Go Stelis!

Presented by Alexander Hirtz at the IV Scientific Conference on Andean Orchids, November 2012, Guayaquil, Ecuador.

My lecture today will cover several features on Stelis, details that become very apparent while studying close-up photography of the flowers. All the photographs used in this lecture were taken in Ecuador, where in many cases they are the holotype of the species.
I will refer only to Stelis in its strict classic sense and outline the various textures and indumenta found on the floral parts,
where most of these features and combination thereof are intended to attract a specific pollinator.
The presence or absence of one particular feature might imply variations of the mechanisms to attract different pollinators and these differentiating attributes should be considered to define a species.
The key characters in Stelis section Humboldtia are the unequal sepals with the lateral sepals variously connate into a concave synsepal.
In Stelis section Stelis the lateral sepals are less deeply connate to the dorsal sepal, than to themselves.
The Stelis section Nexipous, which has the lateral sepals deeply divided, are quite different to the other Stelis and may be a separate genus, a consideration shared by Adam Karremans in his study of the phylogenetics of Stelis.
The subsequent feature to key out Stelis is the growth-habit that may be caespitose, repent, scandent or prolific.
The other features to classify Stelis are the number of veins on sepals and petals and a generalized shape of the lip. Other characters, like the shape of the petals, clinandrium and stigmatic lobes are not taken into consideration.
The importance of identical indumenta on different species may be the key feature to attract the same pollinator. Stelis hirtzii is a unique species,
where the sepals are connate below the middle into a broad, sepaline cup, that reflex above the middle. Most uncommon are the inner surfaces of the sepals covered with minute rounded papillae.
There is another species, which shares this feature of the papillae, Stelis columnaris.
Most surprising, these two endemic species may flower simultaneously on the same branch. It appears that the indumenta of these two otherwise quite different species would attract the same pollinator.
Here, another example of two quite similar species, but with different shapes of the lip and may be found on the same tree.
Few years back, I had an exhibit of macro photography of orchids enlarged to 5 meters height in the Appleton Museum in Ocala, Florida.
I selected from my photo file the most impressive ones and to be as different from each other as possible.
To my shock, three selections had been classified as the same species: Stelis argentata.
Most taxonomists have been classifying or reducing to synonimia almost all Stelis that have a a small apiculum at the center of the margin of the lip into 3 & 5 veined Stelis argentata,
even if some of these populations are otherwise quite different and grow several hundred kilometers away from each other.
Dr. Luer has kept two exceptions in this species complex because of size, when grading into the large Stelis superbians complex or into the tiny Stelis guianensis complex.
For the holotype Stelis argentata, Lindley mentions “minute particles of silver covering the blunt ends of the petals and lip”, where this silvery attribute was used to name this species.
Mark Chase and Donald Peacor follow up on this peculiarity and discovered that these extracellular occurrences are elongated crystals of calcium oxalate hydrate.
Most plants labeled as Stelis argentata have no crystals on them; should these populations be named argentata without any silvery crystals?
Chase and Peacor suggested for these fractile raphides to be attractions to pollinators, possibly as pseudopollen, pseudonectar, or brood-site desceptions, because studies have shown that insects have no need for these crystals. If these crystals are an imperative deceit syndrome in the pollination ecology, the absence of them would suggest that those Stelis have different attraction mechanisms.
Thus, to repeat myself, if the holotype of Stelis argentata has these crystals growing on the petals and lip as a deceit syndrome, any species classified as Stelis argentata without these crystals should therefore be re-classified as a different species.
Close scrutiny shows the presence of these crystals to be quite common in Stelis. In some species the crystals are present only on the apex of the petals,
in others only on the apex of the lip,
occasionally on the stigmatic lobes
and quite often covering the whole surface of the sepals or all parts of the whole flower.
The surface texture of the sepals might vary greatly among Stelis, where some have a thin, shiny, translucent texture.
In these cases, the color change of refractive and reflective light varies greatly; the brilliance and color of the refractive light could be an important feature to attract the insect when the sun shines behind the flower.
Some Stelis have a glabrous, coarse and opaque texture;
others are covered with what appears to be a thin coat of extra-cellular wax, which scratches off easily.
The texture, shape and localized distribution of the pubescence may serve different purposes.
The pubescence may be located along the margin, where these hairs might just prevent crawling insects to enter the flower.
The arrangement of the very long cilia seen under ultraviolet light would appear to be a luminescent blue tunnel, a feature also found with spider webs to lure the pollinator into the blue sky.
Others may serve to prevent the insect from exiting the flower too fast.
The pubescent sepals often resemble the ones of Dracula, where these mimic the surface of rotten wood.
With some Stelis the filaments are like spines, broad at the base and pointed at the end,
while in others the filaments are very thin in all its length.
A few Stelis exude a very strong, often very unpleasant odor, which might be one type of fragrance possibly produced by pubescent glands.
On some sepals the grainy surface appears to be made of extracellular crystals, but other than white calcium oxalate.
In most Stelis the texture of the cells of the sepals are gelatinous and shiny towards the center, in such a way that the embedded petals, lip and column are surrounded by this brilliant surface.
The color of this surface is often different to the remaining area of the sepals, contrasting the center of the flower with very light or very dark tones.
In other Stelis the shiny surface complements the gelatinous texture of the petals and lip, thus enlarging the target to the eye of the pollinator.
In rare occasions the sepals form an apparent bulge that appears to uplift the petals and column.
Most often the petals are cup shaped where the apex is gelatinous, translucent and shiny. The petals might retain the shape of a cup, where the shiny surface at the apex is narrow,
but in most cases the apex is compressed down, forming a broad, flat, belt-like surface.
Most often the calcium oxalate crystals are located on this area of the petals.
In some instances, the petals enclose completely the column and lip.
Rarely, from the center of the acuminate tip of the petals two barbell-like fingers protrude out horizontally,
In some other cases the petals are pubescent at the apex.
In three species of section Humboldtia, the gelatinous texture of the fimbriated petals curl inwards forming a “bubbly” surface around the center of the flower.
or sometimes in section Humboldtia these protusions point downwards parallel to the long apiculate lip forming a trident.
In a few Stelis the inner surface of the petals extend outwards and usually have a coarse opaque texture.
There are dozens of different shapes of the lip, with noticeable differences in the texture of the concave, exposed inner surface, the rim at the apex and the underside of the lip.
Often the rim at the apex of the lip has a gelatinous texture and color similar to the petals forming a ring around the column.
Very important is the visual impact produced by the brightly colored, often gelatinous glenion, which is an elongated tong-shaped depression inside a callus located in the center of the concave exposed surface of the lip.
Most striking is the texture and brilliance of the “glue-like” surface of the stigmatic lobes. In most cases the apical stigmatic lobes are born on arms,
but in few species the lobes are coalesced as one. Garay proposed the new genus Apatostele for the ones having a confluent stigmatic lobe, but this proposal has not been accepted.
In many Stelis the outer side of the petals have a gelatinous texture, where the opaque inside gives a higher contrast to the superimposed shiny stigmatic lobes, which are the key center of attraction to the pollinator, the place to deposit the pollinia.
The opaque borders of the stigmatic lobes are often enhanced with a colorful contrast to the shiny inner surface.
Another very notorious feature is the striking and contrasting color of the anther cap, which is apical and clearly predominates in the center of the flower.
The anther has a very light colored tip, which enhances and almost superimposes the exposed pollinaria, which resembles a drop of honeydew produced by aphids.
It appears that in many Stelis the brightly colored ornamenta is designed for the insect to go straight for the center to the pseudonectar at the tip of the anther,
where the sticky, crystalline, bubble-shaped pollinaria would immediately adhere to the pollinator.
In most cases, the glenion visually enhances the shiny, bubble-like pollinaria located right above this contrasting surface.
I have pointed out several features of the texture and indumenta on Stelis, which have been mostly overlooked in the past as diagnostic elements to differentiate otherwise similar species.
Geographically isolated populations of Stelis argentata anywhere from Mexico down to Argentina, by definition, would not be considered in the Red List as endangered.
If this isolated forest turns to pasture, no ecological harm was done to this apparent non-endangered pan-American species.
Herpetologists have considered it imperative to name geographically isolated populations of frogs, that otherwise appear to be of the same species, as different species,
just to make certain that these populations obtain the required conservation status and care.
The opposite happens with most orchid taxonomists, who prefer to lump previously accepted species into synonimia, mainly because the drawings of the lip appear to be the same, while ignoring the shape of other parts of the flower, the variations of texture and the indumenta. The opposite happens with most orchid taxonomists, who prefer to lump previously accepted species into synonimia, mainly because the drawings of the lip appear to be the same, while ignoring the shape of other parts of the flower, the variations of texture and the indumenta.
Adam Karremans, in his study of Stelis and its relatives, has discussed the phylogenetic informativeness of the most commonly used morphological characters in depth. To quote Dr. Luer, someone is finally taking a good look at the trees in the forest.
It is a very difficult task to structure the various possible branches of the evolutionary tree of Stelis, one of the largest monophyletic genera in the plant kingdom.
Main difficulty is that almost all collectors avoid or turn down Stelis, because they are so common and, at first glance, are alike. The result: at least half of the Stelis have not even been discovered or described yet.
If most botanist and hobby collectors just refuse to collect them, they are even less willing to make a herbarium with the required pickled flower in a fluid that will preserve them, but without dissolving the extra cellular materials or mask the various textures with glycerin.
Of course, to get to know Stelis, it would be imperative to grow them ex-situ to study fresh material.
Also, to fully understand the phylogenetics and epygenetics of Stelis, it will require the whole genome sequencing,
Research will have to take into account phylogenetic error, hybridization, horizontal gene transfer, gene duplication and extinction, introgression of chloroplast from one species to another, orthogenetic macro-mutations in multiples of four and pollinator convergence.
It would also help enormously to discover the pollinators and find out what attracts them to the various mechanisms offered by the Stelis
Unfortunately there will be little time left to do all this, as most insects and Stelis will soon be extinct.
There were about 100 known Stelis for Ecuador 30 years ago; Dr. Luer has described since 350 more, of which I co-discovered over 300 and I expect at least another hundred to be discovered in Ecuador in the near future.
The Stelis of Ecuador represent about half of the known Stelis, which grow from Mexico down to northern Argentina.
The forests in Colombia, Peru and Bolivia are quite similar to the ones in the Andes of Ecuador. The combined surface of these three countries is 14 times larger than Ecuador.
If these countries contain only 30% the abundance of Stelis in Ecuador, one could expect another 2500 species to be discovered.
Additionally, if taxonomists insist to include twenty-two other closely related genera, like Crocodeilanthe, Dracontia, Umbraticolla, Effusiella,
Anathallis, Acianthera, Triuria, Pabstiella, Pupulina,
Elongatia, Physothallis, amog others, as Stelis sensu lato, than we might have to eventually deal with, who knows, 5000 species?
Most of the Stelis are narrowly endemic and their conservation status may be considered vulnerable to critical endangered.
If it takes major efforts for orchid specialists to collect Stelis, it certainly will be a daunting task to expect orchid hobbyists to own representative collections of Stelis.
Hence, in –situ and ex-situ conservation looks dire to the Stelis population, where many will become soon extinct, some never having been named, where we will never know they ever exited. These intriguing plants are easy to grow, are very floriferous and quite attractive. We should make an effort popularizing them and rescue as many as possible in cultivation. I invite you all: lets GO STELIS!!! Thank you.