[Tweeters] RE: Notes on Cordilleran vs Pacific-slope in Latah,
Nez Perce, and nearby counties - in response to the splitters
highsteppe at icloud.com
Tue Jul 15 07:43:14 PDT 2014
I don't have a strong opinion on the Western Flycatcher split (although, being a "lumper" at heart, my initial reaction is skepticism at the split).
However, someone, (Doug, I think) commented that the DNA evidence was objective, or at least more objective than the morphological evidence. I agree that DNA evidence is more quantifiable than morphology. "Region X of the DNA sequence differs by Y% between population A and B" etc.
But is it better at defining species? Well, maybe, maybe not. There is a lot of disagreement among biologists about that. Some very distinct species may have relatively few differences in DNA, but those differences are so critical (e.g., sequences that affect phenology of breeding) that they substantially affect hybrid viability. On the other hand some unambiguous species may show substantial DNA differences but the differences are evidently are not so critical. The DNA evidence is part of the story, but not the whole story.
IMNSHO, the gold standard for vertebrates (who the heck knows about bacteria and such) is not DNA or morphology, but whether hybrids have reduced viability in the hybrid zone. That sort of thing can be difficult to measure in the wild, but a broad hybrid zone with most of the individuals in the hybrid zone being intermediate between the "pure" populations suggests, to me, that the species should not be split.
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