A Taxonomic Analysis and Revised Classification of Centrospermae

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Abstract
Clustering and ordination studies demonstrated a phenetically coherent assemblage of 11 core families of Centrospermae, widely separated from Plumbaginaceae and Polygonaceae. Cladistic analyses based on 71 out-group-polarized characters provided strong evidence for monophyly of centrosperms but only weak support for close sister-group status with Plumbaginaceae and Polygonaceae. Both phenetic and cladistic results indicated divergence between Caryophyllaceae, problematically allied with Molluginaceae, and the betalain-producing centrosperms. Three distinct clades emerged among the betalain taxa: a primitive group of Nyctaginaceae + Phytolaccaceae; an intermediate group of Amaranthaceae + Chenopodiaceae; and an advanced group of succulents-Aizoaceae + Cactaceae, Portulacaceae, and Basellaceae + Didiereaceae. We present a revised classification of Centrospermae, emphasizing cladistic relationships of the 11 core families and including several aberrant or little-known genera subordinated and sequenced according to conventions described by Wiley (1981). The new classification is compatible with recent interpretations of floral homologies and with external data from nucleic acid, ultrastructural, and serological comparisons.