[Taxacom] Hypothesis: How Nothofagus rafted to New Zealand

John Grehan jgrehan at sciencebuff.org
Sun Dec 24 11:09:50 CST 2006

Fred makes a very good observation. Biogeographic is certainly about
probabilities. But what kind of probability may be less than obvious.
Darwinian dispersalist looked to probability as a function of means of
dispersal and one will find in the literature estimates along the line
that if an organisms walked x distance in one day, they multiply that up
by years or millions of years it is possible that such means of
dispersal did indeed effect a migration over vast distances, even around
the world. All it took was sufficient time. But if means of dispersal is
not correlated with biogeographic pattern (which is Croizat's contention
as an empirical falsification of Darwinian biogeography [and it must be
mentioned that Croizat's panbiogeography is a unique empirical test of
Darwin's theory of evolution])  then probabilities are not an essence of
the organisms alone, but its spatial context. Croizat (sorry to name the
'father' but leading Darwinian theorists do it all the time without
rebuke) suggested that tracks represented averages of dispersal as an
outcome of such probabilities. So I would agree with Fred that
probabilities are important, but the spatial context for estimating such
probabilities must not be overlooked.

John Grehan

-----Original Message-----
From: taxacom-bounces at mailman.nhm.ku.edu
[mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Frederick W.
Sent: Sunday, December 24, 2006 11:37 AM
Subject: Re: [Taxacom] Hypothesis: How Nothofagus rafted to New Zealand

Curtis Clark wrote:
> On 2006-12-23 20:03, Ken Kinman wrote:
>>     My hypothesis is that one (or more) Nothofagus cunninghamii trees

>> rafted to New Zealand carrying on their branchs both their own fruit 
>> and their unique fungus Cyttaria gunni.  The tree or trees could have

>> been dislodged due to land slides, massive floods, or even a 
>> tsunami---pick your favorite disaster.
> This is not a hypothesis, since it's not testable. It's evolutionary 
> "tall tales" such as this that give the panbiogeographers ammunition.

* isn't this the crux of the dispersalist/vicariantist
(panbiogeographer/Darwinian) discussion: does one rule out dispersal
events of low but finite probability, just because it's hard to
corroborate their historical occurrence?

Ken does suggest a test for his "emergent drift" hypothesis: "look into
mosses and insects... No telling what all a floating tree could have
carried over." Maybe the biogeographer's job is to understand how those
low annual probabilities add up over millions of years, and how they
affect other events of higher intrinsic probability?

            Bishops Mills Natural History Centre Frederick W. Schueler,
Aleta Karstad, Jennifer Helene Schueler
       RR#2 Bishops Mills, Ontario, Canada K0G 1T0
    on the Smiths Falls Limestone Plain 44* 52'N 75* 42'W
      (613)258-3107 <bckcdb at istar.ca> http://pinicola.ca
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