Naming Species in Phylogenetic Nomenclature

Phylogenetic nomenclature (PN) is a rank-free system of biological nomenclature, designed to name species and clades (de Queiroz and Gauthier, 1990, 1992, 1994; Cantino and de Queiroz, 2006). In this system, the cat-egories species and clade are not taxonomic ranks but different kinds of biological entities. A species is an in-dividuated segment of a metapopulation-level lineage. A clade is a complete system of ancestry and descent, consisting of an ancestor (such as a species, popula-tion, or organism) and all its descendants (de Queiroz, 1998, 1999, 2005a, 2005b, 2005c; Cantino and de Queiroz, 2006). Both are historical entities that compose the Tree of classes in the ontological sense (but see, e.g., Lee and Wolsan [2002] for a notion of the ontological distinction between synchronic individuals and diachronic histor-ical entities). As existing independently of human per-ception rather than being human constructs, species and clades are discovered or inferred rather than constructed by taxonomists (de Queiroz and Gauthier, 1990, 1992