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RE: More tyrant Q & A's

On Wednesday, December 09, 1998 11:40 AM, Norton, Patrick 
[SMTP:Patrick.Norton@state.me.us] wrote:
> Stan Friesen  wrote:
> >On ecological grounds, forms that co-occur in one time-place can really
> only be distinct species if they differ sufficiently to be able to
> minimize competition.<
> Many highly competitive, morphologically similar species have territories
> that overlap to some extent for one reason or another.  _Canis lupus_ and
> _Canis latrans_ , for example, co-exist across broad ranges of Canada and
> the US, probably due to a gradual process of displacement.  Several
> species of _Sciuris_ (also highly competitive and morphologically
> similar) co-occur in the forests of the northeast.  I think that, over
> time, in a stable environment, minimization of competition would
> naturally among the inhabitants.  But I'm not sure it's safe to assume
> that morphologically similar Tyranosaurid species found in the same
> paleoenvironment were engaged in only minimal competition.
This is an interesting example.  Sympatric speciation can't be all that rare. 
 Think of Darwin's finches and Hawaiian Drosophila.  One can easilly see it 
happening when a strain is more efficient at exploiting some subset of the 
resources availible to the original species.  Any mutation that creates 
reproductive isolation then becomes favorable because it locks in that 
advantage.  However, when you're considering a top predator, like T. rex, could 
the same mechanism work?  One might argue that the top predator niche is 
necessarilly a generalist role.  Your example seems to indicate that this isn't 
so.  Do you happen to know what the ecological differences between the two 
Canis species is?

  --Toby White