[Taxacom] panbiogeography

John Grehan jgrehan at sciencebuff.org
Sun Jul 5 13:20:45 CDT 2009

I put the keyword in the subject line as a courtesy to those who find
this subject irritating so they can hit the delete button (so I do not
expect to see any complaints posted). The rest is for those who are
curious or like to see opinions for the sake of it.


I noticed that Michael Ivie managed to express his irritation and then
duck out of further discussion when it suited him - nothing inherently
wrong with that I suppose although it seemed that he has some
interesting biogeographic observations that could have been examined
further, and Michael did try to offer some empirical considerations for
Ivie to consider and discuss further.


I took a look again at Cracraft's 2000 review that Ivie quoted. The
review is probably understandable from one who is taking a phylogenetic
approach to biogeographic analysis, but overall his criticisms
notwithstanding, he said the book should be read. As to the critiques,
mostly they are expressions of a view, not any kind of substantiated
argument. Some are more about criticizing what was not covered in the
1999 book, and that is inevitable in a book of a finites size and


Specifically on the comments listed by Ivie:


"A major weakness of their presentation and the method is the
oversimplistic interpretation of generalized tracks and of the
geological events that are assumed to cause them."


No empirical evidence was given for this view. 


"Most applications of the panbiogeography method tend towards the
narrative rather than the analytical"


He did give the caveat that this was "at least not in the sense observed
in vicariance biogeography"



"...they strongly advocate using biogeographic distributions as evidence
of phylogenetic relationships, but their examples have preconceived
notions of relationships built into them."


He never said how they were preconceived.


"The authors are strong supporters of the importance of systematics, but
they are short on specific analytical procedures of how biogeography
might be used to infer relationships."


This was only one subject among many.


Regarding Ivie's reference to "Serious problems inherent in the
Panbiogeography method, which have been documented in the literature ad
nauseum' the comments by Cracraft do not point to any "serious problems"
that negate the validity of the method, and in particular its real,
predictive achievements (that have to be dismissed by opponents out of
hand even though a corresponding predictive ability in dispersal
biogeography has never been produced).


As Cracraft notes, "each biogeographic method has its strengths and
limitations in describing and explaining biogeographic patterns".
However such views may be applied to panbiogeography is up to each
individual, but so far the rejections of panbiogeography have not been
on the level of empirical falsification (e.g. of the novel predictions,
of tectonic correlations etc.). Even the molecular clock theorists, who
thought they had the falsification, failed by misrepresenting molecular
clock divergence dates as maximal rather than minimal estimates.


John Grehan



Dr. John R. Grehan

Director of Science

Buffalo Museum of Science1020 Humboldt Parkway

Buffalo, NY 14211-1193

email: jgrehan at sciencebuff.org

Phone: (716) 896-5200 ext 372




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