[Taxacom] Chile-New Zealand distributions (rafting as a rare alternative)
kennethkinman at webtv.net
Sun Jul 25 21:54:44 CDT 2010
Well, you might not have been on Taxacom long enough to remember
the following, but a few biotic exchanges between Chile and New Zealand
might not have actually taken the longer route (via Antarctica).
Rafting directly across the Pacific from Chile to New Zealand could not
only explain the distribution of Nothofagus (subgenus Fuscospora), but
any number of little critters (insects, fungi, or whatever) that may
have hitched a ride. Interestingly, the subgenus Fuscospora also is a
single species from Chile which resulted in several new species that
radiated once they reached New Zealand.
Therefore, there's not only more than one way "to skin a cat", but
also more than one way a taxon can travel from Chile to New Zealand (and
then speciate). Read my posting to Taxacom on 23 December 2006 (see
below), especially the last paragraph.
[Taxacom] Hypothesis: How Nothofagus rafted to New Zealand Ken Kinman
kinman at hotmail.com
Sat Dec 23 22:03:21 CST 2006
Now back to dispersal (sorry for the rant
against panbiogeographers who overdo the vicariance thing, but Grehan
really provoked me this time and was asking for it in my opinion; I'm
tired of being called a Darwinian dispersalist when I recognize lots of
vicariance too). Anyway, I got to thinking about the additional evidence
that Nothofagus menziesii of New Zealand sharing the same species of
fungi (Cyttaria gunni) with Nothofagus cunninghamii of Tasmania and
adjacent Australia. Not surprising since they are very closely related
members of subgenus Lophozonia.
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.
Nothofagus can float for very long distances,
even ALL the way from Chile to Tasmania (see Barber, 1959, in the
journal Nature; "Transport of Driftwood from South America to
Tasmania"). Therefore, floating the shorter distance from Tasmania to
New Zealand would have been comparatively easy, especially in some of
the strongest ocean currents in the world.
Some of the fruits would have been held
above the ocean surface, so the salt water couldn't ruin them, and
fruits that might not have been fully ripe yet would have provided
further protection to the seeds inside. In New Zealand, the new
population evolved into a new species (N. menziesii) due to the founder
effect. The Cyttaria gunnii fungi apparently didn't speciate (or maybe
it actually has and it just hasn't been shown yet by molecular testing).
But can't rule out Cyttaria getting to New Zealand at a later time
The same rafting mechanism could have
taken Nothofagus gunnii to New Zealand to found the
truncata-fusca-solandri group (all four form a clade in subgenus
Fuscospora). Or maybe a bird could have done this as well, since these
species apparently have no Cyttaria fungi associated with them (although
one could perhaps even imagine a bird eating both Nothofagus
cunninghamii seeds and Cyttaria spores before taking off for--or being
blown to--New Zealand). Next I need to look into mosses and insects
which may be (like Cyttaria) unique to Nothofagus. No telling what all a
floating tree could have carried over with it, and I need all the
evidence I can in order to get Grehan off my back. But enough for one
day. I'm tired.
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