Revised Taxonomy of theArctotisAnnual Clade (Arctotideae, Asteraceae) from Southern Africa: Integration of Molecular Phylogenetic and Morphological Evidence

Abstract

Abstract—Previous phylogenetic analysis of ITS nrDNA sequence data for Arctotidinae species resolved a strongly supported clade containing all but one of the showy annualArctotisspecies (informally designated theArctotisAnnual Clade). In the present study, phylogenetic relationships in theArctotisAnnual Clade were investigated by Bayesian inference and maximum parsimony analyses of cpDNA (trnT-trnL-trnFandtrnH-psbA) and nrDNA (ITS) sequence data. The cpDNA and nrDNA phylogenies were notably incongruent.Arctotis venustaand a putative unnamed species (A.‘sp. B’) were strongly supported as monophyletic by both data sets. The monophyly ofA. leiocarpawas strongly supported by the ITS data set, whereas the remaining accessions formed a poorly resolved complex (the ‘A. fastuosacomplex’). Within theA. fastuosacomplex,A. hirsutawas monophyletic with strong support in the ITS phylogeny. A statistical parsimony-derived cpDNA haplotype network resolved five broad groups of haplotypes and showed no consistent geographical structure, but species-specific haplotype lineages forA. venustaandA.sp. B were resolved.Arctotis fastuosaaccessions were distributed among four haplotype groups. Incongruence between the data sets and poor resolution within theA. fastuosacomplex may reflect reticulate evolution, ancestral polymorphism, and incomplete lineage sorting, in tandem with the low information content of the data sets. The greatest phenotypic diversification in the clade is in cypsela morphology. Comparison of cypsela morphology with the phylogenies suggests a general trend for reduction in the sizes of the cypsela, abaxial wings, pappus scales, and loss of pubescence during diversification. A revised taxonomy, integrating currently available evidence, accompanied by full descriptive accounts and a key to the taxa are presented. Eight species are recognized, including the nomenclatural noveltiesArctotis chrysantha(sp. nov.) andArctotis namibiensis(sp. nov.). The namesArctotis karasmontana,Venidium fugax, andVenidium macrocephalumare lectotypified.