Deleporte on panbiogeography (+ O. furcatus)

[Ken Kinman]

John,
     Well it is late, and we seem to perceive a lot of mere rhetoric in each
other's arguments.  Perhaps more input from others will help clarify some of
the issues and clear away some of the rhetoric.  Will gladly respond more
fully tomorrow when I am not so tired.
     But let me just say that I don't believe I can be said to have a
distrust of geographic space just because I find minimal spanning of more
limited used in the Pacific.  I think your characterization of my position
is an exaggeration.
     And my point was that the Pacific has been an effective barrier for
long distance dispersal "over the water".  This would not apply in the far
north (Bering Strait) or far south (Antarctica) where the Pacific has been
bridged (or nearly bridged) in the past.   Why panbiogeography would
downplay these disperal routes makes no sense to me at all.
      It's many of your long mid-Pacific tracks from the Americas to
Australia or New Zealand (as the "crow flies", as Pierre termed it) that
bother me the most.  Long distance dispersal over land on either side of the
Pacific) does not bother me since the water gaps are relatively small.  The
gap between South America and Antarctica has never been very large, and the
gap between Antarctica and Australia and New Zealand was certainly much less
in the mid-Cenozoic (when a lot of this clade splitting was probably
beginning).
      Thus from my perspective the longest "oceanic" dispersal of Oreobolus
would be that of O. furcatus to Tahiti and Hawaii which could just as well
be due to human (Polynesian) intervention.  Even if such "speculation" is
wrong, and it was due to natural rafting of some sort, the O. furcatus
dispersal is still far shorter than your Central America to Australia
track----which you find "intriguing", but I find extremely dubious and only
supported by an arbitrary and unproven "minimal" spanning convention and a
cladistic analysis which the author (Seberg) himself admits is rampant with
homoplasy.
       Well, it is getting late, and will enjoy seeing what others have to
say about all of this.   Atlantic minimal spanning tracts I can see as
potentially useful, but for the very wide Pacific (which was even wider in
the past), I think a overall longer trans-Antarctic dispersal (but with much
shorter oceanic gaps to cross) makes a whole lot more sense for most groups.
  Especially for Order Poales (which Stevens admits is heavily Gondwanan in
its origins).
      You have already abandoned your long trans-Pacific track for primitive
frogs, and I predict you will have to do so for a lot of other groups as
well.  If your Oreobolus paper doesn't convince me (someone who thinks
panbiogeography does have great potential, although in a less strict form),
then how can you expect to convince those who don't think panbiogeography
has any potential at all?
      Enough of this for one day.  I've got to get some sleep.  More
tomorrow.
          --------- Ken
****************************************
>From: John Grehan <jrg13 at PSU.EDU>
>Reply-To: John Grehan <jrg13 at PSU.EDU>
>To: TAXACOM at USOBI.ORG
>Subject: Re: Deleporte on panbiogeography (+ O. furcatus)
>Date: Tue, 2 Jul 2002 22:21:16 -0400
>
>Ken Kinman wrote:
>>Oh no,
>>     That's what I was afraid of.  Minimal spanning tracks are another
>>form
>>of strict parsimony.  The longer these tracks are, the more I will
>>distrust
>>them.  Especially in the Pacific which was even wider in the past, while
>>the
>>Atlantic was narrower in the past.
>
>Ken, it seems to me that you exemplify the traditional distrust of
>biologists/systematists for geographic space. There are many philosophical
>reasons one might invoke for disliking tracks, but it seems to me that such
>objections are simply rhetorical devices if they avoid addressing the
>empirical success of the method - such as predicting the composite tectonic
>structure of the Americas before it was known to geologists.
>
>>     I'm sure this works quite well in trans-Atlantic tracks linking South
>>America to Africa or linking North America to Europe.  But the Pacific is
>>a
>>whole different ball game.
>
>In what way?
>
>>In that case, partial "Pacific rim"
>>(amphi-Pacific?)  distributions are going to be more the rule, and
>>trans-Pacific dispersals the rarer exceptions.
>
>Please elaborate what you mean by this - with examples so I may respond.
>
>>As we learn more about the
>>mid-Cenozoic fossil record of Antarctica, I predict that new evidence will
>>bear this out.
>
>In what way?
>
>>     The Pacific seems to have been a very effective barrier to long
>>distance Oreobolus dispersal.
>
>Since Oreobolus is distributed either side of the Pacific basin it seems
>that the Pacific has not been a 'barrier' to Oreobolus dispersal (as
>translation in space and form-making).
>
>>It would not even surprise me if Oreobolus
>>furcatus was somehow carried to Tahiti and Hawaii by humans (such as the
>>early Polynesians), whether by accident or on purpose.
>
>This seems to be just speculation. Is this all there is to biogeography?
>
>>      Panbiogeography (at least as John has been explaining it) seems too
>>restrictive and rigid, especially when applied to the Pacific.
>
>Please explain
>
>>Guess my
>>eclecticism is showing once again.
>
>In what way?
>
>>But I just hate it when pendulums swing
>>too far one way or the other, and biogeography seems to be no exception to
>>controversy growing out of pendulum swinging (instead of seeking middle
>>ground approaches).  Oh well.
>
>Seeking the 'middle ground' seems to me to be just a rhetorical device that
>has political rather than scientific significance.
>
>I look forward to the elaborations if Ken wishes to do so.
>
>John Grehan



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