Posted by:
RSNewton
at Sun Oct 5 00:42:32 2003 [ Email Message ] [ Show All Posts by RSNewton ]
I don't believe DNA study is going to tell us whether two populations are the same species or not. Two populations of the same species form a clade; two sibling species also form a clade. The DNA results for both situations are identical. In some cases DNA data may even mislead. Suppose for example that A is a paraphyletic ancestral species and B is the descendant species. The mtDNA of B may be closer to the population of A from which it evolved than this population is to other populations of A. In fact, B and its parental population in A may form a crown clade, with other populations of A as the basal outgroup! Yet all populations of A are able to interbreed with each other whereas B may not be able to interbreed with its own parental population in A. A naive molecular systematist may group B with one population of A as a single species!
To determine whether two isolated populations represent two populations of the same species or two species, one must scrutinize all aspects of their biology which may present potential obstacles to interbreeding, including for example karyotype, mating behavior, hemipenial morphology, and ecological niche. A population that is nocturnal and desert dwelling is probably not going to interbeed successfully with another population that is a diurnal woodland dweller. A hybrid between the two will most likely not be well adapted enough to suvrive in either type of environment. If Australian populations of Chondropython are only slightly different ecologically than other populations, then subspecies may be recognizable. If the ecological differences are as great as that between diurnal woodland and nocturnal desert dwelling, then perhaps speciation may have occurred.
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RE: Australian Green Pythons - DNA Study Needed - RSNewton, Sun Oct 5 00:42:32 2003