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 species of 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 come on to the scene. 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 other 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 analysis is the best method 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. 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 an organism that is 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.

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.

Photo Credit: Nedra (, gafa kassim (, and dbarronoss (

Further Reading: [1] [2]

Flower Mimics The Smell of Dying Honey Bees to Attract Pollinators


Pollinator deception is rampant in the plant world. There are serious advantages in tricking your pollinators into thinking they are getting a reward without actually providing one. We have discussed sexual deception in the past ([1] [2]), as well as a case of food deception but a recent discovery has shed light on a new form of food deception in the flowering plant world. It is a strategy that has evolved in a distant relative of the milkweeds and it involves smelling like a dying bee. 

The plant in question here is known scientifically as Ceropegia sandersonii. It is a vining species native to South Africa. Like the rest of the members of this genus, C. sandersonii produces bizarrely beautiful flowers that function as pitfall traps. Insects attracted to these blossoms fall down inside and remain trapped for a period of time. As they scramble around inside they inevitably pick up packets of pollen called pollinia. After about a day of imprisonment, the flowers begin to wilt, releasing the insects inside. With any luck these insects will be duped by yet another flower of the same species, and thus pollination is achieved.

How this group of vines goes about attracting potential pollinators varies but, in the case of C. sandersonii, it means smelling like prey. This interesting species requires a unique group of kleptoparasitic flies for pollination. Kleptoparasites are any species that make their living by stealing food from other organisms. The flies in question specialize on sucking the juices out of bees that have been attacked by spiders. As the spider liquefies the hapless bee, these flies sneak in and get their fill.

The researchers noticed these flies were frequent visitors of C. sandersonii flowers so they decided to take a closer look at the chemicals responsible for floral scent. Chemical analyses revealed that the compounds released by the flowers were surprisingly similar to those released by a dying honey bee. In fact, roughly 60% of these compounds were an exact match. What's more, the team hopes that they will discover even more unique forms of food mimicry within this genus.

Photo Credits: [1] [2]

Further Reading: [1]

Live-In Mites

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.

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

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.

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

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. 

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

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

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 evolved in the wild. 

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. 

Hostas in situ

Hostas in situ

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 world wide recognition and will continue to be planted 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] [2]

Further Reading: [1] [2] [3]

Grass Defenses

Cut grass, sword grass, ripgut? All of these names have been applied to grasses. It may seem strange to attach such sharp adjectives to grasses but run through a prairie full of Leersia oryzoides or Spartina pectinata with shorts on and you will quickly learn why. As innocuous as they may look, grasses are well defended.

What looks like the mouth of a shark is actually a blade of grass. As you can see, it is covered in microscopic, razor sharp daggers. The daggers themselves are specialized structures called "phytoliths." Grasses manufacture phytoliths from silica that they absorb from the soil. Not all species produce these daggers. Some distribute phytoliths throughout their leaves, essentially packing themselves with tiny granules of glass. Their presence is an adaptation against herbivory. 

It's not hard to imagine how effective silica daggers can be. Run your finger along the stem or leaves of one of these grasses and you are likely to draw blood. Early settlers coined the term "ripgut grass" because the bellies of horses and other livestock would get seriously lacerated from running through it. Whereas this defense is rather straight forward, the other types of phytoliths are a little more subtle in their effectiveness. 

Silica is tough and chewing on leaves chock full of it can do a real number on your teeth. That is the main reason why the teeth of many grass grazers alive today grow continuously. If their teeth were like ours, the phytoliths within the blades of grass would wear them down to useless nubs. In fact, the evolution of phytoliths in grass is thought to have ushered in a new age of grazing mammals via the extinction of those that could not cope with these microscopic defenses. 

It's not just about teeth either. Insects feeding on blades of grass may be able to get past the phytoliths without an issue but the story changes once it makes it to the gut. Silica particles have been shown to interfere with digestion. Caterpillars feeding on grasses containing high amounts of silica in their leaves had decreased levels of digestion efficiency, which resulted in reduced growth rates. Unlike other plants, grasses can handle certain amounts of grazing because their growth tips are located beneath the soil rather than near the tips. As such, they can afford to gradually weaken the effectiveness of their predators. 

I have gained a new appreciation for grasses since moving to the prairies. This diverse order of plants has shaped the world we see today in a very big way. Because they don't have showy flowers, grasses are often overlooked as nothing more than turf. In reality, they are fascinating organisms supremely adapted to what the environment throws at them. One could only wish to be as hardy as a grass. 

Photo Credits: [1] [2]

Further Reading: [1] [2] 

A Recently Discovered Species From Brazil Plants Its Own Seeds

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

Further Reading: [1]


A Carnivorous Plant and its Bug

Carnivory and symbiosis are two topics within the field of botany that are endlessly fascinating. Because they are static entities, plant evolution has gone through some very interesting pathways for survival. Recently, a group of plants found only on the southern tip of Africa have shone a light on yet another interesting plant/insect relationship that is unlike any other yet known to science.

The genus Roridula contains two species that, for all intents and purposes, look like carnivorous plants. They closely resemble sundews in having leaves packed full of sticky hairs that ensnare hapless insects. However, they are neither closely related to sundews nor do they have any sort of digestive enzyme for breaking down their insect victims. Why then would these plants go through the trouble of producing glandular traps? There must be some adaptive benefit to make up for the cost of production. A closer look at these plants revealed that indeed there is.

Living on Roridula plants are tiny capsid bugs that are covered in a special waxy substance that keeps them from getting stuck in the sticky traps. The bugs move about the sticky leaves, looking for trapped insects. When the insects are found, the capsid bugs impale them with their proboscis and suck them dry. As the capsid bugs feed, their droppings end up littering the Roridula leaves. This is how Roridula gets the added nutrients it needs to survive. Although the plants are not capable of actively digesting the full insects, they are capable of absorbing the components of the capsid bug feces. They are literally getting a little bit of fertilizer every time a capsid bug goes to the bathroom. By offering the capsid bugs a place to live and plenty of free, immobilized prey, the plant is able to get nitrogen-rich meals in return!

Photo Credit: Alex Lomas, CARNIVORASLAND, and Darwiniana

Further Reading:

Rediscovery Brings a Small Plant Back from Extinction

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. 

Photo Credit: Holly Forbes   

Further Reading:

[1] [2]

Cycads and 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 an unrelated individual. What's more, this discovery means that kin selection in plants is not only ancient, 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. Half 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 no 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. The same is not true for plants (click here for another example). What this research does, however, is show us that we probably haven't been looking hard enough. Although extant cycad species are not those that once shared the environment with dinosaurs, the lineage to which they belong is nonetheless quite old. If such cases of kin selection occur in cycads, then it stands to reason that this is an ancient phenomenon. 

Further Reading:

The Largest Single Flower in the World

To find some of the largest flowers in the world, one must find themselves hiking through the the humid jungles of southeast Asia. From there you must be lucky enough to stumble across the flowers of a genus known scientifically as Rafflesia. It contains roughly 28 species spattered about various tropical islands. If you are very lucky, you might even find Rafflesia arnoldii. Producing flowers that are over 3 feet (1 m) in diameter and weighing as much as 24 pounds (11 kg), it produces the largest individual flower on the planet. 

Even more bizarre, these plants are entirely parasitic. They belong to a specialized group called holoparasites. These plants produce no stems, no leaves, nor any true roots. Their entire existence depends on a group of vines related to North America's grapes. Except for flowering, individual Rafflesia exist entirely as a network of mycelium-like cells inside the tissues of their vine hosts.

For a long time, the taxonomic status of this plant was highly debated but recent DNA evidence puts it in the order Malpighiales. From there, things get a little funny. One recent analysis suggested that Rafflesia belonged in the family Euphorbiaceae, however, it most likely warrants its own family - Rafflesiaceae.

So, why produce such large flowers? Well, existing solely within a vine makes it hard to establish a large population in any given area. This makes for a difficult situation in the pollinator department. Somehow plants must increase the odds that any given pollinator will visit multiple unrelated individuals of that particular species. By growing very large and and producing a lot of "stink" (this plant is also referred to as the corpse plant), Rafflesia make sure that pollinators will come from far and wide to investigate, thus increasing their chances of cross pollinating. How this plant goes about seed dispersal, however, remains a mystery.

Most interesting of all, it has been discovered that there is some amount of horizontal gene transfer going on between Rafflesia and its host. Basically, Rafflesia obtains strands of DNA from the vine and uses them in its own genetic code. It is believed this incurs some fitness benefit to Rafflesia but more research is needed to figure out why this may be happening. 

Sadly, many species within this family may be lost before we ever get a chance to get to know them. Forests throughout this region are disappearing rapidly to make room for expanding populations and agriculture. What makes matters worse for Rafflesia is that their lifestyle makes them very hard to study. It is especially difficult to obtain accurate population estimates. As more and more forests are cleared, we could be losing countless populations of these wonderful and intriguing plants. As with large mammals, it would seem that the world's largest flower is falling victim to the unending tide of human development. 

Photo Credit: Tamara van Molken

Further Reading:

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:

The Orchid Mantis Might Not be so Orchid After All

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. Observations from the field have shown that the orchid mantis is frequently found on the flowers of Straits rhododendron (Melastoma polyanthum). A study done in 2013 looked at whether or not the mantis' 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.

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 simply 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 mantises. The adults tend to look rather drab, with long, brownish wing covers. However, they still maintain some aspects of the juvenile traits.

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: Frupus (

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The World's Only Parasitic Gymnosperm

When we talk about parasitic plants, 99.9% of the time we are talking about angiosperms. However, deep in the mysterious forests of New Caledonia grows the single exception to the rule. Parasitaxus usta is the only parasitic gymnosperm known to exist. The sole member of its genus, P. usta is as strange and beautiful as it is mysterious.

P. usta hails from a strange family of gymnosperms known scientifically as Podocarpaceae. Its purple coloration is absolutely stunning. A high concentration of anthocyanin pigments in the vacuoles of its cells is responsible for the purple coloration. Although this strange gymnosperm does in fact produce chloroplasts, they are quite small and the electron transport mechanisms that make photosynthesis possible no longer function.

The true nature of its parasitic lifestyle has remained quite a mystery over the last few decades. A handful of investigations have shown it to be rather unlike any other type of parasitic plant currently known. One of the most bizarre aspects of its morphology is that P. usta does not form any roots. This provided botanists the first clues that it may be a parasite. Further investigation has suggested that, similar to parasitic ericads and orchids, P. usta utilized a fungal intermediary to parasitize the roots of its only known host, another member of the Podocarpaceae family, Falcatifolium taxoides.

Transfer of carbohydrates has been shown to occur through this fungal connection, however, P. usta also seems to obtain nitrogen and water via a direct connection to its host's xylem tissues. In this way it is similar to some mistletoes. As such, it not only can maintain a very high rate of stomatal conductance and a very low water potential, it can also produce cone crops year round. To the best of my knowledge, no other parasitic plant on Earth adopts such a strange combination of strategies.

Despite its unique status, much of the ecology of P. usta remains a complete mystery. For instance, despite being a root parasite, stems of P. usta have been found sprouting from its host tree over 3 feet above the ground. This suggests that P. usta may actually be a strange type of holoparasite. Also, it is entirely unknown how this parasitic gymnosperm becomes established on its host. To date no seed dispersal mechanisms have been described, nor are the seeds sticky. Perhaps its all a matter of chance, which would explain why so few individuals have been found. At the end of the day, the fact that it occurs on a remote island in very few locations means that this bizarrely unique gymnosperm will hold on to its mysteries for many years to come.

Photo Credit: Tim Waters

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Why We Shouldn't Rag on Ragweed

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.

Photo Credit: Frank Mayfield

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The Tiniest Flowers

It is easy to get caught up in grandeur. Finding the largest of something is always fun but what about the smallest? I have talked about the largest flowers in the world ( but how small can a flower get? The answer lies in one of the most common plants on earth, duckweed.

There are roughly 38 species of duckweed out there and all of them represent pretty much the epitome of flowering plant reductionism. They are little more than a pair or so of leaf-like structures that float at or near the waters surface and the occasional taproot. What is even more striking are the flowers. Whereas most duckweed will reproduce clonally, every once in a while a flower will be produced. One genus, Wolffia, produces the smallest flowers of any duckweed. They are also the smallest flowers known to science. As you can see from the picture, they are nothing more than a couple anthers (A1 and A2) and a pistil (Pi). What's more, the male parts mature and die before the female parts, thus limiting the chances of self fertilization. As one would expect, the fruits produced are also the smallest fruits in the world.

This is all quite interesting considering the fact that DNA analysis places duckweeds in the Araceae family, which is home to the largest single inflorescence in the world (! That's right, the arum family produces one of the largest groups of flowers in the world as well as the smallest flower and fruit in the world. Another cool fact about duckweed, specifically Wolffia, is that, gram for gram, it produces the same amount of protein as soy beans. Because of this, it is used as a food plant in many places around the world and more countries are waking up to its potential as both a food plant and a phytoremediation species. Pretty neat for such a small plant.

Photo Credit: Patrick Denny

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