Biogeography's data, again

pierre deleporte pierre.deleporte at UNIV-RENNES1.FR
Thu Apr 18 18:44:57 CDT 2002

A 09:39 18/04/2002 -0600, Alec McClay wrote :

>On Thu, 18 Apr 2002 09:59:07 +1000, Robert Mesibov
><mesibov at SOUTHCOM.COM.AU> wrote:
> >The 'units' in biogeography are the inventories of life in particular
> >places (e.g., the flora and fauna of cedar glades in Tennessee), not
> >individual species and their individual ranges.......
> >Please understand, however, what biogeographers are trying to
> >do. They are NOT primarily trying to write spatial histories to add to the
> >genetic histories in the dossiers of individual species.
>This seems like an arbitrary limitation on the scope of the discipline. No
>doubt, it is an interesting and legitimate enterprise to try to understand
>the spatial and historical relationships of whole biotas on various parts
>of the Earth's surface. But it is surely also a legitimate question to ask
>how a particular taxon came to have the distribution that it does. This is
>a question about the geographical context in which particular biological
>events took place. How does it not belong to biogeography? It's a bit like
>saying that ecology is only concerned with the properties of whole food
>webs or communities, and that therefore a study of the population dynamics
>of a particular species is not an ecological study.

Focusing on one lineage ("taxon"), and particularly for populations and
recent periods, is frequently called "phylogeography", while "historical
biogeography" refers rather to the study of biotas.
I see no reason to oppose these approaches, because accumulating
phylogeographic data provides matter for historical biogeography of the
biotas they compose.
Both approaches are retrodictive. They require a relevant description of
the "present state" of the evolving system (lineages distributed on Earth),
and non arbitrary rules for inferring the past from these data.
Setting clear historical questions to be tested by these historical
reconstructions is also recommended. "Did all organisms dispersed from Mont
Ararat ?" is an example of a very clearly stated historical question. But
setting rules for testing such a simple question is likely not so easy as
it could seem. The historical reconstruction should be able to corroborate
or refute this dispersalist scenario.


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