Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!qt.cs.utexas.edu!yale.edu!cmcl2!panix!pcg
From: pcg@panix.uucp (Paul Gallagher)
Newsgroups: sci.bio
Subject: Re: Coelacanth and Evolution
Message-ID: <1991Jun28.203636.5429@panix.uucp>
Date: 28 Jun 91 20:36:36 GMT
References: <1991Jun14.183157.23713@gpu.utcs.utoronto.ca> <2129@anaxagoras.ils.nwu.edu> <80408@eerie.acsu.Buffalo.EDU>
Organization: PANIX - Public Access Unix Systems of NY
Lines: 30

Concerning sexual isolation and speciation: Ernst Mayr's model of peripatric
speciation, from which the punctuated equilibrium model developed, presents
speciation as occuring when small, isolated populations undergo change.  In
Mayr's model, sexual isolation occurs only afterward, when the changed
population once again comes in contact with the parent population, and
sexual isolation is selected for.  Morphological change 1st, reproductive
isolation later.

However, changes in sexual behavior may have led to speciation.  For
example, sibling species, species so similar as to be almost indistinguishable
from each other, often are prevented from hybridizing only by differences
in courting and mating practices.

Some species originate through the multiplication of chromosomes, by auto-
polyploidy or allopolyploidy, which results in reproductive isolation.
Polyploidy is often induced by plant breeders, sometimes using the
chemical colchicine.  Oats, wheat, cotton, tobacco, potato, banana,
coffee, and sugar cane are all polyploids.

I think the proper term for what's being called "state-space" is niche.
When species converge, the terms "homology" and "analogy" are usually used
to distinguish between similarities that have a similar genetic basis
and similarities which are simply functional or mechanical.

Also, almost all people studying evolution agree that heritable morphological
change has a genetic basis, but that doesn't mean they all become
population geneticists. Most of the living things on earth are identified
and distinguished from other species by gross morphology alone.  Genetic
exams and cross-breeding experiments have been performed on only a small
portion of known species.