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This species is accepted, and its native range is WNW. 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 is a highly localised species, known from an EOO of 5307 km2 in the hyper-arid mountains adjacent to the Skeleton Coast. It has been recorded as locally common by several collectors and was found to be fairly common by the current authors in a small area near Rhino Camp in the Ugab River drainage. Human threats are limited, although there has been some mining in parts of its range, notably the now inactive Brandberg West Mine which was a large-scale tin mining operation. A more plausible threat is that of increasingly prolonged drought along the Skeleton Coast. However, this species appears to be adapted to periods of drought stress, and displays periodic flowering following infrequent rains. It is currently assessed as of Least Concern — LC but climate change may ultimately threaten this species in the longer term. As such, populations should be carefully monitored. It could potentially qualify as “Rare” (sensu Raimondo et al. 2009) in view of it being a habitat specialist and so likely to have a small AOO but this requires further investigation.
Distribution
Endemic to northwestern Namibia (Erongo and Kunene Regions).
Ecology
Barleria solitaria occurs in very arid, sometimes nearly barren terrain on or at the base of open rocky or boulder-strewn hillslopes and cliffs, and in dry scrub with Commiphora; c. 370 – 550 m elevation. It can be the most frequent or only shrublet in this harsh environment, although Petalidium variabile (Engl.) C. B. Clarke sensu lato can also be frequent. It is a constituent of the Welwitschia-desert floristic group of Craven (2009) and occurs in the Western-central Escarpment and Inselbergs and Central Desert vegetation types of Mendelsohn et al. (2002).
Morphology General Habit
Rounded or cushion-shaped shrub, 20 – 50 cm tall and up to 100 cm in diam.; stems ± markedly angular, at first rather succulent, soon turning woody with white bark, the older stems leafless and appearing jointed due to prominent intrapetiolar line and petiole scars; young stems densely white-puberulous, hairs retrorse or appressed, persistent but less dense on older stems
Morphology Leaves
Leaves with petiole to 4 mm long; blade variously obovate, oblong-elliptic, ovate-elliptic or orbicular, 1.2 – 2.3 × 0.8 – 1.5 cm (l:w ratio 1.1 – 2.1:1), base cuneate to rounded, margin entire, apex obtuse to rounded or emarginate, minutely apiculate, surfaces puberulous when young but soon glabrescent except for strigose hairs on margin and main veins beneath, often with few broad subsessile glands towards apex beneath; lateral veins 3 – 4 pairs
Morphology Reproductive morphology Flowers Androecium Stamens
Stamens inserted 6.5 – 7 mm from base of corolla tube; filaments 24 – 30 mm long, curved towards apex; anthers 2 – 3.2 mm long; lateral staminodes 0.5 – 3 mm long, with a broad, pilose basal portion then abruptly narrowed, with or without a slender glabrous apical portion, antherodes absent or well developed, up to 0.9 mm long
Morphology Reproductive morphology Flowers Calyx
Calyx green or blue- to pink-tinged, with paler prominent palmate venation, tardily turning pale-scarious; anterior lobe elliptic or oblong-elliptic, 11.5 – 17 × 4.5 – 8 mm, base cuneate, margin subentire or usually with up to 12 teeth formed from vein endings, each with a terminal bristle, apex usually notched, tips mucronulate, strigulose along main veins and with few to more numerous fine to spreading hairs at least towards base; posterior lobe as anterior lobe but 12.5 – 19 mm long, apex acute, mucronate; lateral lobes linear-lanceolate, 8.5 – 13 mm long
Morphology Reproductive morphology Flowers Corolla
Corolla 32 – 39 mm long, blue or purple with the adaxial lobes partially white with purple speckling, finely eglandular-pubescent externally mainly on tube and lateral lobes; tube 17.5 – 19 mm long, cylindrical, barely widened towards mouth; limb in “2+3” configuration; abaxial lobe offset by 2 – 3.5 mm, obovate, 8 – 12 × 5.5 – 10 mm, apex rounded; lateral lobes (obovate-) elliptic or broadly ovate, 9 – 13.5 × 6.5 – 11 mm, apices rounded, emarginate or obtuse; adaxial lobes 10 – 17 mm but fused for up to half their length, free portions narrowly oblong-elliptic to ovate, 5.5 – 11.5 × 3 – 8 mm, apices rounded
Morphology Reproductive morphology Flowers Gynoecium Pistil
Pistil glabrous; style flattened and rather thick, long-exserted, held well beyond anthers; stigma capitate, to 0.4 mm long, shallowly bilobed
Morphology Reproductive morphology Fruits
Old and immature capsules only seen, 4-seeded, ± 12 mm long, glabrous; mature seeds not seen.
Morphology Reproductive morphology Inflorescences
Inflorescences of single-flowered axillary cymes but often clustered towards stem apices; bracts foliaceous; peduncle 1.5 – 4 mm long; bracteoles linear, oblanceolate or elliptic, 1.8 – 5.5 × 0.3 – 1.5 mm, blade green or green-brown, midrib pale and prominent, margin entire, apex apiculate
Note
This very distinctive species appears to be isolated from other species morphologically within subg. Barleria. The corolla morphology, with both a clearly offset abaxial lobe and a partially fused pair of adaxial lobes, is unusual and more akin to some species in sect. Somalia, such as B. kaessneri S. Moore and allies from central and eastern Africa. It is also odd in having a glabrous pistil and a very long exserted and flattened style.
Type
Namibia, Outjo Distr., Escarpment-Abstieg 20 mls von Torrabay, fl. 1 April 1963, Giess et al. 6181 (holotype M! [M0109625]; isotypes MO* [MO-391184], PRE, WAG* [WAG0072609], WIND! [WIND000031806]).

Native to:

Namibia

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

First published in Mitt. Bot. Staatssamml. München 6: 513 (1967)

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. (2009). Phytogeographic study of the Kaokoveld Centre of Endemism. Ph.D. thesis, University of Stellenbosch. http://hdl.handle.net/10019.1/1325
  • 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. (1967). Beiträge zur Kenntnis der Acanthaceen Südwestafrikas. Mitt. Bot. Staatssamml. München 6: 505 – 515.
  • Meyer, P. G. (1968). 130. Acanthaceae. In H. Merxmüller (ed.), Prodromus einer Flora von Südwestafrika. J. Cramer, Germany.
  • Raimondo, D., Von Staden, L., Foden, W., Victor, J. E., Helme, N. A., Turner, R. C., Kamundi, D. A. & Manyama, P. A. (eds) (2009). Red List of South African Plants. Strelitzia 25. South African National Biodiversity Institute, Pretoria.
  • 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