Reptile & Amphibian Forums

...Back in the good ole' days, I can remember when the C. viridis complex comprised of 9 different subspecies....With recent taxaonmic revisions, it appears that the viridis complex is one big mess....I've heard that cerberus is close to being elevated to full species status, and that oreganus already has been...viridis of course will always be viridis, but it appears that the genetic and morphological differences among the subspecies are so divergent that perhaps re-examination of the entire complex is necessary.

What's more, this appears to be a "work in progress", with many different lines of thinking and classification happening at once...Such is the business of taxonomy I suppose....In some cases, recent work has revealed that the designation of subspecies is perhaps unwarranted in certain animals (i.e. C.v.calingus)

What are everyone's thoughts on this? Does anyone even care? I know many people on this board are of significant east coast influence, so perhaps the classification/organization of the viridis complex isn't a pressing concern....I can assure you that many of us here out west have given it much thought and consideration....Then again, there are plenty here that really don't care one way or the other and aren't concerned with taxonomy....

Anyway, I figured this would be a good conversation starter, and if one feels likewise, then participation is encouraged...

-AzAtrox

I came into understanding rattlesnakes after the oreganus shift had begun and I was neevr deeply rooted with viridis. However much of the text I have and still see refers to the western rattlesnake as viridis. I do however want to look more into this change and the possibility of other changes to come (i.e. why they changed it, what the differences were, etc.) IF you look at how widespread the western rattlesnake is could there actually be a different subspecies that is jsut listed as the "northern pacific"? COuld the entire oreganus species be broken into anotehr species much liek viridis was? But with all of the genetic differences being found I think that there should be a distinction and if that means breaking up previous taxonomy then so be it. Granted it can make it difficult to rememebr what goes where in the grand scheme of things.
Personally, it doesn't matter much to me because I wouldn't call myself a scientist or a full fleged herpetologist. I am more of a naturalist and amature herpetologist. I see this mroe as a hobby for myself rather then a living. However I do enjoy the advancements being made and the changes beign made. It is obvious that it was felt that the distinction was needed, and it is just something more that I can learn. And we never stop learning.
One problem that I feel is leading to all of these changes, is not jsut advances in technology to find the differences, but evolution itself at work. I feel that we may be in the middle of some drastic changes but because they are so small now we do not realize it. But with the technological advances we are finding many differences between some of the previously thought "similar" species. One item of curiosity for myself is why do the Western Diamondback, Mojave, and Red Diamond rattlesnakes all have the alternating black and white bands at the tail and none of the otehr species do and yet, all three of these species are in different species catagories? Now granted there is mroe to taxonomy then color and pattern alone. I'm jsut throwing something out there that I don't understand.
SO that is where I am. Much of it is out of order and seems somewhat confusing. I don't even knwo if I really made a point or if I jsut rambled on for three paragraphs. But if I have added anything to the discussion then yay for me. But I assure you, you are not alone in wondering what is next. Maybe it is a west coast thing.
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Kevin
Southern California Organization for Rattlesnake Research and Education SCORRE05@hotmail.com

While taxonomy could all flush down the toilet as far as I'm concerned, it is more because no one can make up there mind more than my lack of interest. Can you imagine that the whole current system might fall and be replaced by one that takes DNA and genetics into consideration! While this new system makes more sense by basing families along a tree (much as people and there family tree, but with millions of years backing it) as opposed to classifying animals by there phenotype and distribution, it almost makes learning today's changes irrelevent. Another pet peeve of mine is the divsion and subdivision, and further subdivision of animals that are all the same except for the tinest of variation withen the range. It's all a race to be able to name a new species in my opinion.

As far as viridis goes, all I know is that I love my prairie rattles. There is them, and then there are the oreganus west of the mountains. There may be more south of the Canadian border, but these are the 2 different snakes that I can see as being different.

So how was my two cents? Worth it?

np

The more info I recieve the more impressed I am. I do see flaws in many revisions using DNA alone. But Douglas et.al are using two different DNA markers in conjunction with morphology, range and venom composition. And remember they also recommend sinking a couple of forms which refutes the idea that they are just trying to do nothing but make new species. For the last 18 years I have pretty much made chasing the viridis/oreganus complex in n. Arizona my main focus. From what I see in range, morphology and behaviours/social interactions I pretty much have to agree with all they propose so far.

And to touch on something that Kevin said about fast changes. He is absolutely correct. After learning some of the results of the DNA analysis from concolor and abyssus snakes in S. Utah and N. Az. I was rather skeptical because it indicated that the completion of Glen Canyon Dam and the resulting effects on teh Colorado River had in a very short time drastically cut off gene flow and isolated populations. I didn't think it possible to happen that fast. However DNA was recently taken from cerbs at three of my densites and the results were very interesting. Cerbs do not become genetically isolated as many believe. Breeding season for cerbs is primarily mid-summer. During summer foraging males may wander up to two miles and females slightly less. It is common for males from one den to encounter females from another during this time. Two of my dens are on one side of a major freeway. Another is on the opposite side. The one on the opposite side is much closer to either of the other two than they are to each other. Yet it has become apparent that the highway has effectively cut off gene flow in a thirty year period(I have known for some time that cerbs no longer cross this highway). The two dens on the same side of the highway are almost identical genetically, the isolated den has diverged considerably. Not enough of course to say that a new species of subspecies is evolving, but enough to show that family lines are completely different. This has really opened my eyes to the possibilities of what may be happening with this complex. For anyone interested, Douglas et. als' preliminary results can be read in "Biology of the Vipers" from Eagle Mountain Publishing. Of cours the work has progressed a gret deal since then, redoing all the old samples and including over a thousand new samples. It's gonna be interesting!

The work by Douglas et al is certainly a big step in resolving the phylogeography of the complex formerly known as C. viridis. As Rich points out, this research used multiple molecular markers, as well as morphology, range, and venom composition. This is an important point in that their results are not strictly molecular. There are differences between these species beyond the molecular level.

Now, the real meat of the argument, which was somewhat touched on in earlier posts, is nested in the definition of species. Previously, biologist have seemed to adhere to the biological species concept (BSC). This complex is hinged on the ability of an individual within a species to procreate successfully with another individual within that species. The work by Douglas et al does well to illustrate that the BSC is certainly archaic, and consideration for dropping it from the scientific lexicon is valid. I think that the C. viridis work detailed therein is important in that it employs a more holistic approach to phylogeny. Looking at morphology, molecular markers, geographic range, and, in this case, venom compisition paints a more accuarate picture of what is going on within this particular complex. Based on these data (Douglas et al), I feel comfortable with their re-working of the viridis group, and look forward to further resolution.

On to the second topic. It is really quite amazing how quickly divergence can occur within a species separated by relatively short geographic distances. You mention the concolor and abyssus work, but this isn't a novel occurrence. I believe it was Gibbs and Weatherhead that showed considerable molecular divergence in populations of S. c. catenatus in Georgian Bay of Ontario. These massasaugas were not neccessarily isolated geographically (no obvious highways, canyons, etc.), but because of the nature of organism, the species had perhaps isolated as a result of behavior (i.e. small species, small home ranges, high prey/mate abundance = no reason to expand the boundaries of the populations). The genetic drift that occurs as a result of various mechanisms is fascinating at the very least.

I think I've echoed a great deal of what you've said, Rich, but you've hit the nail on the head.