[Taxacom] Woodpeckers, primates, as well as the Wallace Line gauntlet

[Kenneth Kinman]

Hi Michael,
        (1) Well, the early passerines would have faced stiff
competition from a wide variety of well-established Mesozoic bird taxa.
That competition would not be eliminated until the K-T extinction wiped
out most such competition.  And during the early part of the Paleocene,
passerines (like other vertebrates) would have been struggling to
recover, but then spend the rest of the Paleocene radiating into all
those empty niches previously filled by Mesozoic birds.  So hanging
around Australia until the Eocene doesn't seem all that unlikely.  They
faced a lot of challenges during their first 25 million years of
existence.
       (2) As for Coraciiformes (sister or mother group to Piciformes)
being in Madagascar and Australasia, that would have made it even harder
for Piciformes to find an empty niche.  And last night I was thinking
about the aye-aye filling that "prying for grubs and insects" niche.
Did the aye-aye move into that niche due to the absence of woodpeckers,
or had the aye-ayes already filled that niche when any woodpeckers tried
to become established in Madagascar?  Depends on timing.  These are just
more hurdles that such woodpeckers would have faced IF they ever tried
to become established in Madagascar (and we don't actually know that
they did).         
       (3)  It is interesting that there are a couple of woodpecker
species in Sulawesi (just east of the Wallace line).  At least they made
it one island into that part of the gauntlet (but no further).  But they
wouldn't have had aye-ayes competing with them for food (and tarsiers
don't have all those specializations for detecting and digging into wood
for food).  I'll have to read up on the avifauna of Sulawesi to see if
might have less woodpecker competition (for nesting sites or food) than
islands further east or south.  I certainly agree that something
interesting is going on to create these distribution patterns.  Fun
stuff, even if woodpeckers never tried to invade Madagascar (in which
case, it's just an academic exercise in "what ifs").        
           ---------Ken Kinman                            
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Michael wrote:  
      If a group such as passerines dates back to 84 Ma, fossils from
50 Ma don't seem of much relevance to origins or early
migrations. You suggest passerines could have evolved at 84 Ma and
then just hung around in Australia until Early Eocene (50 Ma) when
they emigrated. This doesn't seem very likely.    
You've suggested that woodpeckers aren't on Madagascar because
passerines got there first, and prevented woodpeckers from invading.
Instead of an ecological approach, what about a phylogenetic one?
Looking at the sister group may help. It's not just woodpeckers but the
entire order Piciformes that is conspicuously absent from Madagascar
and Australasia. In its sister group though, Coraciiformes,
several of the families occur on Madagascar (Coraciidae, Meropidae,
Alcedinidae) and one, Brachypteraciidae, is endemic there. Coraciiformes
are also very diverse in Australasia. Thus the absence of Piciformes
from Madagascar + Australasia, and the high diversity and
family-level endemism there in Coraciiformes could be a trace of the
original allopatry between the orders. This could be tested with a
closer look at the distributions and phylogenies.       
Your proposal that competitive exclusion works on islands, but not
the mainland, and only with lemurs, not with lorises, is starting to get
pretty convoluted. If strepsirhines (lemurs and lorises) really do
exclude monkeys from Madagascar it seems odd that they haven't excluded
them from any other island at all in Africa or Asia. Are there really
no other islands that strepsirhines got to before monkeys? And if the
monkeys got there first, why didn't they exclude the lorises?    
Michael   PS - woodpeckers and primates don't stop at Wallace's Line
- they're both in Sulawesi.