Subject: Re: species concepts
Date: Jun 20 09:49:23 1995
From: Dennis Paulson - dpaulson at ups.edu


I agree with much of what David has written about this, but I'd like to
question the comments about "genealogically misleading hybridization," used
as strong evidence against the biological-species concept.

The two examples David is talking about, I imagine, are the orioles, which
he has outlined in the last posting, and the hybridization of Carolina and
Black-capped chickadees, for which molecular data also indicate they are
not each others' closest relatives.

I wonder if it is worth questioning the molecular data. I'm afraid I'm not
convinced, Scott Freeman's dissertation notwithstanding, that Baltimore is
more closely related to Altamira and Bullock's to Streak-backed. In
addition to the fact that Baltimore and Bullock's hybridize fairly readily
where in contact (but not entirely freely, apparently some selection
against hybrids), they seem more similar to one another in just about every
way than either is to their putative closest relatives.

Does Scott make any attempt to clarify these relationships besides the
mtDNA data? If we weren't so enamored of molecular systematics as the
end-all, any parsimonious explanation would still have Baltimore and
Bullock's as each other's closest relative. It's hard for me to swallow
that these two migratory populations converged on one another that much
from an ancestry of two other species that also are rather similar to one
another but quite different from the migratory ones. I would come to this
conclusion even if there were no evidence of hybridization. I should talk
to Scott about this.

The same kinds of comments can be made about the chickadees.

Dennis Paulson, Director phone: (206) 756-3798
Slater Museum of Natural History fax: (206) 756-3352
University of Puget Sound e-mail: dpaulson at ups.edu
Tacoma, WA 98416