Apocynaceae

Bester, Stoffel P., Herman, Paul P. J. & Klopper, Ronell R., 2012, National Herbarium Plant Collecting Programme reveals new country and provincial distribution records from South African National Parks (Apocynaceae, Asteraceae & Xanthorrhoeaceae: Asphodeloideae), Phytotaxa 62 (1), pp. 44-56 : 46-48

Apocynaceae ( Asclepiadoideae – Ceropegieae )

First herbarium record of Orthanthera albida in South Africa at PRE

The genus Orthanthera Wight (1834: 48) is endemic to Africa and currently consists of four species ( Klopper et al. 2006). Orthanthera butayei ( De Wildeman 1904: 192) Werdermann (1938: 240) and O. gossweileri Norman (1929: 98) are restricted to southern Tropical Africa ( Angola and Zambia), while O. albida Schinz (1888: 265) and O. jasminiflora ( Decaisne 1844: 630) Schinz (1888: 265) occur mainly in southern Africa ( Namibia, Botswana and South Africa) ( Victor et al. 2003, Leistner 2005, Bester et al. 2006) although the former also extends to southern Angola.

Previously O. albida was seemingly restricted to Namibia and Angola ( Victor et al. 2003, Bester et al. 2006) and was not listed for South Africa. On a collecting trip to the Richtersveld National Park (RNP) in August 2010, as part of the ongoing NHPCP, it was found in the park ( Figure 2 ). The location seems to be limited to the stream bank vegetation along the Orange River.

Orthanthera albida was, however, previously listed on a checklist of the Augrabies Falls National Park ( Zietsman & Bezuidenhout 1999). On investigation it was revealed that the name was placed on the list based on a report where it was listed for the park ( Werger & Coetzee 1977), but even in this paper no voucher specimens were cited. Attempts to locate vouchers of this plant in NMB, KSAN, PRE and the field herbarium at the Augrabies Falls National Park were unsuccessful and it is concluded that possibly only a sight-record was made.

This species forms shrubs with an untidy appearance of spreading stems. In the RNP where plants were observed, it was severely grazed by goats from the community, shaping them into low rounded and very compact bushes. When stems are crushed, a clear sap emerge which is quite bitter. The stems are somewhat succulent ( Figure 3 ).

Specimens examined: — SOUTH AFRICA. Northern Cape: Richtersveld National Park, north of De Hoop campsite between Gaimus / Stuiweoog and Rooilepel ( QDS: 2817 AA), 12 September 2010, S. P. Bester 10112 ( KMG!, KSAN!, MO!, PRE!) ; Richtersveld National Park, between Richtersberg campsite and Adventure Bush Camp ( QDS: 2817 AC), 14 September 2010, S. P. Bester 10136 ( PRE!) .

The two southern African species of Orthanthera are easily distinguishable from each other. In O. albida plants have a shrubby appearance with much reduced linear leaves (8–30 × 1–3 mm). In comparison, O. jasminiflora has a creeping habit with well-developed elliptic to ovate leaves (20–70 × 5–42 mm). The flowers of O. jasminiflora ( Figure 4 ) are also much larger (12–35 mm long with the lobes ± as long as the tube) and cream, compared to O. albida which have smaller (5–10 mm long with the lobes ± half as long as the tube), yellow to yellow-green flowers.

Orthanthera gossweileri is only known from the type locality in the Cunene Province in southern Angola

( Figueiredo & Smith 2008). The type specimen [Gossweiler 3881 (BM), see JSTOR Plants 2012a] has flowers that range from 20 to 30 mm in length, but the outstanding feature of this species seems to be the 33–67 mm long filiform leaves. The material of O. butayei [Butaye s.n. (BR), see JSTOR Plants 2012b] very much resemble that of O. jasminiflora and needs to be studied in more detail to assess its recognition as a separate taxon.

Figures

FIGURE 2. Known distribution of Orthanthera albida,. New localities, ̝. Specimens housed at PRE and NBG.

FIGURE 3. Orthanthera albida from the Richtersveld National Park, Northern Cape Province, South Africa (photographs by S.P. Bester). A. Plant (in foreground) in habit—transitional zone between Lower Gariep Alluvial vegetation and Richtersveld Sheet Wash Desert (Mucina & Rutherford 2006). B. Close-up of sessile inflorescence, flowers yellow to yellow-green. C. Fruit, cream background mottled maroon. All from Bester 10112 (PRE). Scale bar: A = 45 cm, B = 12 mm, C = 15 mm.

FIGURE 4. Orthanthera jasminiflora from Bloemhof, North-West Province, South Africa (photographs by S.P. Bester). A. Inflorescence and leaves. B. Single flower with swollen base and relatively long segments. C. Trailing stems depicting the habit—individual stems up to 15 m long. All from Bester 5301 (PRE). Scale bars all 30 mm.