Character Description in Phylogenetic Analysis: Insights from Agnes Arber's Concept of the Plant

Abstract

Throughout her work Agnes Arber argues for an inclusive, synthetic concept of the vascular plant as ‘consisting of a unification of every phase of its existence’. Her view of the leaf as a partial-shoot reflects this unification by relating the part (leaf) to the whole (shoot). According to Arber's view of the plant, the part can be fully understood only in the context of the whole. Morphological character description as it is currently practiced in systematics is in sharp contrast with this holistic view of plant structure. Systematic characters are removed from their context when they are described. This problem is greatest when characters are expressed verbally. Verbal descriptions convey little of the content of the character. A shift from verbal to visual characters allows systematists to capture more information, including some of the context in which the character occurs. By using a photograph, the fringe on a labellum of Alpinia spp. (Zingiberaceae) can be viewed in the context of the labellum in a way that the word ‘fringe’ cannot convey. The use of pictorial characters also allows reliable data storage and retrieval from databases, much as DNA sequences are currently being stored and retrieved.