"Duane & Judy Erdmann" <[EMAIL PROTECTED]> spaketh thusly:
I am wondering why we don't see more natural hybridization between orchid species. I'd appreciate an explanation and/or some guidance on which reference(s) might shed some light on this. Thanks
I suppose one would have to ask a few questions about the question.
First off, why would one suppose there is little hybridization between species? Just to pull a favorite genus out of the air, how about cattleyas? How many cattleya species or varieties are putative natural hybrids? Cattleya dolosa as a hybrid between loddigesii and walkeriana; Cattleya guatemalensis as a hybrid between aurantiaca and skinneri; C. hardyana as a hybrid between aurea and warscewiczii; kerchoveana with schilleriana and granulosa as parents; and even intergenetics with laelia as one parent and a cattleya as another.
I don't think there's been a great deal of genetic work with most orchid genera to say offhandedly that there *isn't* significant hybridization going on. Euglossine bees are easily confused; they have busy schedules, are generally myopic, color-blind, and have to work two jobs just to keep up with the joneses. Orchids, of course, cheerfully form hybrids with little challenge. Would anyone seriously notice if any of the Spiranthes were natural hybrids? Indeed, some species clearly are, but only once one starts to tiptoe through the chromosomes.
Let's take a step back and look at how many species of orchids there are: 20,000 at a bare minimum, even if the lumpers have their way. Say half of those (conservatively) are tropical epiphytes. That's a lot of plants that live in a highly specialized niche, doing little more than sucking up bird droppings and making purty flowers. The massive number of species in such an environment speaks to something weird going on, particularly when taking into account little things like, oh, some pretty nasty ecological flux in the past 100,000 years.
For example, there are some good data indicating that the Brazilian rainforest contracted to four relatively small chunks of trees something like 60,000 years ago, after which point they expanded to fill the available space. That such an area could be subject to such contraction and dilation while still enumerating a relatively large number of orchid species (about 2300) is remarkable.
There are several possibilities as to how this could come about.
1) The data are wrong; the rainforest has always been there, always been contiguous, or the number of species has historically been high.
2) Orchids make new species really freakin' fast on their own.
3) New orchid species are spawned as a function of natural hybridization, speciating at a remarkable rate after doing the genetic two-step.
4) ??
Number three is probably too controversial on its own. It does explain one particularly nasty question: Why are orchids capable of forming complex hybrids between genera? Simple- they're not too distantly related. Number two doesn't jibe with anything the molecular phylogenists would like to think. It's like buying a car from some guy named "Crazy Eddie." Maybe a combination of two and three and something else. Like pixies. I dunno.
There's a lot more to say about this subject, but I gotta work sometime. Feel free to pooh-pooh everything I've written. It's largely speculative anyway.
Cheers,
-AJHicks
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