The problem with biogeography

John Grehan jgrehan at SCIENCEBUFF.ORG
Tue Oct 12 09:49:01 CDT 2004

Pierre Delporte wrote (paragraphs in quotes):

"In fact, no consensus can be made between a "principle-less" approach
like panbiogeography and clearly "principle-based" approaches like
vicariance biogeography, or phylogeography, with their phylogenetic
references and their hierarchy of explanatory models of evolutionary
processes like vicariance and dispersal."

Little bit naughty here. It's a bit like a political debate. Of course
panbiogeography is based on principles just like any other biogeographic
method - as anyone who has read the panbiogeographic literature would

"However debatable, these approaches do have an explicit corpus of basic
biological, evolutionary, and geological principles (e.g. some
continental drift scenarios are rather well documented, turtles don't
fly across oceans, and rattlesnakes don't survive a glaciation).
Panbiogeography offers nothing in this respect."

Excellent! Very astute! Of course panbiogeography makes no a priori
claims about geological principles, the survivability or rattlesnakes or
flying turtles. Panbiogeography is about spatial analysis - as anyone
who has read the panbiogeographic literature would know. Of course
panbiogeography has offered novel predictions about the geology of
Galapagos and the Americas etc. Predictions that have since been borne

"... biogeographic pattern is real and detectable...".
Sorry but no, no and no. Straight lines on maps are in no way "real and
detectable". They are traced by Panbiogeographers themselves, I'm sure
(but curiously enough, never through Earth itself, as I hinted long ago
on this list...)."

Whatever philosophical authority one might abase oneself to, the
patterns are real or they would not be informative.

"Panbiogeographers should better tell us WHY they trace such lines this
way, what is the intended meaning of all this graphic activity, and in
this perspective first of all question themselves about their implicit
scientific motivations... if any, beyond perpetuating traditional
formalisms of the Croizatian "school". 

It's all been said, as anyone who has read the panbiogeographic
literature would know. And most people do know why, but just disagree
with the method for whatever reason (even though the method works),
although usually such responses can be traced to the traditional
taxonomist/systematist distrust of spatial evidence.

"Perfectly consistent formalism doesn't make scientific sense in itself.
And as far as I know, Panbiogeography has up to now presented no
justification beyond formalism, which is not scientifically appealing.
And this paper shows no trace of any progress (e.g. don't look after any
non-formal definition of 'spatial homology', already largely debated on
this list)."

People are free to make such choices according to whatever philosophical
authority to which they abase themselves.

" Please keep in mind that its proponents claim that they don't care a
bit about biology and geology."

Tut tut. Naughty!

"They just "connect taxa on the map", feigning to be starting from zero,
and this without even defining "taxon" (it's biological, you know, and
they want to be pure geographers first of all)." 

Again tut tut! Never read the literature?

"They just mean maps for vague "biological things" (their undefined

Always the maps identify the taxon being mapped. Nothing vague about

"and they would like you to take their panbiogeographic schemes (minimal
spanning spatial networks between locations of such "things") as your
starting point for reflexion.


Buy it or not..."

Actually one has little choice about that. Panbiogeography is only for
those interested in spatial data and analysis.

"Of course I never believed one second that panbiogeographers are "pure
empiricist geographers" observing self-evident baselines out there, and
totally unaware of biology and geology and continental drift, unless
they would not object to connect the Zoo of New York to Camberra through
the center of the earth in order to depict co-occurrence of kangaroos,
or they would not be so eager to consider oceans as "baselines" (yes,
oceans, just so...). But they do play this game and we are forced to
consider their argument as they state it."

Ah - but the game works. Croizat got it right about the geology of
Galapagos, the Americas etc when dispersalists like Mayr, Simpson, and
even the early vicariance cladists either got it wrong or did no better
(at least these days some vicariance cladists are admitting Croizat got
things right even without cladistics to boot).

"Tangey's paper ends up on the point of epistemology (I mean, just
writing the word 'epistemology', not developing an epistemological
argument). The lasting burden of empiricist vacuum on some
contemporaneous science, even if marginal, is effectively 'serious'
epistemological concern."

On the other hand I thought Tangey was making a worthwhile point - the
geographic facts of biology are the key to the nature and origin of
knowledge in biogeography. Of course others can, and no doubt will,

John Grehan

More information about the Taxacom mailing list