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Re: (origin of the palaeognathous palate)



On Sun, Sep 12, 2004 at 02:12:30PM -0400, John Bois scripsit:
> On Sun, 12 Sep 2004, Graydon wrote:
> > Extant ratites are opportunistic omnivores.
> >
> > It's not at all surprising that they're going to be more stable in
> > evolutionary time than apex carnivores, which will necessarily have an
> > order of magnitude less population at any particular time.
> 
> Why is this a factor for avain species more so than other clades...I mean,
> if this is such an important cause, why are there carnivores at all?

It isn't more of a factor for avian species; it's a general principle.

Predators have smaller populations than what they prey on; one lion, one
hundred antelope, sorts of things.  That makes predators more vulnerable
to ecological shifts reducing their extant population below viability
levels, and this is worst for large apex predators because their
absolute numbers are the lowest to begin with.

Note the multiple 'saber-toothed cat' radiations in the
Miocene/Pleistocene; this happened three times.  Being a top predator is
very risky over evolutionary time.

There are carnivores at all because there can be carnivores; smaller
carnivores re-radiate into the apex niches after extinctions, and life
goes on.

-- 
"But how powerful, how stimulating to the very faculty which produced
it, was the invention of the adjective: no spell or incantation in
Faerie is more potent." -- "On Fairy-Stories", J.R.R. Tolkien