Ceraria is a former genus of succulent plants now subsumed into the genus Portulacaria within the family Didiereaceae (order Caryophyllales). The plants are indigenous to southern Africa. The genus was historically placed in the purslane family (Portulacaceae), but molecular phylogenetic studies have firmly placed it within Didiereaceae, a family best known for the spiny dryland trees of Madagascar. Further phylogenetic work showed that all Ceraria species nest within Portulacaria, and they have been transferred accordingly. Members of the group are succulent shrubs or small trees with fleshy, water-storing leaves and stems, adapted to arid and semi-arid environments. The type species, Ceraria namaquensis (now Portulacaria namaquensis), is native to the arid Namaqualand region. Other former Ceraria species include C. carrissoana (Angola), C. fruticulosa, C. longipedunculata (Namibia), and C. pygmaea.
Distribution
The group is indigenous to southern Africa, including the arid and semi-arid regions of South Africa (Namaqualand), Namibia, and Angola.
Taxonomy
The genus Ceraria was historically placed in Portulacaceae, but molecular phylogenetic studies moved it to Didiereaceae. Subsequently, phylogenetic tests conclusively placed all Ceraria species within the genus Portulacaria, and they have been formally transferred. GBIF still lists Ceraria as an accepted genus (with zero recorded descendants), while Wikipedia and POWO treat it as a synonym of Portulacaria. The species in the Ploi database, Ceraria namaquensis, is accepted as Portulacaria namaquensis by current taxonomic consensus.
Ecology
As succulent plants of arid southern Africa, members of the Ceraria group (now Portulacaria) are adapted to drought-prone environments with fleshy water-storing tissues. The well-studied relative Portulacaria afra (not a former Ceraria) can switch between C3 and CAM carbon fixation under drought stress, a physiological adaptation likely present across the genus.
