Pacific land snail phylogeography - grad studentproject

john Grehan jgrehan at SCIENCEBUFF.ORG
Wed Dec 4 10:54:23 CST 2002

Frederick Schueler wrote

>* and then, perhaps, a good example of a panbiogeographer's anxiety that
>a Darwinian dispersalist model encompasses the panbiogeographic model,
>since 'disperal' includes 'not dispersing.'

I'm not sure I understand this. The methodology of panbiogeography is not
about dispersing or not dispersing (in the Darwinian sense of migration or

>Glib dispersalism may restrict the kinds of explanations biogeographic
>analysis can come up
>with, but without pointing out flaws in Cowie's 'preliminary study' it's
>equally glib to condemn it for presumed methodological errors.

Perhaps. Whether one is for or against dispersalism, the methodological
issue was the reliance on geohistorical narrative to interpret the
biogeography. It is not a matter of methodological error, but different
methodological frameworks. Naturally I think its a deficient approach to
biogeography to have to rely on geohistorical narrative, but others
naturally find nothing wrong with it.

>Is reciprocal illumination between biogeography and geology appropriate?
>Do "dispersal between islands and archipelagos" and "routes of
>colonization into the Pacific" exclude "other geo-narratives (e.g.
>former island arcs)"?

My point was that the model was presented in terms of one particular
geo-narrative. I agree, such a model may not necessarily exclude another
narrative. And then of course there is the possibility of routes of
'colonization' are out of the Pacific. In either case, the methodology of
dispersalism relies on geo-narratives since it has no independent
biogeographic criteria for predicting the past (at least insofar as I
currently understand) so all explanations are in the light of current

>It seems to me that every phylogeny worked out by
>the student who lands this apparently idyllic position will test
>(=depend on) the overall geo-narrative as well as any smaller scale
>details being particularly studied.

This might be problematic. If one depends on a narrative the concept of
testing may be circular.

John Grehan

John Grehan
Director of Science and Collections
Buffalo Museum of Science
1020 Humboldt Parkway
Buffalo, New York 14211-1293
Voice 716-896-5200 x372
Fax 716-897-6723
jgrehan at

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