Re: "But What About The..." arguments (now rather short!)

[Michael Habib <mbh3q@cms.mail.virginia.edu>]

Its seems that this direct competition/predation model is actually not
very parsimonious.  Reasoning: While competition/predation are
certainly observable today, they are local patterns.  Yes, predation
occurs across the globe, but particular predatory relationships are
regional.  This does NOT scale easily to a global extinction pattern. 


For this to happen, neos would have to take a disproportionate amount
of resources, and eat enantis like mad everywhere within their range,
across the entire globe.  

However, there is another competition model possible here, and one
which probably comes closer to how global-scale replacement typically
works: Something occurred (bolide, in this case) that changed the
rules, and neos did better with the new rules.  This is parsimonious
because a bolide impact is a global event.  You're essentially
changing selection coefficients everywhere in the world, rather than
relying on an overwhelming number of neo-enanti interactions to come
out in favor of the neos on a global scale.  World climate changes (be
it from a bolide or otherwise) are global-scale events, but predation
is not.

Lastly, remember that enantis disappearing and neo diversification is
also reasonable support for a competitive exclusion model; this is
actually likely given that enantis were established (this sort of
"inertia" factor is likely more important than many give it credit,
but that's another topic altogether).  Again, in this case, the
"rules" have to change to flip things around, and an impact is likely
sufficient.

Just a thought,
--Mike Habib

-----------------------------------
> Evidence is enantis disappear and neos diversify.  Note: this is the
same
> evidence for your preferred hypothesis.  But mine is more
parsimonious
> since, a) competition/predation are observable phenomena and are in
> operation today; and 2) the mechanism proposed for bolide-induced
enanti
> extinction requires a lot of angels dancing on pins...