Taxonomy of the Plethodontid salamander Genus ensatina
Highton (1998) argued that published data warrant a taxonomic revision of the Ensatina complex. The complex comprises units that have varying degrees of phenetic and phylogenetic differentiation, but morphological/coloration, protein, and mtDNA data sets are less concordant than Highton believed. We employ different criteria to discover species than did Highton. His proposed species do not fulfill our criteria. Several are not diagnosable, nor do they have identity as evolutionarily independent lineages or as genetically cohesive units. Furthermore, he misinterpreted Stebbins' (1949) conception of a ring species, which was an evolutionary and biogeographic hypothesis. As observed as long ago as Stebbins' original work, taxonomic resolution of the complex is neither simple nor will a changed taxonomy solve the biological problems identified. The biological complexity of Ensatina argues against a simple taxonomic resolution, because the evolutionary realities of diversification in old and persistent complexes require compromises if Linnean taxonomies are to be used. We prefer a taxonomy that clarifies the evolutionary relationships among the components and that highlights, rather than obscures, the complex interactions of the past and present. Accordingly, while we recognize that a new taxonomy may be required when studies in progress are concluded, for the present we recommend continued recognition of the Ensatina complex as a single polytypic taxonomic species.