[Taxacom] Salvadoraceae paraphyletic? (was: North America...)

[John Grehan]

Ken,

This dispersal stories are not disconcerting at all. They are empirically meaningless. If there is direct evidence of such travels then ok, but to just make it up has no scientific merit as far as I am concerned. When instead one sees extensive vicariism and comparable ranges in both supposedly good and poor dispersers, along with correlated tectonics, the imagined dispersal just becomes irrelevant to understanding the spatial differentiation.

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: Thursday, January 05, 2012 9:56 PM
To: taxacom at mailman.nhm.ku.edu
Subject: Re: [Taxacom] Salvadoraceae paraphyletic? (was: North America...)

John,
      Theoretically, a single character may be all that there is in an extremely densely packed series of fast evolving of clades.  However, in the vast majority of cases, there should be multiple synapomorphies, simply because the fossil record is so poor and

thus eliminating the intermediates (which very often wouldn't show the
needed information even if there were more intermediate fossils).                        
  
      In this case, we have a double whammy of an extremely poor fossil record and not sufficient research done on extant taxa (especially on Azima and Dobera).  Morphology (of the flowers, etc.) has

raised more questions than answers, so the answer most likely lies in characters that are biochemical or better yet a lot more molecular sequences.     
  
        Nevertheless, there does seem to be a general trend of Salvadoraceae in the western part of Eurasia living in drier, terrestrial habitats (although often in soils that are somewhat high in salinity). But in eastern Asia, we see a greater ability to live in wetter and even more saline habitats near the coasts.  Genus Azima seems

the most adapted of Salvadoraceae to such wetter saline environments, with the ability to disperse to oceanic islands (such as islands in the Indian Ocean). 

      I can see this as a precursor (pre-adaptation if you wlll) for Azima jumping the Wallace Line and giving rise to genus Batis in New Guinea and Australia.  Azima has seeds (and even their whole bodies) that had become pre-adapted to dispersals (even across the entire Pacific Ocean, although perhaps only once under just the right conditions).  That their ancestors colonized islands in the Indian Ocean

could have been just one step in their subsequent invasion of Australasia and then even the coasts of the tropics of the New World.
                       
               -----------Ken        
                          
P.S. This might seem a bit ironic, since the ancestors of the Salvadoraceae-Bataceae clade no doubt came from eastern North America in

the first place and then migrated to Africa and/or Europe.   However, it is perhaps not surprising that it could have taken a trip around the globe to acquire adaptations to more extreme environments in order to eventually reinvade North America and compete with relatives they left behind many millions of year earlier.  But I guess such a scenario must be disconcerting to someone who finds it hard to accept dispersal as being that important, especially potentially so serially extensive biogeographicaly.
---------------------------------------------              
John Grehan wrote: 
           I am not aware that there is anything preordained about the number of synapomorphies being required for any one clade. One is sufficient. Of course it would only take one other character relationship to make that problematic so it may be regarded as

a 'weak' clade, but then again one character may be all that there is. 



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