to point out some compound leaves. With sunlight pouring through the canopy we were able to make out a set of leaves with a subtle haze around the leaf margins. We followed the leaves to the branches and down to the trunk. It was silvery. There we were standing under a large, healthy white walnut. The next day we stumbled across a few young saplings in some of our vegetation plots. All is not lost. I can't speak for the future of this species but I feel very lucky to have seen some healthy individuals. With a little bit of luck there may be hope of resistance to this deadly fungus. Only time will tell. 

Photo Credit: Dan Mullen (http://bit.ly/2br2F0Z)

Further Reading:
http://bit.ly/2b8GiMV

http://bit.ly/2aLUdMD

Invasion of the Earthworms

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

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

 Shading = Glaciers  [1]

Shading = Glaciers [1]

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

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

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

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

It gets worse too. As earthworms speed up the breakdown of the duff or humus, our native plant species are suffering. They have evolved to germinate and grow in these rich, organic soils. They rely on these soils for survival. As the nutrient rich layers get redistributed by earthworms, native plant and tree populations are suffering. There is very little recruitment and, in time, many species are lost. Our spring ephemerals have been shown to be hit the hardest by earthworm invasions. Earthworms have also been shown to upset the mycorrhizal fungi networks which most plant species cannot live without.

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

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

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

Photo Credit: Peter Hartl

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

Giant Ferns

Although the days of forests full of towering pteridophytes has long since vanished, a few giants still remain. Some of the largest ferns alive today hail from the genus Angiopteris and they are truly massive. To stand beneath their fronds is to be transported back hundreds of millions of years.

The mule's foot ferns (as they are commonly referred to) belong to an ancient lineage. The family, Marattiaceae, is thought to have diverged from the more familiar fern lineages very early on in their evolutionary history. As such, they have more in common with the grapeferns (Ophioglossales), whisk ferns (Psilotales), and horsetails (Equisetales) than they do more familiar extant ferns. One of the more bizarre qualities of this genus is the way in which they disperse their spores. A pressure differential is created inside the sporangium that eventually leads to cavitation. As the air space within implodes, the spores are launched outwards from the fronds at high speeds.

The most obvious feature, however, is their size. Angiopteris are some of the largest ferns on our planet. Arising from an odd looking globular mass are massive fiddle heads. These gradually unfurl into fronds of epic proportions. The record for frond size goes to Angiopteris evecta. An individual growing in Java produced fronds that were 29 feet 6 inches (9 meters) long! Amazingly enough, these fronds are capable of moving up or down depending on the weather.

Such movements are no small feat for a frond of that size. It is all thanks to an area of the petiole known as the pulvinus. The pulvini are swollen regions at the base of the petiole that expand or contract based on water pressure within. Angiopteris evecta produces the largest pulvini of any plant in the world.

Angiopteris can be found growing native from Madagascar and throughout vairous islands of the South Pacific. It is hard to get an accurate species count as the taxonomic status of many "species" are still up for debate. Although something like 200 species have been described, only a small handful of these are recognized in most modern floras. Sadly, many of these are threatened by habitat loss in their home range. The same can't be said elsewhere. Some Angiopteris have become quite invasive in places like Hawai'i and Jamaica. Because of their unique evolutionary history, their bizarre appearance, and their massive size, they been planted far outside of their native range. Research has shown that many of these ferns are much more tolerant of varying environmental conditions than that of their native forests, making any new introductions quite risky.

Photo Credits: [1] [2]

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

The Lowly Lawn Orchid

A new year and a new orchid. It didn't take long for me to spot this little plant poking up between the succulent leaves of a potted aloe. My elation was short lived though. Alas, the sun was setting and I didn't have a flashlight or my camera. I was much luckier the next day. Actually, I shouldn't say lucky. This orchid isn't uncommon.

Meet the lawn orchid (Zeuxine strateumatica). Originally native to Asia, this species is expanding its range throughout many parts of the globe. Here in Florida, it was first discovered in 1936. There was a bit of confusion surrounding its origin on this continent, however, it is now believed that seeds arrived in a shipment of centipede-grass from China.

Since its premiere in Florida, the lawn orchid has since spread to Georgia, Alabama, and Texas. It seems to be quite tenacious, growing equally as well in lawns, floodplains, forests, meadows, and even sidewalk cracks! Despite this generalist habit, it does not seem to transplant well and is probably quite specific about its mycorrhizal partner. Much work needs to be done to sleuth out exactly why this little orchid has been able to spread so far outside of its native range.

Though small flies will visit the flowers, it is very likely that this orchid mostly self pollinates. It doesn't take long to flower and set seed. One plant can easily result in hundreds if not thousands of seedlings. After setting seed, the parent plant dies, however, it will often bud off new plantlets from its roots. Its ubiquitous nature can often stand in contrast to its ability to disappear for a series of time. Large stands that appear one year may not return for many years after. Still, in some areas this little orchid is abundant enough to be considered a nuisance.

Despite whatever feelings you may have towards this little plant, I nonetheless admire it. Its not often you find orchids so adaptable to a wide variety of conditions. At the very least it offers us insights into the success of plant invasions around the globe. And, in the end, its a nice looking little plant.

Further Reading: [1] [2]

The Tumbleweed

What could be a more iconic symbol of the American West than the tumbleweed? From an early age we are indoctrinated with rustic images of tumbleweeds blowing across the high desert. But, did you know that there is very little about this iconic plant that could be considered American? That's right, our most common species of tumbleweed, Salsola tragus, is actually from Russia.

Salsola tragus, also known as Russian thistle, was accidentally introduced to South Dakota in the 1800's in a shipment of flaxseed. It is not actually a thistle at all but rather a member of the family Chenopodiaceae. Since then it has managed to spread throughout most of North America. In arid regions it has become quite a pest.

The tumbling aspect of its ecology has to do with seed dispersal. When the seeds mature, the plant dries up and breaks at the base. As the wind proceeds to blow the tumbleweed around it sprays seeds in every direction. Thanks to this novel method of seed dispersal it is easy to see how this plant is so common as to literally become synonymous with the American West. 

Photo Credit: VancityAllie

Further Reading:

http://1.usa.gov/1UiHDlR

http://bit.ly/1roOXSx

The Curious Case of Hawaii's Endemic Orchids

Orchids and Hawai'i are nearly synonymous. It may come as a surprise then to learn that only three species of orchid are native to this lush archipelago. In fact, there are more non-native species of orchids growing in Hawai'i than there are native. Like much of Hawai'i's endemic flora and fauna, these three distantly related orchid species find themselves on the brink of extinction. How and why only three species of orchid came to call Hawai'i home is a great mystery and it is one that conservationists are struggling to understand before it is too late. 

Orchids produce the smallest seeds of any plants. These dust-like propagules can travel far and wide on the slightest breeze. If any plants were to make it to one of the worlds most remote island chains my bet would be on the orchids. Alas, until settlers arrived, Hawai'i was home to only three - the Hawaiian bog orchid (Platanthera holochila), the Hawai'i jewel-orchid (Anoectochilus sandvicensis), and the Hawai'i widelip orchid (Liparis hawaiensis). The ancestors of these plants must have traveled quite a distance to get to these islands. The Hawaiian bog orchid, for instance, can trace its ancestry back to a related species of Platanthera native to the Aleutian Islands whereas the other two likely blew in from Asia. 

These three species were once found in a variety of locations. Today, however, all of that has changed. Populations of each of Hawai'i's endemic orchids are declining at a rapid rate. In fact, the Hawaiian bog orchid is considered one of the most endangered orchids in the world. The causes of their decline is what one would expect from an island species - habitat destruction, the introduction and subsequent spread of invasive species, and just poor land management in general. It is strange though that so many orchid species from elsewhere in the world are thriving as their endemic cousins are declining. 

Though the exact reasons for this remain uncertain, some of it has to do with another invader - honeybees. Honeybees are native to Europe and are generalists in their foraging abilities. Until bees were were brought to Hawai'i, many introduced orchid species behaved themselves. There simply wasn't anything around to pollinate them. Once honeybees came onto the scene, a few of these introduced species such as the bamboo orchid (Arundina graminifolia) were suddenly able to reproduce. The tropical climate made the land ripe for the taking. But this is only part of the picture. There is another, more interesting conundrum that remains to be solved. 

Orchids absolutely require mycorrhizal fungi to germinate and grow. Why is it then that introduced orchids seem to be doing so much better than the Hawaiian endemics? Good question. Some orchids can be very specific about the fungi they will partner with whereas others are not. It could be that all of the introduced orchids that are naturalizing are generalists whereas the endemics are specialists. It could also be that the endemics simply can't handle the altered disturbance regimes brought on by modern society.

The real reason is probably some combination of these and many more but the fact of the matter remains, Hawai'i's native orchids are in trouble. Since they are not nearly as showy as other orchids they are rather overlooked. This is a shame because if they are lost from their native range, they are gone from the world forever. Luckily there are people out there like Dr. Nicole Hynson of the University of Hawai'i and Dr. Larry Zettler of Illinois College who are working to understand, propagate, and conserve these unique species. 

Photo Credits: University of Hawai'i Museum (http://bit.ly/1K8pjKC), Arkive (http://bit.ly/20kxg17), and G. Daida (http://bit.ly/1K8phCw

Further Reading:
http://bit.ly/1PKOV0C

http://s.si.edu/1QRn0el

http://s.si.edu/1Rjwd1g

http://s.si.edu/1W8bGMb

http://www2.hawaii.edu/~nhynson/Hynson_Lab/Welcome.html

http://www.ic.edu/LarryZettler

Invasive Ants Destroy Plant Sex Lives

image.jpg

For all of the amazing symbioses ants and plants share, there is one thing ants seem to get in the way of... plant sex. That's right, plants have found a use for ants in pretty much every way except for when it comes to reproduction (with some exceptions of course). Ants being what they are, they can easily become a force to be reckoned with. For this reason, many plant species have co-opted ants as defense agents, luring them in with nectar-releasing glands, a resource that ants guard quite heavily. 

When it comes to flowering, however, ants can become a bit overbearing. Research done at the University of Toronto shows that the invasive European fire ant has a tendency to guard floral nectar so heavily that they chase away pollinators. By observing fire ants and bumblebees, they found that ants change bumblebee foraging behaviors. The fire ants often harassed and attacked bumblebees as they visited flowers, causing them to spend significantly less time at each flower, a fact that could very well result in reduced pollination for the plant in question. 

This reduction in pollination is made even more apparent for dioecious plants. Since ants are after nectar and not pollen, male flowers received more bumblebee visits than nectar-producing female flowers. This could become quite damaging in regions with heavy fire ant infestations. 

As it turns out, the ants don't even need to be present to ward off bumblebees. The mere scent of ants was enough to cause bumblebees to avoid flowers. They apparently associated the ant smell with being harassed and are more likely to not chance a visit. Of course, this study was performed on using an invasive ant species. Because so many plant species recruit ants for things like protection and seed dispersal, it is likely that under natural conditions, the benefit of associating with ants far outweighs any costs to reproductive fitness. More work is needed to see if other ant specie exhibit such aggressive behavior towards pollinators. 

Photo Credit: Lalithamba (https://www.flickr.com/people/45835639@N04)

Further Reading:

 http://www.researchgate.net/profile/James_Thomson13/publication/259319739_Ants_and_Ant_Scent_Reduce_Bumblebee_Pollination_of_Artificial_Flowers/links/554b8fd90cf21ed213595eff.pdf