[Taxacom] Nothofagus flying to NZ
kinman at hotmail.com
Sat Dec 23 21:05:04 CST 2006
John Grehan wrote:
>Evidence relating N gunnii tow New Zealand species has nothing to do
with how they got to be where they are now.
How can you possibly believe that such evidence has NOTHING to do with
it? It certainly isn't the whole story, but how can you say "nothing". It
may actually have more to do with it than the timing (which seems to be your
main "beef" with those molecular papers). The timing issue is very
difficult to document, so it is the easiest target to pick on, and you seem
intent on ignoring anything which contradicts your belief that Nothofagus
couldn't possibly disperse over the Tasman Sea and it just HAS to be due to
vicariance. So let's look at the evidence that isn't dependent on the
timing issue or controversial pollen data.
It's not just N. gunnii being closely related to the Fuscospora species
in New Zealand---also, in subgenus Lophozonia, the close relationship of
Tasmania's N. cunninghamii and New Zealand's N. menziesii has a "track" that
is virtually identical. Furthermore, it's not just molecular data, because
morphological evidence show the same "track"---namely Tasmania's fossil N.
cethanica also being closely related to New Zealand's Fuscospora group (too
bad we don't have molecular sequences for N. cethanica to add to the
evidence). Not to mention that this "track" takes us to the nearest
significant landmasses to New Zealand----namely, Tasmania and adjacent
Australia. These are independent, but congruent, lines of evidence
(molecules, morphology, AND biogeography) supporting dispersal across the
I will discuss even MORE evidence (Cyttaria fungi unique to Tasmania's
Nothofagus cunninghamii and New Zealand's N. menziesii) in my next posting
(entitled Hypothesis...). Meanwhile, I have a few more bones to pick with
panbiogeographers. I thought you actually liked having short straight
"tracks" like the one I am drawing from Tasmania to New Zealand, but I guess
insisting that it MUST be vicariance is just too irrestible. Vicariance
actually is often the answer, but let's not get carried away. Let us have a
few dispersal tracks as well.
Now I would like to rant a bit about "main massings". I do not
understand Heads insistence that subgenus Fuscospora has its "main massing"
in New Zealand. Are we supposed to be impressed that it radiated into three
species in New Zealand (and the molecular data indicate they radiated very
recently, so maybe there are only two anyway). In any case, the mostly
likely place for the real "main massing" AND origins of Fuscospora (and
perhaps some of the other subgenera of Nothofagus as well) is in
Antarctica---and the vast majority of the evidence for that is buried under
thick sheets of ice.
He also likes the idea of a "main massing" for the spider genus Migas in
New Zealand. Part of its diversity there is probably due to a radiation
with little competition, and partly because of Dr. Wilton's intensive search
for them in New Zealand (and they are difficult to find). It certainly
doesn't indicate to me that genus Migas originated in New Zealand. Again,
an origin in Antarctica wouldn't surprise me, but extinction there (and
elsewhere) has wiped out most of the evidence.
Panbiogeography simply seems to overestimate the role of vicariance in
New Zealand's biota, and attacks or ignores most evidence that indicates
dispersal. Panbiogeography's main Achilles heel in the Southern Hemisphere
is Antarctica. It is a large and centrally located continent where huge
numbers of taxa originated, but we can't prove it due to the massive (albeit
of most of its former biota, and ice covers most of what fossil record there
might be. I think panbiogeographers are carrying the idea of vicariance TOO
far, and that they "doth protest too much" when they claim dispersal doesn't
play a major role as well (especially in New Zealand).
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