Euphorbia clivicola subsp. clivicola

Bruyns, Peter V., Klak, Cornelia & Hanáček, Pavel, 2020, A review of the Euphorbia schinzii-complex (Euphorbiaceae) in southern Africa, Phytotaxa 436 (3), pp. 201-221 : 206-207

2a. Euphorbia clivicola subsp. clivicola

Bisexual succulent 0.05–0.15(−0.3) × 0.15–0.5 m, without rhizomatous branches, stem often somewhat swollen underground. Branches 20–150 × 5–15 mm, smooth, dull pale bluish green to dark green; tubercles in decussate pairs (to alternating) arranged into 4 rows, with spine-shields 3–5 mm long, ± 1 × 2 mm above spines and 3–4 mm long and deltate below spines (remaining well separated from next), spines 3–10 mm long; leaf-rudiments ± 1–1.5 × 1 mm, with irregularly shaped brown stipular prickle ± 0.25 mm long on either side at base. Styles branched to around or slightly below middle.

Distribution & Habitat: — Subsp. clivicola is known in the high region around Pietersburg (Polokwane) and from there into the mountains along the Olifants River. Further populations are known in Swaziland and Kwazulu-Natal. In Kwazulu-Natal they are widespread in the north from the low-lying coastal area to the dry foothills below the escarpment ( Fig. 2 ).

Subsp. clivicola is usually found in stony to rocky habitats, in some areas between stones and in others wedged tightly into crevices between larger rocks. In some parts of coastal Kwazulu-Natal it occurs in gravelly sand with no obvious rocks. Plants are usually found among short bushes, often in relatively barren spots where the grass-cover is minimal.

Discussion: —In the type collection of Euphorbia clivicola , the branches are short (2−3 cm long, though to 6 cm if sheltered), comparatively thick (± 15 mm) and broadest below the middle, forming dense cushion-shaped clumps arising from a swollen rootstock. This collection was from near Pietersburg (Polokwane) in South Africa. The type specimen is dominated by its thick rootstock ( Dyer 1951b: plate 4), with very short branches. Dyer (1951b) mentioned another collection of a similar plant, also from near Pietersburg. He did not state when these plants flower but it appears to be in June-August ( Fourie 1989). In these collections the tubercles along the branches are not fused into angles. Each tubercle is also abruptly truncate above and narrows below the spines to the axillary bud below. Consequently, from the side the pairs of opposite tubercles are wedge-shaped, broadly shouldered above and tapering below to a narrow waist just above the next pair. Although the tubercles are initially in opposite pairs, their growth may push them out of this opposite arrangement so they appear occasionally to be alternating.

Other collections of similar plants (i.e. with wedge-shaped pairs of tubercles that are not joined into angles along the branches) have been made around Pietersburg (Polokwane), in the valley of the Olifants River between Chuniespoort, Steelpoort and Ohrigstad (e.g., Bruyns 13555 (BOL)) and even from as far afield as the Makhatini Flats near Pongola in Kwazulu-Natal (e.g., Bruyns 11851 (BOL)). In these the branches are 10−30 cm × 5−12 mm and are not broadest below the middle. In some localities the branches are all 5−6 mm thick and they may be shed even during the dry season. Other shared features between these plants and the type of E. clivicola are the pale yellowish grey-green branches (though occasionally they are dark green as well, if growing on dolomites), spine-shields small, ± inverted deltate, usually only 2−3 mm long and acute below the spines (as in Fig. 1 E, G , occasionally longer and narrowly deltate as in Fig. 1 F ) and tiny stipular prickles (± 0.25 mm long) next to the leaf-rudiments. Those from lower altitudes in the valley of the Olifants River (e.g., around Burgersfort and Ohrigstad) have longer and harder, rather ‘meanlooking’ spines, but otherwise correspond in all these features. All these collections mainly differ from E. clivicola by their longer, more slender branches and in some areas (such as Kwazulu-Natal), they may flower between November and February. However, those in the valley of the Olifants River produce their brilliant yellow, slightly sweetly scented cyathia in June−August. All of these are now included in E. clivicola .

Other plants with wedge-shaped pairs of tubercles and minute stipular prickles that deviate slightly from the above have been collected in the former Transvaal between Zebediela and Roedtan. In these, the somewhat rhizomatous branches have paler markings between the angles and the cyathial glands may be brownish yellow. Both of these features suggest similarities to E. venteri . However, they are geographically remote from E. venteri and vegetatively closer to E. clivicola , so they are now included under E. clivicola as subsp. calcritica .

Additional specimens examined: — SOUTH AFRICA. Limpopo: Hill east of Pietersburg (2329DC), Archer 2091 (PRE). Near Dikgale (2329DD), 1380 m, Bruyns 12115 (BOL). 8 km west of Boyne (2429BB), 1145 m, Bruyns 11883 (NBG). Boyne, west side of dam (2429BB), Becker & Möller 665 (UNIN). Sekhukune (2429DB), Becker & Möller 1074 (UNIN); Becker & Möller 1073 (UNIN). Sekhukune, Radingwana village (2429DB), Becker & Möller 1075B (UNIN). 2 miles south of P.O. The Downs (2430AA), 4500’, Codd 3091 (K). 3 km NE of Burgersfort (2430CB), 760 m, Bruyns 13556 (BOL). Ohrigstad (2430DA), Buitendag 1012 (NBG, PRE). Kwazulu-Natal: Above Nomaneni Pan near Ndumu (2632CD), Pooley 291 (K, NU). Itala Game Reserve (2731AD), 700 m, Porter & Ward 36 (NH). Makhatini Flats (2732AB), 60 m, Von Blottnitz 186 (NH). Lebombo Mtns, 3 miles west of Jozini Dam Village (2732AC), 1200’, Edwards 2903 (K, M, NU, PRE). Lebombo Mtns, south side of Pongola Poort (2732AC), 1400’, Ward 3799 (NH, NU, PRE). Jozini Mtn (2732AC), Strey 9794 (NH, PRE). Makhatini Flats (2732CA), 80 m, Bruyns 11851 (BOL). Phinda Game Reserve (2732CD), 180 m, Harrower 5866 (NBG). Okhukhu (2831BA), 300 m, Bruyns 4448 (BOL). 12 miles from Hluhluwe gate towards Hlabisa (2831BB), Wells 2051 (K, PRE). 20 km SE of Ulundi, above tunnels (2831BC), 240 m, Bruyns 11827 (E). Heatonville (2831DB), Hauting (PRE); De Waal sub NH 39198 (NH). 25 km NE of Hluhluwe village (2832AA), 50 m, Abbott 6514 (PRU). Near Hluhluwe Stn (2832AB), Codd 2038 (PRE). Between Eshowe and Empangeni, Forbes 656 (NH). Nyalazi River, Hlabisa distr., 300’, Ward 2872 (NH, NU, PRE). Top of Lebombo Mtns, betweem Mkuzi and Jozini Dam, Strey 4625 (K, PRE, Z). SWAZILAND. Near Peebles (2631CB), 1500’, Compton 31640 (NBG). 5 km along D4 towards Siteki (2631DB), 235 m, Bruyns 11860 (NBG). Near Sipofanini (2631DA), Van der Merwe 1025 (K, NH, PRE). Gollel (2731BD), Coaton 57 (PRE), Van der Merwe 2739 (PRE). 5 miles east of Ingwavuma (2732AA), Codd 2079 (K, PRE).

Figures

FIGURE 1. Tips of branches showing arrangement of tubercles and spine-shields with spines and stipular prickles. A–D, tubercles fused vertically into angles (though fusion of tubercles is the least in D), often with larger stipular prickles (largest inA and B and smallest in D) and spine-shields narrowly elliptic in A and B becoming more narrowly deltate in C and D, E–H, tubercles not fused vertically into angles, with minute stipular prickles and shortly deltate spine-shields, which are especially short in E and G. A, E. schinzii subsp. schinzii, Bruyns 9390 (BOL), ± 8 mm thick. B, E. schinzii subsp. bechuanica, Bruyns 12101 (BOL), ± 10 mm thick. C, E. schinzii subsp. schinzioides, Bruyns 12426 (BOL), ± 8 mm thick. D, E. venteri, Bruyns 12354 (BOL), ± 6 mm thick. E, E. clivicola subsp. clivicola, Bruyns 12115 (BOL), ± 10 mm thick. F, E. clivicola subsp. clivicola, Bruyns 11329 (BOL), ± 6 mm thick. G, E. clivicola subsp. clivicola, Bruyns 13556 (BOL), ± 8 mm thick. H, E. clivicola subsp. calcritica, Bruyns 12045 (BOL), ± 6 mm thick.

FIGURE 2. Distribution of Euphorbia clivicola (circle = subsp. clivicola, triangle = subsp. calcritica).