Paraphyly and names

Thomas Pape thomas.pape at NRM.SE
Fri Jan 18 13:26:49 CST 2002

In response to Zdenek:
> ..... an apomorphy can well be a loss of previously acquired feature.

Yes, I see no problem in that a clade is defined by the acquisition of a 'loss'. That some synapomorphies may be indistinguishable from symplesiomorphies (yet often as morphological outcomes of different replicator blueprints) does not alter the logic behind the reasoning. Homoplasies are difficult to deal with, but that does not provide an argument for naming non-groups.

> If, e.g., we have a pectinate cladogram of species A,B,C,D,E and clades
> A+B and A+B+C+D are supported by many synapomorphies, we will gain the
> most informative taxa by grouping ((A+B)+(C+D))+E. This is a measurable
> fact ....

Wrong. Indeed very, very wrong. If the cladogram is pectinate your analysis provided evidence for (A+B) and for (A + B + C) and for (A + B + C + D). But not for (C + D). With NO informtion on a 'group' (C + D) it would be scientifically misleading to give this 'taxon' a name.

Thomas Pape
Naturhistoriska riksmuseet

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