A phylogenetic analysis of Chamaemelum Mill.: (Compositae:Anthemideae) and related genera based upon nrDNA ITS and cpDNA trnL/trnF IGS sequence variation

Sequences of the nrDNA internal transcribed spacer (ITS) region and the cpDNA trnL/trnF intergenic spacer (IGS) region were analysed for 11 species of Chamaemelum Mill. and its related genera Cladanthus Cass., Mecomischus Coss. ex Benth., Rhetinolepis Coss., and Santolina L. (Compositae, Anthemideae) to study the infrageneric taxonomy and phylogenetic relationships of Chamaemelum and clarify the proper taxonomic position of the enigmatic North African endemic Santolina africana Jord. & Fourr. The results suggest that Chamaemelum in its traditional circumscription is at best paraphyletic, with Cladanthus arabicus (L.) Cass. consistently nested within it. Additionally, the subdivision of Chamaemelum into two monophyletic entities [Ch. sect. Chamaemelum with Ch. fuscatum (Brot.) Vasc. and Ch. nobile (L.) All.; Ch. sect. Santolinopsis Benedi with Ch. eriolepis (Coss. ex Maire) Benedi, Ch. flahaultii (Emb.) Benedi, and Ch. scariosum (Ball) Benedi] based on floret and achene morphological features is corroborated by the phylogenetic analysis of molecular data. Finally, the correct classification of Santolina africana as a member of the genus Santolina is further demonstrated. (C) 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 138, 255-273.