[Taxacom] Transatlantic rafting not uncommon

[John Grehan]

Ken,

Just saying to and look up literature is not an informative response to
your assertion that there is "increasing evidence". Since you are making
the assertion you should have the gumption to be able to back up your
assertion by stating what you consider to be "increasing evidence".
Otherwise there is no way to know.

As Heads has already pointed out, the paper really does not present any
evidence of trans Atlantic dispersal at all, but misrepresents (as is
usually the case in molecular studies) minimal divergence estimates as
actual or maximal. It never cease to amaze me that in biogeography one
makes a virtue out of the vice of misrepresentation.

The paper is full of propaganda claims such as "Because Africa broke
from South America 100 Myr gao, and in the absence of any Laurasian
fossil amphisbaenid, only transatlantic dispersal could explain this
divergence". This is great stuff for teaching language - "only
transatlantic dispersal could explain" - yes if one is intellectually
asleep.

Similarity, "survival would have been possible" - yes if you want to
believe it is so.

"the most probable hypothesis to explain the presence of Cadea obn Cuba
is by an Eocene...transatlantic dispersal from northwestern Africa or
southwestern Europe" Again, only if you want to accept their personal
authority.

"Intriguingly, this pattern is similar to the one observed for the Cuban
geckos species Tarentola Americana, whose closest relatives have a
circum-Mediterreanean origin" Intriguing? Not for the biogeographer who
has some familiarity with biogeographic patterns in general. And in the
case of Tarentola one must invoke some mysterious means by which the
Tarentola group happen to have vicariant distributions - even within the
Macaronesion islands.

So in my opinion to appeal to Vidal et al to support dispersal is just
silly. 

I still prefer the lost continent Atlantis traders hypothesis as best
supporting dispersal for this group, and perhaps Atlantis traders were
also responsible for taking the caecilian amphibians even further,
across the Atlantic to or from western Africa, into southwestern
Ethiopia/southern Sudan, Kenya, Seychelles, India, and southeastern Asia
(but evidently no trading between the greater and Lesser Sunda.

John Grehan



-----Original Message-----
From: taxacom-bounces at mailman.nhm.ku.edu
[mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Kenneth Kinman
Sent: Wednesday, October 19, 2011 8:58 PM
To: taxacom at mailman.nhm.ku.edu
Subject: Re: [Taxacom] Transatlantic rafting not uncommon

John,
       As for Renner's work, just do a google search for:  Renner
transatlantic dispersal.  Lot's of interesting stuff pops up.

      And for amphisbaenian biogeography in particular, I would strongly
recommend reading the 2008 paper by Vidal (Biol Lett., 4:115-118), which
is freely available online.  I am not sure I will completely agree with
their phylogeny and conclusions (this is one group I want to look at
more carefully when I have time).  However, they make a very good case
that purely vicariant explanations of amphisbaenian evolution and
biogeography are very problematic (and overly simplistic) in the face of
more recent data.  And more than one transatlantic dispersal was almost
certainly involved during the Cenozoic.     

       And although I was initially surprised that such subterranean
lizards rafted across the Atlantic, I am not so surprised after thinking
about it today.  Massive land slides giving rise to large rafts of trees
would wash large masses of soil along with them.  Worm lizards washed
out in such an event would have to clamber onto a raft of trees or
perish in the sea.  Burrowing into soil is sort of like swimming, so I
doubt they would have much difficulty swimming in water when their life
depended on it.  The trees would also usually have insects upon which to
feed if the lizards got hungry enough (even if not the kind of insects
they normally would eat).  I don't find it all that terribly mysterious.
Anyway, I look forward to learning more about these lizards.     
              --------Ken  

----------------------------------------------------
John Grehan wrote:  

What increasing evidence? 

The amphisbaenians crossed the Atlantic by mysterious means (this idea
of dispersal being mysterious is periodically invoked by dispersalists).


How does Renner's work support transatlantic dispersal being due to
ocean currents? 
John Grehan 
John Grehan 
-----Original Message----- 
From: taxacom-bounces at mailman.nhm.ku.edu 
[mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Kenneth
Kinman Sent: Tuesday, October 18, 2011 11:58 PM 
To: taxacom at mailman.nhm.ku.edu 
Subject: [Taxacom] Transatlantic rafting not uncommon 
Dear All, 
      I have been reading a lot about increasing evidence for a variety
of taxa whose biogeography was affected by TransAtlantic dispersal,
especially by rafting (which I believe is the most common mode of
dispersal in such cases). 
      However, I was a bit shocked to learn that TransAtlantic rafting
has been proposed for amphisbaenians (worm lizards), burrowing reptiles
which one would think would be far more likely to be affected by
vicariance than by rafting.  See Vidal et al., 2008 (Biol. Lett., 
4:115-118).        
      As for plants, I noticed today that the work of Suzanne Renner
(and colleagues) tends to support my suspicion that TransAtlantic
dispersal of taxa seems to be most commonly due to ocean currents (i.e.,
rafting), rather than by wind or by birds.  I still think Rhipsalis
would have gotten from South America to Africa in that manner, but how
it got from there to islands in the Indian Ocean could be by a 
completely different vector.      
           -----------Ken Kinman 
______________________________________



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