5 Kingdoms

[Bill Shear]

I've always been bothered by the "Kingdom" Protoctista (or Protista, pace
Margulis).  It seems clear that the three multicellular kingdoms arose from
protoctistan ancestors, so some protoctist phyla are more closely related
to multicell organisms than to other protoctistans.  For example, if
animals evolved from choanoflagellates and we consider Animalia a Kingdom,
that makes both Protoctista and Mastigophora (if there is such a group now)
paraphyletic.

If we recognize Fungi, Plantae and Animalia, then Protoctista has to be
broken up into gosh knows how many kingdoms.

Personally, I think that we should stop at phyla--there are few enough so
that one can be familiar with all, or almost all of them.  So long as we
insist on shoehorning all phyla into just 5 kingdoms, the category has no
practical use.

Bill Shear
Department of Biology
Hampden-Sydney College
Hampden-Sydney VA 23943
(804)223-6172
FAX (804)223-6374
email<bills at hsc.edu>