[Taxacom] Dispersal... again

[John Grehan]

It would be hard to remain Mu(te) about this one. As Mike pointed out, there is no necessity for a continental structure in the Pacific, or even continuous land throughout. There are geologist who are proposing various models for former landscapes in the Pacific so its not out of the question from the geological perspective. Its easy enough to take the approach of ridiculing biogeography that supposedly lacks geological support, but the historical geology is only a theorized proposition, not an empirical reality. 

Mayr ridiculed Croizat for proposing former land in the East Pacific as contributing to the biota of the Galapagos. Mayr said if Croizat was so wrong about the Galapagos then he was wrong about biogeography in general. Of course, even about that time there were island arc models being developed that placed the origin of the Caribbean in the eastern Pacific and some recent models even place the Greater Antilles west of the Galapagos in the Mesozoic. One geologist suggested (in correspondence) that the East Pacific island arc contributing to Panama/Costa Rica was "massive" on a scale far larger than the current geography. Croizat even got it right about predicting, before seafloor mapping, the presence of the tectonic center associated with the Galapagos based solely on the biogeography. Interestingly I have noticed that in various papers citing classic examples of oceanic island chance dispersal, that the Galapagos is now sometimes missing from the roles and perhaps even though the biogeography could be ignored (by the biogeographers ironically), the geology is now being seen to be decisive in this respect.

John Grehan

-----Original Message-----
From: taxacom-bounces at mailman.nhm.ku.edu [mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Karl Magnacca
Sent: Wednesday, October 26, 2011 7:50 PM
To: Michael Heads
Cc: taxacom at mailman.nhm.ku.edu
Subject: Re: [Taxacom] Dispersal... again


On Wed, October 26, 2011 1:35 pm, Michael Heads wrote:
> Hi Karl,
> ?
> You say: 'Vicariance is ho-hum because it's how things mostly go'.
> But for the Hawaiian biota?I only know of a single?paper in the last 
> 50 years supporting a vicariance model. Every other paper in?a huge 
> literature supports the same?model: chance dispersal.

Considering that most of the Hawaiian islands (like other isolated island groups) have never even had a land connection to each other (except for Maui Nui, and Molokai-Oahu for a time about 2 million years ago), let alone to a continent, that's hardly surprising.  The only ones who consider vicariance for the origin of the Hawaiian biota are those who believe in the continent of Mu.

Karl


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