The Upside Down World of Orchid Flowers

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Did you know that most orchid flowers you see are actually blooming upside down? That's right, referred to as "resupination," the lower lip of many orchid flowers is actually the top petal and, as the flower develops inside the bud, the whole structure makes a 180° rotation. How and why does this happen?

The lip of an orchid flower usually serves to attract pollinators as well as function as a landing pad for them. The flower of an orchid is an incredibly complex organ with an intriguing evolutionary history. Basically, the lip is the most derived structure on the flower and, in most cases, it is the most important structure in initiating pollination.

 The non-resupinate flowers of the grass pink ( Calopogon tuberosus ) showing the lip on top.

The non-resupinate flowers of the grass pink (Calopogon tuberosus) showing the lip on top.

As an orchid flower bud develops, it begins to exhibit gravitropic tendencies, meaning it responds to the pull of gravity. By removing specific floral organs like the column and pollinia, researchers found that they produce special hormones called auxins that tell the developing bud to begin the process of resupination. The ovary starts to twist, causing the flower to stand on its head.

Not all orchids exhibit resupinate flowers. Grass pinks (Calopogon tuberosus) famously bloom with the lip pointing up as it does in the early stages of bud development. It is an interesting mechanism and serves to demonstrate the stepwise tendencies that the forces of natural selection and evolution can manifest. But why does it occur at all? What is the evolutionary advantage of resupinate flowers?

 Not only are  Dracula  flowers resupinate, many species also face them towards the ground.

Not only are Dracula flowers resupinate, many species also face them towards the ground.

The most likely answer to this biological twist is that, for orchids, resupination places the lip in such a way that facilitates pollination by whatever the flowers are attracting. For many orchids, this means providing an elaborate landing strip in the form of the lip. For the grass pinks, which operate by slamming visiting bees downward onto the column to achieve pollination, placing the lip at the top makes more mechanical sense. When a bee visits the upward pointing lip thinking it will find a pollen-rich meal, the lip bend at the base like a hinge. Anything goes in evolution provided the genes are present for selection to act upon and nowhere is this fact more beautifully illustrated than in orchids.

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

From Herbivore to Pollinator Thanks to a Parasitoid

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In the Atlantic forests of Brazil resides a small orchid known scientifically as Dichaea cogniauxiana. Like most plant species, this orchid experiences plenty of pressure from herbivores. It faces rather intense pressures from two species of weevil in the genus Montella. These weevils are new to science and have yet been given full species status. What's more, they don't appear to eat the leaves of D. cogniauxiana. Instead, female weevils lay eggs in the developing fruits and the larvae hatch out and consume the seeds within. In other words, they treat the fruits like a nursery chamber.

This is where this relationship gets interesting. You see, the weevils themselves appear to take matters into their own hands. Instead of waiting to find already pollinated orchids, an event that can be exceedingly rare in the dense Amazonian forests, these weevils go about pollinating the orchids themselves. Females have been observed picking up orchid pollinia and depositing the pollen onto the stigmas. In this way, they ensure that there will be developing fruits in which they can raise their young.

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Left unchecked, the weevil larvae readily consume all of the developing seeds within the pod, an unfortunate blow to the reproductive efforts of this tiny orchid. However, the situation changes when parasitoid wasps enter the mix. The wasps are also looking for a place to rear their young but the wasp larvae do not eat orchid seeds. Instead, the wasps must find juicy weevil larvae in which to lay their eggs. When the wasp larvae hatch out, they eat the weevil larvae from the inside out and this is where things get really interesting.

The wasp larvae develop at a much faster rate than do the weevil larvae. As such, they kill the weevil long before it has a chance to eat all of the orchid seeds. By doing so, the wasp has effectively rescued the orchids reproductive effort. Over a five year period, researchers based out of the University of Campinas found that orchid fruits in which wasp larvae have killed off the weevil larvae produced nearly as many seeds as uninfected fruits. As such, the parasitoid wasps have made effective pollinators out of otherwise destructive herbivorous weevils.

The fact that a third party (in this case a parasitic wasp) can change a herbivore into an effective pollinator is quite remarkable to say the least. It reminds us just how little we know about the intricate ways in which species interact and form communities. The authors note that even though pollination in this case represents selfing and thus reduced genetic diversity, it nonetheless increases the reproductive success of an orchid that naturally experiences low pollination rates to begin with. In the hyper diverse and competitive world of Brazilian rainforests, even self-pollination cab be a boost for this orchid.

Photo Credits: [1] [2]

Further Reading: [1]

The Extraordinary Catasetum Orchids

 Male  Catasetum osculatum

Male Catasetum osculatum

Orchids, in general, have perfect flowers in that they contain both male and female organs. However, in a family this large, exceptions to the rules are always around the corner. Take, for instance, orchids in the genus Catasetum. With something like 166 described species, this genus is rather unique in that individual plants produce either male or female flowers. What's more, the floral morphology of the individual sexes are so distinctly different from one another that some were originally described as distinct species. 

 Female  Catasetum osculatum

Female Catasetum osculatum

In fact, it was Charles Darwin himself that first worked out that plants of the different sexes were indeed the same species. The genus Catasetum enthralled Darwin and he was able to procure many specimens from his friends for study. Resolving the distinct floral morphology wasn't his only contribution to our understanding of these orchids, he also described their rather unique pollination mechanism. The details of this process are so bizarre that Darwin was actually ridiculed by some scientists of the time. Yet again, Darwin was right. 

  Catasetum longifolium

Catasetum longifolium

If having individual male and female plants wasn't strange enough for these orchids, the mechanism by which pollination is achieved is quite explosive... literally. The Catasetum orchids are pollinated by large Euglossine bees. Attracted to the male flowers by their alluring scent, the bees land on the lip and begin to probe the flower. Above the lip sits two hair-like structures. When a bee contacts these hairs, a structure containing sacs of pollen called a pollinia is launched downwards towards the bee. A sticky pad at the base ensures that once it hits the bee, it sticks tight. 

 Male Catasetum flower in action. Taken from BBC's Kingdom of Plants.

Male Catasetum flower in action. Taken from BBC's Kingdom of Plants.

Bees soon learn that the male flowers are rather unpleasant places to visit so they set off in search of a meal that doesn't pummel them. This is quite possibly why the flowers of the individual sexes look so different from one another. As the bees visit the female flowers, the pollen sacs on their back slip into a perfect groove and thus pollination is achieved. 

  Eulaema polychroma  visiting  Catasetum integerrimum

Eulaema polychroma visiting Catasetum integerrimum

The uniqueness of this reproductive strategy has earned the Catasetum orchids a place in the spotlight among botanists and horticulturists alike. It begs the question, how is sex determined in these orchids? Is it genetic or are there certain environmental factors that push the plant in either direction? As it turns out, light availability may be one of the most important cues for sex determination in Catasetum

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A paper published back in 1991 found that there were interesting patterns of sex ratios for at least one species of Catasetum. Female plants were found more often in younger forests whereas the ratios approached an even 1:1 in older forests. What the researchers found was that plants are more likely to produce female flowers under open canopies and male flowers under closed canopies. In this instance, younger forests are more open than older, more mature forests, which may explain the patterns they found in the wild. It is possible that, because seed production is such a costly endeavor for plants, individuals with access to more light are better suited for female status. 

  Catasetum macrocarpum

Catasetum macrocarpum

Aside from their odd reproductive habits, the ecology of these plants is also quite fascinating. Found throughout the New World tropics, Catasetum orchids live as epiphytes on the limbs and trunks of trees. Living in the canopy like this can be quite stressful and these orchids have evolved accordingly. For starters, they are deciduous. Most of the habitats in which they occur experience a dry season. As the rains fade, the plants will drop their leaves, leaving behind a dense cluster of green pseudobulbs. These bulbous structures serve as energy and water stores that will fuel growth as soon as the rains return. 

  Catasetum silvestre in situ

Catasetum silvestre in situ

The canopy can also be low in vital nutrients like nitrogen and phosphorus. As is true for all orchids, Catasetum rely on an intimate partnership with special mychorrizal fungi to supplement these ingredients. Such partnerships are vital for germination and growth. However, the fungi that they partner with feed on dead wood, which is low in nitrogen. This has led to yet another intricate and highly specialized relationship for at least some members of this orchid genus. 

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Mature Catasetum are often found growing right out of arboreal ant nests. Those that aren't will often house entire ant colonies inside their hollowed out pseudobulbs. This will sometimes even happen in a greenhouse setting, much to the chagrin of many orchid growers. This partnership with ants is twofold. In setting up shop within the orchid or around its roots, the ants provide the plant with a vital source of nitrogen in the form of feces and other waste products. At the same time, the ants will viciously attack anything that may threaten their nest. In doing so, they keep many potential herbivores at bay.  

 Female  Catasetum planiceps

Female Catasetum planiceps

To look upon a flowering Catasetum is quite remarkable. They truly are marvels of evolution and living proof that there seems to be no end to what orchids have done in the name of survival. Luckily for most of us, one doesn't have to travel to the jungles and scale a tree just to see one of these orchids up close. Their success in the horticultural trade means that most botanical gardens sport at least a species or two. If and when you do encounter a Catasetum, do yourself a favor and take time to admire it in all of its glory. You will be happy that you did. 

Photo Credits: [1] [2] [3] [4] [5] [6] [7] [8] [9] 

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

In Search of the Orange Fringed Orchid

In Defense of Plants is finally back for another exciting botanical adventure! This week we explore another wonderful sand prairie in search of one of North America's most stunning terrestrial orchids - the orange fringed orchid (Platanthera ciliaris). Along the way, we meet a handful of great native plant species that are at home in these sandy soils.

Music by: 
Artist: Eyes Behind the Veil
Track: Folding Chair
Album: Besides
https://eyesbehindtheveil.bandcamp.com/

Wet Prairies and the White Lady's Slipper

This week we visit a wet prairie in search of the white lady's slipper orchid (Cypripedium candidum). This is a unique habitat type full of incredible plants and we meet many of them along the way. Special thanks to Paul Marcum (http://bit.ly/2r6SG8s) in making this episode possible! 

If you would like to support orchid conservation efforts here in North America, consider purchasing a stick over at http://www.indefenseofplants.com/shop/

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

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

Twitter: @indfnsofplnts

Facebook: http://www.facebook.com/indefenseofpl...

Patreon: http://www.patreon.com/indefenseofplants

Tumblr: http://www.tumblr.com/indefenseofplants

_________________________________________________________________

Music by: 
Artist: Lazy Legs
Track: Chain of Pink
Album: Chain of Pink
http://lazylegs.bandcamp.com

Seed Anchor

Epiphytic plants live out their entire lives on the trunks or branches of trees. Using their roots, they attach themselves tightly to the bark. Spend any amount of time in the tropics and it will become quite clear that such a lifestyle has been very successful for a plethora of different plant families. Still, living on a tree isn't easy. Epiphytic plants must overcome harsh conditions among or near the canopy.

One of the biggest challenges these plants face starts before they even germinate. This is especially true for orchids. Orchid seeds are more like spores than they are seeds. They are so small that thousands could fit inside of a thimble. Upon ripening, the dust-like seeds waft away on the slightest breeze. In order for epiphytic species to germinate and grow, their seeds must somehow anchor themselves in place on a trunk or branch. Inevitably most seeds are doomed to fail. They simply will not land in a suitable location. It stands to reason then that any adaptation that increases their chances of finding the right kind of habitat will be favored. That's where the strange coils on the tip of Chiloschista seeds, a genus of leafless orchids native to southeast Asia, New Guinea, and Australia, come in. For these orchids, this process is aided by some truly unique seed morphology.

Unlike most orchid seeds that are nothing more than a thin sheath surrounding a tiny embryo, the seeds of Chiloschista have additional parts. These "appendages," which are specialized seed coat cells, are tightly wound into coils. Upon contact with water, these coils shoot out like tiny grappling hooks that grab on to moss and bark alike. In doing so, they anchor the seed in place. By securing their hold on the trunk or branch of a tree, the seeds are much more likely to germinate and grow. This is one of the most extreme examples of seed specialization in the orchid family.

Photo Credit: [1] [2]

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 Peculiar Case of Bird Pollination

When we think of bird pollination, we often conjure images of a hummingbird sipping nectar from a long, tubular, red flower. Certainly the selection pressures brought about from entering into a pollination syndrome with birds has led to convergence in floral morphology across a wide array of different plant genera. Still, just when we think we have the natural world figured out, something new is discovered that adds more complexity into the mix. Nowhere is this more apparent than the peculiar relationship between an orchid and a bird native to South Africa.

The orchid in question is known scientifically as Disa chrysostachya. It is a bit of a black sheep of the genus. Whereas most Disa orchids produce a few large, showy flowers, this species produces a spike that is densely packed with minute flowers. They range from orange to red and, like most other bird pollinated flowers, produce no scent. 

Take the time to observe them in the field and you may notice that the malachite sunbird is a frequent visitor. The sunbirds perch themselves firmly on the spike and probe the shallow nectar spurs on each flower. At this point you may be thinking that the pollen sacs, or pollinia, of the orchid are affixed to the beak of the bird but, alas, you would be wrong. 

Closer inspection of the flowers reveal that the morphology and positioning of the pollinia are such that they simply cannot attach to the beak of the bird. The same goes for any potential insect visitors. The plant seems to have assured that only something quite specific can pick up the pollen. To see what is really going on, you would have to take a look at the sunbird's feet. 

That's right, feet. When a sunbird feeds at the flowers of D. chrysostachya, its feet position themselves onto the stiffened lower portion of the flower. This is the perfect spot to come into contact with the sticky pollinia. As the bird feeds, they pick up the pollinia on their claws! The next time the bird lands to feed, it will inevitably deposit that pollen. The orchids seemed to have benefited from the fact that once perched, sunbirds don't often reposition themselves on the flower spike. In this way, self pollination is minimized. A close relative, D. satyriopsis, has also appeared to enter into a pollination with sunbirds in a similar way. 

Though it may seem inefficient, research has shown that this pollination mechanism is quite successful for the orchid.The pollinia themselves stick quite strongly so that no amount of scuffing on branches or preening with beaks can dislodge them. Once pollination has been achieved, each flower is capable of producing thousands upon thousands of seeds.

Photo Credit: Johnson and Brown

Further Reading: [1]

The Lowly Lawn Orchid

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

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

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

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

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

Further Reading: [1] [2]

Newly Discovered Orchid Doesn't Bother With Photosynthesis or Opening Its Flowers

A new species of orchid has been discovered on the small Japanese island of Kuroshima. Though not readily recognized as an orchid, it nonetheless resides in the tribe Epidendroideae. Although the flowers of its cousins are often quite showy, this orchid produces small brown blooms that never open. What's more, it has evolved a completely parasitic lifestyle. 

The discovery of this species is quite exciting. The flora of Japan has long thought to be well picked over by botanists and ecologists alike. Finding something new is a special event. The discovery was made by Suetsugu Kenji, associate professor at the Kobe University Graduate School of Science. This discovery was made about a year after a previous parasitic plant discovery made on another Japanese island a mere stones throw from Kuroshima (http://bit.ly/2dYN12L).

Coined Gastrodia kuroshimensis, this interesting little parasite flies in the face of what we generally think of when we think of orchids. It is small, drab, and lives out its entire life on the shaded forest floor. Like the rest of its genus, G. kuroshimensis is mycoheterotrophic. It produces no leaves or chlorophyll, living its entire life as a parasite on mycorrhizal fungi underground. This is not necessarily bizarre behavior for orchids (and plants in general). Many different species have adopted this strategy. What was surprising about its discovery is the fact that its flowers never seem to open. 

In botany this is called "cleistogamy." It is largely believed that cleistogamy evolved as both an energy saving and survival strategy. Instead of dumping lots of energy into producing large, showy flowers to attract pollinators, that energy can instead be used for seed production and persistence. Additionally, since the flowers never open, cross pollination cannot occur. The resulting offspring share 100% of their genes with the parent plant. Although this can be seen as a disadvantage, it can also be an advantage when conditions are tough. If the parent plant is adapted to the specific conditions in which it grows, giving 100% of its genes to its offspring means that they too will be wonderfully adapted to the conditions they are born into. 

As you can probably imagine, pure cleistogamy can be quite risky if conditions rapidly change. In the face of continued human pressures and rapid climate change, cleistogamy as a strategy might not be so good. That is one reason why the discovery of this bizarre little orchid is so interesting. Whereas most species that produce cleistogamous flowers also produce "normal" flowesr that open, this species seems to have given up that ability. Thus, G. kuroshimensis offers researchers a window into how and why this reproductive strategy evolved. 

Photo Credit: Suetsugu Kenji

Further Reading:

[1]

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 (http://bit.ly/1dRP2Va)

Further Reading:

http://bit.ly/2c2c6EW

http://bit.ly/2bRQEFu

http://bit.ly/2c5rsqS

http://bit.ly/2cEt00r

The Cranefly Orchid (Tipularia discolor)

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Look closely or you might miss it. Heck, even with close inspection you still run the risk of overlooking it. At this time of year, finding a cranefly orchid (Tipularia discolor) can present a bit of a challenge. At other times of the year the task is a bit easier. If you can find one in bloom, however, you are rewarded with, in my opinion, one of the most unique terrestrial orchids in temperate North America.

For most of the year, the cranefly orchid exists as a single leaf, which is produced in the fall and lasts until spring. It is thought that this orchid takes advantage of the dormancy of its neighbors by sucking up the light the canopy otherwise intercepts during the growing season. Any of you curious enough to look will have noticed that the underside of this leaf is deep purple in color. This very well may be an adaptation to take full advantage of light when it is available. There is some evidence that such coloration may help reflect light back up into the leaf, thus getting more out of what makes it to the forest floor. Evidence for this, however, is limited. It is far more likely that the purple coloration are pigments produced by the leaves that act as a sort of sun screen, shielding the sensitive photosynthetic machinery within from an overdose of sun.

By the end of spring, the single leaf has senesced. If energy stores were ample that year the plant will then flower. A lanky brown spike erupts from the ground. Its purple-green color is subtle yet beautiful. The flowers themselves are a bit odd, even by orchid standards. Whereas most orchid flowers exhibit satisfying bilateral symmetry, the flowers of the cranefly orchid are distinctly asymmetrical. The dorsal sepal, along with the lateral petals, are scrunched up on either side of the column. This has everything to do with its pollinators.

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The cranefly orchid has coopted nocturnal moths in the family Noctuidae for pollination. These moths find the flowers soon after they open and stick around only as long as there is nectar still present in the long nectar spurs. The asymmetry of the bloom causes the pollinia to attach to one of the moth's eyes. In this way the orchid is able to ensure that its pollen is not wasted on the blooms of other species.

As in all plants, the production of flowers is a costly business. Sexual reproduction is all about tradeoffs. It has been found that cranefly orchids that flowered and successfully produced fruit in one year were much less likely to do so in the next. What's more, the overall size of the plant (leaves and corms) were greatly reduced. Its hard to eek out an existence on the forest floor.

What I find most interesting about this species is where it tends to grow. Any old patch of ground simply won't do. Research indicates that the cranefly orchid requires rotting wood as a substrate. It's not so much the wood they require but rather the organisms that are decomposing it. Like all orchids, the cranefly cannot germinate and grow without mycorrhizal associations. They just happen to partner with fungi that also decompose wood. Such a relationship underscores the importance of decaying wood to forest health.

Further Reading:
http://bit.ly/29RSylm

http://bit.ly/29MAEz7

http://bit.ly/29K3UdZ

http://bit.ly/29WAycl

http://bit.ly/2a6fO19

The Ghosts of Florida

 

There are ghosts haunting the Florida Everglades. I'm not talking about the metaphysical kind either. The ghosts I am talking about come in the form of a plant. A strange, mystical, and beautiful plant at that. Growing amongst things like panthers, snakes, palms, ferns, and more mosquitoes than I care to imagine are these rare and endangered plants which have been made famous by court cases, books, and even a Hollywood movie.

If you haven't guessed it by now, I am talking about the ghost orchid (Dendrophylax lindenii). In what is one of Nicolas Cage's best onscreen roles (a close second to Raising Arizona), these orchids were made famous the world over. Based on the book "The Orchid Thief" by Susan Orlean, the movie takes a lot of creative licenses with the story of these orchids.

Ghosts orchids are epiphytes. In Flordia, upwards of 80% of them can be found growing on the bark of pop ash trees (Fraxinus caroliniana). Finding them can be tricky unless you know what to look for. Ghost orchids belong to a group of orchids that have forgone leaf production. No, they are not parasites like Corallorhiza. Instead, they photosynthesize through their long, ambling roots. Pores along their length allow for gas exchange. For most of the year all you will ever see of a ghost is a tangle of roots growing among the moss and lichen on the bark of a tree. 

When a ghost decides to flower, it is easy to see where all the hype comes from. Large white flowers shoot out from the center of the roots, each one with its own twisted pair of tendrils on the lip, which are said to resemble the ghostly outline of a frog jumping through the air. Each flower is also equipped with a long nectar spur. This along with the white coloration and the fact that each flower is most fragrant at night points to the identity of the ghost orchids sole pollinator, the giant sphinx moth. It has a long proboscis that is exactly the length of that nectar spur. No other organism has what it takes to pollinate a ghost. 

The presence of the ghost orchid in southern Florida has everything to do with water. Predominantly a species of the Caribbean, ghost orchids cannot handle frost. In the Everglades, ghosts grow in and around topographical features known as sloughs. Sloughs are ditches that are filled with water for most of the year. Because water has a high specific heat, the sloughs keep the surrounding area cool in the summer and warm in the winter. When Florida experiences hard frosts, these sloughs never get below freezing. This means that these regions are essentially tropical. All these factors combine to make southern Florida the most northerly spot you will ever see a ghost (and many other plant species) growing in the continental United States. 

Sadly, ghost orchids are not doing so hot in the wild. The habitat they rely upon is disappearing at an alarming rate. If you have been to Florida in the last 100 years you can certainly understand. Over half of the Everglades have been drained and developed since 1900 with plenty more of it degraded beyond any hope of repair. Invasive species run amok for the same reasons that the native plants do so well, crowding out some of Florida's most unique flora and fauna. 

To add insult to injury, poaching of ghost orchids is serious business. Despite its difficulty in cultivation and the fact that most wild ghosts quickly die in captivity, there are those out there that will still pay insane prices to have a ghost in their collection. Nursery produced specimens are becoming more common, so with time this should alleviate some of that pressure. Still, there is no end to the senseless greed of some orchid fanatics. 

There is hope on the horizon. Researchers are starting to unlock some of the secret to ghost orchid reproduction. Plants are now being grown from seed in specialized labs. In time, this new generation of ghost orchids will be planted back into southern Florida in hopes of increasing population sizes. 

Photo Credits: Big Cypress National Preserve

Further Reading:
http://bit.ly/24NiqT9

http://bit.ly/1XTqh38

http://bit.ly/21jegSg

http://bit.ly/1PZlKJu

One Orchid Two Colors

Bumblebees are no dummies. Far from being mindless drones whose sole purpose it to benefit the colony, these industrious insects are quite capable of learning and memory. They are constantly evaluating their foraging strategies and are quick to abandon a food source that doesn't deliver. For plants that rely on bumblebees, this presents a particular challenge. 

Of course, plants want to maximize their reproductive effort while at the same time minimizing their energy investments. For this reason, some plant species have foregone any sort of reward. Nectar is costly to produce after all. This non-rewarding strategy is particularly widespread among the orchids. Take for instance the case of the elder-flowered orchid (Dactylorhiza sambucina) of Europe. A species of meadows and alpine grasslands, it prefers calcarious conditions. What is most stunning about this species are its floral displays. 

Its inflorescence is made up of a dense cluster of flowers. Unlike what we are used to with most flowering plants, the flowers of the elder-flowered orchid come in two distinct color morphs - purple and yellow. They are so drastically different that one could be excused for thinking they were two different species. What's more, the different color morphs cooccur throughout the species' range. What could be causing this dimorphism? The answer lies in the flowers themselves. 

The edler-flowered orchid is one of those non-rewarding species. It has no nectar and its pollen is bunched up in sacs called pollinia that bees can't really harvest. The main pollinators of this species are bumblebees. As I have hinted, bumblebees are all about optimizing their foraging efforts. They quickly learn which plants are worth visiting and which plants are not. They do this via a highly tuned search image. Any plant that doesn't give them what they want will soon be shunned. 

This is where having different colored flowers comes in handy. Researchers have discovered that the color ratios of any given orchid population are under what is referred to as "negative frequency-dependent selection." Here's how it works: naive bumblebees that visit a non-rewarding flower of one color (purple in this example) are then much more likely to visit a flower of a different color (yellow). It just so happens that the plant with a different flower color (yellow) often turns out to be the same species of orchid. 

The result of this behavior is that in any given population, the plants with the rarer flower color (yellow) get visited more often. Because flower color is under genetic control, that particular morph (yellow) will gradually rise in frequency. Once it becomes the dominant flower color, the reverse happens and the first color (purple) is then visited more often. 

Over time this causes back and forth shifts in flower color that eventually settles on some sort of stable ratio of purple to yellow flowers. Thus anyone botanizing a high-elevation meadow in Europe can find purple and yellow flowered orchids in the same population. By tapping into the bees' natural foraging tendencies, this non-rewarding orchid species is able to maintain its presence in the landscape without having to invest valuable energy into floral rewards. 

Photo Credit: Emilio (http://bit.ly/22CHigV)

Further Reading:
http://www.pnas.org/content/98/11/6253.full.pdf

The Whorled Pogonia

I live for moments like this. The only downside to that is I can never really predict when they are going to happen. There I was driving up a mountain road in search of a handful of other plant species related to my research. The road was narrow and there was a steep bank on the drivers side. The Southern Appalachian Mountains are brimming with botanical diversity. As such, it can be hard to tease out individual plants, especially while driving. This is why having a refined search image comes in handy. 

I was rounding a bend in the road when something out my window caught my eye. My mind went racing and it wasn't long before a suspicion crept into my head. If I was right, this was an opportunity I was not going to miss. I found the nearest pull off, parked the truck, and ran back down the road. I am so happy that I decided to trust my instincts. There in front of me was a small population of whorled pogonia orchids (Isotria verticillata). 

It was like being in the presence of a celebrity that I had been stalking for years. This was an orchid I have been dying to see. The harder I looked the more I saw. I had to sit down. Here in front of me was a species of orchid that isn't seen by many. In fact, entire populations of these species can go unseen for decades until they have enough energy to flower. 

Flowering in this species is said to be quite erratic. Because they live in shaded environments, building up the energy needed to reproduce can be difficult. Like all orchids, the whorled pogonia relies on an obligate relationship with mycorrhizal fungi to supply the nutrients it needs. In return, the orchids provide fungi with carbohydrates. The problem with erratic flowering, however, is that it makes reproduction difficult. Rarely are two populations flowering at the same time and in close enough proximity for successful cross pollination. More often, these orchids will self fertilize, which can lead to high rates of inbreeding. 

Large bees are the main pollinators of the whorled pogonia. The flowers themselves are reported to produce a feint odor reminiscent of Vanilla. This is interesting to note because in the greater scheme of orchid phylogenetics, this species is placed in the Vanilla subfamily, although such distinctions can get muddled quickly. Regardless, simply being in the presence of this orchid was enough to give me goosebumps. It is a shame that such a species is being lost throughout much of its range. 

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

http://bit.ly/1WEmZzm

An Underground Orchid

Are you ready to have your mind blown away? What you are looking at here is not some strange kind of mushroom, though fungus is involved. What you are seeing is actually the inflorescence of a parasitic orchid from Australia that lives and blooms underground!

Meet Rhizanthella gardneri. This strange little orchid is endemic to Western Australia and it lives, blooms, and sets seed entirely underground. It is extremely rare, with only 6 known populations. Fewer than 50 mature plants are known to exist. This is another one of those tricky orchids that does not photosynthesize but, instead, parasitizes a fungus that is mycorrhizal with the broom honey myrtle (Melaleuca uncinata). To date, the orchid has only been found under that specific species of shrub. Because of its incredibly unique requirements, its limited range, and habitat destruction, R. gardneri is critically endangered.

The flowers open up a few centimeters under the soil. They are quite fragrant and it is believed that ants, termites, and beetles are the main pollinators. The resulting seeds take up to 6 months to mature and are quite fleshy. It is hypothesized that some sort of small marsupial eats them and consequently distributes them in its droppings. Either way, the chances of successful sexual reproduction for this species are quite low. Because of this, R. gardneri also reproduces asexually by budding off daughter plants.

Despite not photosynthesizing, this orchid is quite unique in that it still retains chloroplasts in its cells. They are a very stripped down form of chloroplast though, containing about half of the genes a normal chloroplast would. It is the smallest known chloroplast genome on the planet. This offers researchers a unique opportunity to look deeper into how these intracellular relationships function. The remaining chloroplast genes code for 4 essential plant proteins, meaning chloroplasts offer functions beyond just photosynthesis.

I am so amazed by this species. I'm having a hard time keeping my jaw off the ground. What an amazing world we live in. If you would like to see more pictures of R. gardneri, please make sure to check out the following website:
http://www.arkive.org/underground-orchid/rhizanthella-gardneri/

Photo Credit: Jean and Fred Hort

Further Reading:
http://www.sciencedaily.com/releases/2011/02/110208101337.htm

http://www.eurekalert.org/pub_releases/2011-02/uowa-wai020711.php

http://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=20109

A Litter Trapping Orchid From Borneo

Epiphytes live a unique lifestyle that can be quite challenging. Sure, they have a relatively sturdy place on a limb or a trunk, however, blistering sun, intense heat, and plenty of wind can create hostile conditions for life. One of the hardest things to come by in the canopy is a steady source of nutrients. Whereas plants growing in the ground have soil, epiphytes must make do with whatever falls their way. Some plants have evolve a morphology that traps falling litter. There are seemingly endless litter trapping plants out there but today I want to highlight one in particular.

Meet Bulbophyllum beccarii. This beautiful orchid is endemic to lowland areas of Sarawak, Borneo. What is most interesting about this species is how it grows. Instead of forming a clump of pseudobulbs on a branch or trunk, this orchid grows upwards, wrapping around the trunk like a leafy green snake. At regular intervals it produces tiny egg-shapes pseudobulbs which give rise to rather large, cup-shaped leaves. These leaves are the secret to this orchids success.

The cup-like appearance of the leaves is indeed functional. Each one acts like, well, a cup. As leaves and other debris fall from the canopy above, the orchid is able to capture them. Over time, a community of fungi and microbes decompose the debris, turning it into a nutrient-rich humus. Instead of having to compete for soil nutrients like terrestrial species, this orchid makes its own soil buffet!

If that wasn't strange enough, the flowers of this species are another story entirely. Every so often when conditions are just right, the plant produces an inflorescence packed full of hundreds of tiny flowers. The flowers dangle down below the leaves and emit an odor that has been compared to that of rotting fish. Though certainly disdainful to our sensibilities, it is not us this plant is trying to attract. Carrion flies are the main pollinators of this orchid and the scent coupled with their carrion-like crimson color attracts them in swarms.

The flies are looking for food and a place to lay their eggs. This is all a ruse, of course. Instead, they end up visiting a flower with no rewards whatsoever. Regardless, some of these flies will end up picking up and dropping off pollinia, thus helping this orchid achieve pollination.

Epiphyte diversity is incredible and makes up a sizable chunk of overall biodiversity in tropical forests. The myriad ways that epiphytic plants have adapted to life in the canopy is staggering. Bulbophyllum beccarii is but one player in this fascinating niche.

Photo Credits:
Ch'ien C. Lee - http://www.wildborneo.com.my/

and

Peter AJ Chong - bit.ly/1XLgFE6

Further Reading:
http://www.orchidspecies.com/bulbbeccarrii.htm

An Orchid With Body Odor

Aside from ourselves, mosquitoes may be humanity's largest threat. For many species of mosquito, females require blood to produce eggs. As such, they voraciously seek out animals and in doing so can spread deadly diseases. They do this by homing in on the chemicals such as CO2 and other compounds given off by animals. What is less commonly known about mosquitoes is that blood isn't their only food source. Males and females alike seek out nectar as source of carbohydrates.

Though mosquitoes visit flowers on a regular basis, they are pretty poor pollinators. However, some plants have managed to hone in on the mosquito as a pollinator. It should be no surprise that some orchids utilize this strategy. Despite knowledge of this relationship, it has been largely unknown exactly how these plants lure mosquitoes to their flowers. Recent work on one orchid, Platanthera obtusata, has revealed a very intriguing strategy to attract their mosquito pollinators.

This orchid produces human body odor. Though it is undetectable to the human nose, it seems to work for mosquitoes. Researchers at the University of Washington were able to isolate the scent compounds and found that they elicited electrical activity in the mosquitoes antennae. Though more work needs to be done to verify that these compounds do indeed attract mosquitoes in the wild, it nonetheless hints at one of the most unique ruses in the floral world.

Photo Credit: Kiley Riffell and Jacob W. Frank

Further Reading:

http://bit.ly/1JXP2jk

Fall Leaves of the Putty-Root Orchid

Whereas most plants here in the Northern Hemisphere have largely geared down for the long winter, there is one species that has only recently begun a new stage of growth. Though it may seem damaging to produce leaves when a hard frost is just around the corner, that is exactly what this plant is doing. What's even more bizarre is that the plant in question is an orchid.

The putty-rood orchid (Aplectrum hyemale) may seem strange to most. Though it flowers during the same time as most of our terrestrial orchids (May through June), its display can be hard to track down. In fact, lacking any knowledge of a specific location, it is more likely that you will stumble across one before you pick it out of the hustle and bustle on the forest floor.

Flowering occurs at a different time than leaf out. The solitary flower stalk gives way to a single leaf starting in late summer or early fall. Why the heck would this plant start its photosynthetic lifecycle when everything else is about ready to go dormant? The answer is competition. Summer is not a bright season for those growing on the forest floor. This is especially true for a plant that only produces a single leaf.

What the putty-root is doing with its oddly timed leaf production is taking advantage of a dormant canopy. With trees and herbaceous leaves out of the way, the putty-root is able to soak up as much sun as it can get. This is a similar strategy adopted by spring ephemerals around the globe. But what does the plant have to gain from having leaves in the fall? Why not wait until spring to leaf out?

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As it turns out, it simply doesn't have to. The photosynthetic machinery within the leaves of the putty-root perform exceptionally well at low temperatures. Whereas most plants simply can't photosynthesize when it starts getting too cold, the putty-root is able to photosynthesize at temperatures as low as 2° C (35.6° F)! Not only does this enable the plant to get a jump start come spring, its also able to make food throughout most of fall and even early winter.

There does seem to be a limit to this. Once temperatures drop below 2° C, the machinery can't keep up and photosynthesis grinds to a halt. This is further complicated by the fact that the leaves are often buried under snow for months at a time. Certainly its mycorrhizal associations help feed the plant, even when it isn’t actively photosynthesizing. Regardless, this strategy is a great way of getting an extra kick while everything else is slowing down. Stories such as this bring to mind the story of the tortoise and the hare. Sometimes slow and steady really does win the race!

Photo Credit: Lance Merry (www.lancemerry.com)

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