[Taxacom] "Masteria mystery" solved?

[Michael Heads]

Hi Ken,
 
The only reason you've suggested for Masteria having the distributional breaks that it does (at the Philippines/New Guinea and at northern Colombia) is that it occurs elsewhere but hasn't been collected there yet. You could explain all the other trans-tropical-Pacific groups (and any other pattern, anywhere) in this way, as no group and no area has been perfectly studied, but is this approach really 'empirical'?  
 
Also, why assume that the locality of a paraphyletic basal group (e.g. South American Masteriinae) represents a center of origin? This is based on a theory, not empirical data. South America could just as easily be a center of differentiation (in a widespread ancestor) as a center of origin.
 
I didn't mean to suggest that Masteria itself had been on the Inca Plateau, which is subducted under Peru (Masteria is further north and may have been on other accreted or subducted structures). The groups on a subducting structure will either go extinct or disperse to adjacent land. The latter process may help  to explain the great diversity seen at convergent plate margins, for example in California and New Caledonia.
 
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: Thursday, 12 January 2012 10:00 AM
Subject: [Taxacom] "Masteria mystery" solved?
  
John,        
      Well, at least I could point to actual specimens of all three
genera of Masteriinae from Argentina and Chile and northern South
America.  This seems more empirical than Michael's story that the "lost"

Inca Plateau might have carried them to South America from the central
Pacific.  You can't collect spiders on the Inca Plateau (assuming that
it existed), because this hypothetical plateau got subducted under South

America (which is why they call it the "lost" Inca Plateau).      
          ---------Ken 
--------------------------------------------------------

John Grehan,
     There is no empirical basis for this or any such 'center of origin'

for Masteria. Might as well suggest they came from Mars. 
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, January 11, 2012 12:34 PM 
To: taxacom at mailman.nhm.ku.edu 
Subject: [Taxacom] "Masteria mystery" solved? 
Hi Michael,  
      Well, I suggested that the center of origin of
Masteria was in the Antarctica area.  Antarctica itself was relatively
warm in the Mesozoic, but might have not been warm enough for Masteria,
unless they retreated into caves during the winter months (which is
possible, since many Masteria seem to like caves).    
  
      However, I would lean more toward an origin a bit further north
(perhaps Argentina).  Argentina is likely where the entire Subfamily 
Masteriinae would have originated.                     
                        --------Ken 
                   
P.S. I wonder if anyone has explored any caves in Borneo looking for
Masteria.   
---------------------------------------------- 
Michael Heads wrote: 
Hi Ken, 
  I'm not quite sure that I follow your line of reasoning. Are you
suggesting a center of origin for Masteria in Antarctica? Platnick (AMNH 
spider website) does not accept that the Indian species of Ischnothele 
belongs in the genus (America/India would be a very unusual 
distribution). He lists Euagrus from Taiwan, Guatemala to USA (standard
trans-tropical Pacific) and South Africa (standard
trans-Atlantic). The Atlantic opened about the same time that the
central Pacific plateaus formed (mid-Cretaceous), which suggests a
simple global process for Euagrus.    I don't think Masteria is
(currently) an island-hopper - all the 
species in the Caribbean and all but one in the Pacific are endemic to
single archipelagos, compatible with allopatric differentiation in a
phase of immobilism. On the other hand, its Cretaceous ancestors may
well have been actively dispersing when they colonized the new areas 
of land provided by the plateaus (possibly from prior islands in the
region).   You suggest Mesozoic vicariance for Masteria and I
agree. The large igneous plateaus in the central Pacific have
drifted long distances westward (Ontong Java plateau etc.) and eastward
(Inca plateau etc.). They included forest (or at least trees) and
presumably there were also animals there, so... what happened to
them? Could they have been incorporated into America along with the
plateaus? This might explain the distinctive distribution of
Masteria in America (only in the Caribbean), and in the west Pacific
(west only to New Guinea - Philippines).   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: Tuesday, 10 January 2012 3:53 AM 
Subject: [Taxacom] "Masteria mystery" solved? 
  
Hi Michael,            
    I think I've solved a lot of the mystery surrounding the 
Masteria disjunction.  And thankfully, I didn't need either 
panbiogeography or terranes floating long distances east and west across 
the Pacific.  
  I looked beyond subfamily Masteriinae to other subfamilies 
of Dipluridae, and the distribution of Ischnothele jumped out at me
(neotropics plus one species in India).  Euagrus is somewhat similar, 
but involved South Africa instead of India.      This pretty 
clearly points to vicariance (during the Mesozoic) centered far to the
south (in the area of Antarctica), and of course any intermediate
species still in the southern polar region would have eventually gone 

extinct (from the cold in particular).        So subsequent 
dispersal of Masteria (by rafting, ballooning, or whatever) would have
been over shorter distances, perhaps the longest being east to Fiji. 
This genus is clearly a fairly good island-hopper (in both the Pacific
and Caribbean).  On the other hand, genus Ischnothele didn't need to
island-hop, but simply rode on India as it travelled north to Asia. 
    Therefore, I predict that Masteria will be found on other
islands in the Pacific, perhaps even Borneo.  However, diplurid
spiders seem to have had little luck invading very much of Eurasia
beyond the area around India, so competitive exclusion by other 
mygalomorphs could be a factor (perhaps even in Borneo).     
    --------Ken Kinman  
______________________________________ 



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