Taxonomic identity and evolutionary relationships of South African taxa related to the Spergularia media group (Caryophyllaceae)

Abstract

The taxonomic identity and phylogenetic relationships of several South African perennial taxa often synonymised to the European Spergularia media are discussed. In particular, the case of Arenaria glandulosa Jacq., a species described as native to the Cape region of South Africa, was revisited. We found this taxon to be a Spergularia, endemic to salt-laden coastal (and rarely also saline inland) habitats of the Western Cape and Eastern Cape provinces of South Africa. This taxon is a prostrate to procumbent caespitose herb, densely glandulous all over, with small flowers solitary at the base of each leaf-like bract or in congested dichasial cymes, producing petals about equalling the sepals and free styles, among other characters. Further, we describe a morphologically similar species (often mistaken for S. media and S. bocconei) occurring in succulent Karoo scrub of Namaqualand, as a new species, named S. namaquensis. Both are glandulous dwarf subshrubs considerably differing from the recently discovered S. quartzicola, a soil-specialist endemic from Namaqualand quartzitic outcrops, by many notable vegetative and reproductive features. Molecular analyses of plastid (trnL–trnF region) and nuclear ribosomal (5.8S-ITS2 region) DNA sequence data support the morphological differentiation between the South African species S. glandulosa, S. namaquensis and S. quartzicola, representing an independent lineage when compared with the Northern Hemisphere members of the S. maritima group. Synonymy, new complete descriptions and ecological and distributional data are provided to facilitate further identification of species within the putative S. media group.