Comment on biogeography of Humphries
jrg13 at PSU.EDU
Fri Nov 10 17:15:14 CST 2000
Humphries, C. 2000. Form, space and time; which comes first? Journal of
Biogeography 27, 11-15.
In this article Humphries makes a number of interesting comments both about
biogeography and Panbiogeography. For those interested, I offer some comments
concerning Humphries views about the current state of biogeography and the
qualities of particular approaches. I realize that my views will be in the
and accept that most practitioners will probably see the issues differently.
Humphries notes that there are a variety of different biogeographic methods
and it is hardly surprising to him that Tassy and Deleporte suggest
biogeography was in a mess,
a subject looking for a method.
An alternative view might be that biogeography is not in a mess at all.
Just because there is no tyranny of consensus does not mean a mess. As far
as I can see it is a very, very, very good situation for biogeography to
have a lot of diversity.
Humphries identified the relationship between form, space and time as the
modern three fold parallelism.
It is the sequence of this relationship (that Croizat first brought into
focus) that presents an important difference between panbiogeography and
other biogeographic frameworks. As I have commented before on TAXACOM,
many biogeographers, including vicariance cladists, dont really seem to
(space) so that for them form comes before space and time, whereas Croizat
saw space and time as central to understanding form hence the biological
Humphries notes that Croizat eschewed the somewhat arbitrary areas of
endemism of de Candolle, Wallace etc.
I dont know about somewhat either they are or they are not.
Humphries characterization of the modern ocean basins providing the
boundaries of former historical units is problematic.
I am not aware that they have been circumscribed as geographic areas by
Croizat or Craw, but rather they are biogeographic homologies.
He asserts that panbiogeography has yet to shake off the impediment of
ancestors as part of the explanations it avowed to replace.
The comment is one of the most intriguing as its meaning is obscure (and
to at least one other biogeographer I have contacted).
Humphries asserts that Nelson and Platnick synthesized panbiogeography with
the systematics of Hennig.
This remains one of the most problematic claims of vicariance cladists.
In rejecting Croizats spatial technique, vicariance cladists seem to
have removed any foundation for synthesis.
A key statement is his conclusion that historical biogeography is about
classification of areas amongst biological and spatial co-ordinates.
This is problematic since vicariance cladists reject spatial analysis in
favor of biological cladograms, and in panbiogeography there are no areas
Humphries characterizes much of current biogeography to be narrative with
fossils and centers of origin remaining popular.
This is something with which I can find some agreement as I have noticed
the c continuing plethora of papers of this kind. Perhaps it is not really
surprising. Most of the historical biogeography is generated by
systematists, and perhaps most systematists are not really interested in
patterns of biogeography in general. Hence the number of papers dealing
with taxa as unique events of origin and dispersal cladistics or no
Humphries principal criticism of panbiogeography is the claim that it does
not make a clear statement as to what constitutes relationship between
different areas on the earth, and rather than provide material evidence
(whatever is meant by that) for homology it still kings to the mysteries of
ancestry to hypothesize relationships of areas.
Im not sure whether Humphries really believes that there is no clear
(again whatever that might be) statement, or its really a matter that he
knows what constitutes relationship in panbiogeography (simply minimal
distance with respect to main massings and baseline features for one or
more taxa) and disagrees with it.
Cladistic biogeography is offered by Humphries as the alternative since its
clear correspondence between systematic relationships in similar areas
it provides biogeographically informative relationships of the biotas.
The problem here is that while one may classify the hierarchical order
of biological relationship, the biological cladogram contains no spatial
information by which to determine which geographic sector links the areas.
It is Morrone and his colleagues who have confronted this problem by
suggesting that a panbiogeographic analysis is necessary before biological
area relationships can be interpreted historically.
Humphries sees the future for biogeography in biological and geological
cladograms while at the same time noting that the method is fraught with
problems of combining taxa into general area patterns, delineation and
recognition of areas, and optimizing multiple simple sequences.
All these problems are supposed to take us one step further down the road
to a solution than the panbiogeography program which ultimately sees
made up of
tracks and nodes of life Indeed I support the
concept of biodiversity as a complex of tracks and nodes as something
empirical and unproblematic. Croizat (1958) already provides the main
outlines of biogeographic patterns and homology (that no one whether
dispersalist or vicariance cladist) has yet refuted)
Unlike Humphries, I see the future for biogeography as more diverse than
just trying to figure out a precise idea of what constitutes the relations
(area homologies) and the things being related (areas) in the analyses.
With panbiogeography one can be less worried about such conundrums. The
concept of relations is clearly designated as baseline homologies (spatial
correlation of tracks and geophysical features) and things being related
(taxa at any level mapped as tracks). So for now Ill stay with
These comments present a purely personal perspective. I do not presume to
persuade anyone else of the merits. Food for thought if nothing else.
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