Problems with generic delimitation and subdivision in a large genus, Barleria (Acanthaceae)

  • M.-J. Balkwill
  • K. Balkwill
Chapter

Abstract

Barleria L. is a large, polymorphic, pantropical genus, the subdivision of which into natural groups has long been subject to question. The publication of seven accounts of the genus has not solved this problem due to the regional nature of the classifications. We undertook a re-assessment of the generic limits and subdivision of Barleria on a monographic scale, using a phylogenetic approach. A major thrust of this research was the careful definition of characters and character-states and tracing their distribution within the genus. Many of the problems encountered during this work are typical of large, widespread genera in this and other families. These include: difficulty in obtaining adequate material of all taxa; inability to conduct adequate field work in all areas; restrictions on the kinds of characters that can be effectively utilised; incomplete data sets and difficulties associated specifically with cladistic methodology. A revised infra-generic classification of Barleria is proposed in which 2 subgenera and 7 Sections are recognised. This classification, with a full account of the taxonomy, nomenclature and phylogeny, will be published separately.

Key words

Barleria Generic Delimitation Infra-generic Classification Phylogeny 

Résumé

Barleria L. est un grand genre pantropical et polymorphe, dont la subdivision en groupes naturels a depuis longtemps fait l’objet de controverses. La publication de sept traitements concernant le genre n’a pas résolu ce problème, étant donné le caractère régional des classifications adoptées. Nous avons entrepris de réexaminer les limites génériques et la subdivision de Barleria dans un cadre monographique et suivant une méthode phylogénétique. Un des objectifs majeurs de cette recherche était de définir avec précision les caractères ainsi que leur hiérarchie, et d’établir leur répartition à l’intérieur du genre. Les nombreux problèmes rencontrés durant ce travail sont ceux que l’on rencontre dans l’étude de grands genres à large distribution, dans cette famille comme dans d’autres. Il s’agit entre autres de la difficulté d’obtenir un matériel adéquat de tous les taxons, de l’impossibilité d’effectuer un travail sur le terrain dans toutes les régions concernées, du nombre réduit des caractères auxquels on peut utilement avoir recours, des groupements de données incomplets et des difficultés inhérentes à la méthodologie cladistique. Une révision de la classification infragénérique de Barleria est proposée avec la reconnaissance de 2 sous-genres et 7 sections. Cette classification, accompagnée d’un traitement taxonomique, nomenclatural et phylogénique, sera publiée séparément.

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Copyright information

© Kluwer Academic Publishers 1996

Authors and Affiliations

  • M.-J. Balkwill
    • 1
  • K. Balkwill
    • 1
  1. 1.C.E. Moss Herbarium, Department of BotanyUniversity of the WitwatersrandWitsSouth Africa

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