Chris Hill wrote:

"Well, I'd say that Bob Zink is a pretty well described by Dennis's phrase
'the most fervid phylogenetic-species proponent' ;-) And I have seen him
argue 'very strongly' that flickers, yellow-rumps, sapsuckers et al should
be considered separate species, even if they freely hybridize all along
their contact zone. It is quite possible,
apparently, to have stable hybrid zones persist for thousands of
generations without any significant gene flow across the zone. If the
hybrid zone maintains itself indefinitely without affecting the different
forms on the two sides of the zone, why should we not recognize the two
forms as distinct species?"


I agree basically with your last statement. But did Bob really argue about
the flickers? The hybrid zone between yellow-shafted and red-shafted is
*huge*, and I can show you breeding flicker specimens from Washington that
show hybrid characters. So many hybrids come into our collection here that
I envision flickers to the north and east of us as one huge hybrid swarm.
Gilded and red-shafted hybridize over a much narrower zone, not surprising
as they are somewhat separated ecologically, and it's also not surprising
that the gilded will be split off from the Northern Flicker. But
separating yellow-shafted from red-shafted--I doubt it.

Chris, I wonder if you would agree with me that splitting is a fad right
now (because of a reassessment of species concepts, rather than
arbitrariness), just like lumping was a fad some decades ago (for the *very
same reason*). Bob Zink and other proponents of the PSC concept, much as I
respect them and their work, are merely pursuing vigorously an alternative
hypothesis that could even be called a "bandwagon," the "truth" of which is
no more apparent than that of the BSC. I suppose we could argue clines vs.
step clines vs. truly independent evolution until the cowbirds come home,
and someone would still have to make somewhat arbitrary decisions as to
what constitutes a species. The AOU check-list committee is now favoring
this new concept in its decision-making process.

Having lived through one "revolution" and now being in the midst of another
gives me some perspective on this. It's not too different in certain ways
from the alternation of Democrats and Republicans in power. I have the
greatest love and respect for science (as I wrote a couple of weeks ago),
but it does suffer from the same frailties as all human endeavors, during
the search for truth. Because there is a strong element of subjectivity,
it's very fortunate that we have the tools of molecular systematics to
provide evidence for genetic distances among populations that would be only
speculative otherwise.

But there are still all kinds of anomalies to cause head-scratching
indefinitely, for example populations that look the same but are
demonstrably genetically different and vice versa. How would these be
treated under the PSC?

You know that old saying ".... but you can't please all of the tweeters all
of the time," so I hope at least some of you tweeters are pleased some of
the time with these somewhat esoteric discussions. A lot of birders are
attending the WOS annual meeting in Spokane, or we'd probably be getting a
bit more response to our dialogue.

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