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Re: Copeing with mammals




On Sun, 28 Nov 2004, MICHAEL HABIB wrote:

>...the idea of "evolving into an occupied niche" has a number of
problems with it.  First of all, it makes character evolution sound like
som e sort of hostile takeover or geographic movement.  Introductions are
some what like this, but character evolution is not.

I'm curious as to the state of sympatric adaptation research.  I thought I
had read that novel species can "invade" from within, that this was more
common than supposed.  Your comments on words such as "ecospace" are
appropriate.  These are clumsy words attempting to describe
unfathomable complexity.  Re this argument, niches are not
clearly delineated units.  They are dynamic.  Who can say what a novel
trait will do in a specific habitat?  Traits _change_ niches. Perhaps the
concept of facilitation is useful here.  One species facilitates the
expansion of another and subsequent trait development in the same
dimension.

Re comments on abandoning small size niche.  Directional selection can and
does work in all directions.  The classic character displacement of
Darwin's finches, leading to smaller _and_ larger beaks...as long as their
is a resource that favors reproductive success, organisms will exploit it.
With Cope's Rule we are asked to accept the idea that organisms favor one
direction over another...this _is_ teleological, right?  Again, I can
accept that there are advantages to being big.  And I accept the
"ratchet".  My problem with the dog paper is that no explanation is
offered for the lack of selection for small size.