[Taxacom] Masteria spiders and panbiogeography (was:Salvadoraceae paraphyletic?)

[Michael Heads]

Hi Ken,
 
All organisms move and so you can explain any distribution at all by just saying 'it must have moved there'. Easy! Likewise, all organisms eventually go extinct, so any distribution can be explained by simply saying 'it went extinct everywhere else'. Other common, ad hoc explanations include 'poor collecting', 'imperfect taxonomy', 'movement by indigenous people', etc., etc. None of these require any knowledge at all of geography, general biogeographic patterns, geology, or anything else, and so they're always very popular. But these explanations don't 'go' anywhere - they're not progressive research programs and they don't lead to any new hypotheses. 
 
Masteria reaches west to only to New Guinea and the Philippines. Why there exactly? Why would a group be able to disperse 10000 km across the Pacific and invade New Guinea and the Philippines but not be able to cross a few extra kilometers into Borneo? Eastward, Masteria is only on the Caribbean plate and its margins (Panama, northern Colombia, northern Venezuela, Antilles). Why there exactly?  Is it just chance that all these areas represent accreted Pacific terranes and the boundaries of the group coincide with plate margins - the most important tectonic breaks on Earth?
 
You ask for trans-tropical Pacific distributions in groups with 'little or no dispersal ability'. There are no organisms with no dispersal ability. (Groups with good dispersal ability are sometimes even more impressive for demonstrating the precision of the breaks). Anyway, I was looking at Philippines/Sulawesi distributions to-day and came across these ones:      

1. A clade in the freshwater gastropod family Pachychilidae: Sulawesi (Tylomelaenia) + Torres Strait islands (Pseudopatamis) + Central
America (Pachychilus) (Kohler and Glaubrecht, 2007).
2. The Catesbaeeae–Chiococceae
complex (Rubiaceae): Philippines, Palau, Biak Island (off north-western New Guinea), Solomon
Islands,Vanuatu, Fiji, and
Tonga; tropical America (Motley et al.,
2005).  
3. Schleinitzia(Fabaceae): Philippines, Marianas, New Guinea to the Society
Islands + Kanaloa:  Hawaii + Desmanthus:
warm America and the
Caribbean (Lewis et al., 2005). 
 
The reason for looking at drifting plateaus/island arcs when considering distributions in the Pacific is that this is what the regional geology consists of.  In cratonic areas, such as the Amazon or the Congo, there is no terrane accretion. Instead, the geology involves the last great marine transgressions in the mid-Cretaceous, intracontinental failed rifts again in the mid-Cretaceous, etc., and so panbiogeography looks at these. 
 
Michael
 
Wellington, New Zealand.


My papers on biogeography: http://tiny.cc/HeadsPubs
My new book 'Molecular Panbiogeography of the Tropics': http://tiny.cc/MolPanbio



________________________________
 From: Kenneth Kinman <kennethkinman at webtv.net>
To: taxacom at mailman.nhm.ku.edu 
Sent: Monday, 9 January 2012 3:46 PM
Subject: [Taxacom] Masteria spiders and panbiogeography (was:Salvadoraceae paraphyletic?)
 
John, 
     Well, if you are talking about the panbiogeography
literature in particular, reading it is often like swimming through
molasses.  And even having spent time doing so, I find the methodologies

and resulting conclusions to often be rather questionable.  And I am
clearly not alone in that in that regard.    
      Specifically, I find panbiogeography to be far too
dependent on terranes carrying taxa overly long distances across the
Pacific, and even trying to support dispersalist views by attacking
molecular time estimates which would not chronologically support the
hypothesis of terranes carrying the taxa in question.  The suggestion
that possible mid-Pacific terranes carried taxa west to New Guinea and
east to tropical America is the perhaps the most extreme extrapolation
of such ideas in an obvious effort to explain away more reasonable
dispersalist possibilities.    

       In the case of genus Masteria, they are rather small, even as
adults.  So ballooning by their tiny baby spiderlings over long
distances would not be surprising.  Over millions of years, it would not

be surprising that such babies ballooning off New Guinea would be caught

up in just the right storm to carry them to the American tropics.  And
if you think that improbable, another dispersal possibility is rafting.
Such spiders probably hunt for prey in trees (particularly in those
covered with moss), so rafting on trees is also a possibility (even by
adults).  And thirdly, I would even regard a trans-Beringia dispersal
during a very warm period as just as likely (if not more so) than
Masteria arising in the middle of the Pacific and then being transported

west to New Guinea and east to South America.  Anyway, if Masteria is
one of your best examples of mid-Pacific terranes travelling very long
distances, both to the east and the west, I think you need to find more
and better examples (especially taxa with little or no dispersal
ability).      
            -------------Ken                                          

---------------------------------------------- 
John Grehan wrote: 
 Ken, 
For one who forcefully expresses so much confidence in dispersal ability

as the key to biogeography it is surprising that you express such
ignorance of biogeographic patterns extensively documented in the
literature. At least in support of your systematic arguments you show
familiarity with the systematic literature. Perhaps its time to do the
same for biogeography. 
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: Friday, January 06, 2012 9:57 PM To: taxacom at
mailman.nhm.ku.edu Subject: Re: [Taxacom] Salvadoraceae paraphyletic?
(was: North America...) 
Hi Michael, 
              If such groups are "quite
common", I am surprised that your list of examples is so short. And as
for central Pacific terranes, I am unable to figure out what you mean by

"some including wood fossils". 
                              -----------Ken 
---------------------------------------------- 
Michael Heads wrote: 
            Trans-tropical Pacific groups in New

Guinea and tropical America (matching Bataceae) are quite common.
Examples include the plant groups Polygalaceae tribe Moutabeeae and a
clade in Monimaceae (both from molecular studies), and the spider
Masteria (from Platnick's website). The disjunction may involve central
Pacific terranes (some including wood fossils) that accreted westward to

New Guinea etc., eastward to the Caribbean, Colombia etc.



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