>My taxonomic question deals with how do they determine rankings for any group of similar organisms?  For instance, is the degree of similarity and differences within the family Donacidae, the same as within the family Turridae?  Or going outside of the mollusca, the insect family Carabidae, or even the plant family Cucurbitacea?  Is it possible that a range of differences that might warrent generic or subfamily ranking in one phylum could be given family or superfamily ranking elsewhere?<

Yes, the decision as to what is a genus, family, order, etc. is somewhat arbitrary.  Hopefully they are roughly similar for closely related taxa, but comparision of plant and animal families is probably not too meaningful.  DNA does not particularly help, as the level of variability is different for different taxa.


    Dr. David Campbell
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