The First Genus (Alphabetically)

Photo by Eric in SF licensed under CC BY-SA 3.0

One thing I love about orchids is that they are so diverse. One could spend their entire life studying these plants and never run out of surprises. Every time I sit down with an orchid topic in mind, I end up going down a rabbit hole of immeasurable depth. I love this because I always end up learning new and interesting facts. For instance, I only recently learned that there is a genus of orchids that has been given the unbelievably complex name of Aa.

No, that is not an abbreviation. The genus was literally named Aa. As far as I have been able to tell, it is pronounced “ah” rather than “ay,” but if any linguists are reading this and beg to differ, please chime in! Regardless, I was floored by this silly exercise in plant naming and had to learn more. I had never heard of this genus before and figured that it was so obscure that it probably contained, at most, only a small handful of species. This assumption was wrong.

Aa maderoi. Photo by Dr. Alexey Yakovlev licensed under CC BY-SA 2.0

Though by no means massive, the genus Aa contains at least 25 recognized species. A quick search of the literature even turned up a few relatively recent papers describing new species. Apparently we have a ways to go in understanding their diversity. Nonetheless, this is an interesting and pretty genus of orchids.

From what I gather, Aa are most often found growing at high elevations in the Andes, though at least one species is native to mountainous areas of Costa Rica. They are terrestrial orchids that prefer cooler temperatures and fairly moist soil. Some species are said to only be found in close proximity to mountain streams. Some of the defining features of the genus are a tall inflorescence jam packed with tiny inconspicuous, greenish-white flowers. The flowers are surrounded by semi-transparent sheaths that are surprisingly showy. All in all, they kind of remind me of a mix between Spiranthes and Goodyera.

Close up of an inflorescence of Aa maderoi showing the small, white flowers and large, semi-transparent sheaths. Photo by Dr. Alexey Yakovlev licensed under CC BY-SA 2.0

But what about the name? Why in the world was this genus given such a strange and abrupt moniker? The answer seems to be the silliest option I could think of: to be first. This genus was originally described in 1845 by German botanist Heinrich Gustav Reichenbach who recognized two species within the genus Altensteinia to be distinct enough to warrant their own genus.

According to most sources I could find, he coined this new genus Aa so that it would appear first on all taxonomic lists. There is at least one other report that the name was given in honor of a man by the name of Pieter van der Aa, but apparently this is “highly” disputed. However, all of this should be taken with a grain of salt. Though I can find plenty of literature describing various species within the genus, I could turn up no actual literature on the naming of the genus itself. All I could find is what has been repeated (almost verbatim) from Wikipedia.

So, there you have it. Not only does the genus Aa exist, it is still top of the list of all plant genera. If that truly was the goal Heinrich Gustav Reichenbach was aiming for, he certainly has succeeded!

Photos via Wikimedia Commons

Further Reading: [1]

Drunken Pollinators & Chemical Trickery: Musings on the Complex Floral Chemistry of a Generalist Orchid

There was a time when I thought that all orchids were finicky botanical jewels, destined to perish at the slightest disturbance. Certainly many species fit this description to some degree, but more often these days I am appreciating the role disturbance can play in maintaining many orchid populations. Seeing various genera like Platanthera or Goodyera thriving along trails and old dirt roads, lawn orchids (Zeuxine strateumatica) growing in manicured lawns, or even various Pleurothallids growing on water pipes in the mountains of Panama has opened my eyes to the diversity of ecological strategies this massive family of flowering plants employs.

Of the examples mentioned above, none can hold a candle to the hardiness of the broad-leaved helleborine orchid (Epipactis helleborine) when it comes to thriving in disturbed habitats. Originally native throughout much of Europe, North Africa, and Asia, this strangely beautiful orchid can now be found growing throughout many temperate and sub-tropical regions of the world. Indeed, this is one species of orchid that has greatly benefited from human disturbance. In fact, I more often see this orchid growing in and around cities and along roadsides than I do in natural settings (not to say it isn’t there too). In many areas here in North America, the broad-leaved helleborine orchid has gone from a naturalized oddity into a full blown invasive.

Much of its success in conquering new and often highly disturbed territory has to do with its relationship with mycorrhizal fungi. Like all orchids, the broad-leaved helleborine orchid requires fungi for germination and growth, relying on the symbiotic relationship into maturity. Without mycorrhizal fungi, these orchids could not survive. However, while many orchids seem to be picky about the fungi they will partner with, the broad-leaved helleborine is something of a generalist in this regard. At least one study in Europe was able to demonstrate that over 60 distinct groups of mycorrhizal fungi were able to partner with this orchid. By opening itself up to a wider variety of fungal partners, the broad-leaved helleborine orchid is able to live in places where pickier orchids cannot.

Another key to this orchids success has to do with its pollination strategy. Here again we see that being a generalist comes with serious advantages. Though wasps are thought to be the most effective pollinators, myriad other insects from various kinds of flies to beetles and butterflies will visit these blooms. How is it that this orchid has become to appealing to such a wide variety of insects? The answer is chemistry.

The broad-leaved helleborine orchid is something of a skilled chemist. When scientists analyzed the nectar produced in the cup-shaped lip of the flower, they found a diverse array of chemicals, many of which lend to some incredible insect interactions. For starters, highly scented compounds such as vanillin (the compound responsible for the vanilla scent and flavor of Vanilla orchids) are produced in the nectar, which certainly attracts many different kinds of insects. There is also evidence of some floral mimicry going on as well.

Scientists found a group of chemicals called kairomones in broad-leaved helleborine nectar, which are very similar to aphid alarm pheromones. When released by aphids, they warn nearby kin that predators are in the area. In one sense, the production of these compounds in the nectar may serve to ward off aphids looking for a new place to feed. However, these chemicals also appear to function as pollinator attractants. For aphid predators like hoverflies, these pheromones act as a dinner bell, signalling good egg laying sites for gravid female hoverflies whose larvae gorge themselves on aphids as they grow. It just so happens that hoverflies also serve as important pollinators for the broad-leaved helleborine orchid.

A series of compounds broadly classified as green-leaf volatiles were found in the nectar as well. Many plants produce these compounds when their leaves are damaged by insect feeding. Like the aphid example above, green-leaf volatiles signal to nearby predatory insects that plump herbivores are nearby. For instance, when the caterpillars of the cabbage white butterfly feed on cabbage plants, green-leaf volatiles attract wasps, which quickly set to work eating the caterpillars, relieving the plant of its herbivores in the process. As previously mentioned, wasps are thought to be the main pollinators for this orchid so attracting them makes sense. However, attracting pollinators using chemical trickery can be risky. What happens when a pollinator shows up and realizes there is no plump aphid or caterpillar to eat?

The answer to this comes from a series of other compounds produced in this orchid’s nectar. Few insects will turn down a sugary meal, and indeed, many visitors end up sipping some broad-leaved helleborine nectar. Sit back and watch and it won’t take long to realize that these insects appear to quickly become intoxicated. Their behavior becomes sluggish and they generally bumble around the flowers until they sober up and fly off. This is not happenstance. This orchid actively gets its pollinators wasted, but how?

Along with the chemicals we already touched on, scientists have also found a plethora of narcotics in broad-leaved helleborine nectar. These include various types of alcohols and even chemicals similar to that of opioids like Oxycodone. Now, some have argued that the alcohols are not the product of the plant but rather the result of fermentation by yeasts and bacteria living within the nectar. However, the presence of different antimicrobial compounds coupled with the sheer concentrations of alcohols within the nectar appear to discount this hypothesis and point to the plant as the sole creator. Nonetheless, after a few sips of this narcotic concoction, insects like wasps and flies spend a lot more time at each flower than they would if they remained sober the whole time. This has led to the suggestion that narcotics help improve the likelihood of successful pollination.

Indeed, the broad-leaved helleborine orchid seems to have no issues with sex. Most plants produce a bountiful crop of seed-laden fruits each summer. In fact, it has been found that plants growing in areas of high human disturbance tend to set more seed than plants growing in natural areas. Scientists suggest this is due to the wide variety of pollinators that are attracted to the complex nectar. Human environments like cities tend to have a different and sometimes more varied suite of insects than more rural areas, meaning there are more opportunities for run ins with potential pollinators.

The broad-leaved helleborine orchid stands as an example of the complexities of the orchid family. Few orchids are as generalist in their ecology as this species. Its ability to grow where others can’t while taking advantage of a variety of pollinators has lent to the extreme success of this species world wide.

Photo Credit: [1]

Further Reading: [1] [2] [3] [4] [5] [6]

The Heartleaf Twayblade Orchid

Photo by Cptcv licensed under CC BY-ND 2.0.

The heartleaf twayblade is truly a sight for sore eyes.... that is, if you can find it. This diminutive orchid stands no more than 30 cm tall when in bloom and, for much of its life, exists as a single pair of tiny, heart-shaped leaves. Finding this species in bloom has been one of the major highlights of the last few years of botanizing. Getting to see it up close makes me wonder how many times I may have passed it over completely.

A closeup examination of the flowers will reveal what looks like tiny little humanoids. Indeed, the flowers are complex little structures. Tiny trigger hairs located at the base of the pollinia squirt glue on the back of visiting insects, which affixes the pollen sacs or pollinia. One to two days after the pollinia have been removed the stigmas become receptive to pollen. Though this orchid can self fertilize, differential ripening of sexual parts like this helps ensure cross pollination between different individuals.

With flowers so small, it is a wonder that insects can even find them. As it turns out, the flowers emit a foul smelling odor, though one would be hard pressed to detect it having to bend down so close to the forest floor. This attracts a wide variety of small insects like wasps and flies. The most common visitors, however, are fungus gnats. Ever abundant in the moist duff of the forest, these tiny dipterids offer plenty of opportunity for pollination. The orchid even sweetens the deal a bit by producing a small amount of nectar.

Being so small it is quite easy to overlook this plant. One must put in a bit of searching to find them. Their tiny size also means that they are often under-represented in conservation efforts as well. Entire populations can exist in only a few square meters of forest and thus are quite sensitive to disturbance. Timber harvesting and sprawl represent the largest threats the this species but luckily it has a surprisingly large geographic distribution. Still, keep an eye out for this lovely little species. They may be hard to find but they are well worth the effort!

Photo Credit: [1]

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

The Deceptive Ways of the Calypso Orchid

Photo by Murray Foubister licensed under CC BY-ND 2.0.

Behold the Calypso orchid, Calypso bulbosa. This circumboreal orchid exists as a single leaf lying among the litter of dense conifer forests. They go virtually unnoticed for most of the year until it comes time to flower.

In early spring, the extravagant blooms open up and await the arrival of bumblebees. Calypsos go to great lengths to attract bumblebees. The flower is said to have a sweet scent. Also, the lip sports small, yellow, hair-like protrusions that are believed to mimic anthers covered in pollen. Finally, within the pouch formed by the lip are two false nectar spurs. All of these are a ruse. The Calypso offers no actual rewards to visiting bumblebees.

Not just any bumblebee will do. For the ruse to work, it requires freshly emerged workers that are naive to the orchid’s deception. Bumblebees are not mindless animals. They quickly learn which flowers are worth visiting and which are not. Because of this, the Calypso has only short window of time in which bumblebees in the vicinity are likely to fall for its tricks. As a result, pollination rates are often very low for this orchid.

The most interesting aspect of all of this is that the so-called "male function" of the flower - pollinia removal - is more likely to occur than the "female function" - pollen deposition. The reason for this makes a lot of sense in context; male function requires a bumblebee to be fooled only once whereas female function requires a bumblebee to be fooled at least twice.

The caveat to all of this deception is that a single Calypso, like all other orchids, can produce tens of thousands of seeds. Each orchid therefore has tens of thousands of potential propagules to replace itself in the next generation. Despite that fact, the Calypso orchid is on the decline. Habitat destruction, poaching, deer, and invasive species are taking their toll. If you care about orchids like the Calypso, please consider supporting organizations like the North American Orchid Conservation Center.

Photo by Murray Foubister licensed under CC BY-ND 2.0.

Photo Credit: [1] [2]

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