Barleria senensis Klotzsch

Darbyshire, I., Tripp, E.A. & Chase, F.M. (2019). A taxonomic revision of Acanthaceae tribe Barlerieae in Angola and Namibia. Part 1. Kew Bulletin 74: 5. https://doi.org/10.1007/s12225-018-9791-0

Type

Mozambique, Rios de Sena, fl., without precise date (1842 – 1846), Peters s.n. (lectotype B! [B 10 0190529], selected by Darbyshire, l.c.; isolectotypes B! [B 10 0190528, B 10 0190530]).

Morphology General Habit

Perennial herb or shrub, erect or straggling, 25 – 150 (– 300) cm tall; stems at first 4-angular, later subterete, glabrous or uppermost internodes minutely puberulous on two opposite sides

Morphology General Spines

Axillary spines small, often sparse, sometimes absent, 4 (– 6)-rayed, stalk to 1.5 mm long, longest ray 1.5 – 7.5 mm long

Morphology Leaves

Leaves sometimes immature at flowering, sessile or petiole to 10 mm long; mature blade elliptic (-lanceolate) or somewhat obovate, 4 – 14 × 1 – 6 cm (l:w ratio 1.9 – 3.5 (–4) : 1), base cuneate or attenuate, margin entire, apex acute or attenuate, apiculate, leaf buds densely pale-strigose but mature leaves soon glabrescent except along margin and midrib beneath; lateral veins 4 – 5 pairs

Morphology Reproductive morphology Inflorescences

Inflorescences contracted spikes or heads 1.5 – 8 cm long terminating main and short lateral branches, sometimes with additional flowers in distal leaf axils, each cymule of the spike 1 (– 3)-flowered; bracts often white in proximal half, green above and along main veins, or green throughout, obovate to broadly spathulate, 7.5 – 16 × 3.5 – 12.5 mm, apex rounded, truncate or emarginate then shortly attenuate into a mucro, main veins and margin of distal half strigose, margin of proximal half usually with spreading, bulbous-based hairs, surface with short (rarely subsessile) glandular hairs in distal half, sometimes with interspersed finer short eglandular hairs, few broad sessile glands usually present towards base; bracteoles white with green midrib or more rarely green with pale margin, linear-lanceolate or lanceolate, (5.5 –) 7.5 – 14 × 1 – 2 mm, mucronate, margin entire

Morphology Reproductive morphology Flowers Calyx

Calyx lobes green with paler margins, later turning whitish-green;, anterior and posterior lobes lanceolate, 7 – 12.5 × 2.5 – 4 mm, margin entire, apex acute or attenuate, mucronate, anterior lobe sometimes notched, with few short eglandular and glandular hairs towards apex, sometimes with longer ascending hairs along margin, venation inconspicuous; lateral lobes somewhat narrower

Morphology Reproductive morphology Flowers Corolla

Corolla yellow, orange, apricot or ochre, 23 – 36 mm long, pubescent externally, limb with mixed eglandular and glandular hairs; tube 9 – 15.5 mm long; limb in “4+1” configuration; abaxial lobe offset by 4 – 9 mm, obovate or elliptic, 8.5 – 13.5 × 5.5 – 8.5 mm, apex rounded or obtuse; lateral lobes as abaxial lobe but 10 – 15 × 6 – 9 mm, apices often acute; adaxial lobes 9.5 – 14 × 5.5 – 8 mm

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens inserted 7 – 11 mm from base of corolla tube; filaments 12 – 20 mm long, shortly pubescent in proximal half to two thirds; anthers 2.5 – 3.5 mm long; lateral staminodes 0.5 – 1.5 mm long, pilose, antherodes 0.6 – 1.1 mm long

Morphology Reproductive morphology Flowers Gynoecium Pistil

Pistil glabrous; stigma linear, 0.6 – 1 mm long

Morphology Reproductive morphology Fruits

Capsule 12 – 17 mm long, glabrous; seeds 7.5 – 9 × 4.5 – 6 mm.

Distribution

Southeastern Angola (Cuando Cubango Prov.), northern Namibia (Erongo, Kavango East, Kunene, Omaheke, Omusati, Oshikoto and Otjozondjupa regions); widespread in southern Africa: Malawi, Mozambique, Zambia, Zimbabwe, Botswana and South Africa (Limpopo & Mpumalanga Provinces.)

Ecology

Barleria senensis is recorded from a variety of habitats on sandy soils, most commonly in open to dense bushland, woodland and scrub of variously Acacia, Boscia, Burkea, Colophospermum mopane and Terminalia. It sometimes occurs along riverbanks or dry riverbeds (more commonly so in the eastern part of its range than in our area). It is tolerant of disturbance and is sometimes recorded in overgrazed or disturbed sites including roadsides. It occurs at 1050 – 1550 m elevation. It is a widespread species of southern tropical Africa associated primarily with the Zambesian Regional Centre of Endemism of White (1983). In Namibia, it occurs in the Western Highlands, Thornbush Shrubland, Karstveld, North-eastern Kalahari Woodland and Northern Kalahari vegetation types of Mendelsohn et al. (2002).

Conservation

Barleria senensis is a widespread and common species of southern tropical Africa. Although the complete EOO has not been calculated, it is known to be in excess of 1.5 million km2. Collections data indicate that it is tolerant of some habitat disturbance including grazing pressure. It is not considered to be threatened and is assessed as of Least Concern — LC.

Note

Barleria senensis is easily identified by the terminal flowering spike with obovate to spathulate imbricate bracts which enclose the basal portion of the flowers. In much of its range, the bracts have a white portion towards the base and also have characteristic bulbous-based hairs along the margin. However, the bracts in populations in the southwest of its range often lack the conspicuous white portion and can have less prominently bulbous-based hairs along the margin. This form was previously separated as B. eenii; however, the variation is clearly clinal and cannot be readily separated into distinct taxa. Makholela (2008: 22) cited the type specimen as being from Angola, but Rios de Sena is in Mozambique.