Panbiogeography of the Americas

[Thomas Schlemmermeyer]

Let me, just for the fun of it, throw in my impression while reading Croizat.
Croizat's problem apparently were not marine organisms, it were plants.
Much can be said and done about exact mathematical procedures, such as the
question wether great circle or straight line distances should be taken.
But it seems that Croizat's problem was a roughly logical one. And this is also
my impression I gained in discussion with other panbiogeographers.
They do not think in exact continuous distance measures, rather they seem to
make rough logical connections of the kind: If group X is present on
Madagascar, Sri Lanka, Oceanic Island and Northwest-South-America, than this
organism is pacific (whatever this means), if group Y is present in Africa and
Southeastern Brazil, than it is atlantic (whatever this means), and so on.
As the Croizat machine is an enormous data file of monographies, check-lists
and so on, the task to reinvent it seems to me rather the task to check these
logical connections above mentioned and how they tie in with overall observed
diversity.
Of course, marine organism are a special case, but no coriolis-force can take
them from the Pacific to the Atlantic and vice versa.
But if I recall correctly, the late (in this case the use of the word "late"
seems to be justified) Rosen worked with this problem

  Cheers   Thomas



>If this is the case, ocean currents will largely confound the usefulness of
this
>technique for marine biogeography..  Because of the Coriolis force and because
>continental margins create obstacles around which fluids and the organisms in
>them
>must flow, they seldom travel in straigh lines of minimum distance.   Likewise
>non-linear coastal margins will confound the approach when dealing with coastal
>species.  Perhaps this was a problem with Rosen's analysis.  He used the
>"approximate convex hull" technique for defining tracks as opposed to the
>"minimum
>distance approach."
>
>--
>_____________________________________________________________________
>Stuart G. Poss                       E-mail: Stuart.Poss at usm.edu
>Senior Research Scientist & Curator  Tel: (228)872-4238
>Gulf Coast Research Laboratory       FAX: (228)872-4204
>P.O. Box 7000
>Ocean Springs, MS  39566-7000
>


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Thomas Schlemmermeyer
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