Paraphyly=mistakes? (There's the rub)

SKÁLA Zdenek skala at INCOMA.CZ
Wed Jan 9 10:40:04 CST 2002

-----Original Message-----
Thomas DiBenedetto:
... I think it is
essential that the scientific classification be rigorously aligned with
best inference as to the true historical branching pattern. .... It
seems clear to me
that the only useful approach is to have a classification that
real historical units, and to then map divergences on that tree. 

All this depends on what you consider "true ... pattern" or "real
historical units" or even "mapping the divergence". Evidently, there
still exist people who consider "having common ancestor" a sufficient
*topological* condition placed on the taxa. Cladists often argue that
strict monophlyly (holophyly) is only about topological conditions
(ancestor+all descendants) - which is obviously false. Even for
delimiting the holophyletic taxa you need to use anagenetic information
(taxa limits are placed where "important" number of apomorphies arised).
Otherwise, you would have as many taxa as clades which can be hardly
practically handled.
In sum we have two concepts, both having their topologic and "phenetic"
(anagenetic) part:
- cladism: topologic (ancestor+all descendants); phenetic (most
important groups of apomorphic states)
- eclecticism: topologic (ancestor); phenetic (most imp. grps of apo.
states+most important groups of plesiomorphic states).
There can exist cases where paraphyletic taxa are more information rich
than the holophyletic ones. Here is the rationale for eclecticism: to
use cladogram for communication about the course of phylogeny and to use
taxa for communication about the result of phylogeny.

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