Inclusion of Ihlenfeldtia and Odontophorus in Cheiridopsis (Ruschioideae: Aizoaceae) and insights into generic and subgeneric circumscription in the Conophytum clade

Abstract

Phylogenetic sampling in the Conophytum clade (Aizoaceae) was expanded to include a comprehensive representation of almost all species in the clade (excluding Conophytum, which was selectively sampled) for six plastid regions (matK, rpl16, rps16, trnL-F, trnQ-rps16 and trnS-trnG). The combined phylogenetic data were analysed using maximum parsimony, maximum likelihood and Bayesian inference. The expanded sampling recovered a strongly supported sister relationship between Cheiridopsis and Conophytum in the phylogenetic analyses. Cheiridopsis was, however, not recovered as monophyletic, with Ihlenfeldtia and Odontophorus being embedded in it. In Cheiridopsis, three clades were recovered, largely corresponding to the three subgenera currently recognized. Odontophorus was recovered in the Cheiridopsis subgenus Odontophoroides clade and Ihlenfeldtia in the Cheiridopsis subgenus Aequifoliae clade. Cheiridopsis is here expanded to include Ihlenfeldtia and Odontophorus, with four new combinations made in Cheiridopsis to accommodate the latter. Three species previously classified in Cheiridopsis subgenus Aequifoliae (C. glomerata, C. pillansii and C. purpurea) were recovered in the subgenus Odontophoroides clade, with which they share the erect capsules with rounded tops; they are accordingly here included in this subgenus. A detailed study on morphological characters was conducted for all the species in the Conophytum clade to aid the assessment of generic circumscription and morphological variation in the clade. The old leaves form sheaths that enclose the emerging leaf pairs, which was recovered as a synapomorphic character for the Conophytum-Cheiridopsis clade. Two capsule morphologies were found across the Conophytum clade: simple capsules without covering membranes and closing bodies and complex multilocular capsules with covering membranes and closing bodies. Leaf anatomical characters revealed that most genera in the Conophytum clade possessed papillae on the epidermis, ranging from blunt papillae to trichomes; Enarganthe, Jensenobotrya, Namaquanthus and Ruschianthus were glabrous. Pollen exine and colpus structure were mostly uniform (tricolpate pollen with poorly defined colpi). In Namaquanthus, the exine was extensively micro-reticulate, in Enarganthe pollen was tricolpate with well-defined colpi and in Jensenobotrya pollen was syncolpate with multiple colpi, further separating these morphologically distinct monotypic genera. A key to the genera of the Conophytum clade and an updated key to the subgenera of Cheiridopsis are provided. Revised generic and subgeneric descriptions for Cheiridopsis, with appropriate nomenclatural changes, a list of recognized species, information on species richness and distribution maps for the recircumscribed genus and subgenera are included.