status was already well accepted for animals, plants, and fungi within the eukaryotes) and renamed them Bacteria, Archaea, and Eucarya. There were immediate and strong complaints from key figures in the evolutionary community, principally Lynn Margulis, Ernst Mayr and Tom Cavalier-Smith (Margulis and Guerrero, 1991; Mayr, 1990; Cavalier-Smith, 1992).

The objections touch many of the usual bases in evolutionary debates. Strict cladists would applaud the removal of "bacteria" from the name of the archaea, for instance, and would agree that the term "prokaryote" should not be used as a clade name because it describes a paraphyletic group. However, Woese and colleagues proposed the renaming not from cladist scruples but because of their belief in the profound nature of the phenotypic differences between archaebacteria and eubacteria. Mayr is no cladist either, but as a "gradist" he sees the change in cellular

Figure 6 Currently accepted (Iwabe) rooting and renaming by Woese and collaborators of three primary kingdoms as domains (1990). Microsporidia and Giardia are archezoans thought to have diverged from the rest of the eukaryotic nuclear lineage before the acquisition of mitochondria or plastids through endosymbiosis.



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