My apologies, again, to Dennis and anyone else who might be interested in this topic -- I'm way behind on e-mail. Dennis is correct, of course, in saying that the criterion of interbreeding has its difficulties: that it only works for sympatric populations and that some groups we consider good species often hybridize with one another occasionally. No argument about those matters. But the point I'm trying to make is really not about those matters. I object to using similarities or differences in DNA sequences because the criterion is too blunt a knife or too clumsy a hammer -- choose your metaphor! Two populations may have (Case 1) big differences in DNA sequences that encode proteins with little or no effect on breeding behavior, maybe some proteins of the intracellular machinery that make no difference in outward appearance or behavior and don't affect viability of hybrid offspring; on the other hand, they may have (Case 2) some small difference in DNA sequences that make a big difference in appearance, such as the color of some patch of plumage, so members of these populations don't attempt to breed with one another. Yet by using some criterion of DNA difference, the populations in Case 1 would be judged to be different species while those in Case 2 would be judged to be a single species -- just the opposite of what we would see from looking at the individuals and observing their behavior. Someone wrote -- sorry, I can't get back to the message -- that the DNA of two species of teal (was it Blue-winged and Cinnamon?) are said to be 100 percent identical; yet isn't it obvious to all of us that these ought to be counted as two distinct species? If that's true, it supports my case precisely.

Burt Guttman
The Evergreen State College
Olympia, WA 98505 guttmanb at evergreen.edu
Home: 7334 Holmes Island Road S. E., Olympia, 98503