Studying Mimicry in Orchids Using 3D Printing

Just when I thought I could stop acting surprised by the myriad applications of 3D printing, a recent study published in the journal New Phytologist has me pulling my jaw up off the floor. Using a 3D printer, researchers from the University of Oregon have unlocked the mystery surrounding one of the more peculiar forms of mimicry in the botanical world. 

The genus Dracula is probably most famous for containing the monkey face orchids (Dracula simia). Thanks to our predisposition for pareidolia, we look at these flowers and see a simian face staring back at us. Less obvious, however, is the intricate detail of the labellum, which superficially resembles the monkey's mouth. A close inspection of this highly modified petal would reveal a striking resemblance to some sort of gilled mushroom. 

Indeed, a mushroom is exactly what the Dracula orchids are actually trying to mimic. The main pollinators of this genus are tiny fruit flies that are mushroom specialists. They can be seen in the wild crawling all over Dracula flowers looking for a fungal meal and a place to mate. Some of the flies inevitably come away from the Dracula flower with a wad of pollen stuck to their backs. With any luck they will fall for the ruse of another Dracula flower and thus pollination is achieved. 

Despite being well aware of this mimicry, scientists didn't quite know what specifically attracted the flies to the flower. This is where the 3D printer came in. The research team made exact replicas of the flowers of Dracula lafleurii out of odorless silicone. They also printed individual flower parts. In doing so, the researchers were able to vary the color patterns as well as the scent of each flower. Using the parts, they were also able to construct chimeras, which allowed them disentangle which parts contribute most to the mimicry. 

What they discovered is that the key to Dracula's mushroom mimicry lies in its gilled labellum. This petal not only looks like a mushroom, it smells like one too. The result is a rather ingenious ruse that its tiny fly pollinators simply can't resist. What's more, this approach offers an ingenious way of investigating the evolution of mimicry throughout the botanical kingdom. 

Photo Credit: Luis Baquero (http://bit.ly/21GhYGJ)

Further Reading:
http://onlinelibrary.wiley.com/doi/10.1111/nph.13855/abstract

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

Shhhh... Let Him Finish

Sexual deception is rampant in the orchid family. Orchid genera all over the world produce flowers that trick sexually charged male insects into failed mating attempts. The orchids go to great lengths to resemble females both in appearance and smell. Indeed, many sexually deceptive orchid species emit odors that precisely mimic the pheromones of specific insect species. 

In many instances, the orchids ruse is so powerful that male insects will often preferentially visit the flower over an actual female. For many of the sexually deceptive orchids, all that is required is the male to pay a visit. No attempt at copulation is necessary, though that doesn't stop vigorous attempts. Because of this, it is easy to see how the minute cost incurred to the insects is not enough to drive evolution away from deception. However, there is a group of tongue orchids (genus Cryptostylis) from Australia that seem to throw a wrench into this finely tuned system.... or do they?

The tongue orchids rely on deceiving male wasps in the genus Lissopimpla into mating with their flowers. As mentioned above, the males simply cannot resist the attempt. However, unlike many other reported cases, the male wasps actually mate to completion, depositing their sperm onto the flower. This should be disastrous for the wasps since males not only prefer flowers to wasp females, but they also waste their precious few mating attempts. How could this have evolved?

Most sexually deceptive orchids rely on bees and wasps (family Hymenoptera) for their pollination. Thus, the answer to this evolutionary conundrum lies in the mating system of these insects. Queens are genetically haplodiploid. I will spare you the details on that but basically what it means for Hymenoptera is that female offspring are produced via fertilized eggs whereas male offspring are produced via unfertilized eggs. 

The orchids have (unknowingly of course) tapped into this system to their benefit. If by mating with the flower and not a female wasp meant that no offspring were produced, this system surely would not have evolved to the level that it has. Instead, female wasps that have not been mated with or received less sperm than usual end up producing a higher amount of male offspring.

The orchids are effectively skewing the sex ratio of their pollinators! "How is this a sustainable system?" you may be asking. Well, by causing female wasps to produce more males, the orchids are ensuring that there will be more naive males in the population the next time they are in bloom. Also, by skewing the sex ratio towards males, there are now fewer females to mate with so that males become less choosy and more readily mate with orchids. Finally, with more sexually charged males flying around, each female has a greater chance of being fertilized. Because of the unique mating system that has evolved in Hymenoptera, the orchids have thus been able to evolve this pollination strategy with little harm to the pollinators.

Photo Credit: photobitz

Further Reading:
http://instructional1.calstatela.edu/kfisher2/BIOL360/classroom.activities/species_interact._casestudies/orchid.sex.pseudo.II.pdf

On Orchids and Fungi

It is no secret that orchids absolutely need fungi. Fungi not only initiate germination of their nearly microscopic seeds, the mycorrhizal relationships they form supplies the fuel needed for seedling development. These mycorrhizal fungi also continue to keep adult orchids alive throughout their lifetime. In other words, without mycorrhizal fungi there are no orchids. Preserving orchids goes far beyond preserving the plant. Despite the importance of these below-ground partners, the requirements of many mycorrhizal fungi are poorly understood.

Researchers from the Smithsonian Environmental Research Center have recently shone some light on the needs of these fungi. Their findings highlight an important concept in ecology - conservation of the system, not just the organism. Their results clearly indicate that orchid conservation requires old, intact forests.

Their experiment was beautifully designed. They added seeds and host fungi to dozens of plots in both young (50 - 70 years old) and old (120-150 years old) forests. They continued to monitor the progress of the seeds over a period of 4 years. Orchid seeds only germinated in plots where their host fungi were added. This, of course, was not very surprising.

The most interesting data they collected was data on fungal performance. As it turns out, the host fungi displayed a marked preference for older forests. In fact, the fungi were 12 times more abundant in these plots. They were even growing in areas where the researchers had not added them. What's more, fungal species were more diverse in older forests.

The researchers also noted that host fungi grew better and were more diverse in plots where rotting wood was added. This is because many mycorrhizal fungi are primarily wood decomposers. Nutrients from the decomposition of this wood are then channeled to growing orchids (as well as countless other plant species) in return for carbohydrates from photosynthesis. It is a wonderful system that functions at its best in mature forests.

This research highlights the need to protect and preserve old growth forests more than ever. Replanting forests is wonderful but it may be centuries before these forests can ever support such a diversity of life. Also, this stands as a stark reminder of the importance of soil conservation. Less obvious to most is the importance of decomposition. Without dead plant material, such fungal communities would have nothing to eat. Clearing a forest of dead wood can be just as detrimental in the long run as clearing it of living trees.

Research like this is made possible by the support of organizations such as the Native North American Orchid Conservation Center. Head on over to www.indefenseofplants.com/shop and pick up an In Defense of Plants sticker. Part of the proceeds are donated to this wonderful organization, which helps support research such as this! As this research highlights: What is good for orchids is good for the ecosystem.

Further Reading:

http://onlinelibrary.wiley.com/doi/10.1111/j.1365-294X.2012.05468.x/abstract;jsessionid=3385C965FF5BA4CB83290005DFD47FD1.f01t02

What a Dichaea

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The orchid genus Dichaea includes some of the strangest orchids i have ever seen in person. Take this one for example. My sources tell me this is likely D. globosa. Right off the bat, the bristly seed pods are a tell for this genus. With this particular species, each stem juts off of the trunk of a tree at a near 90 degree angle. The stem itself is horizontally flattened and the subtle yet beautiful flowers emerge from between the leaves and are presented below the plant, facing the ground. I had seen this orchid out of flower in a few places in Costa Rica, however, I was lucky enough to stumble across these individuals in flower while hiking in Panama. An exciting find for this orchid fanatic!

Central America - Part 1: Costa Rica

This journey really began back in April. Grad school was coming to a close and our move to Illinois was scheduled for August. A celebration was in order. Other than a brief exploration of a Caribbean island and a few visits to Florida, I have never really experienced anything remotely tropical. Through documentaries and an obsession with houseplants that borders on hoarding, I developed a longing for the equatorial rainforests of the world. It was high time I visited some. 

We managed to find ourselves some cheap tickets into Costa Rica. My friend and horticultural mentor, Dave Janas, had taken a job at the Wilson Botanical Garden in San Vito. I could not think of a better person to introduce us to the flora and fauna of this region. With our flights set we now had something to day dream about for the next few months. 

In no time at all the day had arrived. We hopped on a plane in Buffalo, NY and in less than half a day we had landed in San Jose, Costa Rica. All we had were our backpacks and some cash. No matter how much you read and prepare there is always going to be some culture shock. This was especially true in my case. I had been to Portugal as a kid, though I hardly remember most of it. Other than Canada and the Caribbean, I have not traveled much outside of the country. I was ready for something new and challenging but very little sleep and my almost non-existent grasp on Spanish made the first few hours a bit trying. After an awkward cab ride from the airport in San Jose to our hostel in Alajuela, I needed to regroup a bit. 

After a small nap, I was ready to get my bearings. It was time to explore Alajuela a bit. We decided to grab some food and see what the parks were like in town. Getting around town proved to be a slow process - not because of transportation or any sort of infrastructure but because every garden was teaming with plants I have either never seen before or only encountered in the indoor section of a nursery or botanical garden. Poinsettias and palms were obvious favorites. They decorated most open lots. There were also a handful of mango trees dotting the city scape. When we finally arrived at the park, I could barely contain myself. 

It wasn't very big but it was packed. The ground was trampled as well. It was obvious that this was quite a popular place. Most of what was growing there were various palms and each palm was adorned with its fair share of tillandsias. It didn't take long for my ever-present search image to locate a few orchids as well. At this point you may be asking "what species?!" and to that I will say that I haven't the slightest idea. I was quickly realizing just how out of my element I was. Other than some of the more obvious plants that decorate houses and offices up north, most of what I was seeing was completely new to me. This was going to be an exciting trip. Never in my life have I been this ignorant to the plants and animals around me. If this is how the dense urban centers were going to be, I could hardly wait to run off into a real rainforest. That leg of the adventure was to begin at dawn the next day. 

We found a fruit vendor and grabbed some dinner for the evening. It consisted of some granadilla (Passiflora ligularis) and rambutans (Nephelium lappaceum). We sat on a bench and ate all the while a pair of crimson-fronted parakeets were loudly tending to something inside a hole in a dead palm. I had finally done it. I was finally about to explore one of these tropical wonderlands.

An Orchid Invader With an Interesting Ecology

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Orchids are notoriously finicky about where they will grow. The family with which they belong (Orchidaceae) may be the most diverse plant family in the world. Because of this massive diversity, orchids have become quite specialized plants. Orchids hedge their reproductive success on production of millions upon millions of tiny, wind-blown seeds. With seeds so tiny there is not much room left to equip them with food in the form of nutrient packed endosperm (the stuff you are eating when you eat coconut) and thus orchid seeds rely on specific species of fungi in order to germinate. Some orchids take this relationship to the extreme but that is a post for another day. Because of all this specialization, orchids are a pretty vulnerable group of plants. Most species are threatened because of poaching and habitat loss and many are endangered. This is why coming across the plant I am writing about may seem shocking.

I am talking about the helleborine orchid (Epipactus helleborine) which originally hails from northern Eurasia. I first came across this plant down on some Nature Conservancy land in Gowanda, NY. This was a few years ago and I did not recognize it for what it was. Over the past few years however, I began seeing this plant in the strangest places including areas in the City of Buffalo with amazingly poor soil. I was lucky to have a few start growing in the garden so watching them develop was fun and easy. They are a very nice looking plant, standing about 7 to 8 inches high. The flowers are readily recognizable as belonging to an orchid and each plant produces a spike full of them.

In its immature stage this plant germinates and grows as an underground rhizome and is considered fully mycoheterotrophic, which means it tricks mycohrrizal species of fungi into associating with it then feeds off of the nutrients that the fungi gain from trees. The orchid can stay in this state of growth for upwards of 10 years before it has enough energy to flower. When the right conditions are present it then begins its adult phase of growth. It throws up a stem, some leaves, and flower buds. At this point it can begin making its own food through photosynthesis but will still use the fungi as well.

Once it begins to flower it then needs to call on the help of wasps for pollination. There has been some amazing research done on how it achieves this. Apparently the plant begins to release compounds called "green-leaf volatiles" or GLV's. Plants such as cabbage produce GLV's when damaged by insects in order to attract wasps that will either lay eggs in/on the insects or take them back to their hive. This is not the orchid's goal. Instead, when the orchid produces GLV's, its doing it for sex. INterestingly enough, the flowers apparently have not evolved structurally sound methods for pollination. Because of this, they utilize yet another ruse.

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Once the wasps get there they are "encouraged" to stick around in a very unique way. There are reports that the flowers produce narcotic drugs and alcohols that dope up the wasps, which causes them to linger and stumble around the flower thus increasing the chance of picking up a pollinia. This process then gets repeated each time a wasp visits another flower. Thus, pollination is achieved.

This plant is a reminder that even invaders are worth a closer look. The fungi that the helleborine orchid partners with are a group of disturbance-loving truffles (not the kind you eat) and therefore can most often be found in close proximity to humans. Keep an eye out for this species. Make sure to spend some time examining this plant for all its worth.

Further Reading:

http://link.springer.com/article/10.1007/s00606-002-0197-x?no-access=true

http://blogs.discovermagazine.com/notrocketscience/2008/05/12/orchid-lures-in-pollinating-wasps-with-promise-of-fresh-meat/#.Va8HhipVikp

http://www.cell.com/current-biology/abstract/S0960-9822(08)00526-5

Primitive Orchids

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The genera Neuwiedia and Apostasia represent something quite interesting. What you are looking at here are believed to be two of the most primitive extant orchid lineages. Unlike most orchids, which have a single fertile stamen fused with a single pistil, these genera have 3 and 2 fertile stamens respectively. Though botanists hesitate to consider these genera ancestral to all other orchid lineages, they nonetheless feel that they represent a very primitive sister-group to other basal orchid lineages such as the cypripediads. They can be found in parts of China, India, Sri Lanka, Southeast Asia, New Guinea, and Queensland, with Neuwiedia having the smallest distribution. 

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Photo Credit: Rachmat Setiawan Saleh (http://bit.ly/Zuy37j), Johannes Lundberg (http://bit.ly/1ydRIah), and chipmunk1 (http://bit.ly/1sjMJTh)

Further Reading: 

http://onlinelibrary.wiley.com/doi/10.1111/j.1095-8339.1993.tb00331.x/abstract

The Amazing Orchid Bees

Bees are some of the most common organisms recruited by flowers to achieve sexual reproduction. Even the least plant savvy among us can tell you that. Individual species of flowering plants go to great lengths to stand out among the background of countless other flowering plants to ensure that bees (and other pollinators) visit their own kind. Some plants get very specific in this way, only attracting a few or even a single pollinator species to do their bidding. Nowhere is this more apparent than in the orchids. There are some orchids that have taken this specificity to the next level. Orchids in the subtribes Stanhopeinae and Catasetinae have turned the tables so that bees require their flowers for their own reproduction, a truly unique strategy for both plants and animals alike.

Decked out in metallic greens, blues, and reds, male Euglossine or orchid bees are a site for sore eyes. However, their behavior may be even more amazing. Before mating, male bees seek out special volatile compounds that they store in special pouches on their back legs. Just as teenage boys utilize various colognes, the male bees are using these scents to attract females. These compounds are not produced by the bees. Instead, they obtain them from the flowers of various species of orchid. Some of the most commonly encountered orchids that offer this service are those belonging to genera such as Stanhopea, Gongora, and Catasetum.

The male bees go to great lengths to track these flowers down. A single blooming orchid can come alive with the buzz of male bees vying for access to the scented compounds. They land on the flowers and begin scraping at the petals with special hairs on their legs. In the process, pollen sacs called "pollinia" get stuck to the backs of the bees. The next time a bee visits a flower it will brush some of the pollen off and reproduction for the orchid is achieved.

Specific species of bee require specific scents to attract females. Because of this, each orchid species often caters to only one species of bee, thus guaranteeing that those bees will only visit orchids of that species. In this way, precious pollen is not wasted. What's more, the influence these orchids have goes far beyond just helping male bees get laid. Euglossine bees are important pollinators throughout the rain forests that they live. Species like the Brazil nut tree (Bertholletia excelsa) rely on large bees such as Euglossines for pollination and will not produce seeds without them.

Photo Credit: Billtacular (http://bit.ly/1LuTn2Q), USGS Bee Inventory and Monitoring Lab (http://bit.ly/1AFD4G0), Ian Morton (http://bit.ly/1924m1R), barloventomagico (http://bit.ly/1xeYPAM), Quimbaya (http://bit.ly/1GXLr3D)

Further Reading:
http://books.google.com/books…

http://link.springer.com/article/10.1023%2FA%3A1021932131526