The problem with biogeography

John Grehan jgrehan at SCIENCEBUFF.ORG
Wed Oct 20 17:16:38 CDT 2004


Ken Kinman wrote:
>       Although I certainly
> understand Pierre Deleporte's qualms about the "straight line"
approach of
> panbiogeography, I am (as I have indicated before) personally most
> concerned about the very long (trans-Pacific) lines between
Australasia
> and the Americas.  I still think many of those would be via
Antarctica,
> and therefore NOT in a straight line at all.  

This might be true if Antarctica were considered a source or a
landbridge for dispersing taxa. Panbiogeographic maps do not include
speculative elements such as this. So a line across the Pacific only
serves to recognize the Pacific as the major tectonic basin crossed by
the track. This would still apply even if representatives were found in
Antarctica (i.e. a taxon in Australia, New Zealand, Antarctica, and
Vancouver would still have a track with a baseline in the Pacific). The
lines can be straight or curved while still linking nearest neighbors if
using the minimum distance criterion and this would apply whether or not
Antarctica were included.

In some ways Ken's position is probably closer to the early Croizat
where he had not quite got away from looking at distributions in terms
of active dispersal and Antarctica as a potential source of major
biogeographic patterns. The later Croizat emphasized spatial
differentiation models.


Within Australasia, I'm sure
> Tangney's analysis does have significant value.  But how Fallaciella
got
> to South America intrigues me (is it a relict there which once
occurred in
> Antarctica as well?; or could it have been transported more directly
and
> more recently by rafting, birds, or even humans?).

Whether or not one might speculate on such possibilities, the critical
first question is whether the dispersal (translation in space + form
making) is congruent with biological and tectonic patterns in general.
That is the component of analysis which is purely biogeographic and
independent of other historical disciplines.

John Grehan




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