Tweeters and obol,

After following the interesting crow taxonomy discussion from a distance,
let me add a couple of comments. I don't have specific information about
the crows, but, as Dennis Paulson points out, Johnston's analysis seems to
be quite clear: that there is a cline between the main crow population
and a smaller northwestern population that was evidently isolated for a
time and was on its way to becoming a distinct species. Some contributors
to the discussion have wondered that no one is doing a molecular genetic
analysis. The question is, what would we look for? In our lab here, we
do research on molecular genetics of bacteriophage, and so, in principle,
we're set up to do all kinds of sophisticated analyses on crow DNA,
assuming we could find a few bucks to buy some of the expensive materials
needed for DNA sequencing, PCR analysis, and so on. (We aren't set up to
do Sibley-type hybridizations.) But how would we do an analysis that
would demonstrate anything not shown by the field observations (voice,
behavior) and morphological analysis of museum specimens? If, for
instance, there is a cline in size through the Washington-B.C. area, then
presumably we would see some kind of clinal change in certain genes over
that range. But what genes, and how would we find them, and if we did
find them, what would it prove? I'm not asking sarcastically; we have a
lot of bright, enthusiastic undergraduates here who regularly get into the
labs and do good projects, and if there were a crow DNA project worth
doing, we could probably find a dozen students eager to do it. But I
can't conceive of a DNA analysis, offhand, that would reveal anything new.
Can any of you?

My second point refers to the issue about species definition and what is
countable. I feel a need to defend the ideal of the biological species
concept and the idea that a species is not just a taxon like all the
others--that a species is not just an arbitrary category of the same type
as genus, tribe, family, etc. The ideal species--and they're certainly
the majority in the animal world, at least--is clearly definable and
identifiable as a set of organisms that share a common gene pool. When a
population reaches the point where it no longer interbreeds with its
parent population, it has become something quite special, a node on the
phylogenetic tree that can live its own evolutionary and ecological
life and start to generate other nodes independently. The trouble, of
course, is that we catch species in the middle of the process, where the
separation isn't complete yet and may never become complete, or where
weird things like rings of subspecies are generated. The crows confuse us
because they're at a stage of just barely separating; as Gene Hunn points
out, the barrier that once separated two populations has probably been
broken down by Euroamerican settlers, and without any genetic isolating
mechanisms the populations are apparently melding back into one. As to
what is countable, I've just sent off a short article to _Birding_
suggesting that part of the answer to the eternal splitting-lumping ballet
is for systematists to formally recognize semispecies and superspecies,
just as species and subspecies are recognized, and then for the ABA--or
whoever else wants to set the rules of the counting game--to decide whether
people should count semispecies or superspecies. Birders would undoubtedly
opt for semispecies--longer, more impressive lists, and more fun meeting
challenges of field identification. So I guess there's a sense in which I
agree with Al Jaramillo--"if you can identify it you can count it"--as
long as the things we're identifying and counting are biological entities
of more status than subspecies and hybrids.

Burt Guttman guttmanb at elwha.evergreen.edu
The Evergreen State College Voice: 206-866-6000, x. 6755
Olympia, WA 98505