Sabicea medusula K. Schumann ex Wernham (1914: 44)

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

9. Sabicea medusula K. Schumann ex Wernham (1914: 44) ( Fig. 19 )

Pseudosabicea medusula (K. Schumann ex Wernham) N. Hallé (1963: 170) .

Lectotype (designated here):— CAMEROON. Bipindi (“Bipinde”), 1912, G. Zenker 4414 (lectotype WU [ WU0033073 ]!; isolectotypes BR [ BR0000013214975 ]!, E [E00190216], G [G00014618], GOET [GOET010507], MO [ MO-391708 ]).

Small, creeping, rhizomatous herb, up to 30 cm tall; stems trailing and decumbent 1.5–2 mm thick, flowering portion ascending, stems villose, with stiff patent reddish hairs 2–2.5 mm long intermingled with short and sparse uncinate hairs. Leaves opposite, strongly unequal, one of them much smaller; smaller leaves with petioles 0–0.3 cm and blades 0.4–0.9 x 0.1–0.4 cm; normal-sized leaves with petioles 0.7–3.5 cm long, with same indumentum as the stems; blades elliptic to obovate, 5–18.8 x 2.8–7.5 cm, asymmetrical at base with proximal side cordate to obtuse and distal side acute to cordate inserted 2–5 mm higher, acuminate at apex, papery, strongly discolorous; upper side green, sparsely villose with stiff hairs 1–2 mm long intermingled with shorter +/- uncinate hairs on the veins above;

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lower side buff to whitish, densely felted with woolly hairs and also sparsely villose (sometimes only on the midrib) with stiff hairs 1–2 mm long below; secondary veins 9–15 on each side of midrib. Stipules opposite, interpetiolar, connate at base with the reduced leaf and very shortly with the petiole of the normal leaf, the free part triangular, entire or shortly bidentate, acute at apex, 7–15 x 1.5–4 mm, erect to reflexed, sparsely villose outside (at least on the margin) and sometimes with sparse woolly hairs also present in the young stage, glabrous inside except the base with silky hairs ca. 2 mm long. Inflorescences axillary on leafy stems, one per node in the axil of the smaller leaf, sessile and densely glomerulate, 1–2 cm in diameter, many-flowered. Bracts and bracteoles ± hidden between the flowers and not enclosing them; bracts 2–4, ovate to narrowly triangular, 4–5 x 1–2.5 mm, shortly connate at base, acute at apex, glabrous or sparsely villose outside, villose on the margin, inside densely villose with long silky hairs at base and glabrous at apex; bracteoles narrowly triangular, 6–6.5 x 0.2–0.5 mm, entire and acute at apex, with same indumentum as the bracts. Flower buds nearly cylindrical, with apex slightly enlarged. Flowers 5-merous, sessile. Hypanthium densely villose, with antrorse, stiff hairs ca. 2 mm long. Calyx green; tube cylindrical, ca. 1 mm long, villose outside, glabrous inside; lobes linear to very narrowly spathulate, 3–5.5 x 0.3– 0.5 mm, acute at apex, +/- canaliculate and gradually bending outwards, glabrescent to densely white-felted outside, villose on the margin, with stiff hairs 2–2.5 mm long, villose inside with sparse long stiff hairs often intermingled with short and denser stiff hairs. Corolla tube dark pink to reddish and lobes white; tube cylindrical or narrowly infundibuliform, 5–6 x 1–2 mm; lobes triangular, 1.5–2 x 1–1.5 mm; corolla tube glabrous outside, lobes villose with stiff hairs ca. 1 mm long outside; mouth densely bearded with white moniliform hairs ca. 0.8 mm long; inside of tube either villose at the very apex and with a separate ring of hairs at the insertion of the stamens in long-styled flowers, or sparsely villose from the mouth down to the base of the anthers and with 5 small tufts of hairs slightly below the middle in short-styled flowers. Stamens included and subsessile, inserted around the middle of the corolla tube in long-styled flowers or at the distal portion of tube with their apex almost reaching corolla mouth in short-styled flowers; anthers ca. 1.3 x 0.3 mm. Disk cylindrical, ca. 0.3 mm long, glabrous. Style glabrous, ca. 6.5 mm long and barely exserted, +/- hidden among the hairs of the corolla mouth in long-styled flowers, ca. 3 mm long, included in short-styled flowers; stigmas broadly elliptic, ca. 1.3 mm long, +/- flat. Fruits red or whitish (when immature?), ellipsoid, ca. 10 x 9 mm when fresh, 7–9 x 6–6.5 mm when dry, densely villose with patent hairs ca. 2 mm long. Seeds pale brown, polygonal, ca. 0.6 x 0.3 mm, with truncate apex, the surface with dense parallel striations.

Distribution:—Lower Guinea and Congolia Domains. The species is common in its main range extending from extreme south-eastern Nigeria to Equatorial Guinea, centered on Cameroon; an apparently isolated and very disjunct population occurs in northern DR Congo, on the lower Uele River ( Fig. 18 ).

Habitat and ecology:—Degraded areas in forest, usually growing in half-shade and often covering the ground on paths; also along forest streams (which are probably the original habitat) and sometimes in cocoa plantations; at 0–580 m altitude.

Phenology:—Flowers in January, April–July, September and November; fruits in February–March, May– September and November.

Discussion: — Sabicea medusula closely resembles S. parmentierae and S. sthenula in the low habit, and the corolla with a pink tube and white lobes. Another similar species, though with an entirely white corolla, is S. mildbraedii . The differences between these four species are shown in Table 5. Wernham’s description of S. medusula is based on two syntypes, Zenker 2095 and 4414. The latter specimen is more complete and agrees better with the description; therefore we choose the specimen Zenker 4414 as type. We have not seen the specimen indicates by Wernham (1914) at BM. The WU sheet of this specimen is the most complete, therefore we choose it as lectotype.

The indumentum of the calyx lobes is somewhat variable in S. medusula : the exterior varies from densely white-felted to green and nearly glabrous; the interior typically bears long stiff hairs intermingled with denser shorter ones, but sometimes only the long hairs are present.

The only collection of S. medusula from DR Congo, despite being geographically distant from the other collections, does not show any morphological differences. The specimen from Nigeria was seen on photograph only, but the identification is certain. We have seen no authentic material of S. medusula from either Gabon or the Republic of Congo, although the species can be expected in both countries; a previous record from the Republic of Congo ( Lachenaud 2009) refers to S. sthenula , while the Gabonese collections cited as S. medusula by Hallé (1971) and Sosef et al. (2006) belong to S. parmentierae and S. sthenula , respectively. Although S. medusula and S.

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sthenula are usually quite distinct species, some collections with intermediate characters have been noted; these are discussed under S. sthenula .

to one of the speies are in bold.

Sonké & Nguembou 3757 (BR, WAG), from the Ngowayang massif in Cameroon, probably belongs to S. medusula but has unusually broad (1.2 mm wide) +/- spathulate calyx lobes. In this character it resembles S. parmentierae , but differs from that species in the entire stipules, the nearly cylindrical flower buds, and the presence of short stiff hairs (together with longer ones) on the inside of the calyx.

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Conservation status:— IUCN Red List Category: Least Concern [LC]. The extent of occurrence is estimated as 321,541.909 km 2 and the area of occupancy as 100 km 2; the latter value falls within the limit for Endangered under criterion B2. However, the species is known from more than 10 locations (sensu IUCN 2012) including three national parks (Cross River in Nigeria, Korup and Campo-Ma’an in Cameroon), is locally common and adapts well to some degree of habitat degradation. Therefore, it is not currently threatened.

Additional specimens examined:— CAMEROON. 12 km from Kribi , Lolodorf road, 14 January 1969 , J.J.

Bos 3648 (BR, MO, P, UPS, WAG); 19 May 1969, J.J. Bos 4573 ( WAG); Mamfe ‘ Overside’ , 17 March 1955, D.E.

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Coombe 198 (BR, P); 28 km on the road from Ebolowa to Lolodorf , 25 July 1975, J.J.F.E. de Wilde 8385 ( BR, MO, P, WAG, YA); Parc National de Campo-Ma’an, aux environs des villages d’Ebianemeyong et Nyabissan, 15 February 2015, V. Droissart, T. Couvreur & N. Kamdem 1873 ( BRLU) ; Dikome , 3 May 1994, N. Ekema, Z. Nchimfor & M. Etuge 870 ( MO) ; Campo-Ma’an area, Bongola , Along the Bongola river, 29 January 2000, M. Elad, G.P. Tchouto Mbatchou, J. Nganwui & Ondoua 1226 (WA G) ; sud-ouest de Nko’Adjap (± 20km est de Campo), 16 May 2009, O. Lachenaud, B. Lemaire, M. Simo & B. Sonké 782 ( BR, WAG, YA) ; Km 29 route Campo- Kribi, 17 May 2009, O. Lachenaud, B. Lemaire, M. Simo & B. Sonké 825 ( BR, YA) ; Littoral : 28 km NE of Douala, along road to Edéa, 18 August 1965, A.J.M. Leeuwenberg 6418 ( BR, MO, P, WAG, YA) ; Près de la rivière Fon, à 12 km à l’est de Kamelon (5 km SE de Sangmelima), 24 November 1966, R. Letouzey 8469 ( BR, P) ; entre Ogurang et Babong, 45 km SW Mamfe, 28 May 1975, R. Letouzey 13661 ( BR, MO, P) ; Southwest : Kumba – Mamfe road Baduma mile 20, 1 July 1987, J. Nemba, P. Mambo & D.W. Thomas 579 ( BR) ; Ekombe-Mofako , 3 June 1994, D. Pouakouyou & M. Etuge 57b ( MO) ; Mokoko F.R., 2 May 1994, B. Sonké 1115 ( BR, WAG) ; Ngoyang , 15 September 2005, B. Sonké & K.C. Nguembou 3882 ( BR, BRLU) ; 3 km W Ngovayang , 17 September 2005, B. Sonké & K.C. Nguembou 3978 ( BR, BRLU) ; Lambi : Massif de Ngovayang, 20 February 2008, B. Sonké 4645 ( BR) ; Nkolembonda : Mont des Eléphants, 15 March 2008, B. Sonké & M. Simo 4706 ( BR) ; Mokoko Forest Reserve , Barombi, 25 May 1994, P. Tchouto 1220 ( MO) ; Lake Tissongo , 24–29 June 1986, D.W. Thomas 6167 ( MO, P, WAG) ; Steep hillside 5 kms due west of Esukutang village, 29 May 1988, D.W. Thomas, F. Namata, B. Satabie, & B.A. Nkongmenek 7985 ( MO) ; Elephant Mont , 10 June 2001, T.R. van Andel, P.J.M. Maas, H. Maasvan de Kamer, B. Mva, M.J. Jansen-Jacobs & F. Essa 3555 ( SCA, WAG, YA) ; South Province : Bipindi, 1 July 1900, G. Zenker 2095 (E, G, K, MO, P, S, WAG, WU) . DR CONGO. Bas-Uele , 17 July 1935, A. Dewulf 644 ( BR) . EQUATORIAL GUINEA. Bata – Pembe : estrada kms 17–18 mas proximo de Sanduma, 4 April 1994, M.F. de Carvalho 5507 ( WAG) . NIGERIA. Oban Group F.R., Itankpini area , 5 August 1865, B.O. Daramola FHI 56390 ( FHI) .

Figures

FIGURE 18. Distribution of Sabicea mapiana and S. medusula.

FIGURE 19. Sabicea medusula. A, fruiting stem; B, calyx and ovary; C, long-styled flower (calyx and ovary removed); D, section of long-styled flower (style, calyx and ovary removed); E, style; F, detail of a node with infructescence, reduced leaf and stipules; G, fruit. From Sonké 1115 (A, F–G) and Sonké 3978 (B–E). Drawing by Antonio Fernandez.