Phylogenetic trees

Don Colless donc at ENTO.CSIRO.AU
Wed Feb 26 14:13:45 CST 1997


 Tom DiBenedetto wrote:

<I think you are right here,,,derived characters were not of course, a
<novel idea in evolutionary theory, but in the world of systematics,
<the notion that one must rigorously discriminate between apomorphy
<and plesiomorphy when reconstructing a phylogeny, was crucial.

     Curiously, this is not directly true in most modern applications of
phylogenetic reconstruction. Using, e.g., PAUP, one inserts an outgroup to
provide a root and the apomorphies and plesiomorphies are read off afterwards!
This is, of course, because the outgroup(s) is/are credited with providing
that information directly to the programme. Any rigorous discrimination will
only come about during the not-very-common practice, of evaluating one's tree(s)
per the implied plesiomorphies, etc.

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               *  Don Colless, CSIRO Div of Entomology, *
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