[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Copeing with mammals

----- 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.