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Protista (vs. rat race)





Tim,
Correction!!! Protista perhaps represent more than 95% of the diversity of: eukaryotic "rRNA sequences" (not of eukaryotic "life"). There's a big difference. And Woese's Three Domain Trees are "Trees of Ribosomes", not true "Trees of Life". Metazoans have slowly evolving rRNA genes. Big deal----all those other genes more than make up for it by orders of magnitude. One-character classifications like the Three Domains have a long history of failure, and this currently popular bandwagon will be no different.
Simply stated, I define Kingdom Protista as all eukaryotes after the removal of Metaphyta and Metazoa, and yes that does make it paraphyletic. Cladists get out your crosses and exorcise it. But while you're at it, go after Woese's two prokaryotic Domains, because they are paraphyletic too.
You may be horrified to learn that I have gone back to including all the fungal groups in Kingdom Protista. If you want to recognize a Fifth Kingdom, best to call it Eumycota, because "Fungi" is highly polyphyletic (which we all agree is bad). And guess what---- microsporidians (which you mentioned) aren't true sporozoans or even archaeoprotists----they are eumycotans!!! How shocking that is to most biologists----I was delighted, but certainly not surprised.
A separate kingdom for saprophytes? (sorry, it doesn't exist). The shift from a 4-Kingdom System to a 5-Kingdom System has caused nothing but trouble and confusion for 30 years, and it has eventually inspired additional Kingdoms, Superkingdoms, and then those awful Domains. When the new Bergey's Manual comes out and we have about a dozen prokaryotic Kingdoms, the protistologists will respond in kind, and we'll have so many kingdoms that most future students will have no idea how they are all related (because many of their professors will be confused as well). Taxonomic inflation is not a good idea. It's a nomenclatural rat race.
Even with the fungal groups included, Kingdom Protista should be subdivided into about a dozen phyla, and instead we have a mess that almost noone understands. Protista is the scapegoat, but it is not the real problem. Watch out what you hope for, because it might come true. Remember this someday when you have students that roll their eyes when you try to teach them about the diversity of life. Best of luck, you'll need it.
--- TGIF, Ken
P.S. All those protist species that died out with the dinosaurs----they had distant cousins in the mammals and birds. At the ordinal level of protists, the K-T extinction was virtually a non-event. Their diversity need not boggle one's mind, but taxonomic inflation certainly will. A nomenclatural rat race, red tape, and bureaucratic mazes---I think I'll just watch from the sidelines.
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Tim Williams wrote:

I hope the term ?Protista? will soon disappear from usage as well. Those single-celled blobs and creepy-crawlies which _Homo sapiens_ have traditionally lumped together as the ?Protista? represent more than 95% of the diversity of eukaryotic life. The multicellular ?higher? eukaryotes (animals, plants, fungi) each occupy a little twig on the tree which we share with diplomonads, microsporidians, trichomonads, trypanosomes, euglenoids, slime molds, ciliates, dinoflagellates and diatoms. Each are each as different from each other as they are from animals, plants and fungi.


And they're just the ones we know about. The mind boggles thinking about how many gut-infesting, fecal-ingesting, blood-infecting little "protists" might have gone extinct with the dinosaurs.
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Timothy J. Williams

USDA/ARS Researcher
Agronomy Hall
Iowa State University
Ames IA 50014

Phone: 515 294 9233
Fax:   515 294 3163
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