MOORE, GERRY. Brooklyn Botanic Garden, 1000 Washington Avenue, Brooklyn, New York 11225-1099. - Should taxon names be explicitly defined?
In traditional nomenclature (TRAD) a type and a rank are attached to a
taxon name. In phylogenetic nomenclature (PHYLO) a name is attached to
a clade by an explicit definition (changes to the definition are
prohibited without the express written consent of the International
Committee on Phylogenetic Nomenclature). In PHYLO, the taxonomist has
no discretion in circumscribing a taxon--a name’s phylogenetic
definition and the accepted phylogeny determine a taxon’s
circumscription. Thus, under PHYLO how the name has been previously
applied (e.g., circumscription, character associations) cannot be
considered when applying the name under a revised phylogenetic
hypothesis. Taxonomists’ hands are effectively handcuffed by the
explicit phylogenetic definitions. In TRAD the names are not shackled
by explicit definitions. Thus classifications using this system are
more flexible and able to accommodate new information with regards to
relationships, while preserving historical usage as much as possible.
Under the rankless PHYLO, the name of a taxon will not change (it may
become synonymized) regardless of how shifts in hierarchical position
(as a result of revised phylogenetic hypotheses) alter the content of
the taxon (clade). Thus the name when used outside the context of a
given phylogeny or taxonomy conveys nothing regarding set exclusivity.
This contrasts sharply with TRAD where the names themselves convey
broad information regarding set exclusivity. TRAD may not be perfect
(no nomenclature can be) but it does an excellent job of communicating
biodiversity information to the multiple constituencies that use taxon
names. Why switch?
Key words: Linnaean nomenclature, phylogenetic nomenclature, taxon name definition, type-based nomenclature