Taxa surviving end-Cretaceous extinction
kinman2 at YAHOO.COM
Tue Nov 16 12:45:07 CST 2004
As I have pointed out many times, I think cladistic analysis is great (and it is getting better all the time). I am also in favor of heavily cladified classifications (as my many examples have shown), but I am clearly against complete cladification. Semi-paraphyletic taxa (or call them semi-holophyletic-----same thing) with exgroup markers are informationally holophyletic, so I see no reason for strict cladists to object to them, and they avoid a lot of the taxonomic problems strict cladism is causing for the rest of us.
But back to the subject of cladistic analysis. Misrooted cladistic analyses are a much overlooked problem, creating false conclusions and exacerbating the taxonomic mess even more. If I am correct about the misrooting in the cladistic analyses of Mollusca and its subgroups, even a modest cladifying of its taxonomy is largely a waste of time (even harmful) at this point. I have seen no indication that anyone ever tested my concerns in the manner suggested by Lindberg back in 2002. I would do it if I had a real computer instead of WebTV, and will eventually do so if no malacologists do so in the meantime. I am still convinced Bivalvia, Gastropoda, and a lot of other mollusc groups are paraphyletic, and assuming their holophyly (much less cladifying their classification) is a huge mistake. So to answer your observation below, cladistic analyses can be very misleading or even wrong in such cases. We have to be more careful about avoiding misrooting (not just molluscs, but also prokaryotes, bilateria, and various other groups where it is a still a major problem).
-------- Ken Kinman
P.S. Lindberg's proposed test and my initial mollusc cladogram are referenced in my taxacom post (#172) dated 28 August 2002.
Barry Roth wrote:
Interestingly, this leads back to another recent thread -- the reason to prefer holophyletic groups when trying to answer questions like this. And the hypothesis that a group of taxa is holophyletic is strongest when it results from a cladistic analysis.
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