[Taxacom] Biogeography of Australasia

Tue Mar 25 01:14:46 CDT 2014

A lot of reef organisms show very high levels of genetic/geographic
structure (allopatry). This discovery has caused a paradigm shift in marine
biology, and the recognition of local endemics. In much the same way, the
high levels of geographic structure even in microrganisms have caused a
revolution and the rejection of the old idea that 'everything is everywhere
and the environment selects'.

Michael

On Tue, Mar 25, 2014 at 5:11 PM, Stephen Thorpe
<stephen_thorpe at yahoo.co.nz>wrote:

> Shallow water species would need to lack actively swimming or planktonic
> or phoretic larvae ...
>
>   *From:* Michael Heads <m.j.heads at gmail.com>
> *To:* Stephen Thorpe <stephen_thorpe at yahoo.co.nz>
> *Cc:* JF Mate <aphodiinaemate at gmail.com>; Taxacom <
> taxacom at mailman.nhm.ku.edu>
> *Sent:* Tuesday, 25 March 2014 5:07 PM
>
> *Subject:* Re: [Taxacom] Biogeography of Australasia
>
>   Many cases of vicariance in island groups are most easily explained if
> the organisms regularly move between nearby islands, as a metapopulation on
> individually ephemeral islands. If the island group is rifted apart, the
> metapopulation may be divided by vicariance into two, as between Vanuatu
> and Fiji for example. This process can  operate on terrestrial biota, but
> also reef groups that require shallow water.
>
> Michael
>
>
>  On Tue, Mar 25, 2014 at 4:50 PM, Stephen Thorpe <
> stephen_thorpe at yahoo.co.nz> wrote:
>
>  The distinction between vicariance vs. dispersal scenarios really only
> makes sense for terrestrial allopatric species separated on oceanic
> islands. Then we can ask if one of the species is derived from ancestors
> which did not need to swim or fly from another island. This would be
> vicariance. Amphibians are good examples, as they can't fly (actively or
> passively) and they can't tolerate seawater.
>
> Stephen
>
>   *From:* Michael Heads <m.j.heads at gmail.com>
> *To:* JF Mate <aphodiinaemate at gmail.com>
> *Cc:* Taxacom <taxacom at mailman.nhm.ku.edu>
> *Sent:* Tuesday, 25 March 2014 4:27 PM
> *Subject:* Re: [Taxacom] Biogeography of Australasia
>
> Hi Jason,
>
> You said:
>
> 'This is a play on words. There is no valid/clear-cut distinction
> between "chance dispersal", "range extension" or your "dispersal" vs
> the meaning of the word as used by most biologists. I understand that
> panbiogeography requires this (non-existant) difference to distinguish
> itself, but in the end you only need a few observed cases of organisms
> crossing barriers to show that, given the right conditions, dispersal
> is a valid mechanism.'
>
> The difference between normal, observed dispersal discussed by ecologists
> (e.g. weeds dispersing into a garden), and chance, 'jump' or 'long
> distance' dispersal as invoked by evolutionists, is that the former does
> not involve differentiation, whereas the latter is proposed as a mode of
> speciation.
>
> Dispersal theory explains range overlap by dispersal, but also explains
> allopatry by dispersal. Vicariance theory explains range overlap by
> dispersal, but explains allopatry by vicariance. Note that the dispersal
> invoked in vicariance theory is caused by geological change, whereas
> dispersal as invoked by dispersal theory to explain allopatry, is caused by
> chance.
>
> Michael
>
>
> On Sun, Mar 23, 2014 at 8:03 AM, JF Mate <aphodiinaemate at gmail.com> wrote:
>
> > Mostly a reply to John but a sprinkling to Michael as well
> >
> > The use of quotes such as "It was Darwin who invoked the concept of
> > miracles for anyone denouncing his theory of centers of origin and
> > dispersal.  You are welcome to believe in extraordinary events ..."
> > suggests that, either by accident or design, you (John) are implying
> > dispersal is a mechanism akin to religion. That and the daily readings
> > suggest baiting.
> >
> > As to why congruence of phylogeny and known geological events is
> > important (your words):  "...sequence of geological events may
> > indicate that the phylogeny predates the geology, is related to a
> > different geology, or that the geological reconstruction is wrong."
> > John, this makes Panbiogeography unfalsifiable. Your fallback line is
> > "geology/genes/phylogeny" could be wrong if they don´t match a purely
> > vicariant model. Yes, I am sure that as more evidence acumulates the
> > biogeographical scenarios of certain groups will have to change. But
> > where panbiogeography fails is in the closed, one size-fits-all
> > mechanism department. Science is never "the last word" but the best
> > fit to facts. By using this to shield Panbiogeography you are
> > purposefully using scientific uncertainty to protect your ideas.
> >
> > As to "The significance of observed cases of dispersal of highly
> > vagile species as evidence of chance dispersal being a significant
> > force in biogeography is questionable and does not predict the
> > tectonic correlations between good and poor dispersers (in the sense
> > of means of dispersal)." There are plenty of examples of species
> > (mostly good flyers) which have crossed significant barriers (even
> > oceans) and colonized new areas in recent history. How are these
> > examples not appropriate to the discussion? As for successful
> > colonization, just look at gardeners in Europe or NA. Thousands of
> > introduced, carefully nurtured plants, often cultured for generations
> > and only a small fraction ever becomes naturalized. I acknowledge the
> > fact that successful dispersal over significant barriers (sea, major
> > ranges) can be an unlikely event on a daily event but over millions of
> > years a small probability can really make a impact. The mechanism is
> > certainly common enough to suggest it does not require divine
> > intervention to happen.
> >
> > "Similarly, repopulation does not substanciate chance dispersal as a
> > significant force in the sense of chance dispersal being a major
> > mechanism in biogeography." and Michael "No-one is arguing that
> > dispersal is a significant force. All organisms have dispersed to
> > their current locations. Dispersal can be observed every day.
> > Vicariance biogeography has never denied dispersal - you can't just
> > have vicariance otherwise there would only be a single taxon in any
> > area."
> >
> > This is a play on words. There is no valid/clear-cut distinction
> > between "chance dispersal", "range extension" or your "dispersal" vs
> > the meaning of the word as used by most biologists. I understand that
> > panbiogeography requires this (non-existant) difference to distinguish
> > itself, but in the end you only need a few observed cases of organisms
> > crossing barriers to show that, given the right conditions, dispersal
> > is a valid mechanism. Maybe not 99% of the time, but chance plays a
> > bigger part in evolution than 0, and that is what matters.
> >
> > Best
> >
> > Jason
> >
> > _______________________________________________
> > Taxacom Mailing List
> > Taxacom at mailman.nhm.ku.edu
> > http://mailman.nhm.ku.edu/mailman/listinfo/taxacom
> > The Taxacom Archive back to 1992 may be searched at:
> > http://taxacom.markmail.org/
>
> >
> > Celebrating 27 years of Taxacom in 2014.
> >
>
>
>
> --
> Dunedin, New Zealand.
>
> My recent books:
>
> *Molecular panbiogeography of the tropics.* 2012. University of California
> Press, Berkeley. www.ucpress.edu/book.php?isbn=9780520271968
>
> *Biogeography of Australasia:  A molecular analysis*. 2014. Cambridge
> University Press, Cambridge. www.cambridge.org/9781107041028
>
> _______________________________________________
> Taxacom Mailing List
> Taxacom at mailman.nhm.ku.edu
> http://mailman.nhm.ku.edu/mailman/listinfo/taxacom
> The Taxacom Archive back to 1992 may be searched at:
> http://taxacom.markmail.org/
>
>
> Celebrating 27 years of Taxacom in 2014.
>
>
>
>
>
> --
>  Dunedin, New Zealand.
>
>  My recent books:
>
> *Molecular panbiogeography of the tropics.* 2012.University of California
> Press, Berkeley. www.ucpress.edu/book.php?isbn=9780520271968
>
> *Biogeography of Australasia:  A molecular analysis*. 2014. Cambridge
> University Press, Cambridge. www.cambridge.org/9781107041028
>
>
>

-- 
Dunedin, New Zealand.

My recent books:

*Molecular panbiogeography of the tropics.* 2012. University of California
Press, Berkeley. www.ucpress.edu/book.php?isbn=9780520271968

*Biogeography of Australasia:  A molecular analysis*. 2014. Cambridge
University Press, Cambridge. www.cambridge.org/9781107041028