Monechma Hochst. s.l. (Acanthaceae) is a diverse and ecologically important plant group in sub-Saharan Africa, well represented in the fire-prone savanna biome and with a striking radiation into the non-fire-prone succulent biome in the Namib Desert. We used RADseq to reconstruct evolutionary relationships within Monechma s.l. and found it to be non-monophyletic and composed of two distinct clades: Group I comprises eight species resolved within the Harnieria clade, whilst Group II comprises 35 species related to the Diclipterinae clade. Our analyses suggest the common ancestors of both clades of Monechma occupied savannas, but both of these radiations (~13 mya crown ages) pre-date the currently accepted origin of the savanna biome in Africa, 5–10 mya. Diversification in the succulent biome of the Namib Desert is dated as beginning only ~1.9 mya. Inflorescence and seed morphology are found to distinguish Groups I and II and related taxa in the Justicioid lineage. Monechma Group II is morphologically diverse, with variation in some traits related to ecological diversification including plant habit. The present work enables future research on these important lineages and provides evidence towards understanding the biogeographical history of continental Africa.

In the first part of a taxonomic revision of the tribe Barlerieae (Acanthaceae) in Angola and Namibia, two of the four major clades of the genus Barleria L. are studied in detail, namely subg. Barleria and subg. Prionitis sect. Prionitis. Using standard morphology-based taxonomic methods, a total of 32 species and 39 taxa are delimited, of which 12 are endemic to Namibia, nine are endemic to Angola, a further four are restricted to the two countries combined and four are largely confined to the region. Hence, nearly 70% of the taxa are endemic or near-endemic to Angola and Namibia. Full descriptions, citations of types and representative specimens, and notes on their habitat(s), ecology and biogeography are provided for each taxon. Seven new species (Barleria calole, B. crabbeoides, B. craveniae, B. deserticola, B. fernandae, B. namba and B. rupicola), two new subspecies (B. lanceolata subsp. tristis and B. prionitoides subsp. strigulosa) and one new variety (B. rigida var. spinissima) are described. In addition, Barleria namutonensis Oberm. is treated as a subspecies of B. prionitoides, and B. dinteri Oberm. is treated as a subspecies of B. coriacea Oberm. and the necessary new combinations are made, whilst B. schenckii Schinz is resurrected as a good species. Eleven names in Barleria are lectotypified. A preliminary assessment of the conservation status and extinction risk is provided for each taxon. Of the 39 taxa enumerated, the majority are assessed to be of Least Concern, but one is assessed as Endangered, four as Vulnerable, one as Near Threatened and six are currently considered to be Data Deficient.

SummaryThe second part of a taxonomic revision of the tribe Barlerieae (Acanthaceae) in Angola and Namibia covers Barleria sects. Somalia and Stellatohirta. Thirty-one taxa including 27 accepted species are treated. Four new species (Barleria eburnea, B. imatensis, B. louiseana and B. thunbergiiflora), one new subspecies (B. kacondensis subsp. glabrescens) and one new variety (B. violascens var. humpatana) are described. In addition, B. taitensis S.Moore var. occidentalis S.Moore is elevated to subspecies status and B. newtonii Lindau is resurrected as a distinct species endemic to the Lubango Highlands of Angola. Full descriptions, citations of types and representative specimens, and notes on their habitat(s), ecology and biogeography are provided for each taxon. Thirteen names in Barleria are lectotypified and a neotype is selected for B. newtonii. A preliminary assessment of the conservation status and extinction risk is provided for each taxon. Of the 31 taxa enumerated, five are assessed as Endangered, two as Vulnerable, two as Near Threatened, and 13 are of Least Concern, whilst nine are currently considered to be Data Deficient. This contribution completes our revision of Barleria in Angola and Namibia, with 59 accepted species, four additional subspecies, four additional varieties and two incompletely known taxa documented in total. A remarkable 75% of the taxa are endemic or near-endemic to Angola and Namibia.

Summary. The three species of the genus Rhinacanthus Nees occurring in Angola and Namibia are documented, including a full description of the new species R. angolensis I. Darbysh. and an expanded description of the scarce species R. kaokoensis K. Balkwill & S. D. Will. A key to their identification is provided, together with notes on their conservation status and species affinities.