On Tue, Nov 27, 2012 at 11:08 AM, Cantino, Philip < cantino at ohio.edu > wrote: > As Kevin pointed out to me in our discussions of this problem over the past > couple of weeks, variability in the application of clade names due to differing > conceptualizations of the species used as specifiers is analogous to > variability in the application of clade names due to differing phylogenetic > hypotheses. I would go even further and say that it's *homologous*, at least where hypotheses are constructed using species as taxonomic units. A phylogenetic hypothesis cannot even be formulated until the relevant life forms are grouped into taxonomic units (whether those units are individuals, populations, species, or something else). Only then can the units be related to each other in terms of descent, creating a phylogenetic hypothesis. So the unit taxonomy is an essential part of the hypothesis. I used to argue that the only type of unit should be the individual, since it's objective, but a discussion with a lichenologist disabused me of that notion. There's no simple, objective way to mandate the composition of any type of taxonomic unit, be it species or individual. The Code avoids this problem by recognizing that it is a taxonomic matter, not a nomenclatural one. -- T. Michael Keesey http://tmkeesey.net/
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