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

Abstract

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.

Motile Gametes of Land Plants: Diversity, Development, and Evolution

“…Cladograms provide a natural basis for classifications, and this approach has been used to revise classifications of green algae and land plants (e.g., Bremer, 1985;Crane, 1985;Crane and Kenrick, 1997;Kenrick and Crane, 1997a b). No classification proposed to date is consis- Critical Reviews in Plant Sciences 2001.20:107-213. tent with the relationships inherent in Figure 3B and also retains a satisfactory resolution to green algal classification.…”

Taxonomy and fossils: a critical appraisal

“…Grouping would be expressed either by reference to a cladogram or in a tabular form using indentation. This approach was adopted by Crane & Kenrick (1997) (e) An alternative method using the annotated Linnaean system where the phylogeny is read from the classification as the sequence of branching is given by the order of listing, with the inclusion of the rankless category plesion for the fossils as meaning plesiomorphic sistergroup. ( f ) An alternative using the PhyloCode system whereby taxa are defined relative to a particular phylogeny.…”

Species Names in Phylogenetic Nomenclature

“…Another drawback of Lin- Wyss and Meng, 1996;Cantino et al, 1997; naean binomial nomenclature is that it en- Crane and Kenrick, 1997;de Queiroz, 1997; courages the creation of monotypic and Kron, 1997;Baum et al, 1998;Härlin, 1998; paraphyletic genera in situations in which Hibbett and Donoghue, 1998;Moore, 1998; relationships among the species in a com Schander, 1998a;Sereno, 1999), but rela-plex of genera are poorly resolved (distively little has been written about the nam-cussed below). ing of species in this system (de Queiroz A formal code of phylogenetic nomenclaand Gauthier, 1992; Graybeal, 1995; Schan-ture (the "PhyloCode") is in preparation.…”