>>CK,



>>But from the current known distribution of the two major clades, it might seem that the Northern Clade arose from (budded off) from the Southern Clade south of the current distribution of the latter clade ----- perhaps even in Baja Calif. On the other hand, is it possible that the Southern Clade is younger and budded off the Northern Clade or that the two clades split off of some extinct parent type?>>



Hi, Richard. I apologize for rewriting my response to this one point, but I would like to address it in greater detail than I did originally. The following paper claims that Baja California was connected to mainland Western Mexico 4-5 million years ago.



http://www.pnas.org/cgi/reprint/97/26/14017



As I pointed out in another response, fossil C. bottae is known from Washington State about 3 million years ago. Depending on how long it took Baja California to arrive at its present location, there may not be enough time for the rubber boa to have originated in Baja and then for Baja to reach its present position, while leaving enough time for it to reach Washington State. 4-5 million years also appeared to be much younger than Rodriguez-Robles' estimate of the age of the Rubber Boa as a species.



Of course the southern and northern subclades once shared a common ancestor, therefore making both subclades the same age. However, this common ancestor is almost certainly a small morph snake, since the small morph phenotype is found in both lineages. To assert that the large morph is ancestral would require a reversal in evolution: i.e. large morph ancestor -> small morph intermediate -> large morph Northwestern subclade. Of course reversals are possible, but most systematists prefer not to assume that it has happened unless there is specific evidence to support it. Since there does not appear to be any good reason to believe there was a reversal, the likely common ancestor of all rubber boas would appear to be the dwarf morph. As such it is assignable to umbratica, since this lineage appeared to have changed very little since it evolved. Hence I believe budding, in which the northern subclade budded off a small isolated population of the southern subclade, seems more likely than splitting, in which two populations of about the same size diverged from each other and from a common ancestor that is unlike either subclade but is now extinct. Budding of course would create a paraphyletic umbratica. Since cladists dislike paraphyletic taxa, they would much prefer to believe that splitting was the process which had created "C. bottae" and "C. umbratica." Nevertheless, it would be difficult to fathom a common ancestor of the northern and southern subclades that is anything other than a small morph population that is virtually indistinguishable for either the Kern County small morph boas or umbratica in Southern California. That means it would appear to be fitting evidence into cladistic dogma to claim that the SRB and the norther populations evolved through splitting instead of budding.



PS I posted several different messages that mysteriously disappeared a few hours later. One of these concern the distribution of C. bottae near Lassen National Park. The Calif. Acad. of Sci. has conducted some recent surveys in this area, and it appeared that there are boas both north and south of the park, with the distance between the northern locality and the southern locality separated from each other by a mere 15 miles or so.

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