A molecular phylogeny of Calenduleae (Asteraceae) supports the transfer of Dimorphotheca polyptera DC. to Osteospermum L.

Abstract

• A novel phylogeny for the daisy tribe Calenduleae is presented. • The phylogeny is based on nuclear and plastid DNA sequences, and morphology. • Dimorphotheca polyptera is not a Dimorphotheca , despite having dimorphic fruits. • D. polyptera is transferred to Osteospermum under O. polypterum . • the genus Osteospermum now has a member with dimorphic fruits. Generic circumscription in the small daisy tribe Calenduleae has been unstable, with various authors recognising between three and twelve genera. Evaluating alternative generic circumscriptions is difficult since existing phylogenetic hypotheses are poorly sampled. We assemble a preliminary phylogenetic hypothesis for the tribe based on nuclear ribosomal and plastid trn L- trn F DNA sequences. We recover a monophyletic Garuleum Cass. sister to the remaining species of Calenduleae. An expanded circumscription of Osteospermum L. is supported, including the former genera Calendula L., Chrysanthemoides Fabr., Monoculus B. Nord., and Tripteris Less., although sampling remains sparse. The genus Dimorphotheca Vaill. ex Moench is recovered in its current, enlarged circumscription including Castalis Cass. and O . sect. Blaxium (Cass.) Norl. However, our analysis identifies D. polyptera DC. as being distant from the rest of Dimorphotheca and embedded within an ‘ Osteospermum sensu amplo clade’, a finding corroborated by the inclusion of additional accessions. We explore the morphological basis for this placement, and transfer D. polyptera to Osteospermum in order to maintain monophyly of Dimorphotheca .