CLADISTICS AND FAMILY LEVEL CLASSIFICATION OF THE GENTIANALES

The most recent classification of the angiosperm order Gentianales (Th orne, 1992) includes four principal families: Apocynaceae, Gentianacea e, Loganiaceae, and Rubiaceae. Ever since Bentham (1857) the status of Loganiaceae has been questioned, and several segregates of that famil y have been proposed both before and after his treatment. In this stud y we present cladistic results that show Loganiaceae, sensu late, to b e a paraphyletic group definable only by plesiomorphies, with members showing closest relationships to other families of the order. As the i mpact of different character-state representations of polymorphic term inals remains largely untested, our morphological and phytochemical da ta were analysed both with restricted polymorphism coding as well as w ith the monomorphic ''subtaxon'' recoding method of Nixon and Davis (1 991). Both approaches yield highly compatible results, and we here dis cuss a new classification of the Gentianales based on (i) monophyletic groups identified by outgroup analysis, and (ii) the maximal portraya l of evidence provided by subtaxon polymorphism recoding. Most promine ntly, the Loganiaceae sensu late are divided into four segregate famil ies, two previously named (Loganiaceae sensu stricto and Strychllaceae ), and two defined as a result of this study (Gelsemiaceae, L. Struwe and V. A. Albert, stat. nov. and Geniostomaceae, L. Struwe and V. A. A lbert, fam. nov.). Apocynaceae (incl. Asclepiadaceae), Gentianaceae (i ncl. Loganiaceae-Potalieae), and Rubiaceae remain as monophyletic fami lies. Outgroup analysis supports both the monophyly of the Gentianales as well as the exclusion from the order of Buddleja, Desfontainia, Pl ocosperma, Polypremum, and Retzia (all Loganiaceae sensu Leeuwenberg a nd Leenhouts).