Smart vs. wise systematists

John Grehan jgrehan at SCIENCEBUFF.ORG
Tue Apr 19 09:16:58 CDT 2005


I have been delayed in responding to the various points given by Robert
which are most appreciated. I have inserted some comments below:

> Humphries, C.J. 2004. 
I can't recall if I have seen this or not. I will check.

He thinks the best way to discover area homologies is
> through cladistic analysis of taxa living in those areas. He stresses
that
> cladistic methods used in this way will only _classify_ areas.

Agreed, although this is the way that space is subordinated to the
homology of biology, whereas panbiogeographic classification looks to
spatial homology.

Humphries' closing remarks:
> 
> "I believe that although there is still a very long way to go in
> uncovering
> biogeographic patterns, 

I'm less in agreement although "a very long way" is rather undefined. In
my view the principle biogeographic patterns were already uncovered by
Croizat and the empirical validity of these patterns has never been
challenged, even by dispersalists (who usually chose to ignore it).
Various vicariance biogeographers also tend to overlook these patterns.
I continue to review papers to review that exhibit this characteristic
while the authors at the same time attempt to declare some link between
panbiogeography and cladistic biogeography.

When this is adequately
> investigated
> it will explain most, if not all, the large-scale distribution
patterns.

I guess it depends on what one has as a criterion for "adequately
investigated".

> Critical changes in biogeographic methodology suggest that the
underlying
> theory of change will be based on an exhaustive analysis of biological
and
> geological cladograms ([refs]). 

That remains to be seen. The comparison of biological and geological
cladograms (representing historical narratives) does not seem to have
done much to change anything about the facts of biogeography uncovered
in Croizat' time. Ironically, the panbiogeographer Craw actually may
have been the first biogeographer to compare biological area cladograms
with geological cladograms constructed from uniquely shared
geological/tectonic features (i.e. not a geohistorical narrative).

This would be more satisfying than a
> continuous outpouring of individual stories for every group of
organisms
> and
> techniques for overcoming the need for taxic homology."

Some biogeographers are not interested in the biogeography of individual
taxa. Some are. Satisfaction depends on the taste buds.

I'd prefer to see biogeography built from bottom up in future, with
> plausible "individual stories" of small areas and small taxa steadily
> accumulating to suggest patterns at larger taxonomic and spatial
scales.

One might argue that the individual tracks Croizat documented represent
the individual stories.


the taxon
> Nothofagus and the break-up of Gondwana, with methodological partisan
> sniping. I'm pleased to hear that local-scale phylogeographic studies
of
> individual Nothofagus species have begun. That's real progress.

I think it remains to be seen whether local-scale phylogeographic
studies make any real difference to the basic biogeographic homology
uncovered by Croizat - which suggests that Gondwana does not represent
the spatial homology of Nothofagus.

John Grehan




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