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Re: [Re: natatory Geochelone]



Ronald Orenstein <ornstn@home.com> wrote:
> At 11:53 AM 02/07/2000 +0200, Juergen Peters wrote:
> > > In the case of the Galapagos tortise, this makes sense to me. Being
cold
> > > blooded, these animals would not need to eat for a long period of time,
> > > and could therefor endure long ocean voyages.
> >
> >But most probably they did not reach the Galapagos Islands by swimming,
> >as someone mentioned here, but as juveniles on drift-wood etc.
> 
> Actually, according to tortoise experts I have talked to about this, there
is every chance that they DID get there by swimming.  It seems that the
tortoises on the Indian Ocean islands at least (and I suspect the Galapagos is
a similar case) are not cases of insular gigantism but relicts of giant
tortoise populations on the mainland; if juveniles were the colonizers you
might expect some smaller tortoise species to be established there as well. 
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Well according to mtDNA sequence done on all the subspecies of _G.nigra_
(formerly _G.elephantopus_) along with a list of South American and African,
mainland tortoises, there closest living relative is the Chaco tortoise
(_G.chilensis_), which happens to be the smallest member of the genus.

So the initial trek to the Galapagos was probably done by a smaller tortoise,
like _G.chilensis_ and then later treks to different parts of the archipelego
probably were done by more elephantine individuals (and indeed mtDNA studies
seem to confirm this).

Jura

Abstract available online at: 
http://www.inform.umd.edu/EdRes/Colleges/LFSC/FacultyStaff/dinouye/scbabstracts/Caccone.htm


Jurassosaurus's Reptipage: A page devoted to the study of the reptilia:

http://reptilis.webjump.com

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