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

[Michael Heads]

Hi Ken, 
I don't think proposing ad hoc changes to the taxonomy to make it fit with a biogeographic theory is very convincing. But even assuming that Salvadoraceae is paraphyletic, if Azima (Africa - Malesia) gave rise to Batis (Australia - America) after crossing Wallace's Line, Batis would be nested in Azima, not sister to it. You would have to propose that Azima is paraphyletic as well.
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, 2 January 2012 3:55 PM
Subject: [Taxacom] Salvadoraceae paraphyletic? (was: North America...)
 
Hi again Michael,              
       It seems that John thinks that my brainstorming is
akin to creationism, rather than a search for new possibilities to
explore.  So I won't waste my time arguing with him.  Unfortunately I
haven't had a lot of time this weekend to explore the possibility (just
a hunch) that Salvadoraceae could be paraphyletic with respect to
Bataceae.              

      Anyway, these families are certain very closely
related (morphologically and molecularly), but as I said, that doesn't
mean that they are sister taxa.  My hunch in that regard is now zeroing
in on genus Azima in particular.  Batis and Azima seem to share the
possession of ovules which are secondarily partitioned by a false septum

(unlike Salvadora and Dobera).  A less convincing similarity is
chromosome number, 2n=22 in Batis and Azima, as opposed to Salvadora
with 2n=24. However, there may be exceptions to this (and not sure of
chromosome number in Dobera).          
      However, the ovule morphology seems significant enough

that I hope to find other characters which are shared by Azima and Batis

(perhaps even molecular ones, although there seems to be few sequences
available at the present time).  Anyway, biogeographically I can see
Azima giving rise to Batis once it crossed the Wallace line, and a
transition from a miohalophyte to more extreme euhalophyte perhaps
making possible (at some point in time) a trans-Pacific dispersal from
New Guinea or Australia to the New World.   

        I would be interested to hear from any botanists

who might know of other similarities between Batis and only Azima among
the Salvadoraceae. If so, perhaps it might be appropriate to bring
Family Azimaceae out of synonymy (back to full family status).  

                -------Ken Kinman  
                              
P.S.  In view of John's criticisms, it should be remembered that
dispersal ability certainly does not ensure that oceanic dispersals will

be successful in most cases.  Being able to disperse long distances is
only the first step, but lack of suitable habitat, and more importantly
competitive exclusion by other taxa already well-established, are
obviously barriers to even good dispersers being automatically spread
geographically.  Such arguments against dispersalist hypotheses are
therefore unconvincing (perhaps simple, but perhaps too often
simplistic).                  
----------------------------------------------                
I wrote: 
          P.S. I will have to look more closely to
see if there is any evidence that Salvadoraceae might be paraphyletic
with respect to Bataceae. In that case, dispersal would be even more
important in explaining their evolution.        



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