[Taxacom] Just one species of Bromeliales in Africa

[John Grehan]

Here I would say that Ken cannot be faulted for asking questions, and in
this case some very pertinent questions. He points out that the
dispersal suggestion immediately generates inconsistencies between
supposed dispersal ability and current range. Ken did not say what the
basis was for the dispersal suggestion. Perhaps it was a molecular
theory such as advanced by Renner and Ricklefs along the lines of the
molecular divergence estimate being later than the opening of the
Atlantic (based on the usual molecular fallacy that molecular dates are
maximal). 

One question Ken did not pose, and one that I think is essential, is to
what extent the bromeliad example is matched by other organisms. For
example, the widespread range of Reismadelphus, with a similar range to
bromeliads in the Americas but confined to Nigeria Cameroon, indicates
that the dispersal inconsistencies Ken raised for bromeliads are
general, not unique. Another example is the dragonfly genus Rimanella of
the Pantepui of S. America related to the genus Peutaphlebia of
Nigeria/Cameroon. In other words, is the case of Bromelia unique or
general? If it is general, to what extent do individual means of
dispersal provide a consistent understanding of the pattern in general,
and is there a need to invoke means of dispersal to cross the Atlantic
in the first place?

Is it the invocation of means of dispersal that determines our
understanding of biogeography, or is it really the other way around,
that our knowledge of biogeographic patterns in general that help us
understand and interpret the role of means of dispersal (the former
being more Darwinian, the latter more Hookerian)?

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: Saturday, October 15, 2011 11:47 PM
To: taxacom at mailman.nhm.ku.edu
Subject: [Taxacom] Just one species of Bromeliales in Africa

Dear All,   
       Bromeliads (Order Bromeliales) are largely a taxon of the New
World, except for the species Pitcairnia feliciana.  It has been
suggested that this species was dispersed (by its seeds) to Africa by
migrating birds millions of years ago (but is that the only
possibility?).                  
      This species is apparently only found on cliffs and rocks near the
coast, so dispersal by migrating birds nesting in those areas seems to
make sense.  However, I wonder why this species failed to spread (either
by birds or wind) inland to other areas of Africa.  

      Is this a case of a dispersed species by sheer luck just barely
establishing itself in marginal habitats on a new continent, but
apparently could not compete with well-established commelinoids beyond
this restricted area?  If so, what was it about this species that
prevented it from spreading into other areas of Africa?  On the face of
it, it seems odd that it could disperse a great distance across an
ocean, but was unable to disperse much shorter distances inland.  Was it
competition or lack of suitable habitat?   
             ----------Ken Kinman
    



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