Re: Copeing with mammals

[David Marjanovic <david.marjanovic@gmx.at>]

----- Original Message -----
From: "John Bois" <jbois@umd5.umd.edu>
To: "MICHAEL HABIB" <habib@jhmi.edu>
Cc: "David Marjanovic" <david.marjanovic@gmx.at>; "DML" <dinosaur@usc.edu>

< Thanks, I don't need Ccs, I read everything I get from the list...

Sent: Saturday, November 27, 2004 9:27 PM

> There are selective forces/advantages for both being big and being small.
> And both have effect in most habitats, I would think. The question is why
> any clade--or population--abandons its ecospace?  This is like people just
> handing over their property...it generally doesn't happen.

I don't like this comparison. It sounds so much like conscious decisions...

> > Just for a conceptual example, it is perfectly reasonable to think that 
> > a
> > clade might drift towards larger size because of INTRAspecific
> > competition (which is being strangely ignored in this thread, I think),
> > namely that large individuals do better than small individuals within a
> > species for some length of time.
>
> And as bigger members move out of the small niche, this provides
> opportunity for smaller members in the small niche.

This works only if a large part of the original species quits the 
intraspecific competition at once and founds it own species. If just a few 
lone members do that, the risk is high that they simply won't get mates.

> > ...most massextinctions seem to be near in time with abiotic pertubations.
>
> I have just read a paper that claims mass extinctions grade into
> non-mass extinctions.

Don't the bigger ones of those coincide with abiotic perturbations, too...? 
OK, OK, there are certainly next to no data on this.