[Taxacom] Nothofagus flying to NZ
jgrehan at sciencebuff.org
Sun Dec 24 10:35:08 CST 2006
My comments (John Grehan) are in quotes for clarity.
From: taxacom-bounces at mailman.nhm.ku.edu [mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Ken Kinman
Sent: Saturday, December 23, 2006 10:05 PM
To: taxacom at mailman.nhm.ku.edu
Cc: biogeography at bohm.snv.jussieu.fr
Subject: Re: [Taxacom] Nothofagus flying to NZ
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".
"Because a statement of biological relationship is a statement of biological relationship, not a statement of biogeographic origin".
It may actually have more to do with it than the timing (which seems to be your main "beef" with those molecular papers).
" Yes! I'm glad that is understood."
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.
"Not true. All I have said, and as Heads has pointed out in an extensive review article in Cladistics, is that fossils provide information on minimal ages of fossilization. Nothing more, nothing less. Molecular theorists turn fossil calibrated estimates into maximal or absolute dates whereas all molecular divergence estimates are, like the fossils they are based on, MINIMAL. So they cannot falsify earlier events, only later."
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 Tasman Sea.
"No. They only show that there is a standard track of biological and biogeographic relationships across the Tasman Sea. This is a well known fact, and one identified by Croizat."
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.
"One may have any possibility, and dispersal over the sea in relatively recent times is a known fact. But molecular clocks cannot falsify a vicariance origin. Sorry. That is all I am saying. If there is some empirical demonstration that one or more trans-Tasman relationships are due to dispersal then fine, but molecular clocks do not do that."
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.
"Main massings are empirical entities, so theoretical propositions that the real main massings are somewhere else is purely imaginary."
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.
"Any main massing may be questioned, and its certainly possible for a massing to be an artifact of collecting. But in the absence of such demonstration the massing as it is known is what we have - and regardless of what theoretical reason one may postulate about the evolutionary mechanism."
Panbiogeography simply seems to overestimate the role of vicariance in New Zealand's biota, and attacks or ignores most evidence that indicates dispersal.
"That has yet to be demonstrated. In the recent resurgence of dispersalism dressed up in the respectability of molecular systematics (which is often misleadingly referred to as 'genetic') there are innumerable claims of dispersal and falsification of panbiogeography, but they are all face the burden of making claims of maximal or absolute divergence for data that really can only provide minimal dates."
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).
"Well, I would not contest Ken's right to have this opinion. But what counts in all of this is biogeographic analysis derived from the facts at hand. My contention is that the magical status of molecular estimates as maximal or absolute divergence is an illusory device."
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