Biogeography and geological evidence etc.

john grehan jgrehan at ADELPHIA.NET
Tue Feb 4 21:56:06 CST 2003

For my five cents worth (bit of inflation here) on Peter's thoughts:

>Pondering these two quotations, it seems to me that Panbiogeography (if I
>may take the utterances of John Grehan as statements of Panbiogeography) is
>eager to have geology/tectonics informed by biogeography, but at the same
>time prohibits biogeography to be informed by geology/tectonics.

Maybe I can't win on this one - depending on how one may chose to apply
terms and concepts. As far as geological theories about the past (the
geo-historical narratives), I do not see them as informing biogeographic
analysis since the narratives are simply conjectures that are the end
product of geological analysis. So in this respect biogeographic analysis
is not 'informed' by geology/tectonics. When it comes to the method of
spatial correlation between geographic patterns of biological distribution
and geographic patterns of tectonics one might argue that biogeographic
method is being informed by geology/tectonics since the geomorphological
concepts of faults, suture zones, spreading ridges, former coastlines,
escarpments, basins etc all have a historical meaning in geology. On the
other hand, whatever these features may mean in geology they have an
empirical presence in the present as observable features just as much as a

>Now I can understand the feelings that drive this position, but I can't
>see its

In terms of Peter's interpretation neither can I.

>If one allows the one to be informed by the other, one
>assumes some sort of connection. Why then is it not allowed to use this
>connection the other way?

The example with the Galapagos was a biogeographic pattern as an empirical
observation informing a geological conjecture. I would not see a
biogeographic conjecture 'informing' a geological method any more than a
geological conjecture 'informing' a biogeographic method. However, once a
spatial correlation is proposed for a tectonic and biological pattern, it
is possible to examine the historical context proposed for the geological
feature - but that interpretation has no influence on the biogeographic
method itself.

I doubt whether any of the above is really all that informative outside the
context of actual applications of panbiogeography. Whether or not one may
or may not inform the other at some level (such as background knowledge -
see Craw and Weston 1984) is perhaps a matter for individuals to decide
according to their taste.

John Grehan

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