On Sat, 24 Apr 2004 04:46:35 +0000 (UTC), tomhendricks474{at}cs.com
(TomHendricks474) wrote:


>This seems to support my 
>
>Model for Selection pressure:
>
>As adaptation fitness increases
>stabilizing selection increases
>and directional and diversifying selection decreases
>
>(this part of the model would fit prokaryotes so well
>adapted to aquatic systems and substrates
>
>and vice versa
>
>As adaptation fitness decreases
>stabilizing selection decreases
>and directional and diversifying selection increases
>
>This part of the model would fit eukaryotes adapting
>to the rigors of dry land
>
>Comment?

We have gone around on this one before, several times probably.

Intro biology teaches that selection can be directional, stabilizing,
or disruptive.  In fact, the condition for stabilizing selection is
that the most common or central or modal (assuming a unimodal
distribution of phenotypes) be most fit and the condition for either
disruptive or directional selection is that one or both extremes
(assuming variation in only one dimension) be most fit. In other
words, a highly adapted population will automatically show stabilizing
selection and one that is not already highly adapted with show
directional selection.

Your observation then tends to be tautological.  It does not really
have any explanatory value and therefore is valid, but rather
uninteresting.
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