In Orchid List Digest (17228) Oliver Sparrow
As my limited understanding of continental drift has it, the Lauresian/ Gondwanan complexes split apart when only the most primitive flowering plants had evolved. How, then, are there such distinctive regional orchid flora, particularly when we know how rapidly orchids evolve when - as in Papua, or Kinanbalu - they are given only a dozen or so million years to do so and a set of brand new ecological niches?...OSWay cool question. :-) I'm not an evolutionary biologist, but I once fondled a first edition of Chuck's "The Origin of the Species", and my undergraduate trauma was that of a geologist, so I'll give it a shot.
Let's start out with the fact that the orchidaceae is broken into many groups, some of which I am completely incapable of pronouncing unless I stub my toe in a particularly painful manner. Most of these groups (most, now- don't go jumping down my throat) are geographically isolated, or have other peculiarities that restrict their range. How they come "to" these areas is hardly a mystery; belonging to the microspermae, the orchids have very tiny seed, and are capable of traveling great distances which endears them to landing in places so obscure that even Jeopardy! hosts have never heard of them.
By way of example, I just performed a quick assay on some Vanilla planifolia seed I received this week; fresh, washed seed weighs about 28 micrograms (28 MILLIONTHS of a gram) per seed, or about a million to the ounce. Some oncidium and vanda seed approaches the size of a fine powder, Vanda tricolor looks very similar to chile powder, and Angraecum sesquipedale is even closer.
I suspect the "proto-orchids" that later diversified and colonized all around the globe (save for the Antarctic) must have believed in the security in numbers, and that their seeds were sent to the far corners of the globe by wind, birds and perhaps other routes yet to be identified. Once they landed, they were given geographic isolation to develop into genera that were closely related such that they "looked" similar, and can today be artifically hybridized "between genera". Fantastic! Few would confuse most "traditional" cymbidiums with grammatophyllums, but they can (and do) make fertile progeny, that belong to the artificial genus Grammatocymbidium.
This is highly unusual in the plant world (i.e., being able to make fertile progeny between genera), and we have used this to our great advantage within the orchidaceae for hybridizers bringing color (like reds from Sophronitis) to larger flowers such as those of Cattleya. Still, we are unable to make hybrids between far-ranging groups, such as oncidiums and cattleyas (to the best of my knowledge).
I digress, but the point is made: either something allows for intrinsic free-lance transgeneric hybridization in the orchidaceae, or they are more closely related than we suspect. I'm not sure what the taxonomists have to say about this issue ("I'm not a taxonomist, and I sure as hell don't play one on TV")... Guido? Anyone else?
From THIS, it's not too much of a jump to see how tiny, isolated colonies in, say, the foothills of Ecuador could form tight niches of plants that may or may not intergrade, and form fertile species. The genus Pleurothallis has over a thousand species; is this chance opportunity, or simply that they have tried to fit the different niches that they fit into?
We find HUNDREDS of orchids with limited range, of which one of the finest examples is that of the *heh* Ecuadorian species Epidendrum ilense, which is now known only from cultivation; salvaged from three live plants on a classic slash-and-burn operation, the plant lived only in one tiny little valley and was wiped out in the wild. (Some now refute this; reports from a bromeliad collector relayed to me by chance state that it MAY still survive in an least one more refugial colony elsewhere, but no collections were taken, so we have to view this at face value).
So; what we see now (after about 150 years of experience with the tropical orchids, most of which revolved around kill them "en masse") is a very narrow slice of how orchids exist in the wild. Perhaps orchid species are fragile, ephemeral constructs, as part of a family whose adaptations are remarkable (witness the pseudocopulation orchids, but don't let the kids see! Yeek!).
Gramatophyllum. The new world almost failed to invent the monopodial...OSI'm not sure what you mean here; New World southern, perhaps. Those of us here that shopped at the "Banana Republic" to get our fair share of khaki clothes are familiar almost exclusively with monopodials (cyps, etc.). Ditto with Phrags down south.
This fits poorly with my understanding of the timing involved in continental splitting. It also raises the issue of how South American species in the Cymbidium group came to be there. Seed in the wind? Comment welcome...OSLook at it this way: continents, like islands, have a certain number of species that may arrive periodically, some of which expire horribly and others that thrive. Occasionally, some may become successful enough to form their own species, and even their own genus or sub-family. These latter two are what cause the great dilemma, and it seems likely that they are due to transfer of viable plants that succeeded wonderfully a long time ago, and are still closely enough related such that they can interbreed with other genera, and still produce viable offspring. Go figure.
Three word answer: yeah, the wind. :-)
AJHicks
Orchid Seedbank Project
Socorro, NM
| 
| 
|
|---|---|---|