Deleporte on panbiogeography (+ O. furcatus)

pierre deleporte pierre.deleporte at UNIV-RENNES1.FR
Wed Jul 3 13:08:16 CDT 2002

A 22:21 02/07/2002 -0400, Ken Kinman and John Grehan wrote:
>Ken Kinman wrote:
>>Oh no,
>>     That's what I was afraid of.  Minimal spanning tracks are another form
>>of strict parsimony.

I would say formal, structural parsimony without clear biological meaning
(think of some avatars around the cladistic school).

>>   The longer these tracks are, the more I will distrust

For me, it depends on the landscape, geological information, and inferred
dispersal abilities of the taxa... precisely not "just-so distance", Ken !

>>   Especially in the Pacific which was even wider in the past, while the
>>Atlantic was narrower in the past.

This is a clear (and thus debatable) geological contribution to total
relevant evidence for infering historical biogeography.

John Grehan:
>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.

Isn't the composite tectonic structure of the Americas appearing from a
vicariance biogeography analysis too ? If so, no supreriority of
Panbiogeography could be claimed, only identity of result in the particular
case, with no guaranty for other cases.
The empirical argument "in worked in this case" is of no use for defending
the logical relevance of a method. the argument should be why it should
"work" in most cases (if "working" makes general sense at all for
historical inference: we have no time machine to go back and check...).

>>    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).

Seems that Ken argues in terms of geological evidence and dispersal
abilities of the concerned taxa, which makes perfect sense for me and is
debatable, and John refers to a formal notion of "translation in space and
form making", which would gain in being explicited in biologically
intelligible terms.

>>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?

Is this unsound speculation? And anyway, isn't any tentative historical
reconstruction more or less convincingly argued "speculation"? So where is
the point?
Better clearly argued speculation than formal graphic illustration.


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