[Taxacom] Seed plants of Fiji

[John Grehan]

Tim,

I admire your thinking, but you are doing the same as Karl by letting
geological theory determine your biogeography. I keep coming back to
Croizat. If he took the same line, that certain biogeographic patterns
were not geologically correlated (personally I feel the term vicariance
to be overly simplistic) he could never have generated his novel
geological predictions. He would have just said, like everyone else,
that the Americas are a tectonic unit or area of endemism and so any
trans-Pacific connections could not possibly suggest otherwise. But he
did not, and it turned out he was right about his geological prediction.

Maybe you do not see the current geological theories proposing former
landmasses or island arcs (not necessarily continental) as being viable.
That does not mean the possibility is not viable. After all, Wegener's
model was not seen as viable even though he turned out to be basically
right (except for the Pacific).

If one wants to invoke dispersal all over the place and all over the
Pacific then one has to make up ad hoc explanations for the existence of
extensive vicariism that would be impossible in the face of such
mobility. For example, Coriaria is supposed to have made the Pacific
run, yet the genus shows two distinct vicariant clades, one
Europe-Philippines, the other New Guinea-South America. Similarity,
Metrosideros is supposed to have made the El Ninio run even though all
three clades are vicariant with only an overlapping node at Fiji
(surprise, surprise), and is it just pure coincidence that one of the
clades connects Hawaii with Tahiti? Just like various other Pacific
plants and even marine shorefishes!

As for your Asteraceae group (which group) the Pacific connection is
nothing surprising as it seems quite a few Asteraceae have Pacific
patterns despite having such great means of dispersal. I have shown in a
book chapter that the genus Microseris is entirely congruent with both a
Pacific biogeography, and accretion tectonics, and Heads has done the
same for the Blenospermatinae (which presume you have read.

In answer to your question "How do you explain a distribution of Cook
Islands, Hawiian Islands and New Guinea+ Australia using vicariance?" I
could only ask why do you need to ask this question if you have read the
biogeographic literature on the Pacific? Also, if you understand the
meta-population concept you will understand that it does not matter to
the concept of Pacific evolution in situ and the appearance or
disappearance of local populations - whether on ephemeral or not so
ephemeral islands.

So by all means make your biogeography fit your accepted geohistorical
beliefs, but try not to do what most dispersalists do, which is ignore
the resulting biogeographic incongruence between supposed mobility and
the empirical fact of Pacific vicariism and track congruence. I'll go
back to hitting my head on a brick wall now.

John Grehan


> -----Original Message-----
> From: taxacom-bounces at mailman.nhm.ku.edu [mailto:taxacom-
> bounces at mailman.nhm.ku.edu] On Behalf Of Tim Lowrey
> Sent: Wednesday, November 15, 2006 5:51 PM
> To: taxacom at mailman.nhm.ku.edu
> Subject: Re: [Taxacom] Seed plants of Fiji
> 
> Indeed.  The group of Asteraceae that I work on has a distribution
that
> could only result from long distance dispersal in the Pacific Basin.
> How do you explain a distribution of Cook Islands, Hawiian Islands and
> New Guinea+ Australia using vicariance?  There are lots of other plant
> examples. For my group it did not get to Hawaii via a lost continent
or
> parts thereof.  There is also an extensive  geologic database, which
> shows the emergence of volcanic islands followed by complete
> submergence with another round of emergence.  That's pretty tough on
> terrestrial plants.  I don't know the geologic history of Fiji but
this
> is certainly the case for a number of South Pacific volcanic  islands.
> 
> Tim
> 
> On Nov 15, 2006, at 3:24 PM, Karl Magnacca wrote:
> 
> > On Wed, November 15, 2006 1:01 pm, John Grehan wrote:
> >> I suggest you read the paper first to evaluate your prediction. As
for
> >> Hawaii, it does fit into the overall pattern of Pacific vicariism.
> >
> > I'd be interested to hear your theories on what Hawaii is vicariant
> > from.
> > Lemuria?
> >
> > Karl
> > =====================
> > Karl Magnacca, UC-Berkeley
> > ESPM Dept., 137 Mulford Hall #3114
> > 510-642-4148
> >
> > _______________________________________________
> > Taxacom mailing list
> > Taxacom at mailman.nhm.ku.edu
> > http://mailman.nhm.ku.edu/mailman/listinfo/taxacom
> >
> Tim Lowrey
> Professor of Biology
> UNM Herbarium
> Dept. of Biology
> University of New Mexico
> Albuquerque, NM 87131
> 
> 
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