Problems in Cladistic Classification: Higher-Level Relationships in Land Plants

Recent cladistic analyses of green plants recognize an extensive hierarchical series of relatively well-supported monophyletic groups. Translating this hierarchical pattern of relationships into a usable and informative written classification is important for purposes of scientific communication, research and teaching. However, in the context of the "Linnean" hierarchy, as manifested in the current International code of Botanical Nomenclature (ICBN), effecting this translation confronts substantial practical difficulties--especially the proliferation of hierarchical levels. These problems are exacerbated by the current emphasis of the ICBN on a hierarchy in which different ranks have different formal rank-based endings. These difficulties could be ameliorated by de-emphasizing the importance of ranks in the ICBN and relaxing the constraints on how they are treated, especially at the higher taxonomic levels. Modifications are needed that permit a more straightforward integration of systematic knowledge and botanical nomenclature, and at the same time foster increased stability in the association between names and the groups of organisms that they designate.