[Taxacom] Just one species of Bromeliales in Africa

[Kenneth Kinman]

 Hi John, 
???????The damselfly genera Rimanella and Pentaphlebia
seem to be a pretty clear case of vicariance, supposedly having diverged

about 150 million years ago.  I know of noone having suggested long
distance dispersal for them. Can't comment on Reismadelphus since I
couldn't find anything on such a genus (is that the correct spelling?).
? ? 
??????Getting back to Pitcairnia feliciana, it supposedly
dispersed to Africa about 9-12 million years (far more recently than the

damselfly genera mentioned above). And yes, that is based on sequences,
but bromeliads have such a poor fossil record, molecular data is by far
our best source of information (even if the dates can only be rough
estimates). ? ? ? 
??????Anyway, I've been thinking more about the reasons
Pitcairnia feliciana might not have dispersed further into Africa. Could

the difficulty be the absence of its primary pollinator (especially if
that had been a hummingbird, and no hummingbirds in Africa)?  Or was it
just a matter of lack of suitable physical habitats?
????????????????-------------Ken Kinman
? ? ?            ? ? ? ? 
P.S.   I just found that genus Maschalocephalus (of Family Rapateaceae,
closely related to bromeliads) has a very similar origin to that of
Pitcairnia feliciana, and Givnish et al. concluded that it was also the
result of almost the same transoceanic dispersal, but perhaps happening
even later (about 7 million years ago).  So it seems that the Pitcairnia

case is not unique, unless both actually occurred in a single dispersal
event (perhaps about 8 million years ago?).  Will have to give this
further thought and try to find if other information is available on
this subject.  Very interesting.  

---------------------------------------------- 
John Grehan wrote: ? ? ? ? ? ? ? ? 
??????????????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