Euphorbia schinzii subsp. bechuanica (Leach) Bruyns, 2020

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 : 214

8b. Euphorbia schinzii subsp. bechuanica (Leach) Bruyns , comb. nov.

Euphorbia malevola subsp. bechuanica Leach (1964: 6) . Type:— BOTSWANA. Halfway between Palapye and Francistown, July 1937, Obermeyer (holotype PRE!, isotypes K!, PRE!).

Euphorbia limpopoana L.C. Leach ex Carter (2000: 960) . Type:— ZIMBABWE. Fulton’s Drift, 25.5 km NNW of Beitbridge, January 1963, Leach 11582a (holotype SRGH).

Distribution & Habitat: — Subsp. bechuanica is widely distributed in Botswana and Zimbabwe and in South Africa from west and north of the Soutpansberg, but is also recorded in the lowveld south-east of Tzaneen ( Fig. 6 ).

Discussion: —Plants belonging to subsp. bechuanica were shown in White et al. (1941: figs 839−841) as a ‘variable form of E. schinzii Pax’ and discussed on page 749. They were first recognized taxonomically as E. malevola subsp. bechuanica Leach (1964: 6) .

Carter (2000) characterized E. limpopoana by ‘lack of rhizomatous branches and its more robust habit, with thicker branches and noticeably much stronger spinescence’. However, even among the specimens she cited, there is wide variation in such features as size of the plant, thickness of branches and length of spines. This variability was indicated previously by White et al. (1941), by referring to it as a ‘variable form of E. schinzii Pax’. The spine-shields may be prominent and they sometimes continue to just above the axillary bud below, but more typically they continue to about halfway down between successive spine-complexes. Hargreaves (1994: 153) showed specimens of E. limpopoana (from NE Botswana) with a tuberous roostock, while this is absent in plants from the eastern side of its distribution near Hoedspruit (e.g., Bruyns 12101 (BOL)), in which the branches also have a paler streak down the grooves between the angles that is absent in Botswanan material. Flowering specimens have been collected between May and November ( Carter 2000), but the main flowering period is June−August.

Euphorbia limpopoana is not always easily separated from what was traditionally known as E. schinzii . In collections such as Bruyns 12079, 12085, 12091, 12291 (all at BOL) from the western part of the former Transvaal and near the border with Botswana, some plants have robust branches with strong spines and some of these robust branches are rhizomatous, while yet others have much less robust branches. For example, from Ramotswa on the Botswanan-South African border, Carter & Leach (2001) cited a specimen under E. schinzii and Hargreaves (1994: 163) showed two excavated plants with tuberous rootstocks and rhizomatous branches no more than 4 cm long above the ground, which he referred to as E. schinzii . Other plants in the area have branches to 20 cm long above the ground and 20 mm thick, with spines to 17 mm long, with the same rhizomatous tendency (e.g., Bruyns 12079, 12291, as in Fig. 7 ). Robust specimens in these populations resemble E. limpopoana and only their rhizomatous tendency suggests what was traditionally called E. schinzii . On the other hand, the daintier plants among them clearly belong to what was traditionally called E. schinzii . As a consequence, rather than an abrupt break between E. limpopoana and what was traditionally called E. schinzii , there appears to be a gradual change from typical E. limpopoana ( Fig. 7A ) to populations where some plants are robust and separable only by their occasional rhizomatous branches from E. limpopoana (e.g., Fig. 7 B, C ) to populations (mainly much closer to Pretoria and at higher altitudes) where the plants are much less robust and are more frequently rhizomatous. Consequently, E. limpopoana is now placed under E. schinzii as a subspecies, at which rank the epithet ‘ bechuanica ’ has precedence.

Selected additional specimens examined: — BOTSWANA. Boboneng (2128CD), 680 m, Bruyns 12404 (M). Serowe (2226BC), Leach & Bayliss 12514 (NBG). Mosolotsane (2226CD), 1220 m, Bruyns 12306 (M). 5 km north of Baines Drift-Pont Drift road (2228BD), 620 m, Bruyns 12409 (NBG). Ikongwe, 20 km south of Shoshong (2324AB), 1070 m, Bruyns 12304 (UPS). 13 km north of Molepolole (2425BA), 1150 m, Bruyns 12295 (BOL). 35 km from Lobatse towards Gaborone (2425CD), Hansen 3149 (PRE). Kanye (2425CD), Hartley 1033 (J). MOÇAMBIQUE. 5 km from Massingir (2331DD), Correia & Marques 967 (WAG). Massingir (2331DD), Schäfer 7174 (BR, K, WAG). 14 km from Massangena towards Madindere, Correia & Marques 3165 (WAG). SOUTH AFRICA. 25.5 km south of Messina (2229DB), Dyer 3971 (BM, K). 64 km north of Louis Trichardt (2229DB), Dyer 3973 (BM, K). Halfway between Wyllie’s Poort and Waterpoort (2229DC), Galpin (BOL). Langdraai (2229DC), Buitendag 1079 (NBG). Near Sand River, Soutpansberg (2229DC), 1700’, Gillett 3868 (BOL). 20 miles north of Louis Trichardt (2229DD), Leach 11679 (K, NBG). 32–35 km north of Louis Trichardt (2229DD), Dyer 3972 (BM, K). Grootgeluk (2229DD), Buitendag 1076 (NBG). North of Masekwapoort (2229DD), Van der Schijff 4439 (W).

Figures

FIGURE 6. Distribution of Euphorbia schinzii (inverted triangle = subsp. schinzii, circle = subsp. bechuanica, upright triangle = subsp. schinzioides).

FIGURE 7. Vegetative variability in E. schinzii in Botswana. A, E. schinzii subsp. bechuanica, plant ± 30 × 150 cm, Mkarikari Pan, Botswana, Bruyns 12336 (S), typical ‘E. limpopoana’ of Leach & Carter (2001). B, plant ± 20 × 30 cm, with the robust branches and spines of subsp. bechuanica and with hardly any rhizomatous growth, Ramotswa, Botswana, Bruyns 12291 (UPS). C, plant with some rhizomatous growth, branches to ± 10 cm tall, stout, with the robust spines of subsp. bechuanica, Ramotswa, Botswana, Bruyns 12291 (UPS). D, plant with strongly rhizomatous growth, branches to 8 cm tall, but more slender and more weakly spined, Ramotswa, Botswana, Bruyns 12291 (UPS). Plants from Ramotswa were referred to as ‘E. schinzii’ by Hargreaves (1994) and Leach & Carter (2001) and here they are treated as E. schinzii subsp. schinzioides.