Real species and ideology
Wed Apr 21 03:21:44 CDT 2004
----- Original Message -----
From: Richard Pyle
Subject: Re: Real species and ideology
> It is often a non-trivial task to distinguish between two
> subspecies separated by a morphocline, on the one hand, and two species
> separated by an area of introgressive hybridization, on the other, but
> genetic tools can often be brought to bear to sort out these issues.
How would you distinguish the two separate patterns (morphocline of
subspecies vs. introgressive hybridization) -- even with the best of genetic
tools? Indeed, is there anything fundamentally different between the two
patterns, other than our artificial imposition of the rank "species" in one
case, and "subspecies" in another?
This gets right to the heart of my original question to you, about defining
the terms "real" and "artificial" in an evolution/species context, and in
supporting one perspective over the other. This thread has taken a
different direction than what I had hoped it would, but the above quote from
Curtis brings it back to what I'm most interested in understanding.
The song said, "Don't mess with Mister In-between"... well, something like
that. Clines are often an illusion in my experience. Refugia and
biogeographical isolation and suture zones reveal that many so called clines
= blend zones are actually tension zones where two once separated subspecies
are now in contact - usually for the first time in their several thousand
year separate evolution from long gone ancestors. Thus, I look at the
reproductively "stable" regional populations (subspecies or species) and
discard the in-betweens (populations or hybrids) OR see them as buffer zones
maintaining the phenotypes (subspecies) or genetic integrity (species) of
the taxonomically delineatable segregates.
If I were looking at the Missouri River and then the Mississippi River I
would see two rivers. Then I could go to where the Missouri flows into the
Mississippi and at the junction (blend zone) try to figure out where one
stops and the other begins - and then expand that intellectual exercise
until I have denied the existence of both the Missouri and Mississippi.
(Perhaps the Mississippi is flowing into the Missouri - perhaps both end and
a third new river begins.) Not seeing the forest for the trees. If it-a
been a snake it would-a bit me. If we major in minors (clines, hybrids) we
will not be able to delineate anything - things that within the boundaries
of their own "kind" are not that hard to see and put a name to.
And in other instances, bringing in the genetic tool only makes it worse by
rendering a false positive.
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