[Taxacom] Panbiogeography

Wed Apr 2 16:00:29 CDT 2014

Seeing the comments by our dispersalist friends, I wonder then, whether Madagascar was empty, a piece of nude rock, before the "great migration" out of Africa?
Juerg De Marmels

> Date: Thu, 3 Apr 2014 05:20:57 +1300
> From: calabar.john at gmail.com
> To: kinman at hotmail.com
> CC: taxacom at mailman.nhm.ku.edu
> Subject: Re: [Taxacom] Panbiogeography
> 
> 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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> > Celebrating 27 years of Taxacom in 2014.
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> Celebrating 27 years of Taxacom in 2014.