[Taxacom] Hypothesis: How Nothofagus rafted to New Zealand

buyck at mnhn.fr buyck at mnhn.fr
Tue Dec 26 12:40:21 CST 2006

Hi to all...I have been following this discussion with a lot of interest but
since I am not at work, I don't know if this mail will reach the Taxacom list.

it seems to me that you all forget one thing. Nothofagus has no roots...it has
mycorrhizas..that is : it is obligatory symbiotic with certain groups of
basidiomycetes (Fungi) that are mostly very specific in their relationship.
Discussing Nothofagus without considering the whole functional entity (fungus +
host) is discussing artefacts....Nothofagus can not establish without its
symbiotic fungi... nor can any of the other Fagacaeae for that matter.
Botanists should consult mycology much more often....and although Cyttaria has
been mentioned, a parasite can be transfered by birds ....root symbionts can
not however.

Considering the whole entity considerably narrows down the dispersal
possibilities....human dispersal can be ruled out safely....since it does not
allow for the gradual development of specific fungal symbionts for the
individual Nothofagus species....and rafting seems the only acceptable
dispersal hypothesis left if vicariance is not the explanation (birds can not
bring the symbionts across)

Unfortunately, we don't know enough about the fungi for the moment to propose a
well supported hypothesis for Nothofagus, but this is one of my fields of
investigation for the moment. One author that discussed the topic more than 20
years ago is Pirozynski (1983 if I remember correctly).

So the brainstorming part is not entirely over yet ...


Selon Ken Kinman <kinman at hotmail.com>:

> John Grehan wrote:
>     >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,
>     Actually that is just the first step in my methodology.  Brainstorming
> all the different possible scenarios, and then seeing whether lines of
> evidence from other organisms fits any of those scenarios better.  If lots
> of organisms show similar patterns supporting a dispersal scenario and
> they contradict a vicariance scenario, then I would say my intuition was
> correct.
>      If those lines of evidence fit a vicariance scenario, then I'll cry
> "uncle" and congratulate John Grehan on his insight.  Vicariance almost
> certainly played a major role in the evolution of the Nothofagus faunas of
> South America, Antarctica, and Australia, but the relatively early
> separation of New Zealand makes me strongly suspect Cenozoic dispersal from
> Tasmania for Nothofagus and its parasites.  We shall see.  The brainstorming
> part is over, and now the more difficult task of gathering various lines of
> evidence, both morphological and molecular (and seeing if they contradict or
> support vicariance).
>     ------Cheers,
>               Ken Kinman
> P.S.  I am still in the brainstorming stage on the question of the northern
> Nothofagus group (New Guinea, etc.).  It has been suggested that lack of
> Cyttaria might indicate it split off first from other Nothofagus groups, in
> contrast to other evidence indicating it was more phylogenetically derived.
> I think I'll keep my "imaginings" on that subject to myself for now (as I am
> sure some people probably think this thread has already gone on too long).
> :-)
> _________________________________________________________________
> Dave vs. Carl: The Insignificant Championship Series.  Who will win?

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