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| Representative species in the sections of Pogonospermum. A sect. Pogonospermum: P. ciliatum (Mali); B sect. Savannicola: P. depauperatum (Guinea); C sect. Virgultorum: P. virgultorum (Angola); E sect. Serotinum: P. serotinum (Namibia); F & G sect. Aridicola: F P. cleomoides (Namibia), G P. grandiflorum (Namibia). in Darbyshire, Kiel, Chase & Manzitto-Tripp, 2022. Photos: A Q. Luke; B C. Jongkind; C D. Goyder; E H. Kolberg; F I. Darbyshire; G E. A. Manzitto-Tripp. |
Summary
Recent molecular phylogenetic results have demonstrated that Monechma s.l., a group of plants with ecological importance in the savanna and succulent biomes of sub-Saharan Africa, is polyphyletic with two discrete lineages recognisable. In the present work, we recognise Monechma Groups I and II at the generic rank, which can be distinguished by differences in inflorescence characteristics and seed morphology. The nomenclatural implications of these findings are investigated. The lectotype of Monechma, M. bracteatum Hochst., is a part of a small lineage of plants closely allied to Justicia L. sect. Harnieria (Solms) Benth. for which the earliest valid name is found to be Meiosperma Raf. Hence, Monechma is synonymised within Meiosperma, which comprises six accepted species and two undescribed taxa. The majority of species of former Monechma s.l. are resolved within the second lineage for which the only validly published generic name is Pogonospermum Hochst. This resurrected genus comprises 34 accepted species plus two undescribed taxa. Pogonospermum displays considerable morphological variation and is here subdivided into six sections based primarily on differences in plant habit, inflorescence form, calyx, bract and bracteole venation, and seed indumentum. The new combinations and new sections are validated, and seven accepted species names are lectotypified.
Key Words: Africa, Justicieae, Justicioid, nomenclature, savanna biome, succulent biome, taxonomy
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| Representative species of Meiosperma. A M. bracteatum (Mozambique); B M. monechmoides (Namibia). Photos: A B. Wursten; B E. A. Manzitto-Tripp. |
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| Representative species in the sections of Pogonospermum. A sect. Pogonospermum: P. ciliatum (Mali); B sect. Savannicola: P. depauperatum (Guinea); C sect. Virgultorum: P. virgultorum (Angola); D sect. Tricostatum: P. rigidum (Angola); E sect. Serotinum: P. serotinum (Namibia); F & G sect. Aridicola: F P. cleomoides (Namibia), G P. grandiflorum (Namibia). Photos: A Q. Luke; B C. Jongkind; C, D D. Goyder; E H. Kolberg; F I. Darbyshire; G E. A. Manzitto-Tripp. |
Meiosperma Raf. (Rafinesque 1838: 64).
Type species: Meiosperma debile (Forssk.) I.Darbysh. & E.Tripp
(basionym: Dianthera debilis Forssk.).
Pogonospermum Hochst. (Hochstetter 1844: 5).
Type species: Pogonospermum ciliare (L.f.) Hochst. (Justicia ciliare L.f.),
(lectotype selected by Pfeiffer 1874: 777) = P. ciliatum (Jacq.) I.Darbysh. & Kiel.
Iain Darbyshire, Carrie A. Kiel, Frances M. Chase and Erin A. Manzitto-Tripp. 2022. The Demise of Monechma: New Combinations and A New Classification in the Resurrected Genera Meiosperma and Pogonospermum (Acanthaceae). Kew Bulletin. DOI: 10.1007/s12225-022-10003-w
