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RE: C. bottae taxonomy - A new wrinkle

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Posted by: CKing at Wed May 21 01:44:15 2008  [ Report Abuse ] [ Email Message ] [ Show All Posts by CKing ]  

>>As for the issue of allopatry of the subclades, here is something else to consider. Because Javier's closest samples between the two subclades occurred in close proximity to Mt. Lassen, he addressed allopatry in a manner that appears to pertained to that specific region. The authors failed to consider (perhaps were not aware) that the species occurs well east of the Mt. Lassen region into far eastern California continuing across the border into western, and northern Nevada (and beyond). Thus, no explanation exists that would
>>advance the notion of allopatry between the two subclades where they occur far beyond Mt. Lassen. (Hind sight becomes ever so sharp after the fact.)>>

Their data shows that the Sierra Nevada subclade is confined largely to the western slopes of the Sierra Nevada mountains, and the general direction of the expansion of the range (gleaned from the mtDNA data) of this subclade is from south to north. In hindsight, you are correct, they did not consider the possibility that the Sierra Nevada subclade may have expanded its range eastward into Nevada to possibly meet the Northwestern subclade in western and central Nevada. Their mtDNA sample did not address this possibility.

>>For instance, I have examined all voucher specimens from Nevada as contained in the U. of Nevada-Reno collection. There are a half dozen specimens from Washoe county which runs from near Reno north to the Oregon border and adjacent to Calif. Wonder to which subclade or subclades those specimens belong?>>

mtDNA data on these specimens would answer that question, because the 2 subclades have different mtDNA haplotypes.

>> What explanation might be advanced to suggest allopatry of the boas in that region? Or would it be more reasonable to suggest that the two subclades are likely to come in contact somewhere in that region?>>

One possible explanation is that the Northwestern subclade has, for some unknown reason, never been able to gain a foothold in the Sierra Nevada mountains, despite having moved north into Oregon as long ago as a couple million years ago. Perhaps volcanic activity prevented it from entering the norther Sierra Nevada and the arid Central Valley prevented it from reaching the Central Sierra Nevada. The absence of the Northwestern subclade from the Sierra Nevada mountains is well supported by mtDNA data; not one single specimen of the boas of the Sierra Nevada has the mtDNA haplotype of the Northwestern subclade. If the Sierra Nevada subclade is in turn unable to inhabit the arid lower slopes of the eastern Sierra Nevada, then these two subclades would be separated by unsuitable habitat for both subclades.

>>I understand the position that until evidence is at hand, one needs to remain open to all possibilities. Thus, without overlap of specimen of each subclade having been documented, one cannot assert that either parapatry or sympatry occurs between the subclades. On the other hand, two random samples 120 km (or 64 km) apart does not constitute verification of anything. (Persistent aren't I?)>>

You may well be correct that allopatry is an artifact of observation. Sometimes we do forget what Robert Inger once said, and I paraphrase him here: the distribution map of the rubber boa is more likely to be a distribution map of human collectors.

>>Another way of viewing the situation is that exiting evidence gives the appearance or perception of allopatry. From my undergraduate training in wildlife science and experience since, if there is one dictum in science to which I adhere is that since perceptions are frequently in error, they should not be taken (nor stated) as if factual. A year ago March, I published a 'Viewpoint' in the Journal of Kansas Herpetology that deals with that very topic. The title was "The Fallacy of Perceptions" and I gave examples where perceptions by professionals and by state wildlife agencies have been grossly in error.
>>One of the best papers in herpetology that deals with 'perceptions' was published by Whit. Gibbons and titled, "Perceptions of Species Abundance, Distribution, and Diversity: Lessons from Four Decades of Sampling on a Government- Managed Reserve". He describes how one particular species was originally considered to be scarce or rare but over time, was found to be far more common and widespread than originally perceived. >>

Of course, I agree with that. Many species that were once thought to be rare are in fact quite common. It is just that we humans do not know them well enough to know where to look.

>>I can't state for certain that Javier's assertion of allopatry is in error but the application of biological concepts suggest that the odds would indicated his position is likely to be incorrect. As a matter of fact, I don't have problems with conjecture if stated as being an option to consider. My main objection is when such speculation is stated in a manner as if it were factual.
>>Richard F. Hoyer

His theory of allopatry may well be proven wrong with additional data. This is normal practice in science. Nearly nothing is considered unchallengeable objective truth. Even something that seems as solidly supported as Newtons' laws of motion turn out to be in need of revision by the discovery of quantum mechanics. If it makes you feel better, Rodriguez-Robles' allopatry theory ought not be taken as unchallengeable objective truth, but nevertheless it is indeed the best theory supported by the currently available data. Can new data falsify the allopatry theory? Absolutely!


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