[Taxacom] Hypothesis: How Nothofagus rafted to New Zealand

[John Grehan]

> From: taxacom-bounces at mailman.nhm.ku.edu [mailto:taxacom-
> bounces at mailman.nhm.ku.edu] On Behalf Of Ken Kinman
> Sent: Monday, December 25, 2006 10:43 PM
> To: taxacom at mailman.nhm.ku.edu
> Subject: Re: [Taxacom] Hypothesis: How Nothofagus rafted to New
Zealand
> 
> 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).

Why should terrane accretion be limited to the Cenozoic, why not
Mesozoic for which there is geological evidence?

> 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.

Falsification is one thing, imagining falsification is another. There is
no evidence whatsoever that the Oligocene necessarily had any particular
impact on the biota, only speculation. Saying that "the resulting
diversity bottleneck probably eliminated Nothofagus there altogether or
at least reduced it to near extinction levels" is just pure imagination.
Not science.

> 
>      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.

Ken's basic methodology seems to be imagining that vicariance is
falsified, then imagining dispersal is the only probable alternative. No
wonder historical geologists don't take biogeography seriously.

John Grehan

> **********************************
> 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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