paraphyly & polyphyly

[Jong, R. de]

James Adams wrote:
>Ah, but you are missing the *most important* difference between
>the two terms -- that the paraphyletic group, though not including
>all descendents, *does* include the common ancestor, whereas a
>polyphyletic group does not.  This *is* an extremely important
>distinction, which I do not feel that virtually anyone doubts on this
>list.

And Curtis Clark wrote:
>It is extremely important, easy to make in theory, but often not easy in
>practice.


So I may be the only one on this list who does doubt the extreme importance
of the distinction between paraphyly and polyphyly. I know there are several
definitions of these terms, but as far as I can see they all boil down to
the following: if I STATE that the group orchid+elephant includes their most
recent common ancestor, the group is paraphyletic, if I DON'T STATE it, it
is polyphyletic. My point is not that we can, in theory, make a distinction
between paraphyly and polyphyly, but that it is useless as we should not use
paraphyletic or polyphyletic groups at all.

Rienk

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