Craterispermum deblockianum Taedoumg & Hamon, 2013

Taedoumg, H. & Hamon, P., 2013, Three new species of Craterispermum (Rubiaceae) from the Lower Guinea Domain, Blumea 57 (3), pp. 236-242 : 237-238

Craterispermum deblockianum Taedoumg & Hamon , sp. nov. — Fig. 1 ; Map 1

C. caudatum Hutch. praecipue propter fructus longe pedicellatos sed etiam propter stipulas acuminatas atque foliorum laminas longe acuminatas proximum; foliorum laminis multinervis (cum nervis lateralibus in 14–16 paribus vs in 6–10 paribus) et majoribus (8.5–25 × 3.2–7.5 cm vs 5–14.5 × 1.7–5.3 cm) atque ramorum novellorum aspectu granulari (vs glabri et cristato in C. caudatum ) ab illo differt. — Typus: Louis AM, Breteler & De Bruijn 1255 (holo WAG; iso MO, WAG), Gabon, old forest along exploitation road, km 2 SE of forestry camp Waka, situated about 32 km SE of Sindara, Waka river basin (S1°14' E10°53'), 10 Dec. 1983.

Etymology. The species is named after Dr Petra De Block, specialist of Rubiaceae and senior researcher in the Department of Phanerogamy of the National Botanical Garden of Belgium, for her contribution to the knowledge of the African Rubiaceae .

Shrub or treelet 1–5 m tall, all vegetative and generative parts glabrous. Twigs pale green or brown or fawnish, with surface granular. Stipules caducous; basal portion 2 – 3 mm long; tip narrowly triangular, 2 –7 mm long. Leaves petiolate; petioles canaliculate, 8 – 20 mm long; leaf blades narrowly obovate or more rarely, narrowly elliptic, 8.5 – 25 by 3.2 –7.5 cm, subcoriaceous, pale green or pale greenish brown above, not discolorous or slightly paler below; base cuneate; apex acuminate, acumen 9 –16 mm long; midrib prominent below; secondary and tertiary venation prominent on both surfaces, 14–16 pairs of secondary veins, tertiary and higher order venation ± regularly reticulate. Inflorescences supra-axillary, borne 1– 3 mm above the nodes, paired and opposite, erect, subcapitate, very compact, 2.8 – 8 by 2 – 5.5 mm, with several to many flowers; peduncle flattened, 0.5 – 5 mm long; bracts broadly triangular, keeled, acuminate, 1–4 mm long; bracteoles broadly triangular, acuminate, c. 0.2 mm long. Flowers presumed heterostylous (but only longistylous morph known), 4-merous, subsessile. Longistylous flowers: calyx creamy white; tube 0.8–1 mm long; lobes triangular, 0.2 –0.4 mm long. Corolla white; tube narrowly cylindrical, 3.5– 4 mm long, sparsely to densely pubescent at throat and upper quarter of the tube inside; lobes c. 3.5 mm long, finely pubescent in the lower half inside, apex acute. Stamens with anthers only 1/3 included in corolla tube, c. 1 mm long; filaments c. 0.4 mm long. Ovary 0.8 –1 mm long. Style exserted for c. 3 mm, stigma bilobed, stigmatic lobes c. 1.5 mm long. Fruits pedicellate with pedicels 2.5 – 5 mm long, subglobose, asymmetrical, 5 –7 mm diam, crowned with persistent calyx, purple or violet when ripe.

Habitat & Ecology — Craterispermum deblockianum occurs in primary or old forest on sandy soil, often near a stream. Altitude 50– 400 m. Flowers: December –January; mature fruits: April.

Distribution — Craterispermum deblockianum is endemic to Gabon and is restricted to the ‘Province du Moyen-Ougoué’. The species is mostly collected from the Njolé area.

Conservation status — Endangered. See Table 1.

Critical remarks — Flowers and fruits are rare on the specimens of C. deblockianum . Only longistylous flowers were seen and measurements were based on only two flowers.

Taxonomic affinities — The affinities of Craterispermum deblockianum appear to lie with C. caudatum in sharing stipules with long narrowly triangular tips, long acuminate leaves, subcapitate inflorescences and long pedicellate fruits. However, C. deblockianum differs from C. caudatum in having the following main characters: the number of secondary veins (14 –16 pairs in C. deblockianum vs 6 –10 pairs in C. caudatum ), the texture of the young branches (with surface granular in C. deblockianum vs smooth with decurrent ridges in C. caudatum ), the size of leaf blades (8.5 – 25 by 3.2 –7.5 cm in C. deblockianum vs 5 –14.5 by 1.7– 5.3 cm in C. caudatum ) and the length of the peduncles (0.5 – 5 mm long in C. deblockianum vs 4 –9 mm long in C. caudatum ).

Additional specimens examined. GABON, Breteler, Jongkind & Wieringa 11061 ( WAG), 5–30 km NNW of Ndjolé, 23Apr.1992; De Wilde JJFE & Sosef 10288 ( WAG), 9 km N of Ndjolé , exploitation track of Forest Exploitation of

Gabon, 28 Jan. 1991 ; Dibata 58 (MO, WAG), Moyen Ogooué, ENE de Belle Vue , layon X , 22 Jan. 1987; Hallé N 1855 ( P), 10 km S de Ndjolé, C.E.T.A. Ayem , 24 Apr. 1963; Wilks 1202 ( WAG), Ngounié, vallée de la Waka, 28 km ENE du confluent Ngounié-Waka , 5 Feb. 1986.

Figures

Map 1 Distribution of Craterispermum deblockianum (●), C. rumpi­ anum (▲) and C. sonkeanum (■). Based on the specimens cited in the text.

Fig. 1 Craterispermum deblockianum Taedoumg & Hamon. a. Fruiting branch; b. detail of higher order venation;c. stipule;d. longistylous flower;e. infructescence with young fruits (a, b: De Wilde JJFE & Sosef 10288; c, e: Wilks 1202; d: Louis AM, Breteler & De Bruijn 1255, all WAG). — Drawn by Antonio Fernandez.