Clades, cladons, and "cladifications"

[HJJACOBSON at AOL.COM]

In a message dated 6/14/2004 12:10:25 AM Pacific Standard Time,
nmf2 at CORNELL.EDU writes:

> >David Hull in his 1979 paper ("Limits of Cladism"; Syst. Zool.,
> 28:416-440) >pointed out the following dilemma: "no methods have been set
> out thus far >which permit the inclusion of both sorts of information
> [genealogy and >divergence] in a single classification in such a way that
> both are >retrievable."
>
> ---This doesn't seem right. One can (and often does) map derived character
> states along branches. These can convey precisely the kind of information
> about "amounts of divergence" or "evolutionary distinctiveness" that, as
> some have claimed, can't be expressed cladistically. One would hope that
> if there really was a deep problem with expressing amounts of
> transformation in cladistics (not just branching patterns), the method
> wouldn't have caught on so broadly by students of evolution.
>

Yes, the number of derived characters can be plotted on the branch showing
the amount of divergence, but what Hull was trying to say is it cannot be
expressed in a classification based on tree topology. The classification is either
based on the tree topology or the degree of divergence not both at the same
time. Ken disagrees, of course.

Herb