dispersal fantasy / panbiogeography

[John R. Grehan]

Pierre Deleporte wrote:

>OK, I have to go and sarch for the answers by myself. I naively thought
>that if the answers existed, they would have been written in Craw et als.
>book, in the introductory chapter, or could be stated in a few sentences
>by trained practitioners of panbiogeography.

Some or all of the 'answers' may well exist in the Craw et al. book. I did
not meant to suggest otherwise.

>>A method cannot be put in empiracal tests through applications if one
>>does not understand what it means in the first place, correct? So, what
>>does a track mean, or may mean?
>  OK, OK, one has to read Croizat and the revelation will come...

Yes - I do think if one is to apply any method effectively this will not
come through some brief answers to a miscellany of questions. It seems to
me that when most people are interested to test the efficacy of a method
they read the literature developed on the subject and then apply their
interpretation of it. This is what I suggest for anyone interested in the
panbiogeographic method.

>This we will know when the answers will have been formulated somewhere.
>Till this time, the suspense is plainly unbearable   :-) :-)
>Suggestion to save time: you just copy the relevant paragraphs in Croizat
>(those answering all my six or seven questions, but not put in Craw et al.).

I think if one is really interested in such questions one does take the
necessary time. When I began my interest in panbiogeography I did not go to
Croizat with a list of questions to tell me how to understand the method or
its application. I read his books. I am always happy to discuss one's
interpretations of panbiogeographic methods, terms, etc.

>Shouldn't an approach, arguably, be stated in simple understandable terms?
>Beyond a formal statement of how to perform the approach, shouldn't some
>notion be given of what it means? What does a baseline means? (in biology,
>geology, what you like). Let every individual reader decide if a
>historical biogeographic approach should or should not have some clearly
>stated biological, geographical and historical meaning.

I have no problem with this. There is a panbiogeographic literature out
there. If Pierre finds that literature to lack what he determines as the
necessary clarity then the subject is open to his critique.

>>This might be interesting as it reflects that classic three phase process
>>of acceptance - first ignore it, then attack it, then finally claim that it
>>has nothing new.
>
>Nice shot! But is it true ?

It will be interesting to see.

>Note that my claim is more than that (the part you cut): a good lot of
>Panbiogeography has merely no explicit interpretative theory.

If Pierre finds panbiogeography to not be worth pursuing because of that
finding then he is free to take that course.

>But when it has, I identify models present in other approaches. True, or
>not true ? Is the answer in Croizat?

Again, that Pierre can make his own assessment.

>>What I do find interesting, from a philosophical perspective, is the way
>>that the development and application of panbiogeography is not homogenous
>>throughout the globe.
>
>An approach resting on an incomplete set of explanatory models or theory
>will inevitably produce varying applications. Seems perfectly natural to me.

It seems like what Pierre is looking for is a recipe so the cake will
always come out of the over the same way. Alternatively, panbiogeography
may be viewed as having a wide latitude of possibilities.

>Useful product of data analysis would be new biogeographical
>interpretation or hypotheses, not "prediction" of retrieving the same
>formally defined pattern.

This is certainly one way of looking at 'utility'. People will certainly
make their judgements about this, and at present most systematists find
Darwinian dispersalism to be the most 'useful' method. There are certainly
new biogeographical interpretations and hypotheses generated in
panbiogeography. Some are covered in the Craw et al book.

>Some people want to understand an approach before using it. I suggest they
>should not be shamed of that... "philosophically speaking".

I concur wholeheartedly, and regret any implication to the contrary.

I appreciate the time Pierre has taken to raise the issues of concern to
him. They will contribute to my understanding of how at least some
systematists have difficulty with understanding panbiogeography and perhaps
highlight some issues that I can address in the future.


John Grehan
Frost Entomological Museum
Pennsylvania State University
Department of Entomology
501 ASI Building
University Park, PA 16802. USA.

Phone: (814) 863-2865
Fax: (814) 865-3048

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