Re: On taxa and clades

["T. Mike Keesey" <tmk@dinosauricon.com>]

On Sun, 28 Oct 2001, [iso-8859-1] Henri Rönkkö wrote:

> Hello!
>
> Does a holophyletic taxon include the stem species, despite the fact
> that the stem species isn't a descendant of itself? Does the same
> apply to a monophyletic taxon? Does this also go for clades?

These are all three the same thing. Well, some people (the ones who use
the term "holophyletic") use "monophyletic" a bit differently.

CURRENT COMMON USAGE:
monophyletic taxon: an ancestor plus all of its descendants
clade: a monophyletic taxon

ALTERNATIVE USAGE:
holophyletic taxon: an ancestor plus all of its descendants
monophyletic taxon: a holophyletic taxon with zero or more internal
holophyletic taxa removed (i.e., holophyletic or paraphyletic)
clade: a holophyletic taxon

In any event, yes, the stem species, or ancestor, is included. (Otherwise
it would be polyphyletic, unless the ancestral species is a chronospecies
with only one descendant species.)

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