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.
The key characters in Stelis section Humboldtia are the unequal sepals with the lateral sepals variously connate into a concave synsepal.
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 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.
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.
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.
Few years back, I had an exhibit of macro photography of orchids enlarged to 5 meters height in the Appleton Museum in Ocala, Florida.
even if some of these populations are otherwise quite different and grow several hundred kilometers away from each other.
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.
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.
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.
others are covered with what appears to be a thin coat of extra-cellular wax, which scratches off easily.
The pubescence may be located along the margin, where these hairs might just prevent crawling insects to enter the flower.
A few Stelis exude a very strong, often very unpleasant odor, which might be one type of fragrance possibly produced by pubescent glands.
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.
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.
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,
Rarely, from the center of the acuminate tip of the petals two barbell-like fingers protrude out horizontally,
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.
In a few Stelis the inner surface of the petals extend outwards and usually have a coarse opaque texture.
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.
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,
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.
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.
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,
In most cases, the glenion visually enhances the shiny, bubble-like pollinaria located right above this contrasting surface.
Geographically isolated populations of Stelis argentata anywhere from Mexico down to Argentina, by definition, would not be considered in the Red List as endangered.
Herpetologists have considered it imperative to name geographically isolated populations of frogs, that otherwise appear to be of the same species, as different species,
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.
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.
Of course, to get to know Stelis, it would be imperative to grow them ex-situ to study fresh material.
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.
Unfortunately there will be little time left to do all this, as most insects and Stelis will soon be extinct.
The Stelis of Ecuador represent about half of the known Stelis, which grow from Mexico down to northern Argentina.
If these countries contain only 30% the abundance of Stelis in Ecuador, one could expect another 2500 species to be discovered.
Most of the Stelis are narrowly endemic and their conservation status may be considered vulnerable to critical endangered.
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.