In Southern Africa
Total Page:16
File Type:pdf, Size:1020Kb
South African Journal of Botany 94 (2014) 238–248 Contents lists available at ScienceDirect South African Journal of Botany journal homepage: www.elsevier.com/locate/sajb The genus Distephanus (Asteraceae: Vernonieae) in southern Africa N. Swelankomo a,J.C.Manningb,c,⁎ a National Herbarium, South African National Biodiversity Institute, Private Bag X101, Pretoria 0001, South Africa b Compton Herbarium, South African National Biodiversity Institute, Private Bag X7, Claremont 7735, South Africa c Research Centre for Plant Growth and Development, School of Life Sciences, University of KwaZulu-Natal, Pietermaritzburg, Private Bag X01, Scottsville 3209, South Africa article info abstract Article history: The southern African species of Distephanus Cass. (Asteraceae: Vernonieae) are revised. Full descriptions, illustra- Received 5 June 2014 tions, distribution maps and a key are provided for the five species recognised in the region. Received in revised form 7 July 2014 © 2014 SAAB. Published by Elsevier B.V. All rights reserved. Accepted 8 July 2014 Available online xxxx Edited by GV Goodman-Cron Keywords: Southern Africa Taxonomy Vernonia 1. Introduction Vernonieae by its trinervate leaves and mostly cream-coloured or yellow (rarely mauve to lilac) florets, neither character occurring The delimitation of the tribe Vernonieae Cass. has remained rel- elsewhere in the tribe, in which pinnate leaf venation and reddish atively unchanged since its description by de Cassini (1816) but to purple flowers are typical. Additional synapomorphies for the circumscription of the core genus Vernonia Schreb. has been Distephanus include simple, shield-like endothecial thickenings drastically narrowed, from a maximum of some 1 000 out of (Robinson and Kahn, 1986). The genus includes Gongrothamnus 1 500 species included in the tribe to its current diminished size Steetz, which was similarly defined by its yellow flowers and and distribution of just 22 species in North and South America trinervate leaves, as well as Newtonia O. Hoffm. It is currently includ- (Robinson, 1999a,b). The immediate consequence of this has edasthesolememberofsubtribeDistephaninae S.C. Keeley & H. Rob. been the resurrection of many old genera and the description of (Keeley and Robinson, 2009). a number of new ones to accommodate various groupings of Although most of the southern African species of Distephanus species that are now segregated from the dismembered Vernonia were treated (as Vernonia) by both Hilliard in her monograph in the broad sense. These segregates include all African members Compositae in Natal and by Pope (1992) in Flora zambesiaca, no com- of the tribe, and Vernonia in the narrow sense is now restricted plete modern treatment of the species exists for the subcontinent. to the New World. Since the transfer of four southern African species to Distephanus One of the earliest and most distinctive elements to be by Robinson and Kahn (1986), one additional combination has resurrected from Vernonia was the paleotropical genus Distephanus been made (Boon and Glen, 2013), and five species are now Cass., described by de Cassini (1817) for the single species Conyza recognised in southern Africa. populifolia Lam. from Mauritius, and named for the characteristic We provide the first comprehensive treatment of the genus for biseriate pappus of 10 short outer scales alternating with 10 longer southern Africa, with full nomenclature, descriptions, a key to the spe- inner bristles. The genus was subsequently included in Vernonia, cies, and distribution maps. where it was treated at sectional or subsectional level until revived by Robinson and Kahn (1986) for 26 species of mostly western Indian Ocean and eastern African shrubs and scramblers. A more re- 2. Materials and methods cent account estimates the number of species at ±45 spp. (Keeley and Robinson, 2009). The genus is distinguished from other Specimens or digital images of all relevant types were examined, as well as all herbarium material from BOL, NBG, PRE and SAM, the ⁎ Corresponding author. primary collections of species from southern Africa (herbarium ac- E-mail address: [email protected] (J.C. Manning). ronyms according to Holmgren et al., 1990). http://dx.doi.org/10.1016/j.sajb.2014.07.007 0254-6299/© 2014 SAAB. Published by Elsevier B.V. All rights reserved. N. Swelankomo, J.C. Manning / South African Journal of Botany 94 (2014) 238–248 239 3. Taxonomy Soc. Linn. Paris 1: 721 (1888). Antunesia O. Hoffm. in Bol. Soc. Brot. 10: 178 (1893), as a replacement name for Newtonia O. Hoffm., 3.1. Genus description nom illegit. Type: Newtonia angolensis O. Hoffm. = Distephanus angolensis (O. Hoffm.) H. Rob. & B. Kahn. Distephanus Cass. in Bull. Sci. Soc. Philom. Paris 1817: 151 (1817). Shrubs or scramblers. Leaves alternate or rarely opposite, shortly Vernonia sect. Distephanus (Cass.) Benth. & Hook.f., Gen. Pl. 2(1): 228 petiolate, blade ovate to lanceolate, usually trinervate, acuminate, (1873). Vernonia subsect. Distephanus (Cass.) S.B. Jones in Rhodora 83: margins entire or undulate-serrate, glabrous to thinly hairy and 68 (1981). Type: Distephanus populifolius (Lam.) Cass. glandular. Capitula in terminal, corymbose panicles, homogamous, Gongrothamnus Steetz in Naturw. Reise Mossambique [Peters] discoid. Involucre campanulate, bracts in several series, imbricate, 6(Bot., 2): 336 (1864). Vernonia subsect. Gongrothamnus (Steetz) lanceolate, ± pubescent. Receptacle epaleate. Corolla usually yellow S.B. Jones in Rhodora 83: 65 (1981). Type: Gongrothamnus to creamy-white or orange-yellow, less commonly lilac or mauve, divaricatus Steetz = Distephanus divaricatus (Steetz) H. Rob. & B. funnel shaped, glandular in upper part, 5-lobed, lobes recurved api- Kahn. cally. Anthers sagittate, apical appendages without glands. Style Newtonia O. Hoffm. in Nat. Pflanzenfam. [Engler & Prantl] 4(5): branches linear, acute, with relatively long hairs on back. Cypselas 285 (1892), illegitimate name, not Newtonia Baill. in Bull. Mens. oblong-obovoid, 5- to 10-ribbed, glabrous or pilose-sericeous. Fig. 1. Distephanus anisochaetoides, Ross 2393 (PRE). 240 N. Swelankomo, J.C. Manning / South African Journal of Botany 94 (2014) 238–248 2a Leaves discolorous, upper surface dark green and thinly puberulous, lower surface whitish-felted; florets 15 to 20 per capitulum, orange fading yellow, corolla 8–10 mm long… 4. D. divaricatus. 2b Leaves concolorous, glabrescent, yellowish green; florets 3 to 5 per capitulum, yellow, corolla 4–6mmlong… 5. D. angolensis. 1b Involucral bracts acute to obtuse; florets whitish to mauve; plants from eastern coastal parts of southern Africa:3a Leaves usually opposite, deltoid-ovate or rhombic to hastiform; inner involucral bracts 4–6mm long; cypselas 5-ribbed; pappus bristles white, acute, 5–6 mm long… 3. D. angulifolius. 3b Leaves alternate, obovate or ovate to cuneate-rhomboid; inner involucral bracts 3.0–3.5 mm long; cypselas 8- to 10- ribbed:4a Leaves broadly obovate to cuneate-rhomboid with cune- ate base; inflorescence laxly paniculate, branches stiffly divaricate and flexuous; florets ±15 to 20 per capitulum; pappus bristles buff, clavate, 4 mm long… 1. D. anisochaetoides 4b Leaves ovate to elliptic with broadly cuneate or rounded base; fl fl Fig. 2. Inflorescence details of Distephanus anisochaetoides, Ross 2393 (PRE). Scale bar: in orescence densely paniculate, branches not strongly exuouse; 5mm. florets ±9 per capitulum; pappus bristles white, acute, 4–6mm long… 2. D. inhacensis Pappus biseriate, of 10 or more shorter, linear scales alternating with 10 or more inner barbellate bristles. Pollen: tricolporate, echinate to 3.3. Species treatment subechinolophate [Type A fide Jones (1981)]. 45 spp., tropical and subtropical Africa, with 5 spp. in southern Africa. 3.3.1. D. anisochaetoides Etymology: From the Greek di = two and stephanus =crowned,al- (Sond.) H. Rob. & B. Kahn in Proc. Biol. Soc Washington 99(3): 499 luding to the biseriate pappus of scales and bristles. (1986). Vernonia anisochaetoides Sond. in Linnaea 23: 61 (1850). Syntypes: South Africa, [Kwazulu-Natal], ‘Port Natal’ [Durban], 3.2. Key to southern African species Gueinzius 591(G, syn.), Gueinzius 320 (MEL, syn.—digital image!). Scandent shrub or semi-climber to 3 m; stem ribbed, greyish, 1a Involucral bracts acute to apiculate; flowers yellow or orange fad- densely felted when young with shaggy hairs concealing large, ses- ing yellow; plants from northwestern and northern and inland parts of sile glands, glabrescent. Leaves alternate, broadly obovate to southern Africa. cuneate-rhomboid, (20–)30–70 × 10–35 mm, margins entire or Fig. 3. Distribution of Distephanus anisochaetoides, ●; and distribution in southern Africa of D. inhacensis, ○. N. Swelankomo, J.C. Manning / South African Journal of Botany 94 (2014) 238–248 241 Fig. 4. Distephanus inhacensis, Nicholson 920 (PRE). irregularly coarsely toothed in distal half, 3(5)-nerved from base, Distribution and habitat. Endemic to the eastern seaboard of South acute to acuminate, base narrowed, felted when young, Africa, ranging from Knysna in Western Cape northwards through the glabrescent, conspicuously gland-pitted beneath, petiole coastal parts of Eastern Cape and KwaZulu-Natal to Stanger in the 5–15 mm long. Capitula in cymose panicles in upper axils on rigidly north, extending inland to Richmond and Bulwer in south-central divaricate, flexuous branches, ±15(to 20)-flowered. Involucre KwaZulu-Natal and to the Ngome and Nkandla forests in northern campanulate, 4–5 mm diam., bracts 3- or 4-seriate,