[Taxacom] Woodpeckers: If any got to Madagascar, they were probably too late

[Kenneth Kinman]

Hi Michael,
     (1)  A southern origin of passerines is NOT based entirely on New
Zealand wrens being a basal clade.  There's the fossil record as well.
Question: Is it just a coincidence that the oldest known passerine
fossils are from the Early Eocene of Australia, but dont show up in
Europe until the Oligocene?  Another question:  where are all the Eocene
passerines in the well-studied North American fossil record (or in
Europe for that matter)?  Seems most parsimonious to me that they just
hadn't dispersed that far west.              
      (2) As for Jamaica (and other islands in that area), it re-emerged
from the sea around the end of the Oligocene.  It was a clean slate
waiting for whatever birds came its way during the Miocene.  Even if
there were many passerine taxa in North America by then, the woodpeckers
would at least have had a fighting chance of competing (and obviously
did).  However, Madagascar was never submerged during the Cenozoic, and
the southern passerines simply got their first, and the northern
woodpeckers were probably john-come-latelies that didn't have much of a
fighting chance finding an unoccupied niche to exploit.  The same goes
for monkeys trying to find an unoccupied niche on Madagascar.  The
lemurs simply got there first and radiated into all the primate niches.
Dispersal is rare, but it is far more difficult to become established
when a similar taxon got there first and is already well-established.                        
      (3)  And as for macaques in New Guinea, they had the advantage of
exploiting human food supplies and crops.  Nothing very natural about
that.  Zebra mussels are spreading like weeds all over the place, but
that too is due to modern human activity.  Not much chance they would
have dispersed at all under natural conditions, unless they evolved the
ability to hitch a ride on marine mammals.
         -----------Ken             
--------------------------------------------------------
Michael wrote:        
       Your argument hinges on a northern center of origin of
woodpeckers and a southern center for passerines. But this is based
entirely on the idea that a basal clade in a group (e.g. New Zealand
wrens in passerines) represents a center of origin for the whole group.
Why can't it be a center of differentiation in a group that was already
cosmopolitan? Anyway, woodpeckers are accepted as good dispersers, e.g.
they are on Jamaica, which as everyone knows was completely submerged by
the sea and the entire biota derived by trans-oceanic dispersal
from the mainland. There are also endemic genera on Cuba
and Hispaniola. But woodpeckers never crossed the 20 km Salue
Timpaus Strait to get from Sulawesi to anywhere in Australasia. Why not?
Could it be something to do with this being the same strait that
monkeys stop at, although when introduced to New Guinea they 
become weeds (macaques)? Both monkeys and woodpeckers are also
absent from Madagascar. 
 This global pattern occurs in the two groups, also sciuromorph
rodents, and many others with completely different
ecology, behavior, means of dispersal etc., so I don't think these
factors can be important in explaining the pattern.