Background. Drosanthemum, the only genus of the tribe Drosanthemeae, is widespread over the Greater Cape Floristic Region in southern Africa. With 114 recognized species, Drosanthemum together with the highly succulent and species-rich tribe Ruschieae constitute the ‘core ruschioids’ in Aizoaceae. Within Drosanthemum, nine subgenera have been described based on flower and fruit morphology. Their phylogenetic relationships, however, have not yet been investigated, hampering understanding of monophyletic entities and patterns of geographic distribution.

Methods. Using chloroplast and nuclear DNA sequence data, we performed network- and tree-based phylogenetic analyses of 73 species of Drosanthemum with multiple accessions for widespread species. A well-curated, geo-referenced occurrence data set comprising the 134 genetically analysed and 863 further accessions was used to describe the distributional ranges of intrageneric lineages and the genus as a whole.

Results. Phylogenetic inference supports nine clades within Drosanthemum, seven of which group in two major clades, while the remaining two show ambiguous affinities. The nine clades are generally congruent to previously described subgenera within Drosanthemum, with exceptions such as (pseudo-) cryptic species. In-depth analyses of sequence patterns in each gene region were used to reveal phylogenetic affinities inside the retrieved clades in more detail. We observe a complex distribution pattern including widespread, species-rich clades expanding into arid habitats of the interior (subgenera Drosanthemum p.p., Vespertina, Xamera) that are genetically and morphologically diverse. In contrast, less species-rich, genetically less divergent, and morphologically unique lineages are restricted to the central Cape region and more mesic conditions (Decidua, Necopina, Ossicula, Quastea, Quadrata, Speciosa). Our results suggest that the main lineages arose from an initial rapid radiation, with subsequent diversification in some clades.

Raw data, code, analysis output, and species occurrence

The zip file contains a ReadMe file and 4 folders: 1_main_data_and_results (the files used to produce the figures in the main text); 2_ML_phylogenetics (raw data, code, and analysis output of ML phylogenetic analyses); 3_MJ_networks (raw data [SNP/sequence motive recoded DNA alignment matrices], and output of median-joining network analyses);