Biogeographic memory

[John R. Grehan]

I was intrigued to read the following recent paper in Journal of Biogeography:

Turner, H., Hovenkamp, P. and P. C. van Welzen. 2001. Biogeography of
Southeast Asia and the West Pacific. Journal of Biogeography 28: 217-230.

In their abstract the authors declare the biogeography of this region to be
the result of dispersal from two centers of origin based upon geological
theory, the centers being Laurasian and Gondwanan. Having asserted this to
be the truth of southeast Asian biogeography they decide to reconstruct the
biotic history using two large data sets analyzed using cladistic methods.
The result  - weakly supported general patterns that do not allow general
conclusions!

So, according to Turner et al, the state of modern biogeography for this
region is such that we cannot even reach general conclusions (echoes of
Nelson and Platnick's 1981 "unanswered questions"?). Perhaps their findings
are not really that surprising since their approach is based on Darwinian
centers of origin and dispersal using the same kind of geological
preformationism. But what is most interesting (or informative  depending on
one's perspective) is the way the place their findings in the historical
context of biogeographic history  or should I say do not place their
findings in historical context. The question of southeast Asian
biogeography is one which calls for consideration of the major approaches,
and in this paper there is a resounding silence about the obvious  that
being the extensive and detailed studies by Croizat (e.g. 1958, 1968). Now
this might just be considered sour grapes on my part, but I hope that it
can be seen to be a troubling aspect of the science. If deliberate
censorship of unwelcome opponents is to be condoned it raises the question
of whether proper academic standards are applicable to biogeography, and in
which case can biogeography be received with respect by the greater
scientific community?

Censorship of this kind results in a misrepresentation of the state of a
science. For example, in contrast to their weakly supported findings that
the constraints of earth history are said to be low and the common patterns
of biotic history cannot be traced with any confidence we may contrast with
Croizat's (1968) insights that include the following:

"Analyzed in regard of different nodes of its distribution, whether in the
Bay of Bengal, the Gulf of Siam, on the approaches of Southern
Formosa/Luzon, Micronesia, by the islands with the triangle
Sumatra-Borneo-Java, Ficus yields ready evidence for palaeogeographic and
tectonic factors tending to make not only possible but fruitful, for
geologists and bigoeographers alike, a much closer collaboration than
heretofore possible. It is strongly indicated that 'modern' dispersal had
its inception around Mid-Jurassic times."

So one has a choice between unresolved speculation of Turner et al, or the
documented correlations between tectonics and distribution by Croizat.
Whatever the 'truth' of Southeast Asia, or anywhere else for that matter, I
think the state of knowledge will not be served well by the absence of
historical memory.

Croizat, L. (1968a). The biogeography of the tropical lands and islands of
Suez-Madagascar: with particular reference to the dispersal and form-making
of Ficus L., and different other vegetal and animal groups. Atti Istituto
Botanico Universita Laboratorio Crittogamico. Pavia, Serie 6. 4, 1-400

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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