[Taxacom] Hypothesis: How Nothofagus rafted to New Zealand

John Grehan jgrehan at sciencebuff.org
Tue Dec 26 08:50:40 CST 2006

> 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
> 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
> 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
> 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
> 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
> of
> Nothofagus from Tasmania or adjacent Australia, and falsification of
> vicariance hypothesis would make even such survivors' continued
> 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
> I
> haven't considered; or (2) very recently by human introduction, which
> 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
> 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
> > > trying to do.
> >
> >Dispersal is specifically not falsifiable, since there is no
> >evidence that would rule out dispersal. Vicariance *is* falsifiable,
> >the sense that a vicariance event would be expected to affect many
> >and so one can develop an area cladogram from the congruence of
> >organismal cladograms and areas. Any phylogeny that does not map to
> >area cladogram is not likely to have resulted from the same
> >events. Dispersal is one alternative. (This is historical
> >in a nutshell, btw.)
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