How North America Lost Its Asters

It's that time of year in northern North America where many of the most famous and easily recognized species come into flower, the asters. Some of my favorite plants once resided in this genus, but did you know that referring to our North American representatives as "asters" is no longer taxonomically accurate?

Since the time of Linnaeus, plants and animals have been categorized based on morphological similarities. With recent advances made in the understanding and sequencing of DNA, a new and more refined method of classifying the relationships of living organisms has been added to the mix. Much of what has been taken for granted for the last few decades is being changed. One group that has been drastically overhauled are the North American asters. At one time there were roughly 180 species of North American flowering plants that found themselves in the genus Aster. Today, there is only one, Aster alpinus, which enjoys a circumboreal distribution. 

Because the concept of "Aster" was developed using an Old World species (Aster amellus), New World asters were not granted that distinction. The New World species have shown to have their own unique evolutionary history and thus new genera were either assigned or created. By far, the largest New World genus that came out of this revisions is Symphyotrichum. This houses many of our most familiar species including the New England aster (Symphyotrichum novae-angliae). Some of the other genera that absorbed New World aster include Baccharis, Archibaccharis, Ericameria, Solidago, and Machaeranthera, just to name a few.

Taxonomy is often a difficult concept to wrap your head around. It is constantly changing as we come up with better ways of defining organisms. Even the concept of a species is something biologists have a hard time agreeing on. Surely, genetic analyses offer some of the best methods we have to date, a fact that the Angiosperm Phylogeny Group is constantly refining.

For some, this is all a bunch of silly name changes but for others this is the most important and dynamic form of natural science on the planet. Having a standard for naming organisms is a crucial component of understanding biodiversity. With a name, you can take the next step in getting to know and understand a beloved species. One thing to consider is that, as species are split and regrouped, often times what was thought to be one species turns out to be many. In the case of organisms which are threatened or endangered, a split like that can unveil a disastrous elevation into a far more dismal ranking.

Further Reading: [1] [2]

Meet the Toad Lilies

Fall is such a great time to take advantage of some awesome deals at your local nursery. Plants that have gone out of bloom or are in the process of going dormant always seem to have a lower price tag on them. What's more, fall is the best time, at least in the temperate zones, to plant most things. However, a fall stroll around a nursery or garden center isn't without floral beauty. One group of plants that are exceptionally beautiful at this time of the year are the toad lilies.

Native to parts of China, Japan, the Himalayas, Formosa, and the Philippines, the genus Tricyrtis is growing in popularity as a horticultural curiosity. It's not hard to believe once the true beauty of this genus is realized. In the wild, these plants are denizens of shady forest hillsides and are often encountered on wet slopes. Being a member of the lily family, the floral parts of these plants are arranged in multiples of three. Genetic analysis puts this genus into the same group as Calochortus lilies and indeed, they do share some superficial similarities.

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

The flowers are the real selling points of this genus. They kind of look like a cross between a lily and a passion flower. The name toad lily comes from the speckled appearance of the leaves and petals. That is by and large the only toad-like qualities these plants have other than preferring moisture of course. There has been a lot of debate over what may pollinate the flowers. It is believed that at least some species such as Tricyrtis nana reproduce mainly via self-fertilization whereas others seem to attract mainly bumblebees.

Further Reading: [1] [2]

Live-In Mites

Photo by Scott Zona licensed under CC BY-NC 2.0

Hearing the word "mite" as a gardener instantly makes me think of pests such as spider mites. This is not fair. The family to which mites belong (Acari) is highly varied and contains many beneficial species. Many mites are important predators at the micro scale. Some are fungivorous, eating potentially harmful species of fungi. Whereas this may be lost on the majority of us humans, it is certainly not lost on many species of plants. In fact, the relationship between some plants and mites is so strong that these plants go as far as to provide them with a sort of home.

Photo by Jsarratt licensed under CC BY-SA 3.0

Domatia are specialized structures that are produced by plants to house arthropods. A lot of different plant species produce domatia but not all of them are readily apparent to us. For instance, many trees and vines such as red oak (Quercus rubra), sugar maples (Acer saccharum), black cherries (Prunus serotina), and many species of grape (Vitis spp.) produce tiny domatia specifically for mites. The domatia are often small, hairy, and function as shelter for both the mites and their eggs.

By housing certain species of mites, these plants are ensuring that they have a steady supply of hunters and cleaners living on their leaves. Predatory mites are voracious hunters, keeping valuable leaves free of microscopic herbivores while frugivorous mites clean the leaves of detrimental fungi that are known to cause infections such as powdery mildew. The exchange is pretty straight forward. Mites get a home and a place to breed and the plants get some protection. Still, some plants seem to want to sweeten the relationship in a literal sense.

Some plants, specifically grape vines in the genus Vitis, also produce extrafloral nectaries on their leaves. These tiny glands secrete sugary nectar. In a paper recently published in the Annals of Botany, it was found that extrafloral nectaries enhances the efficacy of these mite domatia by enticing more mites to stick around. By adding nectar to domatia-producing leaves that did not secrete it, the researchers found that nectar increases beneficial mite densities on these leaves by 60 - 80%. This translates to an increase in fitness for these plants in the long run.

I love research like this. I had no idea that so many of my favorite and most familiar tree and vine species had entered into an evolutionary relationship with beneficial mites. This adds a whole new layer of complexity to the interactions within any given environment. It just goes to show you how much is left to be discovered in our own back yards.

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

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

On Crickets and Seed Dispersal

Photo by Vojtěch Zavadil licensed under CC BY-SA 4.0

The world of seed dispersal strategies is fascinating. Since the survival of any plant species requires that its seed find a suitable place to germinate, it is no wonder then that there are myriad ways in which plants disseminate their propagules. Probably my favorite strategies to ponder are those involving diplochory. Diplochory is a fancy way of saying that seed dispersal involves two or more dispersal agents. Probably the most obvious to us are those that utilize fruit. For example, any time a bird eats a fruit and poops out the seeds elsewhere, diplochory has happened.

Less familiar but equally as cool forms of diplochory involve insect vectors. We have discussed myrmecochory (ant dispersal) in the past as well as a unique form of dispersal in which seeds mimic animal dung and are dispersed by dung beetles. But what about other insects? Are there more forms of insect seed dispersal out there? Yes there are. In fact, a 2016 paper offers evidence of a completely overlooked form of insect seed dispersal in the rainforests of Brazil. The seed dispersers in this case are crickets.

Yes, you read that correctly - crickets. Crickets have been largely ignored as potential seed dispersers. Most are omnivores that eat everything from leaves to seeds and even other insects. One report from New Zealand showed that a large species of cricket known as the King weta can disperse viable seeds in its poop after consuming fruits. However, this is largely thought to be incidental. Despite this, few plant folk have ever considered looking at this melodic group of insects... until now. 

The team who published the paper noticed some interesting behavior between crickets and seeds of plants in the family Marantaceae. Plants in this group attach a fleshy structure to their seeds called an aril. The function of this aril is to attract potential seed dispersers. By offering up seeds from various members of the family, the research team were able to demonstrate that seed dispersal by crickets in this region is quite common. Even more astounding, they found that at least six different species of cricket were involved in removing seeds from the study area. What's more, these crickets only ate the aril, leaving the seed behind.

[SOURCE]

The question of whether this constitutes effective seed dispersal remains to be seen. Still, this research suggests some very interesting things regarding crickets as seed dispersal agents. Not only did the crickets in this study remove the same amount of seeds as ants, they also removed larger seeds and took them farther than any ant species. Since only the aril is consumed, such behavior can seriously benefit large-seeded plants. Also, whereas ant seed dispersal occurs largely during daylight hours, cricket dispersal occurs mostly at night, thus adding more resolution to the story of seed dispersal in these habitats. I am very interested to see if this sort of cricket/seed interaction happens elsewhere in the world.

Photo Credits: [1] [2]

Further Reading: [1]

Color Changing Asters

Fall is here and the asters are out in force. Their floral displays are some of the last we will see before the first fall frost takes its toll. Their beauty is something of legend and I could sit in a field and stare at them for hours. In doing so, an interesting pattern becomes apparent. Have you ever noticed that the disc flowers of the many aster species gradually turn from yellow to red? Whereas this certainly correlates with age, there must be some sort of evolutionary reason for this.

Indeed, there is. If you sat and watched as bees hurriedly dashed from plant to plant, you may notice that they seem to prefer flowers with yellow discs over those with red. The plot thickens. What about these different colored discs makes them more or less appealing to bees desperately in need of fuel? The answer is pollen.

A closer observation would reveal that yellow disks contain more pollen than those with red discs. Of course, this does relate to age. Flowers with red discs are older and have already had most of their pollen removed. In this way, the color change seems to be signaling that the older flowers are not worth visiting. Certainly the bees notice this. But why go through the trouble of keeping spent flowers? Why not speed up senescence and pour that extra energy into seed production?

Well, its all about cues. Bees being the epitome of search image foragers are more likely to visit plants with larger floral displays. By retaining these old, spent flowers, the asters are maintaining a larger sign post that ensures continued pollinator visitation and thus increases their chances of cross pollination. The bees simply learn over time to ignore the red disc flowers once they have landed. In this way, they maximize their benefit as well.

Further Reading: [1]

The Colorful Megaherbs of Sub-Antarctic New Zealand

Photo by twiddleblat licensed under CC BY-SA 2.0

There is a common morphological thread among herbaceous plants growing in the colder regions of the world. Most grow small and take on a cushion-like habit. For these species, it is all about getting sensitive tissues out of the chilling winds and into an insulated microclimate. This convergent morphology seems to have been entirely lost on a cohort of plants native to the sub-Antarctic islands of New Zealand. The aptly named "megaherbs" are characterized by their large size an the often gaudy dark coloration of their blooms. Why would an entire guild of plants growing in such cold, dreary, harsh conditions converge on a strategy that, for most plants of their size, spell certain death? 

The answer to this mystery is heat. In such a harsh environment any advantage, no matter how slight, can make a huge difference. What's more, whereas smaller neighboring species largely reproduce asexually, these bizarre behemoths seem to have sexual reproduction all to themselves. The key lies in their large size and extravagant coloration. A team of researchers looking at six different species of megaherb found that the thick, hairy leaves and dark colored flowers were able to take advantage of the rare occasions when the sun poked through the thick, grey, sub-Antarctic clouds. 

Photo by twiddleblat licensed under CC BY-SA 2.0

On average, leaf and inflorescence temperatures of these megaherbs were significantly higher than the ambient conditions. For instance, in the Campbell Island daisy (Pleurophyllum speciosum), leaf and flower temperatures were consistently 9 and 11 degrees Celsius warmer than their surroundings during periods of sunshine. Because of their large size (think surface area to volume ratio), they were able to hold on to this heat much longer than smaller plant species in the same habitat. In essence, they are creating a glasshouse effect. 

This means more than just a warm microclimate for these plants. Insects in this environment seek out these plants for warmth and shelter. In a region with such a sparse insect community, concentrating pollinators in and around your leaves means a higher chance of pollination, a win-win for both sides. As if this wasn't enough, higher temperatures can also facilitate seed production, adding yet another layer of benefit to growing large and darkly colored.  

Photo Credits: [1] [2]

Further Reading: [1]

A Digestive "On" Switch

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

A common thread throughout the world of carnivorous plants is that all hail from nutrient poor environments. That is why they evolved carnivory in the first place, as a way of supplementing their nitrogen and phosphorous needs. For as amazing as their various adaptations are, the evolutionary histories of the world's carnivorous plants are still largely shrouded in mystery. A recent paper published in the Annals of Botany takes a closer look at what goes on inside the pitchers of the tropical pitcher plant Nepenthes alata. What they found is quite amazing.

As it turns out, N. alata seems to be able to regulate the amount of digestive enzymes within its pitchers based on prey availability. This makes a lot of sense. Since these species live in nutrient poor conditions, it would be very wasteful to continuously produce digestive fluids. Instead, the research team found that the genes responsible for the productive of digestive enzymes turn on in response to certain cues. In this case, its the presence of insect tissues, specifically chitin. The addition of insect prey coincided with a 24 to 48 hour burst in digestive enzyme production followed by a gradual decrease as the insects were digested. As interesting as this is, these were not the only findings to come out of this research.

When the researchers looked closely at what kinds of enzymes N. alata were producing, they discovered evidence in support of a long-held hypothesis regarding the evolution of carnivory in plants. The genetic pathways induced by the addition of insect chitin are nearly identical to those seen in plant defense pathways. These pathways also induced the production of a series of proteins known to play a role in plant defense reactions against microbial pathogens. What's more, many of the enzymes N. alata were producing inside their pitchers are classified as defense-related proteins. Taken together, this is strong evidence in support of the hypothesis that carnivory in plants evolved from defense reactions already in place.

This finding comes in the wake of an earlier discovery that showed similar pathways in the traps of the Venus fly trap. This is yet more evidence for the fact that evolution does not always occur via novel pathways. Instead, systems that are already in place are retooled to fit a new set of challenges.

Photo Credit: [1]

Further Reading: [1]

On the Origin of Hostas

Photo by Chad Horwedel licensed under CC BY-NC-ND 2.0

Hostas are so commonplace in our gardens that it is almost impossible to think of them as originating in the wild. Indeed, for as familiar as we are with this genus, it is actually quite difficult to find out anything about their ecology. As with any garden species, however, Hostas had to come from somewhere!

From phylogenetic analyses, we can infer that the genus Hosta originated in east-central China. The most basal member of the group, H. plantaginea, can still be found growing there today. From its Chinese origin, the genus migrated throughout Asia, into Korea and Russia, and even crossed ancient land bridges into what is now the Japanese archipelago. Once there, the genus went through quite an adaptive radiation. 

In the wild, as in our gardens, Hostas tend to grow in shaded forests with rich soils. However, some species are at home growing on steep slopes or even rock walls. Most take on a growth form we would readily recognize as a Hosta, however, the leaves of wild Hostas do not exhibit the rich variegation we have bred into them. Although many wild species have found themselves in cultivation, it is interesting to note that some of the first specimens brought back to Europe from Japan may not have been wild Hostas at all.

European explorers would often task Japanese locals to collect plants for them. What were once thought of as type specimens were actually taken from ancient temple gardens that had been in cultivation for hundreds of years. As such, plants that were once described as true species, such as Hosta fortunei, have now been reduced to cultivar status. 

Love them or hate them, Hostas are an important part of horticultural history. They have gained worldwide recognition and will continue to be planted in gardens all over the world. However, their horticultural prevalence has overshadowed their ecology. I find this to be a bit sad. It is all too easy to forget that nature has produced these organisms. We have simply tinkered with them. We must not forget that every garden species comes from somewhere. 

Photo Credits: [1]

Further Reading: [1] [2] [3]

A Recently Discovered Species From Brazil Plants Its Own Seeds

Photo Credit: Alex Popovkin [SOURCE]

Life on the ground is tough in the rainforest. There is ample competition and extremely fast rates of decomposition. Anything that can give a plant an advantage, however slight, can mean the difference between death and survival. For a recently discovered plant, this means planting its own seeds.

Spigelia genuflexa was first described in 2011. It was found in northeastern Brazil in an area known as Bahia. It is a small plant, maxing out around 20 cm in height. In actuality, two growth forms have been recognized, a tall form, which produces flowers at heights of 10-20 cm, and a short form that produces flowers at heights of about 1 cm. It has been placed in the family Loganiaceae, making it a distant cousin of the North American Indian pink. It blooms during the rainy season, throwing up a couple of small white and pink flowers. At this point, no pollinators have been identified and morphological evidence would suggest it most often self fertilizes. Overall it is an adorable little plant.

The coolest aspect of this new species is how it manages seed dispersal. S. genuflexa exhibits an interesting form of reproduction called "geocarpy." In other words, this diminutive species plants its own seeds. After fertilization, the flowering stems start to bend towards the ground. In the tall form, the ripe fruits are deposited on the soil surface. The small form does something a bit different. It doesn't stop once it touches the ground. The stem continues to push the fruits down into the soil. This behavior was only discovered after the plant had been collected. Back in the lab, the researchers noticed the flowering stems ducking down under the moss they were growing in. By doing this, the parent plants are helping their precious seeds avoid predation and the myriad other threats to seed survival, thus giving them a head start on germination.

Photo Credit: Alex Popovkin [SOURCE]

Photo Credit: Alex Popovkin

Further Reading: [1]

Rediscovery Brings a Small Plant Back from Extinction

Photo by Lech Naumovich licensed under CC BY-NC-SA 2.0

De-extinction is an exciting premise. Whereas the topic largely rests in the minds of hopeful scientists and Jurassic Park dreamers, occasionally a species is brought out of the extinction bin and ushered back into reality. This is a rare occurrence indeed but one worth celebrating. We don't get many second chances after all. The recent rediscovery of a small species of buckwheat affectionately called the Mount Diablo buckwheat (Eriogonum truncatum), offers us one such second chance. 

Discovered in 1862 on Mount Diablo, a rugged peak located just east of San Francisco, this tiny annual wouldn't readily catch the eye of most passers by. Despite its size, the Mount Diablo buckwheat is quite unique as it is endemic to this single mountain. Despite its special status, this tiny little plant was declared extinct in 1936. The cause of this extinction was the introduction of non-native grasses that now carpet the open areas that once fostered this delicate little plant. 

Everything changed for the Mount Diablo buckwheat in 2005. A graduate student working on a floristic survey of this region found something suspicious. He didn't believe it at first but further investigation revealed that he had rediscovered the Mount Diablo buckwheat. It was a small population, numbering only about 20 plants. Seeds were collected and cultivated from this single remaining population. Attempts to restore viable populations of the Mount Diablo buckwheat were meager at best. Only a small handful of plants established themselves. Still, at that time it seemed that this species was saved from extinction, albeit only marginally.

The situation drastically changed for the Mount Diablo buckwheat in May of 2016. Two botanists spotted a patch of plants giving off a pink hue. Closer inspection and lots of deliberation revealed this to be the largest population of Mount Diablo buckwheat in existence. Estimated at nearly 1.8 million individuals, this population spans nearly half an acre. Somehow they managed to escape being choked out by invasive grasses. This find is an astronomical boost for a species thought to be extinct for nearly 70 years. Again, floral surveys were to thank.

So, the question remains, how did this plant go undetected for all those years? I don't think there is a simple answer to this but a lot of it probably has to do with its lifestyle. Annuals can be tricky. We often think of them as hardy plants that boom and bust in a single season. In reality, annuals can be quite sensitive. Instead of toughing out harsh years like perennials do, annuals sit in wait as seeds until more favorable conditions come along. They can wait months, years, or even decades. It could be that the Mount Diablo buckwheat existed as a dormant seed bank for much of that time. Another factor could be its appearance. It is not a large plant by any means. Also, by the standards of your average botanizer, its definite not "knock your socks off showy." Unless you knew what you were looking for you might easily pass it over. 

Regardless of what it has been doing all this time, it is a wonderful thing that more plants have been found. It is by no means out of the woods as far as extinctions go but this is a major step forward in assuring that this species will be around for our children's children to enjoy. Threats still loom. Invasive plants are always a concern and the very fact that it is extremely rare opens it up to a lot of unwanted attention by hikers and botanizers alike. It would be all too easy to love this species to death. 

The story of the Mount Diablo buckwheat does something else for conservation. It highlights the importance of continued floristic surveys. Often scoffed at by academics and scientific journals alike, floristic surveys are far from the antiquated exercises some folks make them out to be. They serve a very important purpose. Without floristic surveys, this little buckwheat may have teetered off into oblivion without anyone ever noticing. 

Further Reading:

[1] [2]

Cycads & Kin Selection

What is not to like about cycads? They are beautiful, they are ancient, and they have a bizarre reproductive biology. Well, we can now add kin recognition to that list. That's right, cycads can somehow discern when they are growing next to a relative and when they are growing next to a stranger. This discovery means that not only has kin selection been a feature of plants for a long time, it is probably more wide spread than we ever thought. 

Kin selection and cycads starts at the roots. Although it isn't easy to see, competition for root space is critical for most plant species. Roots are how plants obtain water and nutrients so maximizing root growth is of paramount importance for a plant. This often means taking up space before their neighbors can. That is, unless that neighbor is your sibling. Researchers set about testing this phenomenon in the lab. By using specialized growth chambers, they were able to compare how plants "behaved" when grown next to their siblings vs. unrelated individuals. What they found was quite astounding. 

Cycads growing next to their half siblings allocated significantly less energy to root growth than when they were growing next to unrelated plants. This had implications for their overall size as well. Plants growing next to siblings were significantly smaller at the end of the experiment. This may seem like a disadvantage until you consider it from the perspective of their genes. Siblings share 50% of their DNA. Since life is all about getting as many copies of your genes into out into the environment as possible, it stands to reason that competing with copies of yourself is often counter productive. That is not the case when fewer genes are shared. Plants growing next to unrelated individuals responded with increased root mass and thus increased growth. In other words, they were more competitive. 

Examples of kin selection abound in the animal kingdom. Currently, the same is not true for plants (click here for another example). What this research does is show us that we probably haven't been looking hard enough. If such cases of kin selection occur in cycads, then it stands to reason that this is an ancient phenomenon. 

Further Reading: [1] [2]

On Lynx Spiders and Pitcher Plants

On the coastal plains of southeastern North America, there exists a wide variety of pitcher plant species in the genus Sarracenia. These plants are the objects of desire for photographers, botanists, ecologists, gardeners, and unfortunately poachers. Far from simply being beautiful, these carnivores are marvels of evolution, each with their own unique ecology.

Pitcher plants are most famous for capturing and digesting insect prey but their interactions with arthropods aren't always in their favor. Browse the internet long enough and you will inevitably find photographs like this one above in which a green lynx spider (Peucetia viridans) can be seen haunting the traps of a pitcher plant. Instead of becoming prey, this is a spider that uses the pitchers to hunt.

I should start by saying this is not an obligate relationship. Lynx spiders can be found hunting on a variety of plant species. Instead, they are more accurately opportunistic robbers, stealing potential meals from the pitcher plants they hunt upon. However, what this relationship lacks in specificity, it makes up for in being really interesting. Sarracenia are not passive hunters. They do not sit and wait for insects to blindly stumble into their traps. Instead, they utilize bright colors and tasty nectar to lure insects to their demise. This is exactly what the lynx spider is using to its benefit. 

The green lynx spider does not spin a web like an orb weaver. It is an ambush predator. They have keen eyesight and will quickly pounce on any insect unfortunate enough to get too close. The reason the spider itself does not become yet another meal for the pitcher plant is because they utilize their silk as an anchor. By attaching one end to the outside of the pitcher, the can safely hunt on the trap without the risk of become prey themselves. In fact, spiders hunting on traps even go as far as to retreat down into the trap if threatened.

Photo Credit: Zachary Ambrose - nccarnivores

Further Reading:

http://bit.ly/2cyXlvS

http://bit.ly/2cyWTxT

The Orchid Mantis Might Not be so Orchid After All

Here we see a juvenile orchid mantis perched atop a man-made orchid cultivar that would not be found in the wild. Photo by N. A. licensed under CC BY-NC-SA 2.0

The orchid mantis is a very popular critter these days, and rightly so. Native to southeast Asia, they are beautiful examples of how intricately the forces of natural selection can operate on a genome. The reasoning behind such mimicry is pretty apparent, right? The mantis mimics an orchid flower and thus, has easy access to unsuspecting prey.

Not so fast...

Despite its popularity as an orchid mimic, there is no evidence that this species is mimicking a specific flower. Most of the pictures you see on the internet are actually showing orchid mantids sitting atop cultivated Phalaenopsis or Dendrobium orchids that simply do not occur in the wild. Observations from the field have shown that the orchid mantis is frequently found on the flowers of Straits meadowbeauty (Melastoma polyanthum). A study done in 2013 looked at whether or not the mantids disguise offers an attractive stimulus to potential prey. Indeed, there is some evidence for UV absorption as well as convincing bilateral symmetry that is very flower-like. They also exhibit the ability to change their color to some degree depending on the background.

Orchid mantis nymphs are more brightly colored than adults. Photo by Frupus licensed under CC BY-NC 2.0

Despite our predilection for finding patterns (even when there are none) it is far more likely that this species has evolved to present a "generalized flower-like stimulus." In other words, they may simply succeed in tapping into pollinators' bias towards bright, colorful objects. We see similar strategies in non-rewarding flowering plants that simply offer a large enough stimulus that pollinators can't ignore them. The use of colored mantis models has provided some support for this idea. Manipulating the overall shape and color of these models had no effect on the number of pollinators attracted to them.

The most interesting aspect of all of this is that the most convincing (and most popular) mimicking the orchid mantis displays is during the juvenile phase. Indeed, most pictures circulating around the web of these insects are those of immature mantids. The adults tend to look rather drab, with long, brownish wing covers. However, they still maintain some aspects of the juvenile traits.

Adult orchid mantids take on a relatively drab appearance compared to their juvenile form. Photo by Philipp Psurek licensed under CC BY-SA 3.0 DE

The fact of the matter is, we still don't know very much about this species. It is speculated that the mimicry is both for protection and for hunting. As O'Hanlon (2016) put it, "The orchid mantis' predatory strategy can be interpreted as a form of 'generalized food deception' rather than 'floral mimicry'." It just goes to show you how easily popular misconceptions can spread. Until more studies are performed, the orchid mantis will continue to remain a beautiful mystery.

Photo Credit: [1] [2] [3]

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

Why We Shouldn't Rag on Ragweed

Photo by Andreas Rockstein licensed under CC BY-SA 2.0

Common ragweed (Ambrosia artemisiifolia), the bane of hay fever sufferers. This could quite possibly be one of the most despised plants whether people realize it or not. It is ragweed, not goldenrod, that is responsible for causing hay fever. All this is thanks to the copious amounts of pollen it wafts into the breeze. With all that being said, I could not call this In Defense of Plants if I did not come to the defense of ragweed.

Despite all the suffering it causes, ragweeds are enormously important plants ecologically. We already know they produce a lot of pollen, but that pollen is doing more than just making you stuffy and fertilizing other ragweeds. It is also feeding bees. Because it flowers so late into the season, ragweed offers up a prodigious source of protein-rich pollen for bees gearing up for fall and winter. Even before they flower, ragweed is a valuable food source for the caterpillars of many butterflies and moths including species like the wavy-lined emerald and various bird dropping moths. It's not just insects either. The seeds of ragweed are rich in fatty oils. Birds and small mammals readily consume ragweed seeds to help fatten up for the lean months to come.

Ragweed also offers us some cultural significance too. Before European settlement, ragweed is believed to have had a much narrower distribution. Palynologists use pollen taken from lake and bog sediment cores to track ancient climates and plant communities. Because ragweed produces so much pollen, it is a useful species to look for when studying core sediments. As pollen falls out of the air and settles on lakes or bogs, it eventually sinks to the bottom where it can remain buried in a rather pristine state for millennia. Palynologists have actually been able to use ragweed pollen as a way of tracking the settlement history of North America. As colonies advanced further and further, they opened up huge chunks of land, inadvertently creating ample opportunities for ragweed to expand its range. As such, ragweed pollen taken from lake cores has proven to be a pretty precise clue for studying our own history.

For as much as we despise it, ragweed thrives on the kind of disturbance that we humans are so good at creating. We are the ones to blame for our own suffering when it comes to hay fever, not the plants.

Further Reading:

http://bit.ly/2c2HpOG

http://bit.ly/2c7hx6X

http://bit.ly/2c6mtsh

http://bit.ly/2bRPf2T

http://bit.ly/2c7hrwi

Floating Ferns

Photo by Jon Sullivan licensed under CC BY-NC 2.0

Not every tiny plant you see growing on the surface of ponds are duckweeds. Sometimes they are Azolla. Believe it or not, these are tiny, floating ferns! The genus Azolla is comprised of about 7 to 11 different species, all of which are aquatic. Despite being quite small they nonetheless exert a massive influence wherever they grow. 

Like all ferns, Azolla reproduce via spores. Unlike more familiar ferns, however, sexual reproduction in Azolla consists of two markedly different types of spores. When conditions are right, little structures called "sporocarps" are formed underneath the branches. These produce one of two types of sporangia. Male sporangia are small and are often referred to as microspores whereas female sporangia are, relatively speaking, quite large and are referred to as megaspores. The resulting gametophytes develop within and never truly leave their respective spores. Instead, male gameotphytes release motile sperm into the water column and female gametophytes peak out of the megaspore to intercept them. Thus, fertilization is achieved. 

Photo by Miguel Pérez licensed under CC BY-SA 2.0

Azolla are fast growing plants. Via asexual reproduction, these little floating ferns can double their biomass every 3 to 10 days. That is a lot of plant matter in a short amount of time. As such, entire water bodies quickly become smothered by a fuzzy-looking carpet. Depending on the species and the environmental conditions, the color of this carpet can range from deep green to nearly burgundy. They are able to float because of their overlapping scale-like leaves, which trap air. Below each plant hangs a set of roots. The roots themselves form a symbiotic relationship with a type of cyanobacterium, which fixes atmospheric nitrogen. Couple with their astronomic growth rate, this means that colonies of Azolla quickly reach epic proportions.

In fact, they can grow so fast that Azolla may have played a serious role in a massive global cooling event that occurred some 50 million years ago. During that time, Earth was much warmer than it is now. Global temperatures were so warm that tropical species such as palms grew all the way into the Arctic. There is fossil evidence that massive blooms of Azolla may have occurred in the Arctic Ocean during this time, which was a lot less saline than it is now.

Everything red in this picture is Azolla. Photo by Jon. D. Anderson licensed under CC BY-NC-ND 2.0

Though plenty of other factors undoubtedly played a role, it is believed that Azolla blooms would have been so large that they would have drawn down CO2 levels considerably over thousands of years. As these blooms died they sank to the sea floor, bringing with them all of the carbon they had locked up in their cells. In part, this may have led to a massive drop in atmospheric CO2 levels and led to a subsequent cooling period. Evidence for this is tantalizing, so much so that some researchers have taken to calling this "The Azolla Event." However, this is far from a smoking gun. Regardless, it is an important reminder than really big things often come in very small packages.

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

Further Reading: [1] [2]

On the Wood Rose and its Bats

Photo via Nga Manu Nature Reserve

New Zealand has some weird nature. It is amazing to see what an island free of any major terrestrial predators can produce. Unfortunately, ever since humans found their way to this unique island, the ecology has suffered. One of the most unique plant and animal interactions in the world can be found on this archipelago but for how much longer is the question.

The story starts with a species of bat. In fact, this bat is New Zealand's only native terrestrial mammal. That's right, I said terrestrial. The New Zealand lesser short-tailed bat spends roughly 40% of its time foraging for insects on the ground. It has lots of specialized adaptations that I won't go into here but the cool part is they forage in packs, stirring up insects from the leaf litter until they reach a level of feeding frenzy that I thought was only reserved for sharks or piranhas. Along with using echo location, they also have a highly developed sense of smell. This is important for our second player in this forest floor drama.

Enter Dactylanthus taylorii, the wood rose. This plant is not a rose at all but rather a member of the tropical family Balanophoraceae. More importantly, it is parasitic. It produces no chlorophyll and lives most of its life wrapped around the roots of its host tree underground. Every once in a while a small patch of flowers break through the dirt and just barely peak above the leaf litter. This give this species it's Māori name of "pua o te reinga" or "pua reinga", which translates to "flower of the underworld." The flowers emit a musky, sweet smell that attracts these ground foraging bats. The bats are one of the only pollinators left on the island. They sniff out the flowers and dine on the nectar, all the while being dusted with pollen. Recently, it has been found that New Zealand's giant ground parrot, the kakapo, is also believed to have been a pollinator of this plant. Sadly, today the kakapo exists solely on one small island of the New Zealand archipelago.

Both the wood rose and the New Zealand lesser short-tailed bat are considered at risk for extinction. When modern man came to these islands they brought with them the general suite of mammalian invasives like rats, mongoose, cats, and pigs, which are exacting a major toll on the local ecology. The plants and animals native to New Zealand have not shared an evolutionary history with such aggressive mammalian invaders and thus have no adaptations for coping with their sudden presence. The future of the wood rose, the New Zealand lesser short-tailed bat, and the kakapo, along with many other uniquely New Zealand species are for now uncertain.

Photo Credits: Joseph Dalton Hooker (1859) and Nga Manu Nature Reserve (http://www.ngamanu.co.nz/)

Further Reading:

http://bit.ly/2bBw8FT

http://bit.ly/2bKRY90

http://bit.ly/2bKpxfE

The Devil's Walking Stick

The name "Devil's walking stick" just sounds cool. You can imagine my excitement then when I first laid eyes on the species it refers to. Aralia spinosa is no ordinary tree. It is a hardy species ready to take advantage of disturbance. Armed with spikes and a canopy that looks like it belongs in some far off tropical jungle, the Devil's walking stick is a tree species worth knowing. 

I used to think that spikenard (Aralia racemosa) was the most robust member of the aralia family found in North America. Not so. The Devil's walking stick is a medium sized tree capable of reaching heights of over 30 feet (10 m). Most interesting of all, its triply compound leaves are the largest leaves of any temperate tree in the continental United States.

The Devil's walking stick can be found growing in disturbed areas and along forest edges throughout a large swath of eastern North America. When young it is a rather spiny lot. These are not true spines, which are modified parts of leaves, but rather prickles, which arise from extensions of the cortex or epidermis. 

As it grows, however, it loses a lot of its prickliness. Such armaments are costly to produce after all. It is believed that younger plants develop these structures while they are still at convenient nibbling height, only to lose them once they grow big enough to avoid hungry herbivores. Research has shown that most herbivorous mammals alive today do not bother much with the Devil's walking stick, which has led some to suggest that these defenses evolved back when this side of the continent was brimming with much larger herbivores such as elk and bison. 

As if the giant compound leaves of this tree were not stunning enough, the surprisingly large inflorescence is sure to blow you away. Typical of the family, it consists of hundreds of tiny green flowers. Despite their size, they are a boon for pollinators. A tree in full bloom comes alive with bees and butterflies alike. Flowers soon give way to clusters of berries, which are a favorite food among birds. All in all this is one cool tree.

Further Reading: [1] [2]

The Tallest Moss

Photo by Doug Beckers licensed under CC BY-SA 2.0

For all the attributes we apply to the world of bryophytes, height is usually not one of them. That is, unless you are talking about the genus Dawsonia. Within this taxonomic grouping exists the tallest mosses in the world. Topping out around 60 cm (24 inches),  Dawsonia superba enjoys heights normally reserved for vascular plants. Although this may not seem like much to those who are more familiar with robust forbs and towering trees, height is not a trait that comes easy to mosses. To find out why, we must take a look at the interior workings of bryophytes. 

Mosses as a whole are considered non-vasular. In other words, they do not have the internal plumbing that can carry water to various tissues. Coupled with the lack of a cuticle, this means that mosses can be sensitive to water loss. For many mosses, this anatomical feature relegates them to humid environments and/or a small stature. This is not the situation for the genus Dawsonia. Thanks to a curious case of convergent evolution, this genus breaks the physiological glass ceiling and reaches for the sky. 

View fullsize

Photo by Salsero35 licensed under CC BY-SA 4.0

Unlike other mosses, Dawsonia have a conduction system analogous to xylem and phloem. Being convergent, however, it isn't the same thing. Instead, the xylem-like tissue of these mosses is called the "hydrome" and is made up of cells called "hydroids." The phloem-like tissue is called the "leptome" and is made up of cells called "leptoids." These structures differ from xylem and phloem in that they are not lignified. Mosses never evolved the ability to produce this organic polymer. Regardless of their chemical makeup, Dawsonia vascular tissue allows water to move greater distances within the plant.

Another major adaption found in Dawsonia has to do with the structure of the leaves. Whereas the leaves of most mosses are only a few cells thick, the leaves of Dawsonia produce special cells on their surface called "lamella." These cells are analogous to the mesophyll cells in the leaves of vascular plants. They not only function to increase surface area and CO2 uptake, they also serve to maintain a humid layer of air within the leaf, further reducing water loss. 

All of this equates to a genus of moss that has reached considerable proportions. Sure, they are easily over-topped by most vascular plant species but that is missing the point. Through convergent evolution, mosses in the genus Dawsonia have independently evolved an anatomical strategy that has allowed them to do what no other extant groups of moss have done - grow tall.

Photo by Jon Sullivan licensed under CC BY-NC 2.0

Photo Credits: Wikimedia Commons, Doug Beckers, and Jon Sullivan

Further Reading: [1]

Freshwater Sponges

The first true love of my life was the underwater world. I was obsessed with everything aquatic, especially fish. My obsession with fish gave way to a collection of home aquaria that tested the limits of my parents’ patience. Most of my aquariums were landscaped with aquatic plants whose variety boggled the mind. The underwater world is full of incredibly varied habitats that are home to a wide variety of organisms including freshwater sponges. Though I was never able to grow any of them in home aquaria, seeing them in the wild was an incredible experience I won’t soon forget.

Though it is not readily apparent, sponges are animals. They aren't a single animal either. What functions as a single unit is actually a collection of individual organisms working in unison. The entire body of the sponge consists of these microscopic individuals connected by living tissue and held rigid by tiny rods made out of silica. I know what you're thinking, this is not a plant, why am I writing about it? The answer lies in the green color of this sponge.

There are many species of freshwater sponge throughout the world. Here in North America we have somewhere around 30. They are an indicator of clean, clear water. If you see sponges then you know it must be a healthy ecosystem. The freshwater sponges come in many different shapes, colors and sizes. Even within a species there can be a lot of variety between different colonies. Pictured here is a species of Spongilla. Not all Spongilla are green though. Many are brown. The green coloration comes from algae living symbiotically within the tissue of the sponge. Similar to lichens, the algae photosynthesize and provide food to the sponge in return for a safe place to grow.

Though not a plant, the need to photosynthesize has pushed these sponges to grow into shapes not unlike what is seen in the plant kingdom. Depending on water clarity, temperature, and light levels, sponge shapes range from prostrate, creeping forms to upright branching structures. Also similar to plants, sponges can reproduce both sexually and asexually. As the water begins to cool in the fall, the sponges produce what are known as gemmules. These little packets of dormant cells are quite hardy, resisting pretty much anything the environment can throw at them. When the water begins to warm in the spring, the gemmules will grow into new sponge colonies. During the warm summer months, sponges reproduce sexually. Males release sperm into the water in hopes that it will come into contact with receptive females. This is similar to what we see many wind-pollinated tree species do in the spring.

The idea that two completely different branches on the tree of life have converged onto similar biological strategies is a very exciting idea. Indeed, the similarities are striking. I went a long time before I knew that these freshwater sponges even existed. The fact that I live in the Great Lakes region and never encountered them tells me just how poorly we have treated our local waterways.

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

Albino Redwoods

Photo by Cole Shatto licensed under CC BY-SA 3.0

Photo by George Bruder licensed under CC BY-SA 4.0

If you are a very lucky person hiking in the redwood forests of California you may just be able to see a ghost. Not a "real" ghost of course, but pretty darn close. Scattered about these ancient forests are rare and peculiar albino redwood trees! Seeing one is seeing something very special indeed.

Redwoods (Sequoia sempervirens) are some of the largest and oldest organisms on the planet. They are famous worldwide for their grandeur. Aside from their obvious charismatic physical traits, redwoods are quite interesting genetically. These giant gymnosperms are genetically hexaploid, meaning they have 6 copies of their genetic code. What this means for redwoods is the ability to experiment with a wider array of mutations than a diploid organism like you and I. A mutation in one set of chromosomes still leaves 5 other copies to maintain normal genetic function. Whereas this can translate into massive benefits in defenses against pathogens, it also means there is a lot of room for error as well. 

The albino redwoods are an example of a seemingly dead end mutation. For a plant that relies of photosynthesis to survive, the loss of photosynthetic pigments should spell disaster. The question is why do albino redwoods exist at all? Well, the albinos become parasites on their photosynthetic parents. You see, albino redwoods are mutant offshoots of healthy trees. Something in a bud goes awry and the resultant shoot fails to develop chlorophyll. Sometimes chimeras arise which produce leaves that are half photosynthetic and half albino. Still, how do these mutations persist?

Researchers have found that the leaves of albino redwoods have twice the amount of stomata than do normal redwood leaves. This makes them quite susceptible to drought. During dry years, the trees quickly dehydrate and their host trees withdraw all support. The albinos will often die off but then re-sprout when conditions improve. This disappearing and reappearing act further lends to their mythos. However, this does not capture the full picture. The fact that photosynthetic redwoods tolerate the albinos on any level is quite curious. Even photosynthetic branches that don't produce enough energy are shed. What else could be going on?

Recent research might have found the answer. The albinos most frequently occur along the edge of the redwoods range where conditions just aren't that conducive. What's more, the soils around these albinos are often high in toxic metals such as nickle, cadmium, and copper. When researchers took a closer look at the chemical composition of the albinos, they found that they accumulate these toxic heavy metals at much higher rates.

In a healthy tree, these metals interfere with the photosynthetic machinery, making them quite toxic indeed. Because the albino redwoods are incapable of photosynthesis, this is not an issue. This has led to an interesting hypothesis. It could very well be that the photosynthetic redwoods tolerate their albino offshoots because the albinos accumulate the toxic heavy metals in their tissues and thus keep them away from healthy, photosynthetic tissues. This ideas is still in the hypothesis stage but work is being done to see if it plays out in the wild. 

There doesn't seem to be a solid consensus on how many albinos exist in the wild. I have seen numbers as low as 25 and as high as 400. Either way, they are a rare element of the coastal redwood community. With thousands of acres still to be explored, it is likely that more will turn up. While some exist in protected parks, many are under threat with increasing fragmentation of these ancient forests. Very little of the coastal redwood forests are under protection and we may be losing more than we will ever know. 

Photo Credit: Cole Shatto and George Bruder

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