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RE: Willie Wonka and the New Papers
> that: it may be easier than you'd expect, because
> animals pick up bacteria
> (etc.) capable of predigesting food items from the
> food itself.
Pending resolution of the phylogeny, this can be
researched. Even now a preliminary study is possible -
comparing the intestinal "fauna" (or "flora", as the
MDs say) of e.g. a kiskadee and a cotinga. A diet
switch must have taken place there, quite close still
to the base of the passerines.
Presumably this happened after arrival on South
America, or when on adjacent Antarctica. A question of
climate, chiefly - was Antarctica hospitable enough
for a full-blown adaptive radiation of "NW suboscines"
to be later pushed N, or was it more of a
coast-hugging dispersal that fully diversified in SAm
only. Any of the phylogenetic and biogeographic
scenarios that presently make sense has leeway for
either, courtesy of the utter lack of a Cenozoic "NW
suboscines" record, though the latter scenario makes a
bit more sense to me for one does not have to invoke a
load of basal "ghost" lineages to explain the
discrepancy between the basal dichotomy and the huge
explosive diversification later on that has been found
among crown "NW suboscines".
For all we know (which is not very much), the "NW
subsocine" radiation can have happened very very late:
The arrival of oscine competitors (which would
probably have prevented such a diverse radiation)
seems to have started only by the mid-Miocene or so,
generally coming across the island bridge that was
then building up: basal Mimidae, Cinclidae, and
perhaps Passeroidea and Turdidae. They all seem to
have arrived from NAm and most of them ultimately via
Beringia it seems.
Wren and gnatcatcher ancestors diverged somewhere in
the Americas about at the same time. As it seems their
ancestors also took the Beringia-NAm route.
Thus we have a huge time window of about mid-Eocene to
mid-Miocene in which the "NW suboscine" radiation can
comfortably have taken place. The fossil record
actually gives worse constraints than the molecular
data (provided you don't use an old-school
Zuckerkandl/Pauling clock model...).
In any case, the kiskadee-cotinga example looks like
insectivory with some frugivory was the ancestral
condition for both specializations.
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