[Taxacom] An improved definition of cladogenesis

[Curtis Clark]

On 3/15/2010 1:43 PM, Kenneth Kinman wrote:
> Hi Curtis,
>           I am saying that most species boundaries are
> "initially" fuzzy (with exceptions such as  polyploids). The reason so
> many of them are now sharp is that extinction has eliminated the all the
> fuzzy intermediates that initially existed.

That's a rather broad brush to paint "extinction" with. I'd be more 
inclined to say that the intermediate individuals just died, rather than 
becoming (individually) extinct. ("Nobody kill her; she just die.")

> The duck-billed platypus has very sharp
> species boundaries, but it didn't start out that way, so we would need
> to acknowledge that initial fuzziness when discussing its initial
> divergence as a new species.

I wouldn't even begin to discuss the speciation of the platypus, since 
it has no close living relatives and there are few fossils. Echidnas, 
maybe....

>          As for the terms cladogenesis and anagenesis, I
> guess we will just have to agree to disagree.  I believe that they are
> already muddy concepts no matter how you define them, and that is why
> they are confusing a lot of Laura's students.  I would therefore use
> these terms sparingly and with great care in order to minimize such
> problems.

They are certainly muddy the way *you* define them, and I, too, would 
caution anyone against those definitions. :-)

-- 
Curtis Clark                  http://www.csupomona.edu/~jcclark/
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