[Taxacom] Pacific biogeography

[John Grehan]

The trouble with 'our' (whoever that is) improved understanding is that it
does not always appear to be consistently understood. I think the point
about the subsidence is that one cannot assume current topographic
elevations as unchanging and make biogeographic assertions on that basis -
which is what the critics  appear to have done.

John Grehan

On Mon, Dec 17, 2012 at 4:01 PM, JF Mate <aphodiinaemate at gmail.com> wrote:

> 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.
> > _______________________________________________
> >
> > Taxacom Mailing List
> > Taxacom at mailman.nhm.ku.edu
> > http://mailman.nhm.ku.edu/mailman/listinfo/taxacom
> >
> > The Taxacom archive going back to 1992 may be searched with either of
> these methods:
> >
> > (1) by visiting http://taxacom.markmail.org
> >
> > (2) a Google search specified as:  site:
> mailman.nhm.ku.edu/pipermail/taxacom  your search terms here
>
> _______________________________________________
>
> Taxacom Mailing List
> Taxacom at mailman.nhm.ku.edu
> http://mailman.nhm.ku.edu/mailman/listinfo/taxacom
>
> The Taxacom archive going back to 1992 may be searched with either of
> these methods:
>
> (1) by visiting http://taxacom.markmail.org
>
> (2) a Google search specified as:  site:
> mailman.nhm.ku.edu/pipermail/taxacom  your search terms here
>