bwdmorse{at}twcny.rr.com (Bill Morse) wrote in message
news:...
> In article , 
> name_and_address_supplied{at}hotmail.com (Name And Address Supplied) wrote:
> >tomhendricks474{at}cs.com (TomHendricks474) wrote in message
> > news:...
> >> A genetic textbook says, "Four principal causes of change in the 
> >> frequency of alleles are usually distinguised:
> >> Mutation, Migration, Natural Selection, and Random genetic drift.
> >> 
> >> Yet in the end isn't it Natural Selection that makes the final call?
> >> 
> >> For instance all the mutation, migration, and random genetic drift
> >> won't amount to much if the environment stays the same.
> >> Then convergent evolution happens.
> >
> >Perhaps, but the statement specifically discusses genetical evolution,
> >not phenotypic evolution.  A dolphin might look like a shark, but
> >their genetics will be very different.  And which particular alleles
> >reach which particular frequencies will often depend strongly on
> >forces such as drift.  If the selection coefficient is less than the
> >reciprocal of the effective population size, then drift is expected to
> >predominate.  If mutation is of the same order of magnitude as
> >selection, then we expect a not insignificant genetic load.  Migration
> >is conceptually similar to migration, so an analogous migration load
> >can be influential.
> 
> 
> Well, yes, I think we can agree without fear of contradiction that on average, 
> and as long as we don't try to stretch the analogy too far, migration does 
> bear a remarkable conceptual similarity to  migration :-)
> 
> (I probably won't be the only one from whom you get grief about this).

just you so far

Yes, it should read ". . . conceptually similar to mutation, so . .
..".  Apologies to anyone who got confused over this error.
 
> But if you really mean that migration is similar to mutation, I would expect 
> the load from migration to be significant but less random than the mutation 
> load, in ways that are important to the direction of evolution.
> 

Random in what sense?  The nature and occurence of the mutations may
have a huge random element, but the average genomic mutation rate and
average mutational fitness effect are not expected to change very much
in a decent sized population.  There should be a fairly constant
mutation load at mutation selection balance.  If anything, it will
probably be less random than the load due to migration.
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