[Taxacom] Usefulness vs. convenience (Protista)

Kenneth Kinman kennethkinman at webtv.net
Sat Dec 18 19:15:39 CST 2010

Hi Tony and Stephen: 
         The vast majority of heterokonts
(straminopiles) are unicellular, so I personally don't think that
raising Chromista to a Kingdom could be justified because it includes
the brown algae (even if Chromista is actually holophyletic, which is
controversial). Besides, splitting off such new Kingdoms has proven to
be a slippery slope. Cavalier-Smith finally cut his classification of
life back to 6 Kingdoms in 1998 (which was great), but he just doesn't
want to give up on Chromista (which he named). By the way, one could
perhaps even argue that some Cyanobacteria are multicellular (the
filamentous forms).      
        As for rhodophytes (and glaucophytes),
Cavalier-Smith includes them in a very broad Kingdom Plantae. Others
have left them in Protista, but included green algae in Plantae (making
it equivalent to Viridiplantae). I still prefer the traditional
"Plantae" (land plants), because invading land is what ultimately led
them to diversifying into a Kingdom level taxon.  
       Anyway, we therefore presently have at least three different
meanings of Plantae out there, which can be confusing when someone uses
the term. Thus I still prefer calling it Kingdom Metaphyta, which is
unambiguous (as is the synonym Embryophyta). Cavalier-Smith doesn't even
use the name Metaphyta for land plants, but instead uses the older name
Cormophyta.   This seems odd to me, since I don't think bryophytes are
normally considered to be cormophytes (which I always thought was
synonymous with tracheophytes). Cavalier-Smith has produced a lot of
great classifications and new taxa, but a 6th Kingdom Chromista and a
broad Kingdom Plantae are problematic for a variety of reasons.         
             --------Ken Kinman             

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