Biogeographic units and classification
lesk at BIO.BU.EDU
Mon Apr 26 10:07:05 CDT 1999
The search for an objective means of classifying biogeographical units is
laudable, but I don't see how it can be conducted in isolation from
systematics. Of course, unifying the two is a cottage industry.
Biogeography, systematics, and landscape dynamics are inseparable. They
are part of a common history. Different lineages respond differently to
the same confluence of landscape events, but they are interacting with
each other as they do so and are part of a common process.
This, any way, is what we have learned from the Lake Victoria cichlids.
It is what Elizabeth Vrba has been talking about all these years with her
antelopes. Also, centers of origin (meaning only, volatile landscapes
that promote rapid cladogenesis and adaptive diversification) are
spatially complex- they are not single points, but a set of interacting
points, because this is the nature of populations. Interactions among
such centers generate their own emergent patterns, at a higher scale.
Describing all of this can be useful, but ultimately we want to understand
the processes generating the patterns. The patterns themselves are
largely an accident of history, no?
Our work on the spatial dynamics of the Lake Victoria Region cichlid
species flocks is still at an early stage, but if anybody is interested,
take a look at:
Kaufman, L. S. 1997. Asynchronous taxon cycles in haplochromine fishes
of the greater Lake Victoria region. S. Afr. Jour. Science. 93:601-606.
Kaufman, L. S., C. A. Chapman and L. J. Chapman. 1997. Evolution in fast
forward: haplochromine fishes of the Lake Victoria region. Endeavour
and for background (see also literature by Dutch and African authors
cited in all these papers)....
Kaufman, L. S. 1992. Catastrophic change in species-rich
freshwater ecosystems, the lessons of Lake Victoria. Bioscience
Kaufman, L. S. and P. Ochumba. 1993. Evolutionary and
conservation biology of cichlid fishes as revealed by faunal remnants
in lake Victoria. Conservation Biology 7(3):719-730.
Boston University Marine Program
lesk at bio.bu.edu
On Sun, 25 Apr 1999, John Grehan wrote:
> Don McAllister wrote
> >One question that has not been properly addressed by the luminaries cited, is
> >how are the <geographic> units used, determined. Most have arbitrarily used
> >continents or parts of them, islands, lakes, etc. Very few people have used
> >equal-area grids, untied to prior geographic concepts, to identify hotspots
> >of species, endemic species, or higher taxa.
> There is a section of the panbiogeography book that acknowledges the utility of
> equal area grid analysis, particularly for mapping distribution densities. Even
> though these grids are of equal size, they are still arbitrary units, so they
> do not, in my mind, provide biogeographic homologies. However, I see
> potential for an interrelationship between track/node analysis and grid
> The latter, in particular, may be the best way to assign centers of main
> massing, since main massings (centers of diversity) can influence the
> of a track.
> >The other problem biogeography has often ignored, is what higher taxa or if
> >you wish clades, have to contribute to understanding biogeographic patterns.
> >The majority of studies emphasize species-level taxa. But consider that the
> >bumblebees are most speciose in the Andes whilst the higher clades are in the
> >Himilayas. Those facts deserve consideration in biogeographic analyses.
> I agree that this is an important consideration. I understand that efforts to
> develop a weighting system by some cladists are directed to this problem.
> The general question of diversity and rank is also discussed briefly in a
> section on African biodiversity in the panbiogeography book (I don't want
> to seem as if I am claiming we covered every biogeographic subject under
> the sun, but there were a wide range of issues considered). The same point
> is made about species-centric approaches distorting global biodiversity.
> John Grehan
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