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Posted by WW on October 19, 2002 at 12:27:50:
In Reply to: Re: Taxonomy is a matter of evidence...most of the time posted by Langaha on October 19, 2002 at 07:17:09:
::We would see more resolution *within* the three main groups of the Elaphe obsoleta complex - however, many of the ssp. would still go at right angles across the distribution of the three mtDNA cladews, e.g., traditional "E. obsoleta obsoleta" (and some of the others, I believe, but I don't have the paper in front of me at the moment)- it is very hard to see how further resolution within the three clades could recover the validity of this form.
:You are also probably correct here. My point is that, with more molecular characters, I bet that we would see population structure "within" each of their identified clades (i.e., FL specimens would group with other FL specimens instead of with those from far NE localities).
: Then wouldn't this overlap with "some" traditional ssp? It's obvious that you and others do not want to use ssp (and I do not either for some appropriate examples), but what would we then call these populations, nothing? This is one question everyone is avoiding in my previous posts.
Well - either they are independently evolving entities, or they are not. If they are, they are species, if they are not, then I would not give them recognition at any level. This is testable by microsatellites or judiciously used morphological methods.
: And with sampling the Appalachian Mountains (AM) and valleys and to the SW where we believe gene flow exists, I bet that there would no longer be "distict clades" as their "barriers to gene flow" would completely break down.
The mtDNA clades would still exist - very high levels of divergence in the mtDNA of E. obsoleta has been demonstrated, and is not going to go away with more data. The question that would be resolved is, how wide is the zone in which both mtDNA clades overlap geographically, and what happens to nuclear markers in that region - how much genetic exchange is there really. Like you, I rather suspect it is substantial, but that's pure speculation. On the other hand, given how common roadkilled E. obsoleta are, it should not take too much effort to get a decent sampling regime together and do the work - sounds like a pretty good MS project from where I am sitting.
: This is already evident at the Apalachicola River. There is no barrier here, in fact, many of us have seen E. obsoleta swimming across the river and they're commonly found on trees lining both sides. How can these be separate sp? The black phenotype probably did not evolve independently 3x, as this phenotype is also found S of the AM range extending to the north. However, mtDNA quite clearly illustrates that as glaciers retreated E. obsoleta migrated northward along each side of the AM, but gene flow still exists. Like many systematists, I don't believe these "populations" are different species.
I agree that they have not been demonstrated to be different species. More work is needed.