Barleria (Balkwill & Balkwill, 1997)

Dominique Champluvier, 2011, New and overlooked Acanthaceae taxa from D. R. Congo, Rwanda and Burundi: (1) the genus Barleria, Plant Ecology and Evolution 144 (1), pp. 82-95 : 85

2. A vicariant pair in sect. Barleria

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B. molensis Wild, endemic of the southern serpentines of the Great South Dyke in Zimbabwe, is closely allied and very similar to the novelty B. glutinosa ; it can be considered as a vicariant species (fig. 4). There are twenty endemic species of the serpentines of the Great Dyke; Wild (1965) explains that these endemics could have arosen by depletion of “various metal non-tolerant biotypes which formerly allowed the species to exploit a greater variety of habitats”, species of which only serpentine-tolerant biotypes would have survived on the deposits of the Great Dyke.

Following Balkwill & Balkwill (1997), B. molensis belongs to sect. Barleria ; the closely related B. glutinosa can therefore be considered as a member of that section, as it has spiny bracteoles, solitary flowers, a corolla with 2 + 3 configuration, two fertile stamens and three staminodes.

B. aromatica, from Zimbabwe, superficially resembles B. glutinosa , but the plant is not at all glandulous, the leaves are 2 × 0.6 cm, the flowers are rather smaller, with the outer calyx lobe 13 × 6 mm, the corolla tube 2.5 cm long, the upper lobes 1.5 × 0.8 cm, the lower one 1.5 × 1.1 cm and the lateral ones 1.5 × 1 cm.