[Taxacom] Pacific biogeography

[John Grehan]

One can understand such vague assertions about stepping stones if one is
not familiar with the panbiogeographic studies in question.

John Grehan

On Mon, Dec 17, 2012 at 10:34 AM, Richard Zander
<Richard.Zander at mobot.org>wrote:

> What an interesting note, Michael. If there were lots of islands in the
> Pacific long ago, their existence would likely explain certain
> distributions.
>
> Facts about sea floor subsidence may lead to good, pursuable scientific
> theories, which, though having to do with historical science, are
> nevertheless in the broad range of scientific ratiocination.
>
> The problem is with panbiogeographic analysis, the method of which is
> questioned. New facts about the possibility of lots of stepping stone
> islands in the Pacific may not make panbiogeographic "tracks" more
> revealing of historical processes. Submerged islands make poor
> repositories of evidence.
>
>
> ____________________________
> Richard H. Zander
> Missouri Botanical Garden, PO Box 299, St. Louis, MO 63166-0299 USA
> Web sites: http://www.mobot.org/plantscience/resbot/ and
> http://www.mobot.org/plantscience/bfna/bfnamenu.htm
> Modern Evolutionary Systematics Web site:
> http://www.mobot.org/plantscience/resbot/21EvSy.htm
> UPS and FedExpr -  MBG, 4344 Shaw Blvd, St. Louis 63110 USA
>
> -----Original Message-----
> From: taxacom-bounces at mailman.nhm.ku.edu
> [mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Michael Heads
> Sent: Monday, December 17, 2012 2:08 AM
> To: taxacom at mailman.nhm.ku.edu
> Subject: [Taxacom] Pacific biogeography
>
> Dear Taxacomers,
>
> A few months ago we were debating Hawaiian biogeography. In a discussion
> of this topic in the book cited below, I mapped the 2000, 4000 and 5000
> m isobaths of the central Pacific. O'Grady et al. (Taxon 61: 702. 2012)
> have now suggested that this was 'disingenuous', because sea-level has
> not dropped by more than 100 m or so. But the authors overlooked the
> *1000s* of meters of subsidence that the Pacific seafloor itself has
> undergone. This is well-known to geologists and I discussed it in the
> book.
>
> As the seafloor has drifted away from the East Pacific Rise - the
> spreading ridge that produced it - it has cooled (increasing its
> density) over tens of millions of years and has subsided by these large
> amounts. This has led to the submergence of most of the islands that
> were perched on it.
> The current high islands are new ones. Evidence for the subsidence is
> seen in the numerous atolls of the region, formed by coral reefs which
> have grown as the seafloor subsided. The many flat-topped seamounts
> (guyots) located north, south, east and west of Hawaii are former high
> islands that were eroded to sea-level before being submerged with the
> tectonic subsidence.
>
> Michael Heads
> --
> Wellington, New Zealand.
>
> My new book: *Molecular panbiogeography of the tropics. * University of
> California Press, Berkeley.
>
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