Red Nectar

No, your eyes are not playing tricks on you. This flower produces red nectar. Known scientifically as Nescodon mauritianus, this member of the bellflower family (Campanulaceae) grows only on the island of Mauritius. Although it is not alone in producing colored nectar (at least 60 other plant species do so as well) the striking contrast of the red nectar against the blue corolla had botanists wondering what exactly these plants are attracting.

Of course, the obvious answer were birds. It is no mystery that birds see in color much in the same way as us humans. However, multiple tests and observations demonstrated that birds were not the best pollinators for these flowers. In fact, the birds functioned mainly as thieves, stealing nectar without actually coming into contact with any of the necessary floral parts. The same thing happened to a Mauritian relative of the mallows named Trochetia blackburniana, which also produces colored nectar. 

To better understand the signalling mechanisms of these flowers, a team of researchers utilized a series of floral models. By filling the models with different colored nectar, they were able to better understand what they are attracting. As it turns out, the answer to this mystery are geckos. 

Phelsuma geckos visiting the flowers of Trochetia blackburniana (left) and flower models (right). Hansen et al. 2006

Phelsuma geckos visiting the flowers of Trochetia blackburniana (left) and flower models (right). Hansen et al. 2006

Living alongside these plants is a genus of day gecko called Phelsuma. They are endemic to Mauritius and can frequently be found visiting nectar-producing flowers in search of energy-rich nectar. By observing how the geckos responded to various color combinations, the team was able to discover that these geckos seem to prefer red and yellow nectar over clear. What's more, their feeding habits once inside the flower puts them in direct contact with the anthers and the stigma. Thus, the geckos function as the most effective pollinators for these plants. 

The team now feels that the colored nectar of these species serves as an honest reward for pollinating geckos. It is a stark indication that a reward is present. It is possible that because these geckos rely on brightly colored markings when interacting with each other, the selection for brightly colored floral signals has been favored in the evolution of these gecko pollinated plants. More work needs to be done to say for certain. What we do know for sure is that these day geckos are important pollinators in Mauritian ecosystems.

Photo Credits: [1] [2]

Further Reading: [1]

 

Begonia's Hawaiian Cousin

Begoniaceae is a strange family. It consists of two genera - Begonia, which is comprised of roughly 1,400 species, and Hillebrandia, which consists of a single species endemic to Hawai'i (Symbegonia has since been placed back into Begonia). Although I adore the entire family, its that single genus that is the focus of our attention today. Far from being a strange one-off, Hillebrandia has a fascinating evolutionary history.

The sole species, Hillebrandia sandwicensis, is the only member of the family native to Hawai'i. It differs from the genus Begonia in characters such as its petals, which are more numerous and more differentiated, its ovaries, which do not completely close, as well as various morphological characteristics of its fruit and pollen, which I won't go into here. It occurs naturally only on the islands of Kauai, Maui, and Molokai where it inhabits wet ravines in montane rainforest zones. Nowhere is this species considered abundant. 

Since its discovery in 1866, H. sandwicensis has been the object of much curiosity. Where did it originate? How old of a species is it? How did it get to Hawai'i? Thanks to some molecular work, a few of these questions are becoming a bit more clear. For starters, we can now confidently say that Hillebrandia is a sister lineage to all other Begonias. This in turn has provided a crucial step in our understanding of its biogeography.

Molecular dating techniques place the genus Hillebrandia at about 51–65 million years old, much older than any of the Hawaiian islands. As such, it is likely that this lineage is not the results of an adaptive radiation like we see in most of the archipelago's flora and fauna. Instead, it is now believed that H. sandwicensis is the only known relict species in Hawaiian flora. In other words, the ancestor of H. sandwicensis did not arrive at Hawai'i and then evolve into the species we know today. Instead, it is more likely that the lineage arose elsewhere and then, through a random long-distance seed dispersal event, made it to Hawai'i's oldest islands some 30 million years ago and has been island hopping to younger islands ever since. 

Although its recent history and geographic origins are still open to much speculation, the story of this unique genus has gotten a bit clearer. Its status as Hawai'i's only known relict plant species is quite exciting to say the least. What we can say for sure is that its history was likely full of serendipity that should be celebrated each time someone has an encounter with this lovely Hawaiian plant.

Photo Credits: [1] [2]

Further Reading: [1]

 

 

 

 

The Hunt

This week we are going on the hunt for a small member of the carrot family known as the harbinger of spring (Erigenia bulbosa). Along the way we meet a handful of interesting plant species. Will we find our quarry? Watch and find out...

Producer, Writer, Creator, Host:
Matt Candeias (www.indefenseofplants.com)

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

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Early Spring Botanizing

SURPRISE!

Many have commented that a video component was lacking from the hiking podcasts. I have teamed up with filmmaker/producer Grant Czadzeck (www.grantczadzeck.com) to bring you a visual botanizing experience. I'm not sure how regular this will become but let us know what you think. In the mean time, please enjoy this early spring hike in central Illinois.

Thanks, Ducks!

Recent research suggests that certain duck species are crucial for maintaining wetland plant diversity in highly fragmented landscapes. Functioning wetlands are becoming more and more isolated each year. As more land is gobbled up for farming and development, the ability for plants to get their seeds into new habitats is made even more difficult. Luckily, many plants utilize animals for this job. Seeds can become stuck in fur or feathers, and some can even pass through the gut unharmed. What's more, animals can move great distances in a short amount of time. For wetland plants, the daily movements of ducks seems to be paramount. 

By tracking the daily movements of mallards, a team of researchers from Utretch University were able to quantify how crucial these water fowl are for moving seeds around. What they found was quite remarkable. In autumn and winter, the diet of mallards switches over to seeds. Not all seeds that a mallard eats get digested. Many pass through the gut unharmed. Additionally, mallards are strong flyers. On any given day they can travel great distances in search of winter foraging grounds. In the evenings, they return to roosting sites with a high degree of fidelity. 

The research team was able to demonstrate that their movements cover even greater distances in highly fragmented landscapes. It's these daily migrations that are playing a major role in maintaining plant diversity between distant wetlands. This is especially important for wetlands that function as roost sites. Whereas mallards distribute around 7% of the surviving seeds they eat among foraging sites, that number jumps to 34% for surviving seeds at roost sites. Given the sheer number of mallards on the landscape, these estimates can really add up. 

It is likely that without mallards, North American wetlands would be much less diverse given their increasingly isolated nature. However, not all seeds are dispersed equally. Small seeds are far more likely to pass through the gut of a duck unharmed, meaning only a portion of the plant species that grow in these habitats are getting a helping hand (wing?). Still, the importance of these birds cannot be overlooked. The next time you see a mallard, thank it for maintaining wetland plant diversity. 

Photo Credits: [1] [2]

Further Reading: [1]

The Plant That Grows a Perch

For flowering plants, entering into an evolutionary relationship with birds as pollinators can be a costly endeavor. It can take a lot of energy to coax birds to their blossoms. On the whole, bird pollinated flowers are generally larger, sturdier, and produce more nectar. They tend to invest heavily in pigmentation. The plants themselves are often more robust as well. Unlike hummingbirds, which usually hover as they feed, other nectar-feeding birds require a perch. Often this is simply a stout branch or a stem, however, a plant endemic to South Africa takes bird perches to a whole new level - it grows one. 

Meet the rat's tail (Babiana ringens). Though not readily apparent, this bizarre looking plant is a member of the iris family. It is endemic to the Cape Province of South Africa where it can be found growing in sandy soils. It produces a fan of erect, grass-like leaves and, when conditions are right, a side branch full of red tubular flowers. This is when things get a bit strange. 

From that flowering stalk emerges a much longer stalk that is said to resemble the tail of a rat, earning this plant its common name. This stalk rises well above the rest of the flowers. If you look closely at the tip of this stalk you will quickly realize this is yet another flower stalk, though this one is sterile. Such a stalk may seem like a strange structure for this plant to produce until you consider its pollinators. 

The rat's tail has entered into an evolutionary relationship with a species of bird known as the malachite sunbird (Nectarina femosa). To access the nectar within, the malachite sunbird can't simply walk up to and shove its face down into the flowers. Instead, it must access them from above. To do so, it perches itself on the rigid sterile flower stalk. Once in position, the malachite sunbird can dip its long, down-curved beak directly into the flowers. This is exactly what the plant requires. In this perched position, pollen is brushed all over its chest. 

babssunny.jpg

Researchers wanted to know how obligate this relationship really was. By removing the perch on selected plants, they were able to demonstrate a reduction in pollination success . Specifically, male sunbirds were less likely to visit plants without the perch stalk. Although these plants are capable of self pollinating, like any sexually reproducing organism, outcrossing is the key to success. By offering the birds a sturdy perch allowing them exclusive access to their nectar, the plants guarantee sunbird fidelity.  

Photo Credits: [1] [2]

Further Reading: [1]

Spring Has Sprung Earlier

Phenology is defined as "the study of cyclic and seasonal natural phenomenon, especially in relation to climate, plant, and animal life." Whether its deciding when to plant certain crops or when to start taking your allergy medication, our lives are intricately tied to such cycles. The study of phenology has other applications as well. By and large, it is one of the best methods we have in understanding the effects of climate change on ecosystems around the globe. 

For plants, phenology can be applied to a variety of things. We use it every time we take note of the first signs of leaf out, the first flowers to open, or the emergence of insect herbivores.  In the temperate zones of the world, phenology plays a considerable role in helping us track the emergence of spring and the onset of fall. As we collect more and more data on how global climates are changing, phenology is confirming what many climate change models have predicted - spring is starting earlier and fall is lasting longer.

Researchers at the USA National Phenology Network have created a series of maps that illustrate the early onset of spring by using decades worth of data on leaf out. Leaf out is controlled by a variety of factors such as the length of chilling temperatures in winter, the rate of heat accumulation in the spring, and photoperiod. Still, for woody species, the timing of leaf out is strongly tied to changes in local climate. And, although it varies from year to year and from species to species, the overall trend has been one in which plants are emerging much earlier than they have in the past.

https://www.usanpn.org/data/spring

For the southern United States, the difference is quite startling. Spring leaf out is happening as much as 20 days earlier than it has in past decades. Stark differences between current and past leaf out dates are called "anomalies" and the 2017 anomaly in the southern United States is one of the most extreme on record.

How this is going to alter ecosystems is hard to predict. The extended growing seasons are likely to increase productivity for many plant species, however, this will also change competitive interactions among species in the long term. Early leaf out also comes with increased risk of frost damage. Cold snaps are still quite possible, especially in February and March, and these can cause serious damage to leaves and branches. Such damage can result in a reduction of productivity for these species.

Changes in leaf out dates are not only going to affect individual species or even just the plants themselves. Changes in natural cycles such as leaf out and flowering can have ramifications across entire landscapes. Mismatches in leaf emergence and insect herbivores, or flowers and pollinators have the potential to alter entire food webs. It is hard to make predictions on exactly how ecosystems are going to respond but what we can say is that things are already changing and they are doing so more rapidly than they have in a very long time. 

For these reasons and so many more, the study of phenology in natural systems is crucial for understanding how the natural world is changing. Although we have impressive amounts of data to draw from, we still have a lot to learn. The great news is that anyone can partake in phenological data collection. Phenology offers many great citizen science opportunities. Anyone and everyone can get involved. You can join the National Phenology Network in their effort to track phenological changes in your neighborhood. Check out this link to learn more: USA National Phenology Network

Further Reading: [1] [2]  

 

Carnations

Confession: Domesticated carnations make me want to puke. Not the wild ones but rather the horrid mutants being sold in bewildering numbers during this week in February. I don't like feeling this way towards a plant. It isn't the plants fault that we turned it into such a monster. So, today I though I would dedicate this space to honoring the wild congener of the domestic carnation.

When we talk about carnations we are referring to cultivars of the genus Dianthus. The most prominent cultivars we see today originated from Dianthus caryophyllus. It is hard to pinpoint the native origin of this species as it has been cultivated throughout Europe and Asia for nearly 2000 years. Regardless, it is thought that the wild carnation is native to a stretch of the Mediterranean region encompassing Greece and Italy.

Wild carnations are more sleek in appearance than their cultivated cousins. They are modest sized plants each producing flowers with five serrated petals that range in color from white to pink. The flowers are protandrous meaning the male parts mature and senesce before the female parts. This helps to reduce inbreeding. Nectaries are located at the base of the flower and it is thought that long tongued bees and lepidotera make up the bulk of the pollinators.

Following pollination, the petals begin to produce ethylene gasses. This causes near complete collapse of the flowers within 24 hours. Why bother wasting energy on expensive floral parts that can now be directed to seed production? Upon maturity, the seed capsule breaks open at the top. Its position at the tip of the stem allows for a combination of ballistic and wind seed dispersal. As the capsule sways back and forth in the breeze, the tiny seeds are launched from the capsule like shrapnel from a catapult.

The multi-petaled mutants we have selectively bred barely function as viable plants anymore. In the wild, carnations are perennial, producing one to six flowers a season and plenty of wind dispersed seeds. Because we value looks and longevity over biology, cultivated carnations will often flower themselves to death in one season. Also, the duplication of petals has made it so that insects cannot reach the interior to get at the pollen or nectar.

Dianthus caryophyllus isn't alone in this genus. Over 300 species of Dianthus have been described each with their own ecology and distribution. They range in appearance from modesty creeping herbs to woody shrub-like plants. Many of these have been utilized by plant breeders to create new cultivars. Unfortunately this is yet another genus of plants whose cultivars get all the attention.

Photo Credit: Zeynel Cebeci - Wikimedia Commons

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

Pollination with a Twist

Ensuring that pollen from one flower makes it to another flower of that species is paramount to sexual reproduction in plants. It's one of the main drivers of the diversity in shapes, sizes, and colors we see in flowers across the globe. Sometimes the mechanism isn't so obvious. Take, for instance, the flowers of Impatiens frithii.

The flowers of this Cameroonian endemic have been a bit of a puzzle since its discovery. Like all Impatiens, they have a long nectar spur. However, the spur on I. frithii is uniquely curved. This puzzled botanists because most of the Impatiens in this region are pollinated by sunbirds. The curved spur would appear to make accessing the nectar within quite difficult for a bird. Still, just because we can't imagine it, doesn't mean that it's impossible. Something must pollinate this lovely little epiphyte in one way or another. This is where close observation comes in handy.

Thanks to remote cameras and lots of patience, botanists were able to record pollination events. They quickly realized that sunbirds are indeed the primary pollinator of this species. This was a bit of a surprise given the shape of the flower. However, the way in which the flowers deposit pollen on this birds is what is most remarkable. As it turns out, successful reproduction in I. frithii all comes down to that curved nectar spur. 

When a sunbird probes the flower for nectar, its beak follows the contour of the spur and this causes the entire flower to twist. As it twists, the anthers and stigma make contact with the chin of the bird. This is unlike other Impatiens which deposit the pollen on top of the heads of visiting birds.

Such an adaptation is quite remarkable in many ways. For one, it is elegantly simple. Such a small alteration of floral architecture is all that is required. Second, by placing pollen on the underside of the head, the plant guarantees that only pollen from its species will ever come into contact with the stigma. This is what we call reproductive isolation, which is an important driver in speciation.

Photo Credit: [1]

Further Reading: [1]

Convergent Carnivores

A carnivorous lifestyle has evolved independently in numerous plant lineages. Despite the similarities between genera like Nepenthes, Sarracenia, and Cepholotus they are not closely related. Researchers have wondered how the highly modified leaves of various carnivorous plant species evolved into the insect trapping and digesting organs that we see today. Thanks to a recent article published in Nature, it has been revealed that the mechanisms responsible for carnivory in plants are a case of convergent evolution.

This research all started with the Australian pitcher plant Cepholotus follicularis. More closely related to wood sorrels (Oxalis spp.) than either of the other two pitcher plant families, this species offers a unique window into the genetic controls on pitcher development. Cepholotus produces two different kinds of leaves - normal, photosynthetic leaves and the deadly pitcher leaves that have made it famous the world over.

By observing which genes are activated during the development of these different types of leaves, the research team was able to identify which alleles have been modified. In doing so, they were able to identify genes involved in producing the nectar that attracts their insect prey as well as the genes involved in producing the slippery waxy coating that keeps trapped insects from escaping. But they also found something even more interesting.

Next, the team took a closer look at the digestive fluids produced by Cepholotus as well as many other unrelated carnivorous plant species from around the world. In doing so, the team made a startling discovery. They found that the genes involved in synthesizing the deadly digestive cocktails among these disparate lineages have a similar evolutionary origin.

Although they are unrelated, the ability to digest insects seems to have its origins in defending plants against fungi. You have probably heard someone say that fungi are more similar to animals than they are plants. Well, the polymer that makes up the cell walls of fungi is the same polymer that makes up the exoskeleton of insects - chitin. By comparing the carnivorous plant genes to those of the model plant Arabidopsis, the team found that similar genes became active when plants were exposed to fungal pathogens.

It appears that carnivorous plants around the world have all converged on a system in which genes used to defend themselves against fungal infection have been co-opted to digest insect bodies. Taken together, these results show that the path to carnivory in plants is surprisingly narrow. Evolution doesn't always require the appearance of new alleles but rather a retooling of genes that are already in place. 

Photo Credits: [1] [2]

Further Reading: [1]

 

 

Giant Ferns

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

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

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

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

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

Photo Credits: [1] [2]

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

Captive Pollinators

In order to ensure pollination, leafflower trees in the genus Glochidion have entered into an intimate relationship with a small family of moths. Their flowers have become so specialized that no other insect is capable of pollinating them. In return, female moths are provided with an edible place to lay their eggs - the fruit of the tree. One species of leafflower has taken this relationship to the extreme. It holds its pollinators captive. In order to understand this bizarre relationship, we must first take a closer look at this interesting pollination syndrome.

Ecologists refer to this type of pollination syndrome as "brood pollination." In the case of the leafflower trees, pollination is achieved thanks to female moths known commonly as leafflower moths. Gravid female leafflower moths locate the blooms thanks to a special perfume tailored specifically for each species. The females first visit the male flowers where they pick up some pollen. Next they visit the female flowers where they will then deposit the pollen into a special chamber that can only be accessed by the female moths' proboscis.

After pollination, the female leafflower moth will then locate the ovaries of the flower and using a needle-like ovipositor, will deposit eggs within the undeveloped fruits. The larvae within eventually hatch right next to their food source - leafflower seeds. The larvae aren't gluttons. They will only eat one or two of the dozens of seeds developing within the fruit. Although this may seem wasteful on the part of the plant, it makes a lot of sense from an evolutionary perspective. Essentially it reduces the likelihood that the moths will try to cheat the system. Glutenous larvae that eat more than one or two seeds will be penalized in the long run because fewer host plants will be available. By tying the reproductive abilities of the moth to the production of fruit, the tree ensures regular pollination.

For most of the leafflower/moth pairs, once the seed meal is over, the larvae chew out of the fruit and fall to the ground to pupate. However, this is not the case for a leafflower known scientifically as Glochidion lanceolarium. It takes this relationship a step further by holding the larvae captive for nearly a year.

Cut open an fruit of this leafflower and there is a chance you might find a fully formed moth waiting patiently inside one of the swollen chambers. Instead of chewing out before it pupates, the moth is held captive within. Only when the fruits mature and split open will the moths be released. This happens just as the new crop of flowers is opening. The tree is literally controlling when its obligate pollinator is available to do its reproductive bidding.

The uniquely intimate nature of this relationship goes beyond simply being interesting. By studying how these two partners interact in relation to the other leafflower/moth partners around the Old World tropics researchers are gaining a better understanding of how such mutualisms evolve.

Photo Credits: [1] [2]

Further Reading: [1]

On Fungi and Forest Diversity

One simply can't talk about plants without eventually talking about fungi. The fact of the matter is the vast majority of plant species rely on fungal interactions for survival. This mutualistic relationship is referred to as mycorrhizal. Fungi in the soil colonize the root system of plants and assist in the acquisition of nutrients such as nitrogen and phosphorus. In return, most photosynthetic plants pay their mycorrhizal symbionts with carbohydrates. 

There are two major categories of mycorrhizal fungi - ectomycorrhizae (EMF) and arbuscular mycorrhizae (AMF). Though there are a variety of different species of fungi that fall into either of these groups, their strategies are pretty much the same. EMF make up roughly 10% of all the known mycorrhizal symbionts. The prefix "ecto" hints at the fact that these fungi form on the outside of root cells. They form a sort of sheath that encases the outside of the root as well as a "hartig net" around the outside of individual cells within the root cortex. AMF, on the other hand, literally penetrate the root cells and form two different kinds of structures once inside. One of these structures looks like the crown of a tree, hence the term "arbuscular." What's more, they are considered the oldest mycorrhizal group to have evolved. 

The type of mycorrhizal fungi a plant partners with has greater implications that simple nutrient uptake. Evidence is now showing that the dominant fungi of a region can actually influence the overall health and diversity forest ecosystems. The mechanism behind this has a lot to do with the two different categories discussed above. 

Researchers have discovered that trees partnering with AMF experience negative feedbacks in biomass whereas those that partner with EMF experience positive feedbacks in biomass. When grown in soils that previously harbored similar tree species, trees that partnered with AMF grew poorly whereas trees that partnered with EMF grew much better. Additionally, by repeating the experiments with seedlings, researchers found that seedling survival was reduced for AMF trees whereas seedling survival increased in EMF trees. 

What is going on here? If mycorrhizae are symbionts, why would there be any detrimental effects? The answer to this may have something to do with soil pathogens. Thinking back to the major differences between EMF and AMF, you will remember that it comes down to the way in which they form their root associations. EMF form a protective sheath around the roots whereas AMF penetrate the cells.  As it turns out, this has major implications for pathogen resistance. Because they form a sheath around the entire root, EMF perform much better at keeping pathogens away from sensitive root tissues. The same can't be said for AMF. Researchers found that AMF trees experienced significantly more root damage when grown in soils that previously contained AMF trees. 

The differences in the type of feedback experienced by EMF and AMF trees can have serious consequences for tree diversity. Because EMF trees are healthier and experience increased seedling establishment in soils containing other EMF species, it stands to reason that this would lead to a dominance of EMF species, thus reducing the variety of species capable of establishing in that area. Conversely, areas dominated by AMF trees may actually be more diverse due to the reduction in fitness that would arise if AMF trees started to dominate. Though they are detrimental, the negative feedbacks experienced by AMF trees may lead to healthier and more diverse forests in the grand scheme of things. 

Infographic by [1]

Further Reading: [1]

 

 

Semi-Aquatic Orchids

By Jim Fowler. Copyright © 2017

By Jim Fowler. Copyright © 2017

Orchids have conquered nearly every continent on this planet except for Antarctica. In fact, there seems to be no end to the diversity in color, form, and habit of the world's largest family of flowering plants. Still, it might surprise many to learn that some orchids have even taken to water. Indeed, at least three species of orchid native to Latin and North America as well as a handful of islands have taken up a semi-aquatic lifestyle.

Most commonly encountered here in North America is the water spider orchid (Habenaria repens). It is a relatively robust species, however, considering that even its flowers are green, it is often hard to spot. Though it will root itself in saturated soils along the shore, it regularly occurs in standing water throughout the southeast. Often times, it can be found growing amidst other aquatic plants like pickerel weed (Pontederia cordata) and duck potato (Sagittaria latifolia). Because it can reproduce vegetatively, it isn't uncommon to find floating mats of comprised entirely of this orchid.  

By Jim Fowler. Copyright © 2017

By Jim Fowler. Copyright © 2017

Living in aquatic habitats comes with a whole new set of challenges. One of these is exposure to a new set of herbivores. Crayfish are particularly keen on nibbling plant material. In response to this, the water spider orchid has evolved a unique chemical defense. Coined "habenariol," this ester has shown to deter freshwater crayfish from munching on its leaves and roots. Another challenge is partnering with the right fungi. Little work has been done to investigate what kinds of fungi these aquatic orchids rely on for germination and survival. At least one experiment was able to demonstrate that the water spider orchid is able to partner with fungi isolated from terrestrial orchids, which might suggest that as far as symbionts are concerned, this orchid is a generalist.

The flowers of the water spider orchid are relatively small and green. What they lack in flashiness they make up for in structure and scent. The flowers are quite beautiful up close. The slender petals and long nectar spur give them a spider-like appearance. At night, they emit a vanilla-like scent that attracts their moth pollinators. 

Photo Credits: Jim Fowler. Copyright © 2017 www.jfowlerphotography.com

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

Orchid Dormancy Mediated by Fungi

North America's terrestrial orchids seem to have mastered the disappearing act. When stressed, these plants can enter into a vegetative dormancy, existing entirely underground for years until the right conditions return for them to grow and bloom. Cryptic dormancy periods like this can make assessing populations quite difficult. Orchids that were happy and flowering one year can be gone the next... and the next... and the next...

How and why this dormancy is triggered has confused ecologists and botanists alike. Certainly stress is a factor but what else triggers the plant into going dormant? According to a recent paper published in the American Journal of Botany, the answer is fungal.

Orchids are the poster children for mycorrhizal symbioses. Every aspect of an orchid's life is dependent on these fungal interactions. Despite our knowledge of the importance of mycorrhizal presence in orchid biology, no one had looked at how the abundance of mycorrhizal fungi influenced the life history of these charismatic plants until now.

By observing the presence and abundance of a family of orchid associated fungi known as Russulaceae, researchers found that the abundance of mycorrhizal fungi in the environment is directly related to whether or not an orchid will emerge. The team focused on a species of orchid known commonly as the small whorled pogonia (Isotria medeoloides). Populations of this federally threatened orchid are quite variable and assessing their numbers is difficult.

The team found that the abundance of mycorrhizal fungi is not only related to prior emergence of these plants but could also be used as a predictor of future emergence. This has major implications for orchid conservation overall. It's not enough to simply protect orchids, we must also protect the fungal communities they associate with.

Research like this highlights the need for a holistic habitat approach to conservation issues. So many species are partners in symbiotic relationships and we simply can't value one partner over the other. If conditions change to the point that they no longer favor the mycorrhizal partner, it stands to reason that it would only be a matter of years before the orchids disappeared for good.

Photo Credit: NC Orchid

Further Reading: [1]

A Unique Passionflower Endemic to Costa Rica

I love small flowers, especially if they pack in a lot of detail. That's is why this passion flower caught my eye. Meet Passiflora boenderi, a charismatic vine endemic to a small region of Costa Rica. Apparently this species had been sitting around in herbaria for years under a different name. It wasn't until living specimens were observed that botanists realized it is a distinct species.

There is a lot to look at on this species. The flowers themselves are some of the smallest in the genus. They pack in all of the detail of a larger passion flower, just in miniature. The leaves are quite stunning as well. They're bilobed with a tinge of purple and covered in bright, orange-yellow spots. The spots themselves serve an important role in protecting this plant from herbivores.

The genus Passiflora is part of an intense evolutionary arms race with a genus of butterfly known as Heliconius. Their caterpillars feed on the foliage of passion flowers. As such, Passiflora have evolved a variety of means that help them to avoid the attention of gravid female butterflies. The orange spots on the leaves of P. boenderi are one such adaptation and they serve a dual function.

The first is a visual deterrent. Female Heliconius prefer to lay their eggs on caterpillar-free leaves. This makes sense. Why bother laying eggs where there will be ample competition for food. The spots mimic, both in size and shape, the appearance of Heliconius eggs. A female looking for a spot to lay will see these spots and move on to another plant. In addition to the visual mimicry, these spots also secrete nectar. The energy-rich nectar inevitably attracts ants, which viciously defend them as a food source. If a caterpillar (or any other herbivore fore that matter) were to start munching on the leaves, the ants quickly drive them off.

Because of its limited range, P. boebderi is under threat of extinction. Habitat destruction of its lowland habitat for palm oil, pineapples, and vacation resorts is an ongoing threat to the long term survival of this species and many others. I was fortunate enough to have encountered this plant growing in the Cliamtron at the Missouri Botanical Garden but I fear that if we keep on doing what we humans are so good at, botanical gardens may be the only place this species will be found growing in the not too distant future.

Further Reading: [1] [2]

The Longleaf Pine: A Champion of the Coastal Plain

As far as habitat types are concerned, the longleaf pine savannas of southeastern North America are some of the most stunning. What's more, they are also a major part of one of the world's great biodiversity hotspots. Sadly, they are disappearing fast. Agriculture and other forms of development are gobbling up the southeast coastal plain at a bewildering rate. For far too long we have ignored, or at the very least, misunderstood these habitats. Today I would like to give a brief introduction to the longleaf pine and the habitat it creates.

The longleaf pine (Pinus palustris) is an impressive species. Capable of reaching heights of 100 feet or more, it towers over a landscape that boggles the mind. It is a landscape born of fire, of which the long leaf pine is supremely adapted to dealing with. These pines start out life quite differently than other pines. Seedlings do not immediately reach for the canopy. Instead, young long leaf pines spend their first few years looking more like a grass than a tree. Lasting anywhere between 5 to 12 years, the grass stage of development gives the young tree a chance to save up energy before it makes any attempt at vertical growth. 

The reason for this is fire. If young long leaf pines were to start their canopy race immediately, they would very likely be burned to death before they grew big enough to escape the harmful effects of fire. Instead, the sensitive growing tip is safely tucked away in the dense needle clusters. If a fire burns through the area only the tips of the needles will be scorched, leaving the rest of the tree safe and sound. During this stage, the tree is busy putting down an impressive root system. The taproot alone can reach depths of 6 to 9 feet!

Once a hardy root system has been formed and enough energy has been acquired, young longleaf pines go through a serious growth spurt. Starting in later winter or early spring, the grass-like tuft will put up a white growth tip called a candle. This tip shoots upwards quite rapidly, growing a few feet in only a couple of months. This is sometimes referred to as the bottlebrush phase because no horizontal branches are formed during this time. The goal at this point is to get the sensitive growing tip as far away from the ground as possible so as to avoid damaging fires. It is fun to encounter long leaf pines at this stage because like any young adult, they look a bit awkward.

Photo Credit: Woodlot - Wikimedia Commons

Photo Credit: Woodlot - Wikimedia Commons

Once the tree reaches about 6 to 10 feet in height, it will finally begin to produce horizontal branches. This doesn't stop its canopy bid, however, as it still will put on upwards of 3 feet of vertical growth each year! Every year its bark grows thicker and thicker, thus each year it becomes more and more resistant to fire. Far from being a force to cope with, fire unwittingly gives longleaf pines a helping hand by clearing the habitat of potential competitors that are less adapted to dealing with burns. After about 30 years of growth, longleaf pines reach maturity and will start to produce fertile cones.

Before European settlement, longleaf pine savanna covered roughly 90,000,000 acres of southeastern North America. Clearing and development have reduced that to a mere 5% of its former glory. For far too long its coastal plain habitat was thought to be a flat, monotonous region created by early human burning in the last few thousand years. We now know how untrue those assumptions are. Sure, the region is flat but it is anything but monotonous. Additionally, the coastal plain is one of the most lightning prone regions in North America. Fires would have been a regular occurrence long before any humans ever got there. 

Red indicates forest loss between 2011 and 2014. http://glad.umd.edu/gladmaps

Evidence suggests that this coastal plain habitat has remained relatively stable for the last 62,000 years. As such, it is full of unique species. Surveys of the southeastern coastal plain have revealed multiple centers of plant endemism, rivaled in North America only by the southern Appalachian Mountains. In fact, taken together, the coastal plain forests are widely considered one of the world's biodiversity hotspots! Of the 62,000 vascular plants found in these forests, 1,816 species (29.3%) are endemic. Its not just plants either. Roughly 1,400 species of fish, amphibians, reptiles, birds, and mammals rely on the coast plain forests for survival.

Luckily, we are starting to wake up to the fact that we are losing one of the world's great biodiversity hotspots. Efforts are being put forth in order to conserve and restore at least some of what has been lost. Still, the forests of southeastern North America are disappearing at an alarming rate. Despite comprising only 2% of the world's forest cover, the southern forests are being harvested to supply 12% of the world's wood products. This is simply not sustainable. If nothing is done to slow this progress, the world stands to lose yet another biodiversity hotspot. 

If this sounds as bad to you as it does to me then you probably want to do something. Please check out what organizations such as The Longleaf Alliance, Partnership For Southern Forestland Conservation, The Nature Conservancy, and The National Wildlife Federation are doing to protect this amazing region. Simply click the name of the organization to find out more.

Further Reading: [1] [2] [3] [4] 

Giant Trees Discovered in Africa

As far as tall trees are concerned, Africa has long been excluded from the list... until now. During a recent botanical survey of Mt. Kilimanjaro, a research team located a stand of large trees tucked away in a remote valley. Some of these trees were giants.

Tall trees are the result of a perfect storm of evolutionary history and unique environmental conditions. From the redwoods of the Pacific Coast to the Eucalyptus of Tasmania, rich soils, low levels of disturbance, and competition for light have driven some species to grow to mind boggling proportions. It seems fitting then that Africa's tallest mountain was hiding its tallest trees all this time. 

The species in question is known scientifically as Entandrophragma excelsum and belongs to the mahogany family (Meliaceae). A total of 13 giant E. excelsum were found during this expedition. Heights ranged from a modest 53.7 meters (176 ft) to a staggering 81.5 meters (267) in height! Unlike other species in this "Tall Tree Club," E. excelsum produces wood of surprisingly low density. However, it is thought that this low density wood, which is much less costly to produce, allows the trees to grow quick enough to avoid being overrun by vines before it can make it to the canopy. Indeed, very few E. excelsum were found to have vines growing on them. 

Although these are nowhere near the tallest trees in the world, they nonetheless break the African tall tree record, which was previously held by a non native Eucalyptus that died in 2006. The reason these African giants were not found sooner has to do with the remote region in which they grow. The area around Mt. Kilimanjaro has not received much attention from botanists in the past, having been overshadowed by the biodiverse Eastern Arc Mountains further south. 

Aside from discovering these trees, botanical surveys of Mt. Kilimanjaro are revealing this region to be just as biodiverse as the Eastern Arcs. Sadly, because of its long history of agriculture and more recent history of illegal logging, the rich forests of Mt. Kilimanjaro are quickly disappearing. The research team stresses the need to protect this area before one of Africa's biodiversity hotspots, as well as its tallest trees, are lost forever. 

Further Reading: [1]

Ancient Saw Palmettos in the Heart of Florida

When we think about long lived plants, our minds tend to fixate on bristlecone pines (Pinus longaeva), coastal redwoods (Sequoia sempervirens), or that clonal patch of quaking aspen (Populus tremuloides) in Utah. What would you say if I told you that we can add a palm tree to that list? Indeed, recent evidence suggests that the saw palmetto (Serenoa repens) can reach a ripe old age measured in thousands (yes, thousands) of years.

Now, at this point some of you are probably thinking "how can you measure the age of a palm when there are no annual growth rings?!" This is a legitimate hurdle that had to be overcome before such a claim was made. Using a lot of attention to detail and some crafty mathematics, a team of researchers was able to age saw palmettos in Florida's most ancient habitats.

This work was performed on a peculiar geological formation. Aptly named the "Mid-Florida Ridge," this 150 mile sand ridge bisects the middle of the state. Throughout much of the Pliocene and early Pleistocene, sea levels were as much as 50 meters higher than they were today. Nearly all of Florida was underwater during this time. All that stuck out above the water were a series of small islands. These islands served as refugia for flora and fauna pushed south by repeated glaciations. Once sea level receded to its current level, these islands were left high and dry, thus forming the ridge in question. Because of its history as a refugium, the Mid-Florida Ridge is home to a staggering array of plant species, some of which are endemic to this relatively small area of Florida.

Because of its relative stability through time, the Mid-Florida Ridge is a haven for long lived plant species. Thus, it was a prime location for trying to understand the longevity of the charismatic and ecologically important saw palmetto. By tagging individual palms and observing them year after year, researchers were able to get an idea of exactly how fast this species can grow. Depending on the soil conditions of the immediate area, saw palmettos grow at a rate of somewhere between 0.88 and 2.2 cm per year. They certainly aren't winning any speed races at that rate. Regardless, you can begin to see that an estimate of yearly growth rate can shine a light on how long these palms have been around. Measurements of tagged palmettos growing on the sand ridge show that individuals aged at a staggering 500 years are not uncommon!

This estimate gets a bit complicated when we consider another aspect of saw palmetto biology - they are clonal. For a variety of reasons, as saw palmettos grow, their sprawling stem will often branch out, creating clones of themselves. Over time, the trunk portions that connect these clones rot away, giving the impression that they are unique individuals. Genetic analyses showed that many of the palmettos in the study area were actually clones. Using some pretty sophisticated models coupled with their DNA evidence, the research team was able to reconstruct the growth history of many of these clones, thus allowing them to more accurately age these clonal colonies.

Their results are staggering to say the least. Based on the rate of growth and spread, the estimated age of these clonal patches of saw palmetto range anywhere between 1227–5215 years! At this point you should be asking yourself "how accurate are these data?" The truth is that the researchers were actually being quite conservative in their estimates. For instance, there were likely many clones well outside their study area. If so, they were likely underestimating the growth time of these clonal colonies. Additionally, they were only using the growth rates of adult saw palmettos in calculating average growth rates.

Seedling saw palmettos have been shown to have a reduced growth rate compared to adults, only 0.3 cm per year. Thus, they did not take into account the time it takes for seedlings to reach maturity. The team feel that accounting for such variables could increase the age estimates for such clonal patches to well over 8,000 years! I don't think we should be looking into buying that many birthday candles just yet, however, even their reported estimates are shocking to say the least.

What we can say is that for as long as Florida has been above water, saw palmettos have played an integral role in the ecology of the region. Long before humans began developing the state, the saw palmetto was functioning as a major player, shaping these sand ridge communities into the ecosystems they are today. It is without a doubt, a species worthy of our admiration and respect.

Further Reading: [1]

Tomatillos Just Got A Lot Older

Tomatillos and ground cherries just got a bit older. Okay, a lot older. Exquisitely preserved fossils from an ancient lake bed in Argentina are shining a very bright light on the genus Physalis and the family Solanaceae as a whole. Despite the importance of this plant family around the globe, little fossil evidence has ever been found. That is, until now. 

Dated at 52 million years old, these fossils paint a picture of a snapshot in the evolution of the genus Physalis. The fossils are remarkable, allowing for close inspection of minute details like vein structure. Because of the level of detail discernible, experts can say without a doubt that these fossils could be nothing else other than a species of Physalis

One of the most interesting aspects of these fossils is their age. These sediments were deposited during the early Eocene Epoch. The fact that representatives of Physalis were alive and well during this time is quite remarkable. Because fossil evidence for Solanaceae has been so scarce, experts have had to rely solely on molecular dating in order to elucidate the origin and divergence of this family. 

Original estimates placed the origin of Solanaceae at sometime around 30 million years before present. Physalis, being much more derived, was thought to have an even more recent emergence, some 9 million years ago. Boy, was that ever wrong. At 52 million years of age, we can now confidently say that Physalis is at least 43 million years older than previously thought. These findings also tell us that Solanaceae is even older still! If such a derived genus was thriving in Eocene Argentina 52 million years ago, basil members of the family must have gotten their start much earlier than we ever imagined. 

Aside from big picture taxonomical revelations, the fossils also give us a window into the ecology of these ancient Physalis. The most obvious is that inflated bladder which surrounds the berry within. Though it is quite characteristic of this group, little attention has been paid to its function. The fact that the sediments in which they were preserved are of aquatic origin suggests that the inflated calyces may have evolved for aquatic seed dispersal. Experiments have shown that these structures on modern day ground cherries and tomatillos do in fact float, keeping the berry inside high and dry. 

To think that all of this was brought to light from a handful of fossils. It just goes to show you the importance the paleontological discoveries can have. Just think of the countless amount of museum drawers and shelves that are chock full of interesting fossils waiting to be looked over. Who knows what they might tell us about our planet. 

Photo Credit: Ignacio Escapa, Museo Paleontológico Egidio Feruglio

Further Reading: [1]