The Botanical Review

, Volume 54, Issue 2, pp 107–128 | Cite as

Paraphyly, ancestors, and the goals of taxonomy: A botanical defense of cladism

  • Michael J. Donoghue
  • Philip D. Cantino


Cronquist (1987) criticizes cladism for its rejection of paraphyletic groups, which he would retain if he feels they are “conceptually useful.” We argue that paraphyletic higher taxa are artificial classes created by taxonomists who wish to emphasize particular characters or phenetic “gaps,” and that formal recognition of such taxa conveys a misleading picture of common ancestry and character evolution. In our view, classifications should accurately reflect the nested hierarchy of monophyletic groups that is the natural outcome of the evolutionary process. Such systems facilitate the study of evolution and provide an efficient summary of character distributions. Paraphyletic groups, such as “prokaryotes,” “green algae,” “bryophytes,” and “gymnosperms,” should be abandoned, as continued recognition of such groups will only serve to retard progress in understanding evolution. Contrary to Cronquist’s (1987) assertions, cladistic theory is not at odds with standard views on speciation and the existence of ancestors. Groups of interbreeding organisms can continue to exist after giving rise to descendant species, and there are several ways in which such groups, whether extant or extinct, can be incorporated into cladistic classification. In contrast, paraphyletic higher taxa are neither cohesive (integrated by gene flow) nor whole, do not serve as ancestors, and are unacceptable in the phylogenetic system. Fossils may be of great value in assessing phylogenetic relationships and are readily accommodated in cladistic classification. Cladistic studies are helping to answer major questions about plant evolution, and we anticipate increased efforts to develop a truly phylogenetic system.


Green Alga Botanical Review Monophyletic Group Common Ancestry Cladistic Analysis 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Cronquist (1987) critique le cladisme pour son rejet des groupes paraphylétiques, qu’il voudrait conserver quand ceux-ci sont “conceptuellement utiles.” Nous avançons l’argument que les taxons supérieurs paraphylétiques sont des groupes artificiels, définis par des taxonomistes qui désirent souligner certains caractères ou certaines “lacunes” phénétiques, et que la reconnaissance formelle de tels groupes donne une fausse impression de descendance commune et sur l’évolution de caractères. À notre avis, une classification doit refléter fidèlement la hiérarchie des groupes monophylétiques emboités, le résultat naturel du processus de l’évolution. Ces classifications facilitent l’étude de l’évolution et fournissent d’efficaces sommaires de la distribution phylétiques des caractères. La reconnaissance des groupes paraphylétiques, tels les “Prokaryotes,” les “Algues vertes,” les “Bryophytes,” et les “Gymnospermes,” devrait etre abandonnée, car elle ne peut que retarder notre compréhension de l’évolution. Contrairement à ce que Cronquist suggère, l’analyse cladistique n’est pas en désaccord avec les vues classiques sur la spéciation et l’existence d’ancêtres. Les groupes d’individus unifiés par le flux génétique peuvent continuer à exister après avoir donné souche à une nouvelle espèce, et il y a plusieurs moyens d’incorpores de tels groupes, qu’ils soient actuels ou disparus, dans une classification cladistique. Par contre, les taxons supérieurs paraphylétiques ne sont ni cohésifs (unifiés par le flux génétique) ou entiers, ne peuvent pas servir d’ancêtres, et sont inacceptables dans un systeme phylogénétique. Les fossiles peuvent être très utiles pour évaluer les rapports phylogénétique, et sont aisément incorporés dans une classification cladistique. Les analyses cladistiques contribuent à la solution de questions majeures de l’évolution des plantes, et nous prévoyons des efforts renouvelés pour le développement d’un systême réellement phylogénétique.


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Copyright information

© The New York Botanical Garden 1988

Authors and Affiliations

  • Michael J. Donoghue
    • 1
  • Philip D. Cantino
    • 2
  1. 1.Department of Ecology and Evolutionary BiologyUniversity of ArizonaTucsonUSA
  2. 2.Department of BotanyOhio UniversityAthensUSA

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