Remarkably, some
cladists have understood the union of numerical
Cladists, on the other hand, distinguish between two types of similarity - those that are derived through descent from a common ancestor (synapomorphies), and those representing retained ancestral characters (symplesiomorphies) - and argue that only the former count as evidence when assessing degrees of relatedness.
radiating into new taxa, rather than becoming extinct, as
cladistsPolyphyletic species are abhorrent to
cladists - this was set up as a rule to eliminate polyphyly caused by improper classification and taxonomy, but polyphyly is also caused by hybridization and introgression of traits from one species to others, including sister clades.
Cladists, by contrast, in opting for phylogenetic criteria, assume that any adequate response to the species problem must make patterns of descent explicit.
Whereas there is a substantial body of literature investigating the ability of hierarchical systems to transmit taxonomic information--much of it embodied in the debates among
cladists, pheneticists, and evolutionary taxonomists--there seems to be little in the way of what I would view as objective analysis of the attributes of systems of nomenclature.