Introduction

The genus Pteronia L. belongs to the family Asteraceae, tribe Astereae, and comprises 76 species (Bello et al. 2017; Bello 2018; Bello et al. 2020). It is a genus of shrubs endemic to southern Africa, with its centre of diversity in the Greater Cape Floristic Region (GCFR), particularly the Succulent Karoo Biome (Manning & Goldblatt 2012; Snijman 2013; Bello 2018). The genus was a priority for taxonomic work in South Africa, where most of the species occur (Victor & Smith 2011; Victor et al. 2013; Von Staden et al. 2013). The morphology of the genus is diverse with regards to habit, leaf shape and florets (Shearing 1997; Viljoen et al. 2010). A comprehensive revision of the genus was produced more than a century ago (Hutchinson & Phillips 1917), with a recent synopsis of the Namibian species (Kolberg & Van Slageren 2014). Many of the species are poorly known (Shearing 1997) and some have been reported to have medicinal value (Shearing 1997; Hulley et al. 2010, 2011). Hutchinson & Phillips (1917) recognised four sections within Pteronia based solely on the presence or absence of a leaf indumentum, viz. sect. Incanae Hutch & E.Phillips, sect. Papillatae Hutch & E.Phillips, sect. Ciliatae Hutch & E.Phillips and sect. Glabratae Hutch & E.Phillips. This classification is largely artificial as it was based on artificial characters (Saupe 2007; Goswami 2013). In addition, it was noted that the section Ciliatae is invalid, and should rather be section Pteronia seeing as it includes the type species of the genus, Pteronia camphorata (L.) L. (Kolberg & Van Slageren 2014). The classification resulted in the placement of the infraspecific taxa of the polymorphic Pteronia camphorata in two different sections: Pteronia camphorata var. armata Harv. and P. camphorata var. longifolia Harv. in sect. Ciliatae, whereas P. camphorata var. laevigata Harv. was placed in sect. Glabratae. A taxonomic treatment of the Pteronia camphorata group by Bello et al. (2017) raised P. camphorata var. laevigata to species level as Pteronia cederbergensis Bello, Magee & Boatwr.

The informal morphological group, hereafter called the Pteronia uncinata group, includes five species (P. diosmifolia Brusse, P. fasciculata L.f., P. paniculata Thunb., P. teretifolia (Thunb.) Fourc. and P. uncinata DC.). This group can easily be distinguished from the rest of the genus by their closely set leaves, narrow involucres and densely clustered capitula with more than eight (8) heads (solitary, sometimes in clusters of 2 – 8 in the other species of Pteronia). Pteronia teretifolia has previously been erroneously conflated with Pteronia trigona E.Phillips, with the latter treated as a synonym (Gibbs Russell et al. 1987). The two species have a similar distribution and are vegetatively similar. However, the capitula of P. teretifolia are narrower, pedunculate and arranged into corymbs while those of P. trigona are broader, sessile and solitary. Also, the leaves of P. teretifolia are decussate while those of P. trigona are alternately arranged. These diagnostic features support the recognition of P. trigona as a distinct species from P. teretifolia, and unrelated to the Pteronia uncinata group.

All the species of the Pteronia uncinata group have a conservation status of Least Concern (LC), except for P. diosmifolia that is Vulnerable D2 (Victor 2002; Raimondo et al. 2009; SANBI 2020). This species is a limestone endemic with an extremely localised distribution in small colonies that are potentially threatened by encroachment from invasive species such as Acacia L. (e.g. Acacia cyclops A.Cunn. ex G.Don; Heydenrych 1994; Herman et al. 2006). Three members of the P. uncinata group (P. diosmifolia, P. teretifolia and P. uncinata) are recorded from limestone soil with only one endemic to this soil type (Brusse 1990). The limestone soil is alkaline and occurs within the Fynbos Biome, restricted to the soils of the Bredasdorp geological formation. About 42% of species found in this limestone habitat are local endemics with narrow distribution ranges (Heydenrych 1994). Economically, limestone habitats are important for low-intensity grazing and wild-flower harvesting, with species found in this habitat having great horticultural potential (Heydenrych 1994). On the other hand, antibacterial activities have been demonstrated for various extracts and essential oils of the non-limestone species (P. fasciculata and P. paniculata; Coovadia 2007).

The current study assessed the circumscriptions of the species within the Pteronia uncinata group. A taxonomic treatment of the species as well as a key to the species is presented with detailed description, diagnostic characteristics, geographical distributions, ecological information and conservation status. A description of Pteronia trigona is also presented to clarify its identity.

Material and Methods

Extensive examinations were carried out on herbarium collections from BOL, NBG, PRE and SAM. These collections as well as images of type material from G-DC and UPS-THUNB were studied (acronyms according to Thiers 2021, continuously updated). Descriptions of the species were based on characters observed on herbarium specimens and compared with descriptions from published literature. Specimens were observed under a stereomicroscope and measurements taken using a ruler or measureIT software with measurements taken on rehydrated material of the florets. Information on the flowering times, habitat, distribution, elevation, and soil type were obtained from the herbarium labels on the collections. Additional specimens examined are cited by country and province following the Quarter Degree Reference System for South Africa (Edwards & Leistner 1971; Leistner & Morris 1976). The recorded geographical distributions of the species were ascertained from Leistner & Morris (1976) and these were used to produce maps for the species.

Results

The species of the Pteronia uncinata group are erect, evergreen, perennial shrubs, 0.3 – 1.5 m in height. The leaves of all members are decussate (Fig. 1A – D), with P. uncinata sometimes having a 3-whorled arrangement in addition to the decussate leaf arrangement. This species also differs from the rest of the species in the group by the recurved/hooked leaf apices (Fig. 1C). The leaves are coriaceous and keeled to trigonous in P. diosmifolia, P. fasciculata, P. teretifolia and P. uncinata but succulent and subterete in P. paniculata. The group can be classified into two subgroups based on the leaf attachment and the presence or absence of glands on the cypselae. Free leaves and eglandular cypselae are diagnostic of a group of three species (P. diosmifolia, P. teretifolia and P. uncinata: Fig. 1C), while connate leaves, which give rise to persistent sheaths forming distinct sclerified scales on the branches, and the presence of glands on the cypselae, in addition to the cypselae hairs, are diagnostic for P. fasciculata and P. paniculata (Fig. 1A, B, D, E). The capitula are homogamous, discoid and terminal; they occur in dense clusters that are often arranged in a compound corymb. This is in contrast to the solitary capitula observed in P. trigona, which differentiates it from P. teretifolia or any member of the P. uncinata group. Pteronia fasciculata is distinct in its sessile, 1 – 2-flowered capitula (Fig. 1A, D) and the long pappus (9 – 10 mm: ≤ 8 in other species). In the remaining species (P. diosmifolia, P. fasciculata, P. teretifolia, and P. uncinata), the involucre is generally obconical in shape, except in P. paniculata that has a cylindrical involucre. The involucral bracts are generally glabrous with entire membranous margins in P. teretifolia, sparsely ciliate in P. diosmifolia and P. uncinata and hyaline-lacerate in P. fasciculata and P. paniculata. The pappus bristles are straw-coloured in P. fasciculata, P. paniculata and P. teretifolia but whitish in P. diosmifolia and P. uncinata.

Fig. 1
figure 1

Some species of the Pteronia uncinata group. A P. fasciculata; B P. paniculata (arrow showing persisting leaf sheath); C P. uncinata; D P. fasciculata (arrow showing sclerified scale on branches); E P. fasciculata cypsela (arrow showing glands). Voucher: E Cattell & Cattell 168 (NBG). Scale: E = 1 mm. Source: A – D iNaturalist.org. photos: a felix riegel; b nicola van berkel; c kooscl; d sally adam; e a. o. bello.

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Key to species of the Pteronia uncinata group

  • 1. Capitula solitary, occasionally in terminal clusters of 2 – 8 remaining species of Pteronia

  • Capitula in terminal cluster of 10 – 60, often arranged into a dense compound corymb2

  • 2. Leaves free, leaf bases not persisting as scales on branches; cypselae not glandular.3

  • Leaves basally connate, leaf sheath differentiated into a distinct, sclerified scale which persists on branches; cypselae glandular5

  • 3. Involucral bract margins entire membranous; pappus straw-coloured...1. P. teretifolia

  • Involucral bract margins ciliate; pappus whitish.4

  • 4. Leaves with conspicuously recurved, hook-like apices; cypselae oblong 2. P. uncinata

  • Leaves with straight apices; cypselae urceolate3. P. diosmifolia

  • 5. Leaves lanceolate, coriaceous, flattened, 3 – 5 mm wide, margins scabrous; capitula 1 – 2-flowered, sessile; pappus 9 – 10 mm long.4. P. fasciculata

  • Leaves linear, succulent, subterete, 1 – 2 mm wide, margins entire; capitula 4 – 5-flowered, pedunculate; pappus 4 – 5 mm long.5. P. paniculata

Taxonomic Treatment

1. Pteronia teretifolia (Thunb.) Fourc. (Fourcade 1932: 87). Osteospermum teretifolium Thunb. (Thunberg 1800: 166; 1823: 713). Osteospermum trigonum Spreng. (Sprengel 1826: 628) nom. illeg. superfl. Pteronia baccharoides Less. (Lessing 1832: 196); de Candolle (1836: 357); Harvey in Harvey & Sonder (1865: 98); Hutchinson & Phillips (1917: 311) nom. illeg. superfl. Type: South Africa, Western Cape, ‘Caput Bonae Spei’ [Cape of Good Hope], Thunberg s.n. sub UPS-THUNB 20850 (holotype UPS-THUNB — microfiche!).

Pteronia acerosa DC. (de Candolle 1836: 357); Walpers (1843: 970). Pteronia acerosa var. triflora DC. (de Candolle 1836: 357) nom. superfl. autonym. Type: South Africa, Zw. Gamtos und Kroem Rivier R. I., 1 Jan. 1835, Drège 3977 [G00457856] (lectotype G-DC — image!, selected here).

Pteronia acerosa var. quinqueflora DC. (de Candolle 1836: 357). Type: South Africa, Eastern Cape, 50.5. Albany, 1 Jan. 1835, Ecklon & Zeyher 1864 [G00457847] (lectotype G-DC — image!, selected here).

Pteronia acerosa var. multiflora DC. (de Candolle 1836: 357). Type: South Africa, Eastern Cape, Port Elizabeth (3325): 5.7. Uitenhage (–CD), 1 Jan. 1835, Ecklon & Zeyher 218 [G00457852] (holotype G-DC — image!).

Evergreen perennial shrub c. 1 m in height, much branched; branches erect. Leaves decussate, free from each other at base, slightly spreading, simple, linear, 6 – 12 × ± 1 mm, trigonous, coriaceous, glabrous, apex acute, margins entire. Capitula 2 – 3-flowered, homogamous, discoid, terminal, corymbose (10 – 25 capitula), pedunculate to 6 mm long, bearing smaller linear bracts; involucre narrowly obconical, 8 – 10 × 2 – 3 mm, 4 – 5-seriate; involucral bracts glabrous, narrow, margins entire, membranous, outermost bracts lanceolate, 3 – 4 mm long, apex obtuse, middle bracts ovate to lanceolate, 6 – 7 mm long, apex obtuse, innermost bracts narrowly lanceolate, 9 – 10 mm long, apex subacute. Florets bisexual; corolla yellow, tubular, 8 – 9 mm long, limb 5-lobed, tube glabrous; anthers 4 – 5 mm long, apical appendages acuminate; filament slightly swollen distally; style branched, 9 – 10 mm long, branches flattened, c. 3 mm long, stigmatic-papillate. Cypselae turbinate, 1 – 2 × 1 mm, contracted into a neck at apex, setulae of twin-hairs appressed villous, eglandular; pappus bristles barbellate, biseriate, connate at base, 7 – 8 mm long, slightly shorter than florets at fruiting stage, straw-coloured. Fig. 2.

Fig. 2
figure 2

Morphology of Pteronia teretifolia. Voucher: Vlok 564 (NBG).

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distribution. This species is restricted to fynbos vegetation, from the Outeniqua mountains to Knysna in the Western Cape through to Grahamstown and Port Elizabeth in the Eastern Cape. Map 1.

Fig. 3
figure 3

Morphology of Pteronia uncinata. Voucher: Boucher 93 (NBG).

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specimens examined. south africa. Western Cape. 3322 (Oudtshoorn): Die Hoek, N of Outeniquas (–DD), 15 Jan. 1947, Esterhuysen 13602 (BOL, NBG); Paardekop, Knysna (–DD), 3 June 1952, Compton 23576 (NBG). 3323 (Willowmore): Near Keurbooms R. Mouth (–CD), August 2007, Baard 871 (PRE). 3420 (Bredasdorp): Potberg Estates, near Cape Infanta (–BD), 18 June 1974, Bayliss 6712 (NBG). 3423 (Knysna): Keurbooms River Hill (–AB), May 1908, Fourcade 181 (BOL). Precise locality unknown: Cape of Good Hope, Thunberg s.n. sub UPS-THUNB 20850 (holotype UPS-THUNB). Eastern Cape. 3323 (Willowmore): Kouga Dwaasrivier, Joubertina (–DA), 23 Feb. 1976, Manson 250 (NBG); Louterwater (–DC), 30 April 1935, Compton 5225 (BOL, NBG); Joubertina (–DD), 2 April 1959, Van Breda 526 (PRE). 3324 (Steytlerville): Between Essenbos and Assegaaibos, Suuranysberge (–CD), 5 March 1990, Joffe 804 (PRE); Humansdorp Division, top of hill between Thornhill and Hankey (–CD), Lewis 66115 (SAM); Cambria (–DA), 13 April 1952, Barker 7861, 7915 (NBG); Hankey hills, Humansdorp (–DD), 12 April 1952, Compton 23415 (NBG). 3325 (Port Elizabeth): Groendal Wilderness Reserve, Uitenhage (–CA), 28 March 1975, Scharf 1804 (PRE); Groendal State Forest track above Springfield, Uitenhage (–CB), 9 March 1983, Vlok 564 (NBG, PRE); Loerie road from Hankey (–CC), 18 May 1976, Bayliss 6322 (PRE); Uitenhage (–CD), 14 April 2005, C.R.E.W. CR579 (NBG); 5.7. Uitenhage (–CD), 1 Jan. 1835, Ecklon & Zeyher 218 (G-DC — P. acerosa var. multiflora holotype). 3326 (Grahamstown): Albany Division, Assegaaisbos (–AD), Ecklon & Zeyher s.n. [two sheets], 254, 255, 277 (SAM); Drège s.n. (SAM); Trumpeters Drift, Albany (–BB), 6 April 1975, Bayliss 1387 (PRE); Featherstone Kloof (–BC), 21 Feb. 1932, Rennie & Rennie 210 (BOL); Near Grahamstown (–BC), May 1926, Dyer 449 (PRE); Farm Brooklands, 17 m from Grahamstown, Bathurst (–BC), 30 March 1955, Johnson 1135 (PRE); Clivis mountain, Grahamstown (–BC), MacOwan 148 (SAM); Albany (–DA), April 1947, Story 2275 (PRE), c. 3.22 km [2 miles] from Assegaaibosch station (–DA), 3 Feb. 1943, Fourcade 5954 (NBG); Hopewell Farm, Batrurst (–DB), 7 July 1947, Compton 19838 (NBG). Precise locality unknown: Zw. Gamtos und Kroem Rivier R. I., 1 Jan. 1835, Drège 3977 (G-DC — P. acerosa lectotype); 50.5. Albany, 1 Jan. 1835, Ecklon & Zeyher 1864 (G-DC — P. acerosa var. quinqueflora lectotype); Ecklon & Zeyher 1858 (G-DC); Uitenhage, Albany, Swellendam distr., Ecklon & Zeyher s.n. (M); Gauritz, Burchell 4721 (G-DC), Burchell 5009 (G-DC).

habitat. Sandy or stony soil, sometimes limestone outcrops, from 130 – 860 m above sea level (a.s.l.).

conservation status. This species does not fall into any threatened category in the Red List of SANBI’s Threatened Species Programme. Its conservation status is of Least Concern (LC) in South Africa (SANBI 2020).

phenology. Flowering is from late summer to the early winter (February to June).

vernacular name. Naaldgombos (Afr.), Needle Gumbush (Eng.).

notes. Pteronia teretifolia shares the free leaf bases and the eglandular cypselae with P. diosmifolia and P. uncinata (Fig. 1C) but is distinguished by the straw-coloured pappus and entire membranous involucral bract margins (pappus white and bract margins ciliate in P. diosmifolia and P. uncinata). This species shares the linear, trigonous, glabrous, entire leaves with P. trigona but differs by the decussate leaf arrangement and the narrow (2 – 3 mm wide), pedunculate and corymbose capitula (alternate leaf arrangement and broad [8 – 10 mm wide], sessile and solitary capitula in P. trigona).

Five collections of Pteronia acerosa var. triflora were cited by de Candolle. Drège 3977 is selected as lectotype because it is the most complete specimen. For Pteronia acerosa var. quinqueflora, there are two original collections of Ecklon & Zeyher from Albany in G-DC, both mounted on a single sheet. The Ecklon & Zeyher 1864 collection is selected as lectotype as it has more complete features.

2. Pteronia uncinata DC. (de Candolle 1836: 357); Harvey in Harvey & Sonder (1865: 99); Hutchinson & Phillips (1917: 310). Type: South Africa, Western Cape, Clanwilliam (3218): ‘Langevaley R.I.’ [Lange Valley] (–BC), 1 Jan. 1835, Drège 2762 [G00457858] (lectotype G-DC — image!, selected here; possible isolectotypes HAL0110988, HBG505179, K000273460, K000273462 — 3, P027285 — 7, images!).

Pteronia verticillata DC. (de Candolle 1836: 357). Type: South Africa, Western Cape, Simonstown (3418): ‘Nordhook’ [Noordhoek] (–AB), Reçu en 1816, Anon. s.n. [G00457853] (holotype G-DC — image!).

Evergreen perennial shrub to 1 m in height, much branched; branches erect, sulcate. Leaves decussate or 3-whorled, free from each other at base, dense, simple, acicular, 5 – 13 × ± 1 mm, sulcate above, convex below, coriaceous, glabrous, apex acute, recurved, margins entire. Capitula 4 – 5-flowered, homogamous, discoid, terminal, corymbose (10 – 40 capitula), pedunculate (5 – 10 mm long); involucre narrowly obconical, 9 – 11 × 4 – 5 mm, 3 – 5-seriate; involucral bracts glabrous, narrow, margins sparsely and shortly ciliate, rarely entire, outermost bracts narrowly ovate, 3 – 4 mm long, apex obtuse, middle bracts oblong, 6 – 7 mm long, apex obtuse, innermost bracts linear to lanceolate, 9 – 10 mm long, apex subacute. Florets bisexual; corolla yellow, tubular, 7 – 8 mm long, limb 5-lobed, tube glabrous; anthers 3 – 4 mm long, apical appendages acuminate; filament not swollen distally; style branched, 11 – 12 mm long, branches flattened, c. 2 mm long, stigmatic-papillate towards tips. Cypselae oblong, 2 – 3 × ± 1 mm, contracted into a neck at apex, setulae of twin-hairs finely villous, eglandular; pappus bristles barbellate, biseriate, connate at base, 7 – 8 mm long, as long as florets at fruiting stage, whitish. Fig. 3.

Fig. 4
figure 4

Morphology of Pteronia diosmifolia. Voucher: Burgers 3226 (NBG).

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distribution. This species is restricted to strandveld vegetation along the Western Cape coast from Clanwilliam through to Riversdale. Map 2.

Fig. 5
figure 5

Morphology of Pteronia fasciculata. Voucher: Midgley & Bosenberg 87 (NBG).

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specimens examined. south africa. Western Cape. 3218 (Clanwilliam): Coastal Strandveld dunes off Elandsbaai road (–AD), 25 June 1968, Boucher 93 (NBG); ‘Langevaley R.I.’ [Lange Valley] (–BC), 1 Jan. 1835, Drège 2762 (G-DC — P. uncinata lectotype; possible isolectotypes HAL, HBG, P); Rocher Pan Nature Reserve (–CB), 28 July 1981, Le Roux & Van Rooyen 52 (NBG). 3317 (Saldanha): Danger Point, Saldanha (–BB), 8 March 1953, Hall 631 (BOL, NBG). 3318 (Cape Town): Massenberg (–AA), 6 Sept. 1996, Desmet 61 (NBG); Near Langebaan Lagoon (–AA), 16 March 1970, Axelson 159 (NBG); Langebaan, Saldanha Bay (–AA), Foley 12124 (SAM); Yzerfontein (–AC), 28 March 1973, Taylor 8376 (NBG). 3418 (Simonstown): Noordhoek (–AB), Feb. 1918, Rogers 14272 (BOL), Reçu en 1816, Anon. s.n. (G-DC — P. verticillata holotype); Chapmans Peak (–AB), 24 Feb. 1918, Pillans 2999 (PRE); Krom R., Cape of Good Hope Nature Reserve (–AD), Feb. 1964, Taylor 5694 (NBG). 3419 (Caledon): Gansbaai, Uilandskraal Mond R., N side of the road from Franskraal to Pearly Beach (–CB), 17 March 2008, Bennett, Pekeur & Wall MSBP 3664 (NBG); Gansbaai (–CB), 14 March 1976, Hall 4608 (NBG); Buffeljachts Farm, Bredasdorp (–DA), 23 March 1982, Boucher 5055 (NBG). 3420 (Bredasdorp): Bontebok Park (–AB), 17 Feb. 1951, Compton 22628 (NBG); Dunes W of Heuningnes R. Mouth (–CA), 8 June 1983, O'Callaghan 619 (NBG). 3421 (Riversdale): Still Bay (–AD), May 1915, Muir 1989 (BOL), Muir 441 (SAM).

habitat. Pteronia uncinata favours sandy soil at ±300 m (a.s.l.).

conservation status. Pteronia uncinata does not fall into any threatened category according to the SANBI’s Threatened Species Programme. The South African conservation status for this species is evaluated as Least Concern (LC; SANBI 2020).

phenology. Flowering is in mid to late summer (December to April).

vernacular name. Strandgombos (Afr.), Beach Gumbush (Eng.).

note. Pteronia uncinata is easily distinguished from the other corymbose species by the conspicuously recurved, hook-like leaf apices, as alluded to by the species epithet (Fig. 1C). The species shares the ciliate bract margins and the whitish pappus with P. diosmifolia but is distinguished by the oblong cypselae (urceolate in P. diosmifolia).

De Candolle cited only the Drège collection from Lange valley and this collection was traced in G-DC with some possible isotypes in several other herbaria. As de Candolle worked in G (Stafleu & Cowan 1976), the G-DC collection is selected as lectotype of Pteronia uncinata.

3. Pteronia diosmifolia Brusse (1990: 151). Type: South Africa, Western Cape, Bredasdorp (3420): Elandvlei farm, 1.2 km NE of farm house (–CA), 27 Feb. 1984, Burgers 3226 [PRE0691399-0] (holotype PRE — image!; isotypes K000273524 — image!, NBG0200168-0!, STE!).

Evergreen perennial shrub to 0.5 m in height, much branched; branches erect. Leaves decussate, free from each other at base, spreading, lanceolate, 5 – 8 × 1 – 2 mm, keeled, coriaceous, glabrous, apex acute, margins sparsely and minutely ciliate, rarely entire. Capitula 2 – 3-flowered, homogamous, discoid, terminal, corymbose (10 – 20 capitula), pedunculate to 7 mm, bearing smaller lanceolate bracts; involucre narrowly obconical, 7 – 10 × 4 – 6 mm, 4 – 6-seriate; involucral bracts glabrous, narrow, apex subacute, margins scantily and minutely ciliate, rarely entire, outermost bracts lanceolate, 2 – 3 mm long, middle bracts lanceolate, 5 – 6 mm long, innermost bracts linear to lanceolate, 8 – 9 mm long. Florets bisexual; corolla yellow, tubular, 6 – 7 mm long, limb 5-lobed, tube glabrous, ribbed near base; anthers 3 – 4 mm long, apical appendages acute; filament slightly swollen distally; style shortly branched, 8 – 9 mm long, branches somewhat flattened c. 1.5 mm long, stigmatic-papillate. Cypselae urceolate, 1 – 2 × 1 mm, contracted into a neck at apex, setulae of twin-hairs finely villous, eglandular; pappus bristles barbellate, biseriate, connate at base, 5 – 6 mm long, slightly shorter than florets at fruiting stage, whitish. Fig. 4.

Fig. 6
figure 6

Morphology of Pteronia paniculata. Voucher: Van Breda & Joubert 2152 (PRE).

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distribution. This species is endemic to fynbos vegetation on the Agulhas plains between Bredasdorp and Arniston in the Western Cape. Map 3.

Fig. 7
figure 7

Morphology of Pteronia trigona. Voucher: Viviers 862 (NBG).

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specimens examined. south africa. Western Cape. 3420 (Bredasdorp): De Hoop (–AD), Van der Merwe 2013 (NBG); Kliprug farm, 5 km from Arniston on road to Bredasdorp (–CA), Burgers 3253 (NBG); Elandvlei farm, Bredasdorp (–CA), 15 March 1977, Hugo 837 (NBG); Elandvlei farm, 1.2 km NE of farm house (–CA), 27 Feb. 1984, Burgers 3226 (PRE holotype; isotypes K, NBG, STE).

habitat. Pteronia diosmifolia favours limestone habitats, very rarely on shale, at ≤300 m (a.s.l.).

conservation status. The South African conservation status for Pteronia diosmifolia is Vulnerable D2 (VU D2; SANBI 2020). The locality of this species is threatened by invasive aliens (Herman et al. 2006).

phenology. Flowering is in late summer (February and March).

notes. Pteronia diosmifolia shares the ciliate involucral bract margins and white pappus with P. uncinata but is distinguished by the straight leaf apices and the urceolate cypselae (leaf apices hooked (Fig. 1C) and cypselae oblong in P. uncinata).

4. Pteronia fasciculata L.f. (Linnaeus filius 1782: 357); Linnaeus (1796: 1202); Thunberg (1800: 143); Poiret (1804: 733); Thunberg (1823: 630); de Candolle (1836: 360); Harvey in Harvey & Sonder (1865: 103); Hutchinson & Phillips (1917: 310); Compton (1931: 313). Henanthus fasciculatus (L.f.) Less. (Lessing 1832: 195). Type: South Africa, Western Cape, ‘Caput Bonae Spei’ [Cape of Good Hope], Thunberg s.n. sub UPS-THUNB 18674 (holotype UPS-THUNB — microfiche!).

Evergreen perennial shrub, 0.3 – 1.5 m in height, much branched; branches erect. Leaves decussate, connate at base with leaf sheath persisting on branches, crowded, closely overlapping, viscid, simple, lanceolate, 15 – 40 × 3 – 5 mm, flattened and slightly keeled on upper part with somewhat sunken midrib, coriaceous, glabrous, apex acute to acuminate, margins minutely scabrous. Capitula 1 – 2-flowered, homogamous, discoid, terminal, compound-corymbose (12 – 60 capitula), corymbs aggregated into compound heads, sessile; involucre narrowly obconical, 14 – 17 × 4 – 6 mm, 3 – 4-seriate; involucral bracts glabrous, narrow, apex acute, with narrow hyaline-lacerate margins, outermost bracts lanceolate, 4 – 6 mm long, keeled, middle bracts linear, 10 – 12 mm long, innermost bracts linear, 14 – 15 mm long. Florets bisexual; corolla golden yellow, tubular, 9 – 10 mm long, limb 5-lobed, tube glabrous, ribbed near base; anthers 4 – 5 mm long, apical appendages acute; filament not swollen distally; style branched, 10 – 11 mm long, branches somewhat flattened, c. 3.2 mm long, stigmatic-papillate at tips. Cypselae narrowly ovate, 2 – 3 × 1 – 2 mm, contracted into a neck at apex, glandular on surface, setulae of twin-hairs densely appressed, whitish villous, glandular; pappus bristles barbellate, biseriate, connate at base, 9 – 10 mm long, as long as florets at fruiting stage, straw-coloured. Fig. 5.

Map 1
figure 8

Known distribution of Pteronia teretifolia.

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distribution. This species occurs in succulent Karoo vegetation from Lokenburg near Calvinia in the Northern Cape, through to Uniondale in the Western Cape. Map 4.

Map 2
figure 9

Known distribution of Pteronia uncinata.

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specimens examined. south africa. Northern Cape. 3119 (Calvinia): Lokenburg, 21 m S of Niewoudtville (–CA), 10 Oct. 1953, Story 4289 (PRE). Western Cape. 3219 (Wuppertal): Hill slopes S of Wuppertal (–AC), 11 Oct. 2010, Koekemoer 3962 (PRE); Matjiesrivier Nature Reserve (–AD), 5 Oct. 1997, Lechmere-Oertel 828 (NBG); Cederberg, Oudekraal Farm, between Ramkraal and Oukraal (–AD), Koekemoer 2437 (PRE); Ramkraal (–AD), 14 Sept. 2002, Bruyns 9301 (BOL); Blinkberg Pass, Between Ceres and Clanwilliam (–CB), 24 Oct. 2000, Koekemoer 2040 (PRE); Cederberg (–CB), 13 March 1997, Lechmere-Oertel 608 (NBG); Swartruggens (–DC), 1 Oct. 1991, Bean & Viviers 2751 (BOL); 60 km NE of Ceres, Swartruggens (–DC), 4 Dec. 2008, Jardine & Jardine 1040 (NBG). 3319 (Worcester): Bokkeveld, between Montagu and Triangle (–AB), Barnard 751 (SAM), Thorne 53126 (SAM); 22.54 km [14 miles] S of Worcester near Breede Rivier (–CA), 20 Nov. 1969, Stayner s.n. (NBG); Worcester (–CB), 23 Dec. 1939, Barker 502 (NBG); Villiersdorp (–CD), 30 Nov. 1976, Walters 1611 (NBG); 1 km NE of Hammansberg (–CD), 10 Nov. 1987, Midgley & Bosenberg 87 (NBG); Hex R. Mts (–DA), Lamb 1557 (SAM); Riviersonderend Mts, Jonaskop (–DC), 14 Jan. 1979, Boucher 4245 (NBG). 3320 (Montagu): 2 km N of Rooinek Pass (–BD), 7 Nov. 1985, Bayer 5024 (NBG); Cogmanskloof (–CC), 10 Nov. 1946, Middlemost s.n. (NBG); Anysberg (–DA), 8 Oct. 1982, Van Zyl 3414 (NBG); S slope of Touwsberg (–DB), 5 Oct. 1993, Bean 2903 (BOL); Farm Zorgvliet (–DB), 5 Oct. 1993, Germishuizen 6811 (PRE); Swellendam in Kannaland, between Kogmanskloof and Gourits R. (–DC), Drège 141 (SAM), Ecklon & Zeyher 243, s.n. (SAM), Mund 16169 (SAM); Warmwaterberg (–DD), 7 Oct. 1993, Cloete 2449 (PRE). 3321 (Ladismith): Witteberg, Laingsburg (–AC), 10 Nov. 1935, Compton 5917 (BOL), 23 Oct. 1939, Compton 8006 (NBG), 8 Nov. 1948, Compton 21181 (NBG); Little Karoo, Ladismith (–CA), 6 Jan. 1951, Van Zinderen Bakker 288 (PRE); Bailey Peak (–CB), 12 Nov. 1974, Oliver 5468 (NBG); Calitzdorp (–DA), 9 Nov. 1998, Meyer 1752 (PRE); Gamka Mt Reserve (–DB), 21 Sept. 1982, Cattell & Cattell 168 (NBG). 3322 (Oudtshoorn): Tierberg, Prince Albert (–AB), 12 Nov. 1989, Dean 720 (BOL), 8 Nov. 1988, Taylor 12020 (NBG); Oudtshoorn Division, Swartberg Mts (–BC), Stokoe 59948 (SAM); Kandelaarsrivier, George (–CA), 3 Dec. 1951, Compton 23092 (NBG); Near Kandelaarsrivier between Oudtshoorn and Robinson Pass (–CA), Lewis 3752 (SAM); 20 km from Oudtshoorn on the road to George (–CB), 11 Nov. 1978, Botha 2221 (PRE). 3323 (Willowmore): Tourberg hills, N of Georgida (–AD), Nov. 1941, Fourcade 5446 (NBG); Uniondale (–CA), 4 Dec. 1950, Maguire 779 (NBG), 11.20 km [7 miles] N of Uniondale (–CA), Jan. 1928, Fourcade 3590 (NBG).

Precise locality unknown: Between Montagu and Ladismith, Thorne 53126 (SAM); Cape of Good Hope, Thunberg s.n. [1254745] (LD), Thunberg s.n. sub UPS-THUNB 18674 (UPS-THUNB holotype).

habitat. Pteronia fasciculata occurs on sandstone and rocky soil from 300 – 1000 m (a.s.l.).

conservation status. The conservation status of Pteronia fasciculata in South Africa is given as Least Concern (LC; SANBI 2020). This species is not considered to be threatened in its natural habitat (Vlok & Schutte-Vlok 2010).

phenology. Flowering occurs in spring to mid-summer (October to January).

vernacular name. Rank Gumbush (Eng.).

notes. Pteronia fasciculata and P. paniculata are readily distinguished from the other species in this group by the basally connate leaves with the leaf sheath differentiated into a distinct, sclerified scale which persists on the branches (Fig. 1B, D). Both species also have glands on the surface of their cypselae in addition to the villous hairs (Fig. 1E). Pteronia fasciculata can further be distinguished by the lanceolate, flattened, coriaceous leaves with scabrous margins and the sessile, 1 – 2-flowered capitula (Fig. 1A, D) (linear, subterete, succulent, entire leaves and pedunculate, 4 – 5-flowered capitula in P. paniculata: Fig. 1B).

5. Pteronia paniculata Thunb. (Thunberg 1800: 143; 1823: 629); de Candolle (1836: 365); Harvey in Harvey & Sonder (1865: 102); Hutchinson & Phillips (1917: 312); Compton (1931: 314); Dinter (1931: 168); Merxmüller (1967: 157); Merxmüller & Roessler (1984: 90); Herman (2003: 278); Kolberg & Van Slageren (2014: 25). Type: South Africa, Western Cape, ‘Caput Bonae Spei’ [Cape of Good Hope], Thunberg s.n. sub UPS-THUNB 18685 (holotype UPS-THUNB — microfiche!).

Evergreen perennial shrub c. 0.9 m in height, much branched; branches erect, greyish. Leaves decussate, connate and encircling the branches at base, forming a persistent sheath of c. 5 mm long on branches, dense, simple, linear, 5 – 27 × 1 – 2 mm, subterete to slightly concave, succulent, glabrous, viscid, apex subobtuse to obtuse, margins entire. Capitula 4 – 5-flowered, homogamous, discoid, terminal, compound-corymbose (10 – 30 capitula), pedunculate to 6 mm long; involucre narrowly cylindrical, 8 – 14 × 2 – 4 mm, 3 – 4-seriate; involucral bracts glabrous, narrow, margins narrowly hyaline-lacerate, outermost bracts ovate-oblong, 3 – 4 mm long, apex obtuse, middle bracts oblong, 5 – 6 mm long, apex obtuse, innermost bracts oblanceolate, 8 – 10 mm long, apex subobtuse. Florets bisexual; corolla yellow, tubular, 6 – 10 mm long, limb 5-lobed, tube glabrous; anthers c. 3 mm long, apical appendages acute; filament not swollen distally; style branched, 8 – 9 mm long, branches somewhat flattened c. 1.6 mm long, stigmatic-papillate towards tips. Cypselae obovate, 2.5 – 3.0 × 1 – 2 mm, contracted into a neck at apex, glandular on surface, setulae of twin-hairs long villous with long tufted ring of hairs at base, eglandular; pappus bristles barbellate, biseriate, connate at base, 4 – 5 mm long, shorter than florets at fruiting stage, straw-coloured. Fig. 6.

Map 3
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Known distribution of Pteronia diosmifolia.

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distribution. This is a widely distributed species found in fynbos, renosterveld, strandveld and succulent Karoo vegetation. It is widely distributed from southwestern Namibia to Springbok in the Northern Cape of South Africa, through to Mossel Bay in the Western Cape and further east to Port Elizabeth and Grahamstown in the Eastern Cape. Map 5.

Map 4
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Known distribution of Pteronia fasciculata.

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specimens examined. south africa. Northern Cape. 2917 (Springbok): On road from Springbok to Kleinzee, near Tierhaak (–DA), 5 Feb. 1991, Koekemoer 518 (PRE); O’okiep, Namaqualand (–DB), Scully 1166 (SAM). 3017 (Hondeklipbaai): Spoeg R. Mouth (–AD), 18 Oct. 1980, Le Roux & Parsons 57 (NBG); Namaqua National Park, Coastal section between Sarrisaam and the sea (–DA), 29 Dec. 2010, Koekemoer 4002 (PRE). 3119 (Calvinia): Akkerendam Nature Reserve (–BD), 30 Nov. 1986, Germishuizen 4042 (PRE). Western Cape. 3118 (Van Rhynsdorp): 10 km from Koekenaap to Nuwerus (–AD), 4 Dec. 1981, Stirton 10134 (NBG); Knersvlakte (–BC), 8 Dec. 1988, Van Blerk 21 (NBG); Vredendal (–CB), 10 Oct. 2009, Bergh 2087 (NBG); Holrivier (–CB), Hall 178 (NBG); Doring R. Valley (–DD), 29 Nov. 2001, Boucher 6875 (NBG). 3218 (Clanwilliam): Clanwilliam (–BB), 14 Dec. 1957, Rodin 3048 (PRE). 3219 (Wuppertal): W slopes between Clanwilliam and Langkloof (–BC), 28 Nov. 1910, Pillans 5339 (NBG); Swartruggens, 60 km NE of Ceres (–DC), 4 Feb. 2010, Jardine & Jardine 1291 (NBG). 3319 (Worcester): Leeuwerfontein (–BC), 5 Nov. 1923, Kotzé 49 (NBG); Between Karoopoort and Houtpansdrift (–BC), Pearson 5017 (SAM); Worcester Veld Reserve (–CB), 6 Dec. 1965, Van Breda & Joubert 2152 (PRE); Karoo Garden (–CB), 20 Dec. 1946, Compton 18968 (NBG), 6 Dec. 1948, Compton 21206 (NBG); On road from Villiersdorp to Moordkuil (–CD), 17 Feb. 1992, Joffe 971 (PRE); Villiersdorp (–CD), 30 Nov. 1976, Walters 1612 (NBG); Mowershoogte (–DA), 3 Nov. 1959, Van Rensburg 338 (NBG); Farm Doringkloof, near Homestead (–DA), 22 Nov. 1985, Morley 461 (NBG); Keisies Doorn (–DB), Oct. 1922, Levyns 221 (BOL); 35 km beyond Montagu on road to Matroosberg (–DB), 6 Dec. 1976, Venter 1337 (PRE); Riviersonderend mts, Jonaskop (–DC), 14 Jan. 1979, Boucher 4246 (NBG); Vrolijkheid Nature Reserve, Robertson (–DD), 28 Dec. 1974, Burgers 22 (PRE). 3320 (Montagu): Near Touws R. Railway Station (–AC), Bolus 1046 (SAM); Witteberg, Laingsburg (–AD), 30 Nov. 1924, Compton 2811 (BOL), 10 Nov. 1935, Compton 5923 (BOL); Laingsburg (–BB), Jan. 1918, Thode 2898 (NBG); Montagu (–CC), Oct. 1923, Levyns 430 (BOL); Barrydale, Swellendam (–DC), 11 Dec. 1964, Rycroft 2759 (NBG). 3321 (Ladismith): Springfontein (–CC), 14 Jan. 1992, Bohnen 9252 (NBG); Muiskraal (–CC), 1 Dec. 1992, Bohnen 9339 (NBG); 7 km S of Van Wyksdorp (–CD), 16 Dec. 1992, Bohnen 9344 (NBG); Muiskraal c. 10 km W of Garcia’s Pass on road to Barrydale (–DA), 22 Nov. 1983, Mauve, Van Wyk & Pare 53 (PRE); Between Herbertsdale and Van Wyksdorp (–DC), 10 Jan. 2011, Koekemoer 4070 (PRE); George, between Gouritzrivier and Langekloof (–DC), Ecklon & Zeyher 247 (SAM). 3322 (Oudtshoorn): Tierberg, Prince Albert (–AB), 12 Nov. 1989, Dean 722 (PRE); 12.88 km [8 miles] N of Robinson Pass, Mossel Bay (–CC), 2 Dec. 1951, Compton 23049 (NBG); George (–CD), Nov. 1927, Fourcade 3416 (BOL). 3418 (Simonstown): Hangklip (–BD), 23 Nov. 1958, Taylor 5883 (NBG). 3419 (Caledon): Hottentotskloof (–AA), 29 Nov. 1939, Compton 8206 (NBG). Precise locality unknown: E of Montagu, Adamson 39051 (SAM). Precise locality unknown: Cape of Good Hope, Thunberg s.n. sub UPS-THUNB 18685 (UPS-THUNB holotype). Eastern Cape. 3325 (Port Elizabeth): Karoo-like hills by the Zwartkop R., Uitenhage Distr. (–CD), Ecklon & Zeyher 404 [two sheets], 814 [two sheets] (SAM). 3326 (Grahamstown): Riebeek E (–AA), 11 Oct. 1976, Bayliss 7958 (NBG); Near Brandkraal, Grahamstown (–BC), MacOwan 449 (SAM — three sheets).

habitat. Pteronia paniculata occurs on stony or rocky soil from 700 – 1400 m (a.s.l.).

conservation status. The Namibian conservation status of this species is of Least Concern (LC; Kolberg & Van Slageren 2014). It also has a status of LC in South Africa (SANBI 2020). This widely distributed species is unpalatable and can be toxic and lethal to livestock. For this reason, the species is rarely browsed by herbivores (Vlok & Schutte-Vlok 2010).

phenology. Flowering is in late winter to mid-summer (August to January).

vernacular name. Gombossie, Kambro-bos, Kraak-kraak (Afr.), Common Gumbush (Eng.).

notes. Pteronia paniculata shares the basally connate leaves and persisting leaf sheaths with P. fasciculata (Fig. 1B), but can readily be distinguished by the linear, subterete, succulent leaves with entire margins (lanceolate, flattened, coriaceous leaves with scabrous margins in P. fasciculata) and the pedunculate, 4 – 5-flowered capitula (sessile, 1 – 2-flowered in P. fasciculata).

Resurrected species

Pteronia trigona E.Phillips in Hutchinson & Phillips (1917: 318). Type: South Africa, Eastern Cape, Port Elizabeth, between Krakakamma and the upper part of Leadmine R., 7 Feb. 1814, Burchell 4577 [K000273477] (lectotype K — image!, selected here).

Evergreen perennial shrub c. 0.7 m in height, much branched; branches erect, glabrous. Leaves alternate, dense, simple, linear, 5 – 13 × ± 1 mm, trigonous, succulent, glabrous, apex subacute, mucronate, margins entire. Capitula 10 – 15-flowered, homogamous, discoid, terminal, solitary, sessile; involucre obovoid, 10 – 15 × 8 – 10 mm, 5 – 6-seriate; involucral bracts glabrous, margins thinly membranous, outermost bracts ovate, 3 – 5 mm long, apex rounded, middle bracts oblong, 7 – 8 mm long, apex obtuse, innermost bracts linear or lanceolate, 10 – 11 mm long, apex obtuse. Florets bisexual; corolla creamish, tubular, 9 – 10 mm long, limb 5-lobed, tube glabrous; anthers 3 – 4 mm long, apical appendages acute; filament swollen distally; style branched, 9 – 10 mm long, branches flattened, c. 3 mm long, densely stigmatic-papillate at tips. Cypselae oblong, 1.5 – 2.0 × ± 1 mm, slightly contracted into a neck at apex, setulae of twin-hairs shortly villous, eglandular; pappus bristles barbellate, biseriate, connate at base, 6 – 7 mm long, shorter than florets at fruiting stage, brownish-yellow. Fig. 7.

Map 5
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Known distribution of Pteronia paniculata. The distributions recorded elsewhere that were not available in this study are mapped with triangles. Information from Kolberg & Van Slageren (2014).

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distribution. Pteronia trigona is distributed on Mountains from Steytlerville through Port Elizabeth to Grahamstown in the Eastern Cape. Map 6.

Map 6
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Known distribution of Pteronia trigona.

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specimens examined. south africa. Eastern Cape. 3324 (Steytlerville): Smitskrall, Enkeldoorn track (–CB), 8 Dec. 1982, Viviers 862 (NBG, PRE). 3325 (Port Elizabeth): Uitenhage, Vanstaadens Mts (–CD), MacOwan 1072 (GRA); Port Elizabeth between Krakakamma and the upper part of Leadmine R., 7 Feb. 1814, Burchell 4577 (K lectotype). 3326 (Grahamstown): 38.64 km [24 miles] E of Grahamstown, Albany (–AC), 30 Nov. 1950, Maguire 652 (NBG). Featherstone Kloof near Grahamstown (–BC), Atherstone 3293 (SAM). 3424 (Humansdorp): Bush buck Gardens, N back of Kromme R. (–BA), 13 Nov. 2009, Logie FBG 507 (NBG).

habitat. Pteronia trigona favours sandy, clay and shale soil from 90 – 975 m (a.s.l.).

conservation status. There is no information available on the conservation status of Pteronia trigona. Therefore, it is believed that no assessment has been made to determine the conservation status of this species because it was hitherto treated as a synonym of P. teretifolia. Due to lack of information, the Data Deficient (DD) status is assigned to this species.

phenology. Flowering is in summer (November to December).

notes. Pteronia trigona and P. teretifolia are similar in their linear, trigonous, glabrous, entire leaves and in their distribution. These vegetative and distributional similarities probably explain why the two species have been treated as synonyms. However, these two are different in their leaf arrangement and reproductive characteristics. The leaves of P. trigona are alternately arranged and the capitula are broader (8 – 10 mm wide), 10 – 15-flowered, solitary and sessile as opposed to the decussate leaf arrangement and the narrower (2 – 3 mm wide), 2 – 3-flowered, corymbose and pedunculate capitula observed in P. teretifolia. This evidence clearly indicates that these two species are different from each other, as a result, P. trigona is here resurrected as a distinct species.

Pteronia trigona can also be confused with P. cederbergensis in having glabrous branches; linear, glabrous, entire leaves and broad capitula but can be distinguished by the alternate leaves and villous cypselae compared to the opposite leaves and glabrous-glossy cypselae found in P. cederbergensis.

Hutchinson & Phillips (1917) cited three collections from Uitenhage (MacOwan 1027), Port Elizabeth (Burchell 4577) and Albany (MacOwan s.n.). Of these three, only the collection from Uitenhage (MacOwan 1027) was traced in GRA initially, and no other specimens of P. trigona were found elsewhere. However, after a thorough search, the collection from Port Elizabeth (Burchell 4577) was later traced in K, which was filed under the name Pteronia teretifolia. As Hutchinson & Phillips worked at K (Stafleu & Cowan 1979), and this being the only collection available in K, out of the three cited, the Burchell 4577 collection is therefore selected as lectotype.