[Taxacom] Pacific biogeography

[Michael Heads]

Hi Rich and Jason,

I'm not sure that subsidence is well known these days. Darwin and others
understood its significance in the 19th century, Mayr, Zimmerman and others
knew about it the 20th century, but the authors of the Taxon review seemed
unaware of it. I guess they are not the only ones, which is why I mentioned
it.

Michael

On Tue, Dec 18, 2012 at 10:51 AM, Richard Pyle <deepreef at bishopmuseum.org>wrote:

> I agree with Jason here.  Pacific biogeography has been one of my areas of
> interest for the past quarter of a century (and it continues to be so), and
> these things (rates of subsidence, sea level changes, seamounts as current
> and historical stepping stones) were common knowledge and points of
> discussion back when I was an undergrad in the mid-1980s.
>
> Aloha,
> Rich
>
> > -----Original Message-----
> > From: taxacom-bounces at mailman.nhm.ku.edu [mailto:taxacom-
> > bounces at mailman.nhm.ku.edu] On Behalf Of JF Mate
> > Sent: Monday, December 17, 2012 11:01 AM
> > To: Taxacom
> > Subject: Re: [Taxacom] Pacific biogeography
> >
> > The email feels like it was meant for someone else. Although our improved
> > understanding of the geological history of the Pacific has helped to
> solve
> > some problems (i.e. taxa older than the islands they currently inhabit)
> it
> is
> > not very clear to me how seafloor subsidence (a well known phenomenon
> > BTW) would significantly alter the biogeographical status quo or how this
> can
> > be invoked to support panbiogeographical theories. Any ideas?
> >
> > Jason
> >
> > On 17 December 2012 09:07, Michael Heads <m.j.heads at gmail.com> wrote:
> > >  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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-- 
Wellington, New Zealand.

My new book: *Molecular panbiogeography of the tropics. *
University of California Press, Berkeley.