Ceropegia marronina Bruyns & Hanáček, 2020

Bruyns, Peter V., Klak, Cornelia, Mazuch, Tomáš, Gelle, Faysal Jama, Elmi, Hassan Sh Abdirahman & Hanáček, Pavel, 2020, New species of Ceropegia (Apocynaceae) from the Horn of Africa, Phytotaxa 441 (2), pp. 195-202 : 198-199

Ceropegia marronina Bruyns & Hanáček , spec. nov.

Type:— ETHIOPIA. Tigray Region, 40 km east of Agula, 1700 m, Nov. 2017, Bruyns 13247 (holotype BOL!, isotype ETH!). Figs 1 , 3 .

This new species differs from C. abayensis ( Gilbert 1978: 46) Bruyns in Bruyns et al. (2017: 426) by the larger, deep maroon, bowl-shaped corolla with a tube that contains ± all of the gynostegium (in C. abayensis the tube is ± 1 mm long and the gynostegium projects some distance above the rotate corolla). The gynostegium differs in being ± uniformly broad to its base (it becomes narrower towards the base in C. abayensis ) with much longer inner lobes that exceed the anthers and are gathered into a small column in the centre above the style-head.

Small loosely mat-forming non-rhizomatous succulent perennial 80–300 × 25–60 mm. Branches many, fleshy, decumbent, 30–80 × 8–12 mm (excluding teeth), glabrous, greyish green with irregular purple blotches, tubercles 5–12 mm long, spreading, deltoid, slightly laterally flattened and joined into 4 angles along branch, with slight grooves between angles, tapering into short caducous teeth. Inflorescence usually 1 per branch near tip, with 1 to 2 flowers developing in gradual succession from alongside leaf-axil, with 1–2 narrowly attenuate bracts 1–2 mm long at base; pedice l 2–4 × 1.5 mm, ascending and holding flower facing slightly upwards, grey-green; sepals 2.5–4 mm long, 1.5 mm broad at base, ovate-lanceolate. Corolla ± rotate with slightly reflexed lobes, 30–40 mm diam., emitting faint bad odour; outside pale green with brownish stripes, glabrous and smooth; inside dull deep maroon (white near base of tube), glabrous (though covered with minute bristle-like papillae), faintly radially rugulose; tube conical, 7–8 mm deep and 8–10 mm diam. at mouth; lobes broadly ovate-deltate, 10–17 mm long, 6–9 mm broad at base, acute, convex inside with margins reflexed. Corona 5–6 × 7–8 mm, somewhat cupular in outline, glabrous, without basal stipe; outer lobes ascending, forming broad bays opposite guide-rails and between inner lobes, ± 4 mm long, dark chocolatebrown, shiny, emarginate in middle; inner lobes adpressed to backs of anthers and exceeding them to meet in centre and rising there in short column, ± 3 mm long, paler brown than outer lobes, dorsiventrally flattened, linear, obtuse or slightly emarginate. Follicles and seed unknown.

Distribution & Habitat:—Only known in northern Ethiopia on the steep slopes of the Rift Valley descending to the Afar Region, this new species is found on flattish places on stony, east-facing schistose slopes at around 1500–1700 m. Here it occurs under low bushes, with a wealth of other stapeliads such as C. baldratii (A.C.White & B. Sloane 1937: 268) Bruyns in Bruyns et al. (2017: 426), C. cereiformis ( Hooker 1871: t. 5930) Bruyns in Bruyns et al. (2017: 417), C. planiflora ( Bally 1956: 109) Bruyns in Bruyns et al. (2017: 418) and the much larger shrubby C. penicillata ( Deflers 1889: 169) Bruyns in Bruyns et al. (2017: 413). Rainfall in these areas is unknown, but will be less than the ± 560 mm recorded as the annual average at Mekele on the top of the plateau above these slopes. Rain falls here mainly in summer.

Discussion:—This species, with its grey-green branches mottled with purple, with relatively long tubercles that taper into a slender, soft tooth, clearly belongs to sect. Orbea ( Haworth 1812: 37) Bruyns in Bruyns et al. (2017: 426). It is the first new species of this section to be discovered in Ethiopia since the pioneering work of Gilbert (1978) in exploring Ethiopia for members of this section and for stapeliads more generally. Because of its non-rhizomatous habit and relatively short branches, these plants were initially thought to belong to C. abayensis , though the branches are shorter and their tubercles are longer than they usually are in the eastern forms of C. abayensis that occur on the plateau between Mekele and Wikro. These were at one time known as Orbea gilbertii ( Plowes 1994: 116) Bruyns (2002: 46) , but are now treated as synonymous with C. abayensis ( Bruyns et al. 2017) . The quite broad, deep maroon corolla, where the corona is almost wholly contained in the obvious, bowl-shaped tube is unlike any other known species, since, in most of those with a prominent tube, the tube is much deeper. In C. abayensis the corolla faces horizontally and is similar in size (28–40 mm diam.), it is more or less flat with a very short tube about 1 mm long in the centre. In this case the tube is so short that it only contains the base of the quite large corona (which is up to 4 mm tall), which then projects far beyond the tube ( Bruyns 2002: fig. 17). Other unique features of C. marronina are the manner in which the gynostegium remains more or less equally broad towards its base and the slender, comparatively long inner coronal lobes that rise in the centre in a short column (in C. abayensis they are deltate and do not exceed the anthers). The only species of sect. Orbea that occurs together with C. marronina is C. baldratii . Ceropegia baldratii was not previously recorded from Ethiopia and was believed to be endemic to Eritrea ( Gilbert 1978; Bruyns 2002; Gilbert 2003: 187). This species has strongly rhizomatous branches, which may spread underground for up to 10 cm or more. Its flowers are also very different to those of the new species, where the corolla is divided nearly to the centre into slender linear lobes and there is more or less no tube in the centre around the corona ( Bruyns 2002: fig. 30).

The flowers of C. marronina appear towards the end of summer but usually before those of C. baldratii .

Figures

FIGURE 1. A, B, Ceropegia buraoensis. A, branch with flower. The rearward-pointing bases of the leaf-rudiments can clearly be seen here. B, branch showing rear of corolla. C, Ceropegia marronina, Bruyns 13247 (BOL), D, Ceropegia pseudorhynchantha, Bruyns 11584 (BOL, E. MO). Photographs by:A, B, T. Masuch. C, D, P.V. Bruyns.

FIGURE 3. Ceropegia marronina. A, branch (scale 4 mm). B, side view of dissected corolla (scale 3 mm). C, face view of gynostegium (scale 2 mm). D, pollinarium (scale 0.25 mm). Drawn from Bruyns 13247 (BOL, ETH) by P.V. Bruyns.