[Taxacom] Dispersal... again

[Kenneth Kinman]

Michael,
      I was a bit surprised by what you wrote below.  Just "ditching"
the center of origin/dispersal paradigm and replacing it with vicariance

is extremely one-sided and short-sighted.  Mayr's "pluralism" in
biological explanation is more even-handed, even if he found more
evidence for dispersal than vicariance (not surprising since birds are
so mobile). 

     That's one reason why he refered to dispersals as "primary"
discontinuities and vicariance as "secondary" discontinuities.  Another
reason is that it makes sense that a species has to disperse to increase

its range (a primary event) before it can become subject to secondary
events (like vicariance).  Your "mirror" analogy makes no more sense to
me than it does to Jason, except perhaps in a small minority of cases.
It does not reflect the kind of paradigm that would have broad
applicability, especially by "ditching" the idea of centers of origin
outright.  

        If you place too much faith in vicariance alone, you are
shutting yourself off from the wide variety of ways nature has had of
increasing its biological diversity.  Mayr practiced pluralism, even if
he did not embrace vicariance as much as you might like.  I don't know
about Hooker's or Huxley's views of speciation, so can't judge if they
were as one-sided as you suggest (largely "ditching" centers of origin
and dispersal).        

      However, I'm certainly not going be like Gaylord Simpson and
suggest that vicarianists (like Croizat) write from insane asylums, but
if they are that one-sided, perhaps I should be like Mayr and simply
ignore them.  As I said before, these threads don't seem to be getting
anywhere.  Banging my head on this brick wall is really giving me a
headache, so I guess I should take a clue from Mayr and just ignore the
wall (which doesn't mean ignoring vicariance, but just vicariance in
excess---all things in moderation is the best policy).            
            ----------Ken                                   
----------------------------------------------------------  

Michael Heads wrote:  
     It doesn't really have anything to do with plate tectonics, it's
the center of origin/dispersal model for speciation that's the problem.
Hooker and Huxley didn't know about plate tectonics, but they made very
important?progress in biogeography. This was?because, to a large
extent, they ditched the center of origin/dispersal paradigm and
accepted vicariance, not?movement,?as the model for speciation.? 
????