Re: [asa] Lab speciation

> (1) Are my remarks re "detrimental, usually fatal" effects of mutations a
> fair assessment of the data - or an expression of ignorance of same?

The vast majority of mutations have no evident effect (though in
theory they are making it easier or harder to evolve particular
changes). Many others have minor effects, either positive or
negative. Others have major effects. Of course, whether something is
helpful or harmful depends on the particular environment as well as on
the exact mutation. Whether a mutation is helpful or harmful also
depends on the starting point. If you want to evolve something new,
then there's plenty of room for big improvements. If you are looking
at a feature that's been functioning for millions or billions of years
in organisms, probably fiddling with it will not create major
improvements in that function. It's the old do-it-yourself
principle-if it ain't broke, don't fix it. (This is also why
organisms that show little change over long interevals of geologic
time do not pose a challenge to evolution-what they have works, and
the evolutioanry pressure is to not change. This also ties into the
balance between more punctuated and more gradual change.)

An additional twist is that some mutations normally have no effect but
do have an impact under certain conditions (usually stress-heat,
etc.). Many proteins that help stabilize other proteins also are
involved in stress response. Alterations can be concealed because the
other proteins compensate, but when the helper proteins are called off
to the front in an emergency, the changes may show themselves.

> (2) How does the finding in the snippet from your post (above) strike
> practicing biologists? Is it remarkable or merely mundane?

> (2a) If remarkable, is it so because it confirms what has been suspected but
> not experimentally open to confirmation, or because it is actually quite
> unexpected?

Being able to keep a project going for twenty years in a poorly-funded
field is somewhat remarkable, though I might sound less cynical if
someone would hire me.

> (2b) If mundane, am I right in thinking there must be OTHER confirmatory
> examples of mutations which are in themselves harmful, but when taken in
> conjunction with other mutations have provided a net benefit?

Yes, plenty, with the major caveat that harmful or beneficial depends
on the environment. One similar study on bacteria gave the bacteria
an energy source they couldn't use, so they would grow little if any
unless they developed the mutation to allow using it. (I think this
involved an induced mutation, disabling an existing gene.) Some
bacteria did have the required mutation. Confusingly, when the new
gene was disabled, the bacteria were able to mutate back more rapidly
than before. Was this Lamarckian evolution in action? No, it turned
out that the bacteria had a mutation in a gene involved in DNA copying
or error checking. As a result, the bacteria had a generally high
mutation rate. That's usually not a good thing, but when you're
desparate for a change, it can be good. Additional examples also
exist of apparently neutral mutations that eventually become important
for a different function.

-- 
Dr. David Campbell
425 Scientific Collections
University of Alabama
"I think of my happy condition, surrounded by acres of clams"
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