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Issue: Vol. 626 No. 3: 23 Nov. 2023
Type: Article
Published: 2023-11-23
DOI: 10.11646/phytotaxa.626.3.2
Page range: 159-169
Abstract views: 137
PDF downloaded: 116

Reinstatement of the name Petalidium ovatum (Acanthaceae), with an amplified description of the species

Independent Researcher; P.O. Box 21168; Windhoek; Namibia; H.G.W.J. Schweickerdt Herbarium; Department of Plant and Soil Sciences; University of Pretoria; Pretoria; 0002 South Africa
School of GeoSciences; Kings Buildings; University of Edinburgh; Edinburgh EH9 3FF; United Kingdom; Royal Botanic Garden Edinburgh; 20a Inverleith Row; Edinburgh EH3 5LR; United Kingdom
School of GeoSciences; Kings Buildings; University of Edinburgh; Edinburgh EH9 3FF; United Kingdom
H.G.W.J. Schweickerdt Herbarium; Department of Plant and Soil Sciences; University of Pretoria; Pretoria; 0002 South Africa; South African National Biodiversity Institute; Private Bag X101; Pretoria; 0001 South Africa
Eudicots desert endemism flora Kaokoveld Kaokoveld Centre of Endemism Kunene Region Ruellieae Khorixas Bergsig lectotypification taxonomy

Abstract

The name Petalidium ovatum is reinstated and an amplified description is provided for a species of Petalidium confined to Namibia. Petalidium ovatum used to be treated as a synonym of the widespread P. englerianum, but morphological characters support the reinstatement. Petalidium ovatum is a range-restricted species, only known from the Khorixas-Bergsig area in the Kaokoveld Centre of Endemism, northwestern Namibia, where it grows on arid hillsides and along ephemeral riverbeds and drainage lines. Diagnostic characters for P. ovatum include the pale grey, often almost white, appearance of the plants, vegetative parts with a dense white indumentum of both stellate and dendritic trichomes, flowers borne in short few-flowered dichasia, bracts oblanceolate with apices acute or obtuse, and bracteoles widely ovate. The flowers of P. ovatum are distinctive in having the anterior corolla lobe partly or completely yellow, the others burgundy, and with the two upper lobes connate towards the base for almost half their length. A comparison of some of the more prominent morphological features to differentiate Petalidium ovatum from P. englerianum, its morphologically most similar relative, is provided. Based on IUCN Red List categories and criteria, a conservation assessment of Least Concern (LC) is recommended for the reinstated species.

 

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