[Taxacom] Panbiogeography

Wed Apr 2 11:20:57 CDT 2014

What is baffling is that Ken continues to assert a falsehood - that the
importance of dispersal is minimized in panbiogeography. Reminds me a bit
of American politics (perhaps politics in general) that if something is
claimed often enough it must be true. It is not. Hence the key
panbiogeographic formulation: dispersal = translation in space + form
making.

As for Madagascar, it is not about whether or not dispersal occurred, but
under what circumstances. Claims that much or all of the biota originated
via chance overwater dispersal from Africa may be reasonable as a
conjecture, but there is no analytic evidence in support (and molecular
divergence estimates based on fossil or island ages, no matter how recent,
do not .preclude earlier events involving continuity of land).

John Grehan

On Thu, Apr 3, 2014 at 2:20 AM, Ken Kinman <kinman at hotmail.com> wrote:

> Hi Jason,
>         Thanks for passing along that weblink.  It baffles me that John
> and Michael continue to minimize the importance of dispersal, especially
> when it comes to Madagascar.  The real question in my mind on that subject
> is not whether rafting was the major factor, but how that rafting was
> caused.  Was it massive river flooding in adjacent Africa washing large
> rafts of vegetation (and any fauna that hitched a ride) into the ocean, or
> was it tsunamis doing the same thing?  Perhaps both, although in the case
> of Madagascar, I would tend to favor river flooding over tsunamis.  On the
> other hand, dispersal over longer distances (as in the Pacific) might
> require much larger rafts of vegetation, and tsunamis would be better at
> producing the rare monster rafts containing a very large number of trees
> tangled together.
>                 ---------------------Ken Kinman
>
> ---------------------------------------------------------------------------------------------------
> > Date: Tue, 1 Apr 2014 00:54:51 +0200
> > From: aphodiinaemate at gmail.com
> > To: taxacom at mailman.nhm.ku.edu
> > Subject: Re: [Taxacom] Panbiogeography
> >
> > What do you know, Rupert sent me this link regarding potential ocean
> > dispersal resulting from the Tohoku earthquake:
> >
> > http://dx.doi.org/10.1038/495013a
> >
> > This surely qualifies as a "black-swan" event, also known as "chance"
> > (not the probability concept mind you,) ;) .
> >
> > Best
> >
> > Jason
> >
> > On 28 March 2014 21:51, Stephen Thorpe <stephen_thorpe at yahoo.co.nz>
> wrote:
> > > Dispersal can also occur passively, by rafting on floating chunks of
> > > habitat, or phoresy on other animals
> > > From: JF Mate <aphodiinaemate at gmail.com>
> > > To: Taxacom <taxacom at mailman.nhm.ku.edu>
> > > Sent: Saturday, 29 March 2014 9:43 AM
> > > Subject: Re: [Taxacom] Panbiogeography
> > >
> > > Dear John
> > >
> > > after looking at you replies I have realised that we are chasing each
> > > other in circles and that you constantly refer to Michael?s book when
> > > I seek a more concrete answer. This makes it rather difficult and
> > > unproductive. So, I will simply state the following definitions under
> > > which I operate:
> > >
> > >
> > > -Dispersal: change in location. The difference between long range and
> > > short range is merely in the probability of each resulting in
> > > successful (i.e. surviving and reproducing). "Short" and "long" are
> > > taxon and site specific.
> > >
> > > -Barrier: impediment to movement. When I defined what a barrier was I
> > > failed to consider partial blockage but instead opted for a binary
> > > barrier. I see this was a mistake on my part, so I hope this will
> > > clear the matter.
> > >
> > >
> > > Dispersal by insects >100Km from the source (mostly coastline) are
> > > very common, even when flying a few meters above the surface.
> > > Transoceanic flights by large, easily noticed insects (mostly
> > > butterflies) have been documented several times in recent times.
> > > Considering that there are observed examples of organisms dispersing
> > > beyond barriers (usually crossing bodies of water) I think dispersal
> > > is a valid mechanism.
> > >
> > > Furthermore the lack of genetic structure in many insect species, even
> > > in discontinuous ranges spanning thousands of kilometers indicates a
> > > fair degree of dispersal. Granted that the opposite is true and
> > > particularly striking examples are common (headwater stream insects
> > > for example). But since examples from both mechanisms can be found, I
> > > don?t feel this somehow disproves the other.
> > >
> > > As to your statements, I feel a couple are inconsistent. I would be
> > > grateful for a clearer explanation:
> > >
> > > "... but when there is a biogeographic break correlated with a
> > > tectonic break there is reason to consider that they are related. ...
> > > The panbiogeographic method is about pattern analysis. In principle,
> > > distribution data provide an empirical resource. Speculations about
> > > imagined chance dispersal does not."
> > > So what happens when a biogeographic break and a tectonic one do not
> > > coincide? Furthermore, correlation is not necessarily causation, so
> > > don't panbiogeographers also speculate?
> > >
> > > "No, the patterns make the theory problematic as the patterns are
> > > incongruous with the expectations of chance dispersal. ... However you
> > > chose your words, the point is that panbiogeographic analysis shows
> > > that distance is not a predictor of distribution range for
> > > differentiated taxa so the 'probabilities' are contingent upon the
> > > relevant factors of geological, climatic, or human disruption.'
> > > If dispersal is random, the result of the interaction of numerous
> > > factors, is it suprising that simply using one (distance) doesn't
> > > work? An island may be upwind and therefore rarely receive flying
> > > insects from the minland whereas a more distant, downwind island can
> > > receive a fairly constant rain of wind-carried organisms. Gillespie et
> > > al provide a nice review.
> > >
> > > "When it comes down to explaining vicariant patterns the principal
> > > choice has been to frame the origin in terms of dispersal from centers
> > > of origin."
> > > I feel otherwise.Can you please support this argument?
> > >
> > > Best
> > >
> > >
> > > Jason
> > >
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> > >
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> > >
> > >
> >
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> > Celebrating 27 years of Taxacom in 2014.
>
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> Celebrating 27 years of Taxacom in 2014.
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