Clades, cladons, and "cladifications"

Peter Stevens peter.stevens at MOBOT.ORG
Mon Jun 14 08:12:47 CDT 2004

>  >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.

I think what Hull was saying is more like morphological differences
can never trump monophyly (if that is one's guiding light). I do find
morphology and monophyly largely compatible, but monocots are rather
different from other angiosperms, and podostems very different from
other broad-leaved angiosperms, and if one recognises
monocots/dicots, Podostemales/any other -ales, one loses information
about phylogeny as the "price" for recognising morphology.  In
situations like this both kinds of information are not retreivable.
You pays your money and takes your choice; I am happy to us monophyly
as the guiding principle.


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