Crassula stylesii Gideon F.Sm. & N.R.Crouch, 2021

Smith, Gideon F. & Crouch, Neil R., 2021, A new species of Crassula (Crassulaceae subfam. Crassuloideae), C. stylesii, from the Maputaland-Pondoland Region of Endemism in KwaZulu-Natal, South Africa, Phytotaxa 518 (3), pp. 223-230 : 227-229

Crassula stylesii Gideon F.Sm. & N.R.Crouch , spec. nov. ( Fig. 1A–D )

Type:— SOUTH AFRICA. KwaZulu-Natal province.—2930 (Pietermaritzburg): KwaNyuswa, (–DB), at the edges of shallow soil that overly a granite basolith overlooking the Mngeni River , 14 March 2021, D. G . A . Styles, N . R . Crouch & A . Heiduk 5898 (holotype BNRH!; isotype NU!) .

Diagnosis:— Crassula stylesii shows similarities with the autonymic varieties of C. setulosa and C. obovata . However, it can reach a height of 45 cm, which is taller than both C. setulosa and C. obovata . Pseudo-rosettes do not develop basally in the case of Crassula stylesii , but are characteristically present in both C. setulosa and C. obovata , particularly the former. The white flowers of C. stylesii are never red-tinged as in C. setulosa , nor cream-coloured as sometimes found in C. obovata . The flowers of C. stylesii are always shorter than in C. obovata , but similar in proportion and size to C. setulosa . Additionally, not only are the inflorescences of C. stylesii much larger than those of the close relatives compared here, but their structure is characteristically more open and branched. The leaves of C. stylesii are always uniformly hairy whilst in C. obovata they are variably hairy depending on location, even within the Durban region where plants with either glabrous or hairy laminae may be encountered. Crassula stylesii leaves lack the differentiated marginal cilia present in both C. setulosa and C. obovata .

Description:—Perennial, small to medium-sized, many-leaved, densely hairy, succulent, sparsely sprouting from base; to 45 cm tall when in flower. Roots fibrous. Stems erect to leaning, straight or rarely variously curved upwards, purplish brown, hairy; hairs white, 0.3–0.5 mm long, usually pointing down. Leaves densely arranged in 4 ranks in young plants, widely spaced as stem elongates when flowering approaches, opposite in pairs, straight to gracefully recurved, succulent, convex above, convex below, very densely hairy, often with soil and plant debris lodged in hairs, dull midto light green, strongly purple infused at times of environmental stress; petiole absent; blade 10–25(–35) × 7–10 mm, lanceolate to shield-shaped, not folded lengthwise, covered in white hairs on both surfaces; base narrow; apex pointed, dark-tipped; margins entire, hairy, without differentiated cilia. Inflorescence an erect, few- to many-flowered, flattopped thyrse consisting of several dichasia, to 20 mm long; peduncle an elongation of and hardly distinguishable from stem, leaves and leaf-like bracts smaller upwards. Flowers erect to slanted horizontally, white with faint central light brown stripe with age, 3–5 mm long; pedicels 2–4 mm long. Calyx light green, fleshy, very hairy, contrasting against white corolla; sepals 5, 1.5–2.5 mm long, basally adnate, elongated-triangular, hairy, tapering to blunt tip. Corolla flared open, more or less cup-like, distinctly shaped like 5-pointed star when viewed from above; petals 5, basally fused, 3–5 × 1–2 mm, white with faint central light brown stripe with age, oblong to elongated-triangular, with raised median ridge in distal half, apical half recurved, apiculate, margins flat, persistent after anthesis. Stamens attached very low down in corolla tube, well-exposed between petals, not exceeding petals; filaments ± 2 mm long, thin, light greenish white; anthers 0.3–0.4 mm long, yellow turning yellowish brown to purplish brown especially when dry. Pistil consisting of 5 carpels; carpels 1.75–2.00 mm long, light green; styles ± 0.65 mm long; stigmas very slightly capitate, brown; squamae transversely oblong, 0.1 × 0.4 mm, apex indented. Follicles 1.75–2.00 mm long, light green, slightly purple-infused towards apex, drying creamy white, soon becoming brittle and disintegrating. Seeds 0.25–0.40 mm long, somewhat cylindrical, light creamy white to light brown-infused; weakly self-fertile. Chromosome number: unknown.

Distribution:— Crassula stylesii has been collected only from KwaZulu-Natal province, South Africa, from where it is known to occur at two sites (17 km distant) within the Mngeni River catchment to the west of Durban. Both localities occur within the Ethekwini Metropolitan area ( Fig. 3), which falls entirely within the Maputaland-Pondoland Region of Endemism ( Van Wyk & Smith 2001: 82–85).

Habitat:— Crassula stylesii occurs on both sandstone and granite, co-occurring with a number of leaf succulent species including Aloe candelabrum Berger (1906: 246) (Asphodelaceae) , Huernia hystrix ( Hooker 1869: Tab. 5751) Brown (1876: 795) ( Apocynaceae ), Kalanchoe rotundifolia ( Haworth 1824: 188) Haworth (1825: 31) ( Crassulaceae subfam. Kalanchooideae), and Cyanotis robusta Obermeyer (1981: 438) (Commelinaceae) . It occurs at the type locality within Dry Coast Hinterland Grassland (Gs 19) ( Jewitt 2018) that has been infiltrated by closely proximate Eastern Valley Bushveld (SVs 6) ( Rutherford et al. 2006). This site is considered to be relatively transformed and, although a savannah vegetation type, was historically likely to have been more open as a dry grassland mosaic with fewer woody elements. At Cato Ridge it occurs along ridges and exposures within grassland (KwaZulu-Natal Sandstone Sourveld (SVs 5)) ( Rutherford et al. 2006). Plants occur largely exposed, growing in lithosols on the edges of moderately steep sheets of weathered rock ( Fig. 1C ), and at the type locality ( Fig. 1E ) are usually found at the base of stunted specimens of A. candelabrum . Plants may be found on northwestern, northern, and northeastern aspects, at elevations of 440– 710 m.

Phenology:—Flowers ( Fig. 1A, C ) late-summer to autumn, peaking in March (southern hemisphere). The flowering periods of C. stylesii and C. obovata coincide, but C. setulosa flowers slightly earlier (mid-summer to autumn).

Eponymy:— This species is named for Mr David G. A. Styles (Bulawayo, Zimbabwe, 7 January 1968 –) ( Fig. 1F ), botanical consultant and explorer who has discovered many novel plant taxa from the KwaZulu-Natal and Eastern Cape provinces of South Africa. His various finds include this species, which he first observed in situ on 8 March 2013 .

Conservation status:—At the KwaNyuswa type locality ( Fig. 1E ) where plants are locally numerous (ca. 250 individuals) the habitat is subjected to over-frequent burning, and grazing and trampling by cattle; this facilitates alien plant invasions by the likes of the herbaceous Bidens pilosa Linnaeus (1753b: 832) and shrubby Lantana camara Linnaeus (1753b: 627) . At the Cato Ridge site the vegetation is in good condition, but plants are sparser with fewer than 100 individuals. KwaZulu-Natal Sandstone Sourveld at the Cato Ridge location is considered an Endangered vegetation type by Skowno et al. (2019), although a provincial-level assessment categorises this vegetation unit as Critically Endangered ( Jewitt 2018). Eastern Valley Bushveld (SVs 6) is considered Least Concern ( Rutherford et al. 2006), whereas Dry Coast Hinterland Grassland is assessed as Vulnerable by both Jewitt (2018) and Skowno et al. (2019). Altogether, the species occurs within sites of conservation concern, with neither locality formally protected. Using IUCN (2019) criteria the species would be considered Vulnerable (D1).

Discussion:—The closest relatives of C. stylesii are C. obovata and C. setulosa . Apart from the autonymic variety, Tölken (1985: 170–172) recognised four additional varieties in C. setulosa . All four of these occur well distant from the location at which C. stylesii was collected in KwaZulu-Natal, with: (1) C. setulosa var. jenkinsii Schonland (1929: 239) known only from north-central South Africa; (2) C. setulosa var. deminuta Diels (1907: 467) Tölken (1975: 118) from northeastern South Africa; (3) C. setulosa var. rubra ( Brown 1895: 145) Rowley (1978: 53) from the high altitude interior of KwaZulu-Natal, the Free State, Lesotho, and northeastern Cape; and (4) C. setulosa var. longiciliata Tölken (1975: 119) from northeastern South Africa. None of these varieties have been recorded at the low altitudes and from the area from where C. stylesii is known. Therefore, for comparative purposes, only C. setulosa var. setulosa ( Fig. 2C ), in this account referred to only as C. setulosa , is of concern. Crassula setulosa is an altogether more gracile species of higher altitudes than those at which C. stylesii is found, and does not occur in the greater Durban area.

In the case of C. obovata, Tölken (1985: 179–180) recognised one additional variety apart from the autonymic one. Crassula obovata var. obovata ( Fig. 2B ) is widespread in the eastern parts of the Eastern Cape province and southern KwaZulu-Natal, while C. obovata var. dregeana ( Harvey 1862: 346) Tölken (1975: 113) ( Fig. 2E ) is an edaphic specialist that is restricted to sandstone outcrops in southern KwaZulu-Natal. Crassula obovata var. dregeana has leaves that are generally arranged in pseudo-rosulate clusters that remain low-growing and is very different from both C. obovata var. obovata and C. stylesii . Therefore, for comparative purposes, only C. obovata var. obovata , in this account referred to only as C. obovata , is of concern. Crassula obovata grows sympatrically with C. stylesii at the Cato Ridge locality, but is readily distinguishable there on account of its different habit and relatively large flower size ( Fig. 2A, D ; Table 1).

Although we consider C. stylesii to best be accommodated within C. sect. Rosulares we note that plants of this species lack a key characteristic of this section, viz. that plants have leaves arranged in basal rosettes or clusters of rosettes in resting or young plants (exampled by Fig. 2C ) ( Tölken 1985). Pending molecular analyses to refine its position, we tentatively place the species here.

Figures

FIGURE 1. Crassula stylesii from KwaNyuswa, KwaZulu-Natal province, South Africa. A. Inflorescence with white flowers. B. Stem section with leaves distinctly 4-ranked in young plants, dorso-lateral view. C. Habit. D. Shoots with uniformly hairy leaves becoming strongly purple-infused when stressed. E. Habitat at type locality. F. David Styles (1968–) for whom the species is named. Scale bars: A: 15 mm; B: 17 mm; C: 15 cm; D: 20 mm. Photographs by the authors (A–D, F) and D.G.A. Styles (E).

FIGURE 2. A. Inflorescences of C. obovata (Cliffdale) (left) and C. stylesii (KwaNyuswa) (right). B. Flowering plant of C. obovata (Cliffdale). C. Flowering plant of C. setulosa subsp. setulosa (Organ Pipes Pass, central Drakensberg). D. Flowers of C. stylesii (KwaNyuswa) (left) and C. obovata (Cliffdale) (right). E. Colony of C. obovata var. dregeana (Mtentu, Eastern Cape province). Scale bars:A: 25 mm; B: 50 mm; C: 30 mm; D: 5 mm; E: 10 mm. Photographs by the authors (A–C, E) and D.G.A. Styles (D).