Species, Taxonomy, and Systematics 423the activities of naming and classifying separate, Hennig’s system overcomes the
naming problems highlighted earlier.
Consider the affect taxonomic revision has on Linnaean names. In the Linnaean
hierarchy, a name indicates a taxon’s classification, so a change in classification
requires a change in name. In the positional system, taxonomic revision requires
a change in a taxon’s positional number, but the name of the taxon remains the
same. Unlike the Linnaean rules, names remain stable during taxonomic revision.
The positional system also avoids the problem posed by taxonomic disagreement.
In the Linnaean hierarchy, when two biologists disagree on the rank of a taxon,
they must assign that taxon different names, each indicating the different ranks
assigned to the taxon. With positional numbers, a taxon has a single name, and
biologists display their disagreement over that taxon’s placement by assigning that
taxon different positional numbers. Hence, the use of positional number avoids
the semantic confusion caused by the Linnaean rules. Finally, recall the problem
of hasty classification caused by the Linnaean binomial rule. In the Linnaean
hierarchy, a biologist must first determine the genus of a species before she can
name it, even though she may lack adequate empirical evidence for assigning a
species to a genus. In Hennig’s system, a species can be named before knowing
that species’ classification; a name is assigned to the species, and its positional
number is determined later.
The positional number system nicely overcomes the ranking and naming prob-
lems outlined above. However, some proponents of non-Linnaean systems think
that further changes in nomenclature are necessary. For example, a current con-
troversy among proponents of non-Linnaean systems is what to do with the names
of species. Some post-Linnaeans suggest converting species binomial to unino-
mials (Cantino et al. 1999). There are two motivations for doing so. One is
the belief that because there is no species category in nature, those taxa we call
‘species’ should not be given a special notational device; all taxa should have
uninomial names. Another motivation for eliminating binomials has to do with
revision. Taxa with binomial names may be assigned to more inclusive positions
in classifications. If that occurs, then taxa with binomial names occur at various
hierarchical levels in a classification. Classifications would then have the confusing
feature of binomials referring to non-basal taxa.
How, then, should binomials be converted to uninomials? According to one
suggestion, a binomial should be converted to a uninomial by placing the specific
and generic name together. The binomialCanis Familaris would become the
uninomial ‘Canisfamilaris.’ According to another proposal, the generic name of
a species should be dropped and a registration number should be added to the
specific name.Canis Familariswould become ‘Familaris5732,’ for example. The
registration number is added to avoid homonyms.