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This species is accepted, and its native range is Namibia.

[KBu]

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

Conservation
This species has a narrow range in west-central Namibia; it has an EOO of 38,234 km2 but if the disjunct and somewhat anomalous Hardap population is removed the EOO of its core range is only 15,365 km2. S. Schubert et al. (SS394) recorded it as common on lower mountain slopes at their site near Aba Huab. Much of its range falls within communal livestock farming areas and there is a possible threat to some populations from high browsing pressure from goats, although the impact of browsing on this species is not known. There has also been some mining activity in parts of its range, for example at Uis and near Brandberg, but this is very localised and the threat to this species appears to be minimal. It is provisionally assessed as of Least Concern — LC but with more information desirable on the impacts from livestock.
Distribution
Endemic to western Namibia (Erongo, Hardap and Kunene Regions).
Ecology
Barleria merxmuelleri occurs on open rocky hillslopes, outcrops, and at the base of cliffs often on granite or sandstone but also recorded from serpentine in Hardap, usually growing in dry exposed sites, on sandy or sandy-loam soils associated with drainages such as the Huab River; 400 – 1750 m elevation. It occurs in the Western Highlands, Western-central Escarpment and Inselbergs and (for the Hardap outlier) Desert-Dwarf Shrub Transition vegetation types of Mendelsohn et al. (2002). The northern part of its range falls within the Kaokoveld Centre of plant endemism (sensu van Wyk & Smith 2001).
Morphology General Habit
Harshly spiny shrublet, 10 – 60 cm tall, usually wider than tall, cushion-shaped; stems soon turning woody and then whitish, young stems white-puberulous, the hairs restricted to or concentrated in two opposite lines, retrorse or spreading, also sparsely strigulose
Morphology Leaves
Leaves (oblong-) elliptic or somewhat obovate, 0.8 – 2.6 × 0.3 – 0.9 cm (l:w ratio 1.75 – 3.1 (– 3.9):1), base cuneate or attenuate, margin entire, apex acute, obtuse or shortly attenuate, prominently mucronate, strigulose at least on the margin and veins beneath, young leaves sometimes finely white-puberulous; lateral veins 2 – 4 pairs, inconspicuous; petiole to 4.5 mm long
Morphology Reproductive morphology Flowers Androecium Stamens
Stamens inserted ± midway along corolla tube; filaments 16 – 23 mm long; anthers 1.9 – 2.4 mm long; lateral staminodes 2 – 3 mm long, pubescent, antherodes well developed, 0.7 – 0.8 mm long
Morphology Reproductive morphology Flowers Calyx
Calyx at first bluish-green to pale mauve with darker venation, soon turning pale-scarious; anterior lobe lanceolate to oblong-elliptic, 11 – 13.5 × 2 – 4 (– 5.5) mm, base cuneate, attenuate or subparallel, margin with up to 4 spines in the distal half per side or entire, apex spinose or bispinose, surface ± sparsely strigose along the veins, rarely also with minute patent glandular hairs; posterior lobe as anterior but (oblong-) lanceolate 12.5 – 16.5 mm long, apex long-spinose, margin distally always with 1 – 4 spines (1.5 –) 3 – 5 mm long; lateral lobes lanceolate, 6 – 8 mm long
Morphology Reproductive morphology Flowers Corolla
Corolla 30 – 36 mm long, pale blue, pink or purple, eglandular-pubescent externally; tube 19.5 – 23 mm long, cylindrical, barely widened or narrowly campanulate towards mouth; limb subregular; abaxial lobe ± broadly obovate (-elliptic), 9.5 – 13 × 8 – 9 mm, apex rounded or obtuse; lateral lobes elliptic or obovate, 10 – 13.5 × 7 – 8 mm, apices obtuse or rounded; adaxial lobes as laterals but 6 – 6.5 mm wide, apices acute to obtuse
Morphology Reproductive morphology Flowers Gynoecium Ovary
Ovary with a ring of minute crisped white hairs at attachment point of style; style glabrous; stigma linear or narrowly clavate, 0.7 – 1 mm long
Morphology Reproductive morphology Fruits
Capsule 4-seeded, 10.5 – 13 mm long, glabrous; seeds ± 3.5 × 3.3 mm.
Morphology Reproductive morphology Inflorescences
Inflorescences axillary, contracted unilateral (scorpioid) cymes up to 2.5 cm long but usually much shorter, each 2 – 7-flowered or flowers solitary; bracts foliaceous; bracteoles spinose, pairs unequal in length, the longer (13.5 –) 15 – 28 × 0.5 – 0.8 mm, triangular in cross section, margin with (1 –) 2 – 5 (– 7) ± patent spines per side (1.5 –) 2.5 – 5 mm long, appearing ladder-like, sterile bracteoles persisting at lower nodes as paired axillary spines, then turning white
Note
Volk 12603, from an isolated population in Hardap region, differs from the remainder of the material in having short glandular hairs scattered on the calyx and in the posterior calyx lobe having shorter and less harsh lateral spines. In addition, the stem indumentum is finer and denser, and extends onto the inflorescence axes. More material from this region is needed to see if these differences are consistent — it is likely to warrant at least subspecies status. This species is closely allied to Barleria lanceolata. Whilst the two are usually easily separated, there are a few specimens from Erongo region in the southern part of the core range of B. merxmuelleri (e.g. Jensen 302 from Farm Onanis; Jensen 49/1433 from Namib Park; Schmidt 1016 from Tumasberg) which appear intermediate. They have the dense shrubby habit and ladder-like lateral spines on the bracteoles of B. merxmuelleri but have a very finely and rather densely puberulent stem, broader, more ovate calyx lobes and ± broader bracteoles with a narrow blade, all characters tending towards B. lanceolata subsp. tristis. These are possibly a result of past hybridisation where their ranges overlap(ped). However, the two species are usually so distinct that it seems right to maintain B. merxmuelleri as a distinct species.
Type
Namibia, Distr. Swakopmund, Durchfahrt zwischen Spitzkoppe und den Pontokbergen, fl. 27 March 1954, Kinges 3685 (holotype M! [M0109631]).

Native to:

Namibia

Barleria merxmuelleri P.G.Mey. appears in other Kew resources:

First published in Mitt. Bot. Staatssamml. München 2: 382 (1957)

Accepted by

  • 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): 1-85. Royal Botanic Gardens, Kew.
  • Govaerts, R. (1996). World Checklist of Seed Plants 2(1, 2): 1-492. MIM, Deurne.

Literature

Kew Bulletin

  • Craven, P. (ed.) (1999). A checklist of Namibian plant species. South African Botanical Diversity Network Report No. 7, SABONET, Windhoek.
  • Darbyshire, I., Tripp, E. A. & Dexter, K. G. (2012). A new species and a revised record in Namibian Barleria (Acanthaceae). Kew Bull. 67: 759 – 766.
  • Klaassen, E. & Kwembeya, E. (eds) (2013). A checklist of Namibian indigenous and naturalised plants. Occasional Contributions No. 5, National Botanical Research Institute, Windhoek.
  • Klopper, R. R., Chatelain, C., Bänninger, V., Habashi, C., Steyn, H. M., de Wet, B. C., Arnold, T. H., Gautier, L., Smith, G. E. & Spichiger, R. (2006). Checklist of the flowering plants of sub-Saharan Africa. An index of accepted names and synonyms. South African Botanical Diversity Network Report No. 42, SABONET, Pretoria.
  • Mendelsohn, J., Jarvis, A., Roberts, C. & Robertson, T. (2002). Atlas of Namibia. A portrait of the land and its people. Ministry of Environment & Tourism and David Philip, Cape Town.
  • Meyer, P. G. (1957). Beitrag zur Kenntnis der Acanthaceen Südwestafrikas. Mitt. Bot. Staatssamml. München 2: 368 – 385.
  • Meyer, P. G. (1968). 130. Acanthaceae. In H. Merxmüller (ed.), Prodromus einer Flora von Südwestafrika. J. Cramer, Germany.
  • Van Wyk, A. E. & Smith, G. F. (2001). Regions of Floristic Endemism in Southern Africa. A review with emphasis on succulents. Umdaus Press, Hatfield.
  • Welman, W. G. (2003). Acanthaceae. In: G. Germishuizen & N. L. Meyer (eds), Plants of southern Africa: an annotated checklist. Strelitzia 14: 92 – 106. National Botanical Institute, Pretoria.

Kew Backbone Distributions
The International Plant Names Index and World Checklist of Selected Plant Families 2021. Published on the Internet at http://www.ipni.org and http://apps.kew.org/wcsp/
© Copyright 2017 World Checklist of Selected Plant Families. http://creativecommons.org/licenses/by/3.0

Kew Bulletin
Kew Bulletin
http://creativecommons.org/licenses/by-nc-sa/3.0

Kew Names and Taxonomic Backbone
The International Plant Names Index and World Checklist of Selected Plant Families 2021. Published on the Internet at http://www.ipni.org and http://apps.kew.org/wcsp/
© Copyright 2017 International Plant Names Index and World Checklist of Selected Plant Families. http://creativecommons.org/licenses/by/3.0