FW: Islands, Science and Creationism

John R. Grehan jrg13 at PSU.EDU
Mon Apr 15 18:20:35 CDT 2002


Les Kaufam wrote:

>Would somebody please explain to me how panbiogeography works for marine
>systems.  Take, for example, species like the pelagic dolphin or black
>durgeon triggerfish, which are pantropical, as compared to the splendid
>toadfish, restricted to the Central American shelf?

Panbiogeography works for marine systems just like any other. Some species 
will be widespread, others localized. This is true of marine, sessile, and 
aerial life. So one would apply the same biogeographic tools as for all of 
them. With most current applications of the method the interest is in the 
relative geographic disposition of differentiation (e.g. taxa), so in the 
case of a species being widespread, this of itself may be uninformative, 
but if there is some kind of biological difference that can be mapped 
geographically then panbiogeography provides some analytical tools for 
characterizing and comparing the geometry of this differentiation 
(form-making).  Even where a taxon may be widespread overall there may be 
geographically restricted elements such as breeding grounds that may have 
general biogeographic significance.

One panbiogeographic paper on a marine group is:

Rogelio Aguilar-Aguilar and Raul Raúl Contreras Medina. 2001. La 
distribución de los mamíferos marinos de México: un enfoque 
panbiogeográfico. In J. Llorente, and J. J. Morrone  (Eds.) Introduccion a 
la biogeografia: Teorias, conceptos, metodos y aplicaciones.Universidad 
Nacional Autónoma de México, Mexico City, pp. 181-196.  Pp. 213-219.

Bill Shear wrote

Now I'm confused. The present-day Galapagos cannot be demonstrated to have
had any land connection with previous archipelagos, and always has been
separated from the South American continent or any other land mass by water.
What possible other means of dispersal than "overwater" could account for
the terrestrial biota found there?

The lack of any land connection with previous archipelagos is a theoretical 
prediction that may or may not be true. However, assuming it is true, it 
does not eliminate the island arc origin of the modern biota as 
inter-island dispersal (also necessary under the overwater dispersal from 
S. America model) would allow for local persistance.


John Grehan






the geographic sector through baselines.


>Bill Shear wrote:
> >
> > ------ Forwarded Message
> > From: Bill Shear <wshear at email.hsc.edu>
> > Date: Mon, 15 Apr 2002 11:41:49 -0400
> > To: John Grehan <jrg13 at PSU.EDU>
> > Subject: Re: Islands, Science and Creationism
> >
> > > This is exactly what Darwinian biogeography did for the Galapagos 
> with all
> > > its assertions of overwater dispersal being the only possible origin for
> > > the Galapagos biota. Croizat's approach did not rely on accepted 
> historical
> > > geological reconstructions and his method took theory ahead of the 
> current
> > > knowledge of the time and generated predictions of future empirical
> > > discovery. Regardless of philosophical and rhetorical objections and the
> > > priority traditionally given to other disciplines over biogeography,
> > > panbiogeography actually works.
> >
> > Now I'm confused.  The present-day Galapagos cannot be demonstrated to have
> > had any land connection with previous archipelagos, and always has been
> > separated from the South American continent or any other land mass by 
> water.
> > What possible other means of dispersal than "overwater" could account for
> > the terrestrial biota found there?
> >
> > Bill Shear
> >
> > ------ End of Forwarded Message
>
>--
>Les Kaufman
>Biology Department
>Boston University
>5 Cummington St.
>Boston, MA 02215
>lesk at bu.edu
>617-353-5560 office
>617-353-6965 lab
>617-353-6340 fax
>
>and
>
>BUMP
>7 MBL St.
>Woods Hole, MA 02543
>508-289-7579 office
>508-289-7950 fax

John Grehan
Frost Entomological Museum
Pennsylvania State University
Department of Entomology
501 ASI Building
University Park, PA 16802. USA.

Phone: (814) 863-2865
Fax: (814) 865-3048

Frost Museum
http://www.ento.psu.edu/home/Frost/index.html




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