CKing



"What distinguishes Dr. Lee from most (but not all) other cladists is his willingness to analyze his characters. By doing so, he is able to achieve more reliable results than most cladists, who, in the words of Kurt Schwenk, "...cannot judge the quality of a character..." and must therefore merely "...assume that [all] characters are independent and hope that...enough 'good' characters will outweigh [the bad characters]". "Hope" is not a good tool for phylogenetic analysis; character analysis (e.g. comparative anatomy) is far better."



ME



Yes I agree with this. I see that there has been two basic ideologies on the analysis and coding of morphological characters. The first is find everything you can asign it a number and crunch it. Gaffney used this in his paper on Turtle phylogeny of 1977 which placed Chelodina, Hydromedusa and Chelus as a monophyletic grouping.



Examination of the actual characters in detail, looking at development, function and their relationship to the bauplan of the turtles showed that none of these genera are closely related and that Hydromedusa was pretty much basal to the Chelidae, Chelus is closer to Phrynops and Chelodina is basal to the Australian radiation of the Chelidae. This was presented by Pritchard and received enormous condemnation for its "lack of objectivity".



Molecular analysis confirmed Pritchards view and demonstrated that Gaffney's phyllogeny was incorrect and was being effected by parallelisms. He did not predict that Long-necked piscivory could evolve on 3 occasions, in fact it may have evolved on four occasions. All the characters that united the "long-necks" in Gaffney 1977 were related to piscivory and required morphological adaptations for strike and gape mode hunting.



From my own research I no longer consider Chelus a long neck, though it has an appearance of being one. If one looks closely at the ratios of vertebrae length and shell length it actually has the same neck length as an equivalently sized Phrynops, but has a shorter shell. In other words its long neck is a bit of an illusion.



The reason I feel that molecular systematics can get a better tree than morphology when using methods similar to Gaffney is similar to what CKing was alluding to. The molecular sequence will be overpowered by the neutral genes due to the sheer number of characters used, whereas the morphology if not subjected to careful comparative anatomy will be overpowered by adaptive morphology. A good morphological character set with all characters justified by comparative anatomy can be as powerful a tool as a molecular one.



Cheers, Scott
-----
Scott Thomson



http://www.carettochelys.com

http://ittn.net

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