[Taxacom] Dispersal example

Mon Apr 21 04:20:56 CDT 2014

Hi Pierre,

Historically, Nelson, Platnick and Rosen's vicariance biogeography was
meant to be a fusion of Croizat's panbiogeograpy, Hennig's phylogenetic
systematics, and Popper's falsifiability criterion of good science. In
practice, there was a strong emphasis on lots of cladograms, very
little geology (just the standard breakup sequence of Pangaea), and
practically no ecology. The term 'vicariance biogeography' was probably
misleading, as dispersal was always accepted (as the means of generating
overlap). But the emphasis was on vicariance as the main explanation for
allopatry (as in panbiogeography). In practice, traditional, strict vic.
bio. came to a bit of a dead end, because many groups do not show simple
phylogenetic congruence with the breakup sequence of Pangaea. This can be
caused by, for example, differentiation during pre-drift rifting
(which lasts for millions of years) or by post-drift accretion.

I like Gillespie et al.'s (2012 TREE 27:47) characterization: ?Dispersal
biogeography? is a research program that explains the geographical
distribution of organisms (allopatry and overlap) by dispersal, while
?vicariance biogeography? explains distribution (allopatry and overlap)
with reference to geological events. (Strictly speaking, this really
describes panbiogeography rather than vicariance biogeography).

Your point about using fine-grained maps is important, and in theory this
should solve the problems of a using priori areas. But in practice, if you
look at the many biogeographic ('ancestral area') analyses that are coming
out, using programs such as DIVA, DEC etc., they all use traditional areas
(e.g. 'western Malesia', 'Borneo', 'South America', 'New Zealand',
'Australia', 'New Caledonia' etc.). These are all tectonic and
biogeographic composites, and this can badly undermine the analyses.

With respect to mutation, I agree that it must come before selection. But
in the modern synthesis, mutation does not orient the course of evolution:

Evolution is not primarily a genetic event. Mutation merely supplies the
gene pool with genetic variation; it is selection that induces evolutionary
change. (Mayr, 1963: 613).

Darwinism and the Modern Synthesis can be defined as: ?the theory that
selection is the only direction-giving factor in evolution.? (Mayr, 1980:
3).

Mutation rates are so low that mutation pressure by itself will not bring
about significant changes in gene frequencies in populations... mutation
pressure, whatever its strength, cannot be an orienting force in
evolution... Orientation or directedness in evolution is brought about by
other evolutionary forces. (Grant, 1985: 52-53).

This is why Nei's 'mutation-driven evolution' is so interesting.

On Mon, Apr 21, 2014 at 10:51 AM, Pierre Deleporte <
pierre.deleporte at univ-rennes1.fr> wrote:

>
> Hi Michael,
>
> thank you for your comment
>
> for me this makes just more similarity
> between panbiogeography and vicariance biogeography
> (I mean similarity in methodological principles,
> not the practice of such or such biogeographer).
>
> As for pre-defined biogeographical areas,
> recent developments make use of grids of different spatial grains
> so that the areas of endemism emerge from and objective analysis
> of distributional data -
> And again, this can make no methodological difference
> (both methods can use such an approach).
>
> As for "orthogenesis", for me it's a completely different matter -
> hardly connected with historical biogeography
> ("Croizat dixit" is not sufficient for me);
> mutation is the primary evolutionary process
> (it must logically preceed any possible selection) -
> but orthogenesis can't be invoked /a la legere/,
> and certainly not as way to discard standard phylogenetic patterns
> when they would contradict some panbiogeographical scenario
> (hence tending to make it unfalsifiable)
>
> just trying to make up my methodological mind,
> nothing personal
>
> Best,
> Pierre
>
>
> Le 21/04/2014 00:00, Michael Heads a ?crit :
> > Hi Pierre,
> > You write: 'I wonder what are exactly the differences between
> > vicariance biogeography and panbiogeography maybe the rejection of
> > geological arguments by the latter...'.
> > In fact, panbiogeography engages much more
> > with geology than traditional vicariance biogeography does. E.g.
> > Nelson & Platnick's (1981) standard text on vicariance biogeography
> > has long discussions about the possible cladistic relationships
> > among Borneo, Java and Sumatra. In contrast, panbiogeography (like
> > geology) does not use geographic areas as a priori entities and
> > instead looks at distributions  and tectonics, which turn out to
> > deconstruct Borneo, Sumatra and Java.
> > Panbiogeography has introduced many geological concepts to
> > biogeography. For example, it was the first to look at terranes in
> > relationship to distributions, in New Zealand in the 1980s. This is
> > now a standard approach in work on the Mediterranean. In another
> > example, panbiogeography has studied disjunctions along transform
> > (strike-slip) faults. In another, recent example, I stressed the
> > significance of the Musicians Seamounts off Hawaii. These are now
> > known to be flat-topped (eroded to sea-level) and so were former
> > islands. I don't know of any other biogeographic work that has
> > mentioned these.
> > Other examples of geological structures where the potential
> > biogeographic effects were first examined by panbiogeography include
> > the accreted terrane/craton boundary in western Colombia, the accreted
> > terrane/craton boundary in New Guinea, the central African rift system
> > (not the Great Rift), and the Lebombo monocline in southern Africa.
> > Michael
> >
> >
> > On Mon, Apr 21, 2014 at 8:05 AM, Pierre Deleporte
> > <pierre.deleporte at univ-rennes1.fr
> > <mailto:pierre.deleporte at univ-rennes1.fr>> wrote:
> >
> >
> >     agreed, but this part is not an exclusive property of
> panbiogeography,
> >     it is a basic methodological concept of standard "vicariance"
> >     biogeoraphy
> >
> >     from the moment when panbiogeographers make use of phylogenetic
> >     relationships
> >     (and not just distributional patterns of "taxa" connected by
> >     "track" lines)
> >     I wonder what are exactly the differences
> >     between vicariance biogeography and panbiogeography
> >
> >     maybe the rejection of geological arguments by the latter,
> >     while Nelson and Platnick (1981 - Systematics and biogeography:
> >     cladistic and vicariance)
> >     explicitely stated that biogeographical patterns are just patterns,
> >     that should be explained via the integration of geological
> >     considerations
> >
> >     Nelson and Platnick even underlined that some patterns
> >     can be produced via vicariance as well as via coordinated
> >     dispersal over
> >     barriers,
> >     which should somewhat temperate the vicariance-dispersal dispute...
> >
> >     best,
> >     Pierre
> >
> >     Le 20/04/2014 20:41, Curtis Clark a ?crit :
> >     > On 2014-04-17 4:26 PM, John Grehan wrote:
> >     >> ...dispersalist have
> >     >> for a long time asserted that chance dispersal can account for any
> >     >> distribution.
> >     > Thus dispersal cannot be falsified. It only serves as an
> explanation
> >     > when all falsifiable alternatives have been falsified. IMO
> >     > panbiogeography has a lot of unnecessary baggage (orthogenesis
> >     being a
> >     > major one), but this part makes sense.
> >     >
> >
> >
> >     --
> >     Pierre DELEPORTE
> >     UMR6552 EthoS
> >     Universit? Rennes 1
> >     CNRS
> >     Station Biologique
> >     35380 PAIMPONT
> >     t?l (+33) 02 99 61 81 63 <tel:%28%2B33%29%2002%2099%2061%2081%2063>
> >     fax (+33) 02 99 61 81 88 <tel:%28%2B33%29%2002%2099%2061%2081%2088>
> >
> >
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> >
> >     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—80520271968
> > <http://www.ucpress.edu/book.php?isbn—80520271968>
> > /Biogeography of Australasia:  A molecular analysis/. 2014. Cambridge
> > University Press, Cambridge. www.cambridge.org/9781107041028
> > <http://www.cambridge.org/9781107041028>
>
>
> --
> Pierre DELEPORTE
> UMR6552 EthoS
> Universit? Rennes 1
> CNRS
> Station Biologique
> 35380 PAIMPONT
> t?l (+33) 02 99 61 81 63
> fax (+33) 02 99 61 81 88
>
> _______________________________________________
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> 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—80520271968

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