[Taxacom] Dispersal... again

[Michael Heads]

Hi Karl,
?
You don't need continuous land (e.g. a lost continent) for vicariance. For example, two metapopulations on an active island arc?(surviving in situ on individually ephemeral islands) can be separated by rifting. There has been extensive volcanism over large areas of the Pacific plate since the time of its origin, and on the Hawaiian chain at least back to 85 Ma (at which point the chain disappears into the Aleutian trench).?The dispersal model for Hawaii relies entirely on the suggestion that?there was a period (33-29 Ma) in which no islands (Clague et al, 2009:1) or no high islands (Clague et al., 2009: 10)?were emergent, but the calculation this was based on is dubious. For example,?it predicts current elevations of the Hawaiian volcanoes to be much lower than they actually are, so it probably also underestimates the heights of earlier islands. 
??Michael

Wellington, New Zealand.


My papers on biogeography are at: http://tiny.cc/RiUE0


________________________________
From: Karl Magnacca <kmagnacca at wesleyan.edu>
To: Michael Heads <michael.heads at yahoo.com>
Cc: "taxacom at mailman.nhm.ku.edu" <taxacom at mailman.nhm.ku.edu>
Sent: Thursday, 27 October 2011 12:49 PM
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