[Taxacom] Restless natives
Richard.Zander at mobot.org
Wed Apr 8 19:25:28 CDT 2009
Taxacom natives are restless, so maybe it's time for a short paraphyly manifesto:
The difference between molecular and morphological cladistic analyses has been misinterpreted as convergence, though convergence is a rare possibility and must be examined.
Phylogenetic paraphyly and polyphyly (heterophyly) may well be due to a deep shared ancestor diagnosable at the lowest rank inclusive of the exempars.
Elimination of information on heterophyly by reclassification by holophyly eliminates information on ancestor-descendant relationships.
Darwinian evolution is ancestor-descendant relationships, or paraphyly. Phylogenetic polyphyly is paraphyly with multiple instances of autophyly unless demonstrated otherwise. A deep shared ancestor is a better explanation of heterophyly than dismissal as convergence.
Cladistics does not diagnose ancestors (nodes) although traits might be mapped. Mapping of traits is dubious if some lineages consist of a surviving ancestor and its multiple daughter (peripheral isolate) species, in which case the surviving ancestor provides the pleisiomorphic traits. Cladistics cannot diagnose ancestors (either as unknown or as one or the other apparently descendant sister-group being the surviving ancestor), and thus cannot demonstrate evolution as descent with modification.
ANY demonstrable paraphyly is preferable to sister-group relationships as evidence of evolution, and therefore paraphyly is important in classification on an evolutionary basis.
Richard H. Zander
Missouri Botanical Garden
PO Box 299
St. Louis, MO 63166 U.S.A.
richard.zander at mobot.org
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