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RE: C. bottae taxonomy

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Posted by: CKing at Thu Nov 27 11:14:10 2008  [ Report Abuse ] [ Email Message ] [ Show All Posts by CKing ]  
   

>>CK,
>>Concerning your point #2: You may recall that Javier suggested that a break occurred in the distribution of the boa in the area of Mt. Lassen National Park and thus indicated the two subclades had an allopatric distribution. New information suggests that no such break in the species' distribution occurs in the region of Mt. Lassen for the following reasons: >>

Their conclusion was scientific because it was based on the available evidence at the time. If and when the available evidence changes, then the theory must also change. I have no problem with the provisional nature of all scientific theories.

>>1) Two samples of the Northwestern subclade occur well south of Mt. Lassen in northern Butte County and almost due west of where a specimen tested by Javier near Quincy aligned with Sierra Nevada subclade. Butte County adjoins Plumas County to the southwest. Three other samples tested from southeastern Butte County align with the Sierra Nevada subclade. That is, both subclades occur in Butte County with continuous suitable habitat connecting the two regions. >>

Yes, and according to what you said about the mtDNA of these samples, they belong to the Northwestern subclade, not the Sierra Nevada subclade. That is almost the reverse of the situation seen in Lampropeltis zonata. In L. zonata, the mtDNA haplotype that are found in this region happened to be L. z. multicincta, the Sierra Nevada Mountain haplotype, not L. z. multifasciata. In fact, L. z. multicincta was so successful that it swarmed the previously arrived L. z. multifasciata in Oregon and Northern California (north of the S.F. Bay). There is but one single sample with the L. z. multifasciata haplotype found in Rodriguez-Robles' paper, and it was sample 31, found in the area of Ashland, Jackson Co, Oregon.

That shows that both L. zonata multifasciata and Northwstern clade C. bottae, despite migration along the coast earlier their the Sierra Nevada conspecifics, were both unable to invade the Sierra Nevada Mountains, leaving this mountain range free for the invasion by L. zonata and C. bottae from Tulare County. The question then becomes: what barrier was presented by nature that had successfully prevented both L. z. multifasciata and C. bottae (Northwestern subclade) from entering the Northern Sierra Nevada? This question requires further investigation.

It seems that whatever barrier may have existed, it is now gone, because L. z. multicincta was able to traverse it and migrate north and west beyond the Sierra Nevada Mountains, to reach not only Washington but coastal Oregon, and Northern California from Sonoma County north to the Oregon border. And this migration was so successful that it swamped the pre-exisiting L. z. multifasciata haplotypes, leaving L. z. multifasciata represented by a single locality in the sample. Phenotypically, the snakes in this broad contact zone still exhibits some traits of L. z. multifasciata (e.g. the wider red bands). L. z. zonata is apparently little more than L. z. multifasciata x L. z. multicincta minus the red snout of multifasciata.

Turning our attention back to C. bottae, we don't see any evidence of the Sierra Nevada subclade in Oregon, Washington or in coastal California. The success of L. z. multicincta has not been duplicated by Sierra Nevada subclade C. bottae. Instead, the latest data shows that Northwestern subclade C. bottae made it all the way to the northern edge of the Sierra Nevada Mountains. Why the difference? Is it possible that the Sierra Nevada boas are poorly equipped to compete against the Northwestern subclade except in the higher elevations of the Sierra Nevada Mountains? What then accounts for the tremendous success of L. z. multicincta? These are fascinating questions that invite further investigation.

>>2) As mentioned above, in Javier's study, the one sample he tested (and overlooked in his treatment of the subclades) from just east of Quincy in central Plumas County aligned with the Sierra Nevada subclade. An additional sample in the new study just west of Quincy also aligns with the Sierra Nevada subclade.
>>However, two samples in extreme northwestern Plumas county just northwest of Chester align with the Northwestern subclade. Here again, we have both subclades occurring in Plumas County with suitable boa habitat occurring throughout that region.>>

Fascinating. It appears then that the Northwestern subclade has indeed invaded the Sierra Nevada Mountains. But again, why? Why hasn't the Sierra Nevada subclade successfully migrated into Northwestern subclade territory? It appears then, from analyzing the mtDNA haplotypes of both L. zonata and C. bottae that there is no current or recent barriers to migration of either species between the Mt. Lassen region and the Sierra Nevada Mountains. Therefore one must look for biological reasons for the differences in the success of the Sierra Nevada populations of C. bottae and L. zonata.

>>3) The two samples from northwestern Plumas County plus two specimens found and tested from extreme northeastern Tehama County are in the area where a break in the species' distribution was support to occur. The two Tehama County specimes also align with the Northwestern subclade.
>>
>>4) This summer, a biologist with the CDFG observed a specimen on a road located at the east central side of Lake Almanor. The locality of that specimen cuts the distance about in half between the specimens near Quincy and the specimens northwest of Chester thus adding support to the likelihood that the two subclades are at least parapatric and more than likely sympatric. It makes no difference to which subclade that specimen would align.>>

It is now clear to me that the Northwestern subclade has successfully invaded the Sierra Nevada Mountains, and judging from the lack of Sierra Nevada subclade specimens in the Mt. Lassen region, the Sierra Nevada subclade is being driven south by the Northwestern subclade. Give it some time, perhaps a few tens of thousands of years, or perhaps a couple of million years, and we may see no trace at all of the Sierra Nevada subclade haplotype within the Sierra Nevada Mountains. A conservation biologist of the future may need to designate the Sierra Nevada subclade as a threatened or an endangered species.

>>But I agree that in spite of a few glitches, the paper by Javier was an exceptional contribution to our understanding of the species.
>>
>>Richard F. Hoyer

I agree. Rodriguez-Robles' mtNDA studies are consistent high in quality. The same cannot be said of some of the molecular studies I have seen from other researchers.


   

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