Bristly versus juicy: Phylogenetic position and taxonomy of Sphaerocoma (Caryophyllaceae)

The phylogenetic position of the Afro-Asian genus Sphaerocoma is investigated using DNA sequences from plastid rps16 and ndhF, as well as from nuclear ITS and RPB2. Seven accessions of Sphaerocoma, representing all three currently recognized taxa, are analyzed along with sequences from genera that have been found to be closely related to Sphaerocoma in broader studies of Caryophyllaceae. The Afro-Arabian Pollichia is indicated as sister to Sphaerocoma, and this Sphaerocoma- Pollichia clade is sister to a clade with Macaronesian Polycarpaea and the widely distributed Polycarpon prostratum. A close relationship between the anemochorous Sphaerocoma and the endozoochorous Pollichia has never previously been suggested, but some similarities in, e.g., floral characters are pointed out. Sphaerocoma is strongly supported as monophyletic, but no significant molecular variation within the genus could be detected. A new taxonomy of Sphaerocoma is proposed, where a single species with two geographically and morphologically defined subspecies are recognized: S. hookeri subsp. hookeri in coastal areas along the Red Sea in Egypt, Sudan and Saudi-Arabia, near Aden in Yemen, and in Somalia, and S. hookeri subsp. aucheri comb. & stat. nov. in coastal areas in south-eastern Yemen, Oman, United Arab Emirates, Bahrain, Iran, and Pakistan. A lectotype is designated for S. hookeri.