Polydora angustifolia ( Steetz) H.Rob.

Swelankomo, N., Simango, N. & Manning, J. C., 2018, The genus Polydora Fenzl (Asteraceae: Vernonieae) in southern Africa *, South African Journal of Botany 119, pp. 335-339 : 336-338

Polydora angustifolia ( Steetz) H.Rob. in Proc. Biol. Soc. Wash. 112: 232 (1999).

Crystallopollen angustifolium Steetz in Peters Reise Mossamb., Bot. 2: 366 (1864). Vernonia poskeana var. vulgaris Hiern., Cat. Afr. Pl. Welw. I , 3: 519 (1898). Vernonia erinacea H.Wild in Kirkia 11: 2 (1978), as nom. nov., non V. angustifolia Michx. (1803) .

Type: Mozambique, Rios de Sena, Peters s.n. (B†, holo.). Neotype, designated by Wild in Kirkia 11: 55 (1987): Malawi, Zomba Plateau , 30 May 1946, Brass 16,090 (SRGH, neo.; K, MO, BR [BR0000008883810]—digital image!; US—[ US 00065384] digital image!, isoneo.).

Vernonia poskeana Vatke & Hildebr. in Oesterr. Bot. Zeitschr. 25: 324 (1875), syn. nov. Polydora poskeana (Vatke & Hildebr.) H.Rob. in Proc. Biol. Soc. Wash. 112(1): 233 (1999). Type: Tanzania, Zanzibar Island, Hildebrandt 1014 (W, holo.; BM [BM000629307]—digital image!, K [K000273024]—digital image!, iso.).

Crystallopollen angustifolium var. chlorolepis Steetz in Peters, Reise Mossamb. Bot. 2: 366 (1864) [non Vernonia chlorolepis S.Moore (1914) ]. Vernonia poskeana var. chlorolepis (Steetz) O.Hoffm. in Bol. Soc. Brot. 10:171 (1892). Type: Mozambique, Inhambane, Peters s.n. (B†).

Vernonia steetziana Oliv. & Hiern in Fl. Trop. Afr. 3: 273 (1877), syn. nov. Polydora steetziana (Oliv. & Hiern) H.Rob. in Proc. Biol. Soc. Wash. 112(1): 233 (1999). Type: Mozambique, Kaimba Island opposite Tete, 1860, Kirk s.n. (K [K000273122]—digital image!, lecto., designated by Hilliard in Compos. Natal : 38 (1977).

Vernonia elegantissima Hutch. & Dalz., Fl. West Trop. Africa ed. 1, 2: 164 (in key), 167 (1931). Vernonia poskeana var. elegantisima (Hutch. & Dalz.) C.D.Adams in J. West African Science Assoc. 3(1): 121 (1957). Type: Nigeria, Lokoja, Mt. Patti, 6 November 1908, Dalziel 36 (K [K000272836]—digital image!].

Vernonia poskeana subsp. bracti fi mbriata Mendonça, Contrib. Conhec. Fl. Angola, Compositae: 7 (1943). Vernonia bracti fi mbriata (Mendonça) G.V. Pope in Kew Bull. 41(1): 42 (1986). Type: Angola, Huila, Excell and Mendonça 2474 (BM, lecto designated by Pope in Kew Bull. 41(1): 42 (1986); COI, LISJ, isolecto.).

Vernonia samfyana G.V.Pope in Kew Bull. 41(1): 42 (1986). Vernonia poskeana subsp. samfyana (G.V.Pope) G.V.Pope in Fl. Zambes. 6(1):148 (1992). Type: Zambia, Samfya , Mutimushi 1126 (K, holo.).

Vernonia poskeana var. botswanica G.V.Pope, Kew Bull. 41(1): 39 (1986). Vernonia poskeana subsp. botswanica (G.V.Pope) G.V.Pope [‘as V. poskeana subsp. botswanica G.V.Pope’] in Fl. Zambes. 6(1):148 (1992). Type: Botswana, Khutse , Coleman 60 (K, holo. [K000273120]— digital image!; SRGH, iso.).

For additional synonyms from tropical Africa see Pope (1992).

Erect, slender or ± robust annual herb from a slender taproot, 0.1–2.0 m high; stem simple or diffusely branched, ribbed, gland-dotted and sparsely to roughly appressed-pubescent with L-shaped or asymmetrically T-shaped hairs. Leaves sessile, filiform to linear or narrowly elliptic, 20–100 × 1–6 mm, subacute to apiculate, margins weakly or strongly revolute, midrib raised beneath, upper surface finely pubescent or glabrescent with L-shaped hairs, lower surface more thinly so except on midrib, gland-dotted on both surfaces. Capitula few to many, terminal and corymbiform cymose or paniculate, peduncles slender, up to 60 mm long, pubescent. Involucre obconic or urceolatecampanulate, ± as wide as long, 6–12 × 6–11 mm when pressed; involucral bracts ±5- to 7-seriate, imbricate, scarious at margins and purple-tipped distally, pubescent to finely pilose, acute, emarginatemucronate, aristate or awned with awn up to 1.0 mm long; outer involucral bracts spreading, ovate to lanceolate, 0.5–2.0 mm long; middle involucral bracts oblong to obovate, erect or recurved apically; inner involucral bracts linear to lorate, 4–8 mm long. Corolla mauve-purple, 6–12 mm long, exserted beyond involucre, tubular in lower half and narrowly funnel-shaped above, perianth tube 3–7 mm long, lobes linear-lanceolate, 3–5 mm long. Cypselas narrowly obconic-turbinate, 0.5–4.0 mm long, (5)8 to 10(12)-ribbed, setose with twin hairs on ribs and gland-dotted between ribs. Pappus biseriate; outer series of short, oblong-oblanceolate, ± overlapping fimbriate scales ±0.75 mm long, inner series of brownish barbellate bristles ± 6 mm long. Flowering time: throughout the year, depending on the rainfall. Fig. 1 .

Distribution and ecology: widely distributed through tropical and south tropical Africa, in Angola, Zaire, Zambia, Zimbabwe, Malawi, Mozambique, Botswana, northern and central Namibia and the northern parts of South Africa and Swaziland ( Pope 1992); in South Africa recorded from Limpopo, Northwest, Gauteng, Mpumalanga and northern Free State provinces ( Fig. 2 ); in drier grassland and savanna or open woodland, at altitudes of 300–1850 m, often along pans or depressions, along roadsides or railways, or as a weed of cultivated land.

Notes: Authors have differed widely in their circumscription of Polydora poskeana and its allies. Wild (1978) treated P. poskeana broadly, including several synonyms under the name. In contrast, Pope (1986, 1992) circumscribed the species very narrowly, arguing that although there were only small vegetative differences within the complex, these could be related to discontinuities in fruit and capitulum characters, and on this basis he recognised several segregate species. Within P. poskeana sensu stricto he further segregated the southwestern populations (including those from southern Africa) as subsp. botswanica on the basis of their slightly larger capitula (no dimensions given) and 8- to 12-ribbed cypselas vs. 5- to 7 ribs in subsp. poskeana . This taxonomy was rejected by Robinson et al. (2016), who also included V. bracti fi mbriata, V. centaureoides and V. samfyana , all three recognised as distinct species by Pope (1986), as synonyms of P. poskeana . The inclusion of V. centaureoides as a synonym of V. poskeana by Robinson et al. (2016) is evidently erroneous as they had earlier ( Robinson and Skvarla 2014) transferred the species to the genus Oocephala on the basis of its [sub]plumose pappus bristles, a placement that they retained in their later treatment ( Robinson et al. 2016), where the species is thus listed separately in two genera, both as O. centaureoides (Klatt) H.Rob.& Skvarla and as a synonym of P. poskeana under the combination P. centauroides [sphalm.] (Klatt) H.Wild. Despite the close morphological similarity between O. centaureoides and P. poskeana , the difference in pappus bristles appears to be a real one and the two taxa are evidently distinct ( Hilliard 1977; Pope 1992).

Pope (1986) recorded the three species Polydora angustifolia , P. poskeana and P. steeziana as occurring in southern Africa, and this treatment was followed by Robinson et al. (2016). Polydora angustifolia was distinguished from P.poskeana solely by its lower and median involucral bracts tipped with a short straight or flexuous awn 1 mm or more long ( Fig.1D ). In contrast, P. poskeana was considered to have the bracts variously obtuse to emarginate or mucronate to shortly apiculateawned ( Fig. 1F ). This distinction is arbitrary as we consider the variation to be continuous, having encountered a complete range among the southern African material, even within a single capitulum, from obtuse bracts typical of P. poskeana through mucronate or apiculate bracts to the awned bracts typical of P. angustifolia .

Polydora angustifolia in the strict sense as circumscribed by Pope (1986) was listed by him ( Pope 1992; under the name Vernonia erinacea Wild. ) as occurring from east tropical Africa through Zimbabwe and Mozambique to South Africa,where it was recorded from the ‘Transvaal’ without more precise information. In the later account of the tribe in southern Africa by Robinson et al. (2016) the distribution of the species in southern Africa was emended to ‘Natal’, again without more precise information. Significantly, the species is not included in Hilliard's (1977) detailed monograph of Compositae in Natal. This uncertainty as to its distribution evidently reflects the difficulty that has been experienced by authors in distinguishing between P. angusifolia and P. poskeana . Having examined extensive material from the region we are unable to distinguish between them and have no hesitation in treating them as conspecific.

The key differences between Polydora poskeana and P. steetziana are similarly subtle, even by Pope's (1986) admission. Polydora steetziana was defined as having the inner or median involucral bracts ± markedly expanded at the apex, hyaline or purple-tinged and rounded to truncate-emarginate above, and often mucronate or shortly aristate; and the involucre was considered to be larger and campanulate with a rounded base ( Fig. 1E, F ). Polydora poskeana , in contrast, was considered to have the inner involucral bracts gently tapered to ±rounded and not expanded apically although sometimes mucronate; and the involucre was thought to be smaller and obconic or subfusiform, and ± tapered at the base ( Fig. 1C, D ).

According to Pope (1986), these two species are allopatric in southern Africa, with P. poskeana recorded from the drier northwestern parts in Northwest, Limpopo and Gauteng provinces, and P. steetziana restricted to the wetter eastern parts, in Swaziland and in Mpumalanga and northern KwaZulu-Natal provinces.

We have examined numerous collections from southern Africa under both of these names but are unable to recognise two species on the basis of these differences, or any others. Thus herbarium specimens from Swaziland and Mpumalanga (e.g. Venter 1722; Koekemoer 2189; Theron 1252) may have an obovoid or obconic involucre that matches the type V. poskeana more than V. steetziana . Other specimens (e.g. Swelankomo UNIV05) have both ±obovoid and obconic involucres on the same plant. We are also unable to corroborate the supposed differences in bract shape and apex. We have also looked at the dimensions of the mature involucre of both P. steetziana (eastern populations) and P. poskeana (western populations), and find no difference between them, with the involucre of P. steetziana ranging from 6 to 10 × 8.0–10.5 mm, and P. poskeana from 8 to 11 × 6–12 mm. In conclusion, we are unable to maintain the distinction between P. poskeana and P. steetziana proposed by Pope (1986) and accordingly treat both names as synonyms of P. angustifolia .

Oocephala centaureoides (Klatt) H.Rob. & Skvarla is vegetatively similar to P. angustifolia and easily confused with it although the stems are generally more densely leafy, with axillary shoots, and the inner pappus bristles are subplumose, the latter character regarded as diagnostic for the genus ( Robinson and Skvarla 2014). The species is considered to be perennial but this is not always clear.

3.3. Additional specimens examined from southern Africa

Botswana. 2025 Mumpswe: Makgadigadi pans just north of the Makomojena veterinary check point, (–DC), 27 Sep 2009, Koekemoer 3850 (PRE). 2223 (Koatwe Pan): Central Kalahari Game Reserve, sandveld, (–BD), Apr 1975, Owens 32 (PRE). 2424 ( Dikgomo Di Kae ): Southeast Botswana, Jwaneng , ± 5 km from Sese Village , South Jwaneng, (–DB) , 16 Apr 2000, Cole 1593 (PRE). 2425 (Gabarone): NW of Molepolole, (–BC), 15 Jun 1955, Story 4899 (NBG, PRE); Thamaga, (− DA), 21 Apr 1977, Camerik 170 (PRE). 2522 (Sanie): Molopo River, Mogopong, (− DD), Mar 1935, Taylor TRV 35855 (PRE) .

Namibia. 1724 (Katima Mulilo): Forestry area, just outside Katima Mulilo, (–CB), 26 Apr 1989, Maggs- KÖlling GMK 781 (PRE). 1819 (Karakuwisa): Mile 46 Research Station, Observatory Plot Station, (− AD), 21 Apr 2001, Strohbach BS 5129 (PRE). 1918 (Grootfontein): 20 km north of Otjiwarongo, sandy roadside, (–BD), 23 May 1974, Goldblatt 1915 (NBG, PRE). 2119 (Epukiro): Epukiro Reservaat, Eiseb Omuramba, (–DC), 10 Apr.1967, Giess 9761 (PRE). 2216 (Otjimbingwe): Claratal, SW from Windhoek, (− DA), 5 Jun 1985, Botha & Bredenkamp 3568 (PRE). 2217 (Windhoek): Otjihundu farm; at turn-off past Omitara on the road to Witvlei, (–BD), 3 Mar 1997, Germishuizen 9293 (PRE); 10 miles [16 km] NE of Windhoek, (–CA), 22 Jul 1949, Steyn 179 (NBG); road between Windhoek-Goreangab dam, 3 km north- west of Windhoek on road side, (− DA), 9 Mar 1968, Wanntorp 95 (PRE).

Swaziland. 2631 (Mbabane): 20 km from Piggs Peak, at Nkomati New Bridge, (− AA), 2 Mar 1993, Germishuizen 5980 (PRE); Mbabane, (–AC), 29 Mar 1957, Compton 36,812 (NBG); 13 Apr 1961, Dlamini s.n. (NBG); Stroma, (–AC), 20 Mar 1955, Compton 25,034 (NBG); Mananga Mountain, (–BB), 1 Mar 1977, Venter 1722 (PRE).

South Africa. LIMPOPO. 2229 (Waterpoort): Parkfield 725 MS, (− DD), 17 Mar 1985, Raal 403 (PRE). 2230 (Messina): Venda, 48 km from Punda Maria in Kruger National Park to Louis Trichardt, (− DD), 26 Apr 1989, Koekemoer 233 (PRE). 2328 (Baltimore): Melkrivier 6.5 km from main gate of Lapalala Wilderness: Doornleegte farm, (–CD), 29 Mar 2004, Rampho 5 (PRE), Bredenkamp 3031 (PRE); road to Lapalala Nature Reserve, just after Sifikile School, (–CD), 28 Apr 2004, Van Wyk, Klein & Nkuna 806 (PRE). 2329 (Pietersburg): Pietersburg [Polokwane], (–DB), no date, Kleinberg 20,398 (PRE); Pietersburg [Polokwane], on farm Melkboomfontein 1919 LS, to the east of Masele Hill, east of Pietersburg [Polokwane], (–DC), 1980, Fourie 1359 (PRE); 18 km E of Pietersburg [Polokwane] on road to Houtbosdorp near Dieprivier Bridge, (–DC), 1980, Fourie 1179 (PRE). 2330 (Tzaneen): Middelkop, (–CC), 5 Jul 1930, Lozeby 11,156 (NBG); Venda, Thengwe, on road to Shikunda-Malema by Vuvha, (− DA), 11 Apr 1980, Van Wyk 4005 (PRE); Hans Merensky Nature Reserve, (− DA), 19 Dec 1969, Oates 108 (PRE); Venda, Tshidsini (Tshamutshedsi) west side of mountain, (–DB), 9 Apr 1980, Van Vyk 3738 (PRE). 2428 (Nylstroom): Uitvlug near Crecy District, Naboomspruit (–DB), 6 Apr 1974, Botha 835 (PRE); Nylstroom, (–DB), Apr 1919, Van Dam 19,669 (PRE). 2429 (Glen Cowe): Uitkyk, 1 km from Glen Cowe on road to Phokwana, (− DD), 4 Mar 1986, Germishuizen 3773 (PRE).

NORTHWEST. 2626 (Klerksdorp): 6 miles [9.6 km] West of Oberholzer on Ventersdorp road, (–BA), 24 Mar 1967, Vahrmeÿer 1558 (PRE). 2627 (Potchefstroom): Transvaal Botanical Garden- Roodepoort, (–BB), 15 Mar 1983, Behr 441 (NBG) .

GAUTENG. 2528 (Pretoria): Kwandebele, Boekenhoutfontein farm, (–BB), 17 Mar 1981, Hoepen 1672 (PRE); Lichtenburg, Grasfontein, (− DD), 21 May 1930, Sutton 443 (PRE) .

MPUMALANGA. 2530 (Lydenburg): Buffelskloof Nature Reserve, (–BC), 17 Feb 2002, Koekemoer 2189 (PRE); 11 Mar 2003, Klein 176 (PRE); Nelspruit, (–BD), Oct 1917, Breyer 17,920 (PRE). 2531 (Komatipoort): Nyamazane Bantu Trust, 10 miles [16 km] from gate, eastern slope, (–AC), 7 Mar1970, Buitendag 502 (NBG, PRE); Kruger National Park, Skukuza, 5 km S of Skukuza, on road to Pretoriuskop (–BA), no date, Zambatis, GZ 219 (PRE); Barberton, Saddleback pass, (–CD), 16 Nov 2015, Manning 3569 (NBG); Louw's Creek, (–DB), Mar 1920, Van Dam 21,134 (PRE); Barberton, (–DC), Apr 1924, Murphy 24,938 (PRE); 1 Nov 1930, Liebenberg 2538 (PRE).

FREE STATE. 2627 (Potchefstroom): Free State, Sasolburg, Wonderwater (− DD), 22 Apr 1991, Kroon 11352A (PRE) .

Edited by GV Goodman-Cron

Figures

Fig. 1. Polydora angustifolia A.Habit (Namibia:Windhoek,Steyn 179 NBG);B.Flowering plant (Mpumalanga:Barberton,Manning 3569 NBG).Photograph:J.C.Manning; C.Obconic capitulum and E.detail of middle bract with aristate apex (Steyn 179 NBG);D. Campanulate capitulum and F.detail of middle bract with obtuse apex (Swaziland: Mbabane, Compton 26,812 NBG);G.Cypsela with setose ribs and glandular furrows, and biseriate pappus (Limpopo:Tzaneen, Lozeby s.n. NBG). Scale bars:C,E, 1.5 mm; D, F, 0.5 mm; G, 1 mm.

Fig. 2. Distribution of Polydora angustifolia in southern Africa.