Sabicea bequaertii De Wildeman (1924: 229)

Zemagho, Lise A., Liede-Schumann, Sigrid, Lachenaud, Olivier, Dessein, Steven & Sonke, Bonaventure, 2017, Taxonomic revision of Sabicea subgenus Anisophyllae (Ixoroideae, Rubiaceae) from Tropical Africa, with four new species, Phytotaxa 293 (1), pp. 448-450 : 448-450

5. Sabicea bequaertii De Wildeman (1924: 229)

Pseudosabicea arborea subsp. bequaertii (De Wildeman) Verdcourt (1976: 183) .

Type :— DR CONGO. Kabango, 3 November 1914, Bequaert 6178 (holotype BR [ BR0000008851949 ]!; isotypes BR [ BR0000008851970 , BR0000008852007 ]!) .

Sarmentose shrub or woody vine; stems up to 5 m long, 1.5–3.5 mm thick, with alternate branching, densely white-felted in the young stage, later glabrescent. Leaves opposite, equal to slightly unequal; petioles 0.5–1.5 cm, covered all around with a soon caduceous felt of woolly hairs, and persistently villose on the upper side with stiff hairs ca. 1 mm long; blades elliptic, 3–11 x 1.5–4.6 cm, symmetrical, acute at base, acuminate at apex, chartaceous to slightly coriaceous, strongly discolorous; upper side green, sparsely white-felted in the young stage above, soon glabrate; lower side whitish to buff, densely felted with woolly hairs below; secondary veins 9–15 on each side of midrib. Stipules opposite, free, interpetiolar, ovate to triangular, 4–8 x 2.5–5.5 mm, entire, acute to obtuse at apex, erect, glabrous outside or sparsely felted on margins, glabrous inside except the base with stiff hairs ca. 1 mm long. Inflorescences axillary on leafy stems, one per node, sessile, densely glomerulate, 0.6–1.5 cm in diameter, few- to many-flowered. Bracts conspicuous and surrounding the inflorescence; outer pair of bracts shortly connate at base, ovate, 7–10 x 5–7 mm, concave, entire, acute and +/- bending outwards at apex, glabrous at base and +/- felted towards the apex outside, almost entirely villose inside with silky hairs ca. 1.2 mm long; inner bracts spathaceous, concave, +/- bilobed, 4.5–8 x 3–5 mm, outside glabrous at base and pubescent at apex with a mixture of short woolly and long silky hairs, inside almost entirely villose with long silky hairs; bracteoles free, narrowly obovate to narrowly elliptic, 3–5 x 0.8–1.8 mm, acute, with indumentum similar to the inner bracts. Flower buds slightly enlarged at apex. Flowers, 5-merous, sessile. Hypanthium densely white-felted throughout, villose near the base, with stiff hairs ca. 1 mm long. Calyx tube cylindrical, 2–2.5 mm long, outside mostly glabrous (or very sparsely villose) with the base white-felted, inside densely villose with silky hairs directed upwards and 0.8–1.5 mm long; lobes 0.5–1.3 mm long, triangular to linear, acute at apex, erect, villose outside with erect silky hairs ca. 1 mm long, villose inside like the tube. Corolla white; tube narrowly cylindrical, (6.5–) 9–13 x 1–2 mm; lobes triangular, 4–6 x 1.2–2.5 mm; corolla densely villose outside, with appressed silky hairs 0.5–1.2 mm long on the lobes and upper half of tube, the base of the tube glabrous; distal portion of tube and mouth sparsely pubescent inside, with hairs ca. 0.2 mm long; lobes densely papillose inside. Stamens included, inserted slightly above the middle of the tube in long-styled flowers, half-exserted with the apex bending outwards, inserted at the upper portion of the tube in short-styled flowers; anthers subsessile, ca. 2 x 0.4 mm. Disk cylindrical, glabrous, ca. 0.5 mm long. Style glabrous, 11–14 mm long, exserted in long-styled flowers, ca. 9 mm long, included in short-styled flowers; stigmatic lobes 2–2.5 mm long, narrowly cylindrical. Fruits red, ellipsoid, 6 x 4.5 mm when dry, sessile, sparsely pubescent, with long stiff and short woolly hairs intermingled. Seeds dark brown, polygonal, ca. 1 x 0.7 mm, reticulate.

Distribution: —Afromontane region. Restricted to the highlands of eastern DR Congo (Kivu), Rwanda (Nyungwe forest) and southwest Uganda ( Fig. 10 ); apparently frequent to common in its limited range.

Habitat and ecology: —The species usually grows in montane forest and on wet banks of roads, at 1600–2400 m altitude. The type specimen is noted as having been collected in “steppe with Acanthus ”, which might be an error.

Phenology: —Flowers in January–May and July–September; fruits in February and July.

Discussion: — Sabicea bequaertii has been treated by recent authors either as a synonym ( Hallé 1964) or as a subspecies ( Verdcourt 1976: 183; Verdcourt & Bridson 1988: 455) of S. arborea . The two taxa are very similar in leaf and inflorescence characters, and are probably vicariants occuring in different mountain ranges. However, in S. bequaertii , the stipules are subovate, 8–13 x 6–9 mm long with felt of woolly hairs sometimes intermingled with

TAXONOMIC REVISION OF SABICEA SUBGENUS ANISOPHYLLAE

Phytotaxa 293 (1) © 2017 Magnolia Press • 27 long appressed hairs (ca. 1 mm long) outside and glabrous or with short straight hairs on apex inside in S. bequaertii (vs. elliptic to oblong, 6–9 x 4–6 mm, outside with felt of woolly hairs on both sides in S. arborea ), the calyx tube is glabrous (vs. villose), the calyx lobes are 4–5.8 x 0.8–1.2 mm long, glabrous inside sometimes with short hairs (ca. 0.8 mm long) at the apex, margins ciliate (vs. short lobes 1–2 x 0.4–1 mm long, with woolly hairs intermingled at base with long straight hairs (ca. 1 mm long) inside, margin not ciliate). Because of differences between these two taxa we prefer to treat them as separate species (see Table 2).

Notes: — Sabicea bequaertii is not to be confused with S. becquetii , which is closely related and has a confusingly similar name.

Conservation status:— IUCN Red List Category: Vulnerable [VU B1ab(i,ii,ii,iv,v) + B2ab(i,ii,ii,iv,v)]. The extent of occurrence is estimated as 17196,970 km 2 and the area of occupancy as 60 km 2, respectively within the limits for Vulnerable and Endangered under criteria B1 and B2. The species is known from 12 subpopulations representing 7 locations (sensu IUCN 2012). Most of the subpopulations occur in protected areas, Nyungwe National Park in Rwanda, Kahuzi-Biega N.P. in DR Congo, and Bwindi-Impenetrable N.P. in Uganda. However, in view of the high population pressure and political instability of the region, a decline in the extent of occurence, area of occupation, habitat extent and quality, number of locations and number of individuals can be expected, and the species qualifies for Vulnerable status under the conditions B1ab(i,ii,ii,iv,v) and B2ab(i,ii,ii,iv,v).

Additional specimens examined:— DR CONGO. Lwamisole , 15 June 1949, F.L. Hendrickx 5953 ( BR) ; Kahusi , 11 March 1959, A. Léonard 3422 ( BR) ; Kahusi , 28 April 1959, A. Léonard 3989 ( BR) ; Route Bukavu– Astrida , 23 July 1959, A. Léonard 5106 ( BR, P); Kivu, 29 km au S de Butembo, 14 April 1973, S. Lisowski 17605 ( BR) ; Route Kalongi vers 52 km de Bukavu, 13 July 1972, J. Ntakiyimana 270 ( BR) ; Réserve du Kahusi-Biega, Km 21,5 route Kavumu-Walikale, 19 March 1957, R. Pierlot 1509 ( BR) . RWANDA. Forêt de Nyungwe , km 120, 19 January 1971, G. Bouxin 34 ( BR) ; Forêt de Nyungwe au km 101, bord du marais Kamaranzovu, 26 January 1971, G. Bouxin 187 ( BR) ; Forêt de Nyungwe , route Butare–Cyangugu, sentier au km 100, 20 August 1959, G. Bouxin & M. Radoux 695 ( BR) ; Forêt de Nyungwe , environs de Busozo, 20 May 1971, G. Bouxin 826 ( BR) ; Forêt de Nyungwe , environs du Kamiranzovu, 15 September 1971, G. Bouxin 1140 ( BR) ; Environ de Rangiro , piste vers le mont Ruheru, 7 February 1980, D. Bridson 334 ( BR, WAG) ; Kamiranjovu , 17 March 1956, A.R. Christiaensen 1399 ( BR) ; Territoire de Shangugu , 14 February 1958, G. Michel 5111 ( BR) ; Km 99, route Butare–Cyangugu; forêt de Rugege, 10 May 1973, C. Nuyt 98 ( BR) ; Forêt de Rugege , km 104 route Astrida–Bukavu, 28 February 1957, R. Pierlot 1490 ( BR) ; Rutovu , km 62 de la route Astrida–Shangugu, 14 April 1958, M. Reynders 296 ( BR) ; Route Bukavu–Astrida , environs d’Uwinka, colline Kwinzira, 6 March 1959, G. Troupin 9805 ( BR) ; Bukavu , vers km 93, environ d’Uwinka, colline Bunyangurube, 8 January 1960, G. Troupin 11506 ( BR) ; Route Bukavu–Astrida , environs d’Uwinka; colline Lutoyi, 7 July 1960, G. Troupin 12423 ( BR) . UGANDA. Kayonza forest , Kigezi , October 1940, W.J. Eggeling 4172 (K); Marambo, Kayonza, Kigezi, March 1947, J.W. Purseglove 2387 (K) .

Figures

FIGURE 10. Distribution of Sabicea batesii and S. bequaertii.