Galapagos Iuridae scorpion outlier

John R. Grehan jrg13 at PSU.EDU
Mon Apr 22 10:53:51 CDT 2002

Pierre wrote

>In my view the methodological principle involved is in no way peculiar to
>panbiogeography: it is the requirement of using total relevant evidence for
>scientific explanation. You cannot discard some evoidence (Meditterranean
>location of the (axon under study) unless you argue convincingly (and not
>merely state) that these data are irrelevant to historical biogeography of
>the taxon in general, or to the specific question you are asking
>(concerning circumpacific distributions if I understand well).

There was no evidence 'discarded' as the Mediterranean record was not
necessary for describing the East Pacific track - no more, than for
example, describing a West Coast track within New Zealand for a taxon that
might otherwise also be present in Australia.

>John, I must suggest that you cannot answer such general methodological
>questions by merely stating "it is like that in panbiogeography".

I was not being asked a general methodological question, I was being asked
about my decision regarding the Iuridae and the issue raised was over my
application of  panbiogeographic methodology, not biogeographic methodology
in general.

>panbiogeography or others. Discarding possibly relevant evidence is
>unjustified in any scientific approach. If it is not part of
>panbiogeography, this must be stated clearly, and discarding evidence must
>be avoided as methodologically flawed.

As pointed out above, and in other postings, there was no relevant evidence
discarded. The Mediterranean record was not necessary to describe the
eastern Pacific track. It was, however, relevant to assigning the Ocean
baseline, and that is where it was used. Where the Mediterranean record
does become relevant for the East Pacific track is where one might be
interested in the relative biogeographic polarities of the different tracks
comprising the East Pacific track. For example, some taxa may have a
Pacific baseline, others and Atlantic, or the Pacific baseline may itself
be divided into different components (e.g. Tethys correlations, East
Pacific Rise etc.).

>Biogeography is obviously far from having definitely clarified its
>principles and methods. Being or not being part of the "present state of
>the art in panbiogeography" is not an argument in itself. We have to
>consider that panbiogeography MAY be flawed, as any other approach may be,
>otherwise there is no possible progress in the debate.

Agreed. So far published objections to panbiogeography have been largely of
a rhetorical nature. People object to it because it conflicts with some
other view they hold about systematics, historical geology, fossils, age of
taxa, molecular clock theories, theories about dispersal, theories about
method, theories about biological differentiation etc.). What will be
interesting (for me at least) will be to see the critics actually carry out
a comparative analysis using panbiogeographic and other techniques to argue
the case and demonstrate, for example, by that application how
panbiogeography is deficient in its predictive power, or how its past
predictions were illusions (a claim already made by one dispersalist), or
the current spatial correlations (between tracks, with geology) do not
really exist etc. The Galapagos could be an interesting 'test' case.

John Grehan

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

Frost Museum

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