> The problem illustrated by David's fish example is a consequence of > our having broadened the PhyloCode's operational definition of the > species category to accommodate those who do not accept the idea that > a species is a population lineage segment. Really? Here's my example again: --+--A `--+--B `--+--C `--+--D `--E A and E can interbreed with each other, but all other combinations don't work. All nodes should be considered parts of the species A + E; they were all able to interbreed. The species is (multiply) paraphyletic, not polyphyletic. Does that not count as a lineage segment? > I am not suggesting that we revisit that decision, which I personally > support, but if we retain a broad operational definition of "species" > in the code, we may simply have to accept that differences in species > concepts or hypotheses of species boundaries will result in > occasional changes in the application of the names of low-level > clades whose contents coincide with or overlap the membership of > those species. 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 disagree. Disagreements about phylogenetic hypotheses are (hopefully) scientific disagreements -- different datasets supporting different topologies, that kind of thing. Disagreement about which species concept should be called "species" are purely semantic. That's, as I said, _precisely_ what the PhyloCode is supposed to stop. One of the most important ideas behind phylogenetic nomenclature is to turn the question "does organism X belong to taxon Y?" into a scientific hypothesis. Consequently, I still think species shouldn't be used as specifiers. Phylogenetic nomenclature is about clades; mixing species in causes trouble.
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