[Taxacom] Hypothesis: How Nothofagus rafted to New Zealand

[Ken Kinman]

Curtis,
      That is my main goal, to try to FALSIFY that it was due to vicariance, 
because dispersal seems the most likely hypothesis from my perspective at 
the present time.

     But it seems to me that dispersal is the ONLY alternative to 
vicariance.  In the case of New Zealand, I would say vicariance is by land, 
either by direct connection to Gondwanaland by 75-80 million years ago, or a 
later terrane in the Cenozoic rapidly travelling to and smashing into New 
Zealand (for which there is no evidence whatsoever that I've seen).  
Although Grehan is no doubt correct that Nothofagus had spread to New 
Zealand before 80 million years ago, the Oligocene submersion of much of New 
Zealand and the resulting diversity bottleneck probably eliminated 
Nothofagus there altogether or at least reduced it to near extinction 
levels.  Either way, this would leave New Zealand ripe for a new invasion of 
Nothofagus from Tasmania or adjacent Australia, and falsification of the 
vicariance hypothesis would make even such survivors' continued existence 
there very unlikely.

     Therefore, the only likely alternative is dispersal by two 
possibilities:  (1) natural dispersal by birds, rafting, or something else I 
haven't considered; or (2) very recently by human introduction, which I 
don't dismiss, but I think much less likely.  Are there any other 
alternatives that I haven't considered?  Seems to me that if the vicariance 
alternatives are falsified, we only have two dispersal hypotheses left, by 
natural means or by humans.  Either vicariance by land or dispersal by sea 
or air.  Are there any other possibilities?  I can't thing of any.  So 
dispersal is the only probable alternative to vicariance from my 
perspective.
    ----Cheers,
            Ken Kinman
**********************************
Curtis Clark wrote:
>On 2006-12-24 09:29, Ken Kinman wrote:
> > Dispersal of some kind is indeed a testable
> > hypothesis, and I'm glad to see Fred Schueler understands what I am
> > trying to do.
>
>Dispersal is specifically not falsifiable, since there is no conceivable
>evidence that would rule out dispersal. Vicariance *is* falsifiable, in
>the sense that a vicariance event would be expected to affect many taxa,
>and so one can develop an area cladogram from the congruence of multiple
>organismal cladograms and areas. Any phylogeny that does not map to the
>area cladogram is not likely to have resulted from the same vicariance
>events. Dispersal is one alternative. (This is historical biogeography
>in a nutshell, btw.)

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