form and

Steyn, Hester & Van Wyk, A. E., 2024, Notes on morphological characteristics and life history strategy of the genus Acanthopsis Harv. (Acanthaceae), Bothalia (a 7) 54 (1), pp. 1-15 : 2-3

Life form and habit

The genus Acanthopsis comprises different life forms according to the classification of Raunkiaer (1934). Most of the species are considered chamaephytes, with A. disperma Nees and the annual form of A. hoffmannseggiana (Nees) C.B.Clarke as therophytes. The perennial rosette form of A. hoffmannseggiana may be classified as a hemicryptophyte.

Within Acanthopsis , the shrublet (dwarf shrub) group is one of the most readily recognisable entities in a genus otherwise characterised by acaulescent herbs or compact subshrubs. There is a gradual increase in woodiness, branching and internode length from annual/perennial herbs to subshrubs and shrublets. The shrublet group can be distinguished in usually being virgate, up to 25–40(–60) cm tall, with well-developed branches and clearly visible internodes; the latter are usually up to 10–20(–25) mm long. Shrublet species usually have scattered leaves (well-spaced) along woody stems ( Figure 1C & D ). The shrublet group includes the following species: A. dregeana H.M.Steyn , A. erosa H.M.Steyn , A. horrida (Nees) Nees and A. spathularis (Nees) Schinz.

Subshrubs are much more compact plants, up to 25(– 30) cm tall, with gnarled stems and reduced (usually not visible) internodes, usually <5(–8) mm long, with fascicled leaves ( Figure 1B ). Compact subshrubs are the most common in the genus and include A. adamanticola H.M.Steyn , A. carduifolia (L.f.) Schinz, A. dispermoides H.M.Steyn , A. glabra (Nees) H.M.Steyn , A. glandulopalmata H.M.Steyn , A. glauca (E.Mey. ex Nees) Schinz , A. hoffmannseggiana , A. insueta H.M.Steyn , A. ludoviciana H.M.Steyn , A. nitida H.M.Steyn , A. pagodiformis H.M.Steyn , A. scullyi (S.Moore) Oberm. , A. tetragona H.M.Steyn , A. tuba H.M.Steyn and A. villosa H.M.Steyn.

Acaulescent/rosulate herbs, with leaves in a basal rosette, are almost restricted to the annual or short-lived perennial species of A. disperma and A. hoffmannseggiana , while young plants of A. dispermoides , A. glabra , A. pagodiformis and A. scullyi could appear acaulescent ( Figure 1A ).

Certain species have pioneer or weedy tendencies, and they thrive under conditions of disturbance and degradation often caused by overgrazing (e.g., Acanthopsis carduifolia , A. disperma , A. hoffmannseggiana and A. scullyi ). However, these species have never been observed to become invasive.

Figures

Figure 1. Different habits found in Acanthopsis. A, acaulescent herb; B, compact subshrub; C, shrublet (cushion-shaped); D, shrublet (virgate). Photographs: A, B, the authors; C, D: M. Koekemoer.