Subject: Species concept (fwd)
Date: Jul 6 16:53:00 1994
From: Mark Crotteau - CROTTEAU%WSUVM1.BITNET at ARIZVM1.ccit.arizona.edu

I would like to take exception to recent comments about whether species are
real or contrived. The species is in fact the only biological taxon that
has any reality in the natural world. It is the higher taxa or genera,
families, orders, classes, etc. that are constructs of the human mind. I
should perhaps qualify this to say that the biological species concept is
the only one that describes what is actually going on in nature. Having
said this, it is immediately apparent that there are cases where species
do not seem to be as discrete as the BSC would seem to indicate that they
should be. The thing that must be kept in mind here is that species are
constantly evolving. The vast majority of species will at any moment in
time have evolved reproductive isolating mechanisms that will make them
distinct from every other species. For all such species we humans will
have no problem determining which species an individual belongs to,
provided that we have figured out what makes each species unique, and can
manage to distinguish those characteristics in the living bird. The problem
arises when species have not yet evolved isolating mechanisms that work 100%
of the time. The case of the Blue-winged/Golden-winged Warbler hybrids form
a case in point in this regard. The reduced fertility of hybrid individuals
indicates that the two taxa have moved far enough apart that they are no
longer capable of freely interbreeding. Thus they can no longer be viewed
as a single population with unhampered gene flow among all individuals, and
so can not be regarded as a single species. There will be other cases, but
these will be rare where the two populations have not differentiated enough
for us to tell whether they form two species or one. It is only in these
rare instances that we can say that the species concept has no meaning, but
even here if we remember the context of species evolving, the reason why it
makes no sense makes sense.

The other point that I feel compelled to make agrees with the chatter who
argued that what was said about the species concept really doesn't apply to
the question of what can be counted on a big day. Since the observer who
identifies a tern only as far as the genus level has not identified an
individual of a single known species any more that has the person who
positively identifies a hybrid, the definition of species doesn't enter into
it. In both cases the bird in question can be assigned to at one of at least
two different species, and as long as the possibilities do not duplicate
anything already on the list I don't see why it shouldn't count. It seems
very odd to me that you can count a bird that would be countable by every
other criteria except that you can't assign it to a single species.

Mark Crotteau
Pullman, WA