Craterispermum capitatum Taedoumg & De Block, 2017

Taedoumg, Herman, Sonke, Bonaventure, Hamon, Perla & Block, Petra De, 2017, Craterispermum capitatum and C. gabonicum (Rubiaceae): two new species from the Lower Guinean and Congolian Domains, PhytoKeys 83, pp. 103-118 : 104

Craterispermum capitatum Taedoumg & De Block sp. nov. Figs 1 , 2

Diagnosis.

Resembling C. robbrechtianum Taedoumg & Sonké, 2011 by the coriaceous leaves, the obscure intersecondary venation especially in fresh condition and the ovoid shape of the young fruits, but differing from this species by the capitate structure of the inflorescence (vs branched and subcapitate in C. robbrechtianum ), the ovoid shape of its fruits at maturity (vs asymmetrically subglobular), the granular texture of the young branches (vs smooth), and the leaf blades generally glossy above in dry condition (vs dull).

Type.

DEMOCRATIC REPUBLIC OF THE CONGO. Yangambi , à 6,5 km au NW du Poste, 0°46'N, 24°27'E, 470 m, 6 March 1937 (fr), J.L.P. Louis 3440 (holotype BR [0000008055132])

Shrub or treelet up to 8 m tall; all vegetative and reproductive parts glabrous externally. Stems pale grey, ca. 10 cm in diameter; young branches grayish to brownish, often granular in outlook, often with more or less quadrangular sections, generally canaliculate near the final nodes. Stipules persistent, sheath 1-3 mm long, truncate to subtruncate or rarely with short awn ca. 0.5 mm long. Leaves petiolate; petioles canaliculate, 10-17 mm long; leaf blades narrowly elliptic or narrowly oblong to obovate, 8-20.5 × 3-7 cm, coriaceous, green, greenish brown or gold green and glossy above, paler green below; base cuneate; apex acuminate, acumen 7-10 mm long; margins somewhat revolute; midrib prominent below; secondary nerves 8-9 pairs, somewhat prominent on both surfaces, intersecondary venation obscure on both surfaces, almost invisible in fresh condition. Inflorescences supra-axillary, borne 1-5 mm above the nodes, erect, capitate, 4-9 × 1.8-4 mm, pauciflorous to multiflorus; peduncle flattened, 1.5-7 mm long; bracts and bracteoles broadly triangular, 1-1.6 mm and ca. 0.8 mm long respectively, apex obtuse or truncate, margins sometimes bearing sparse colleters. Flowers presumed heterostylous (but only longistylous morph known), 5-merous, sessile. Longistylous flowers: Calyx greenish white; tube 0.5-0.7 mm long, subtruncate or with short, obtuse teeth ca. 0.3 mm long, margins sometimes sparsely bearing colleters. Corolla white; tube narrowly cylindrical, 4-5 mm long, sparsely to densely pubescent in the throat and upper quarter inside; lobes ca. 2.5 mm long, glabrous or sparsely pubescent in the basal half inside, tips acute. Stamens inserted below the level of the throat, only apices exserted from corolla tube at anthesis; anthers ca. 1.1 mm long, white; filaments ca. 0.2 mm long. Ovary ca. 1.1 mm long, greenish white. Style and stigma exserted from the corolla tube at anthesis, ca. 6 mm long, glabrous; stigma bilobed, stigmatic lobes ca. 1.4 mm long. Infrutescences carrying (2-)4-10 fruits. Fruits sessile, ovoid, 8-10 mm diam., successively green, whitish green and dark violet at maturity.

Taxonomic affinities.

This species is morphologically close to C. robbrechtianum because of its coriaceous leaves, its obscure intersecondary venation especially in fresh material, the length of its peduncles and the shape of its young fruits. However, it differs from this species by the capitate structure of its inflorescence (vs branched and subcapitate in C. robbrechtianum ), the ovoid shape of its fruits at maturity (vs asymetrically subglobular in C. robbrechtianum ), the granular texture of the young branches (vs smooth in C. robbrechtianum ), and its leaf blades generally glossy above in dry condition (vs dull in C. robbrechtianum ). In addition, fruiting herbarium specimens tend to retain more fruits [(2-)4-10 fruits] (vs ca. 1-2 fruits in C. robbrechtianum ).

The specimens of C. capitatum studied were almost all previously identified as C. cerinanthum Hiern. But this species clearly differs from C. capitatum by its relatively long pedunculate, branched and lax inflorescences.

Phenology.

Flowers: March - May (Nigeria), July (Cameroon); October (Republic of the Congo); Fruits: March - May, September - December (Democratic Republic of the Congo); April (Nigeria).

Distribution and habitat.

Craterispermum capitatum is known from Western Cameroon, the Democratic Republic of the Congo, South-Eastern Nigeria and the Republic of the Congo. It grows in semi-deciduous primary and secondary forest between 0 and 470 m elevation (Fig. 2 ).

Vernacular name and uses.

Democratic Republic of the Congo - Botele bo lokonda (Turumbu); Djeli na Kupi (-). Leaves are used as fetish to avoid panthers.

Preliminary conservation status.

IUCN status:-Vulnerable: VU B2b(iii). The extent of occurrence (EOO) of C. capitatum is 1,134.21 km², and its area of occupancy (AOO) is 52 km² using a cell width of 2 km. The species is distributed in 7 subpopulations, 2 of which are located in protected areas: the Omo-Oluwa-Shasha Forest Reserve located in Ondo State in Nigeria and the Korup National Park in Cameroon and Cross River National Park in Nigeria, which are in fact contiguous. Habitat loss outside the protected areas is a serious threat for C. capitatum , but loss of forest is also documented for the Omo-Oluwa-Shasha Forest Reserve and the Cross River National Park in Nigeria ( Ite 1997; Adedeji and Adeofun 2014).

Field study is required to fully assess the AOO of C. capitatum and, given the fact that the Democratic Republic of the Congo is not well collected, the number of locations for the species is likely to increase.

Etymology.

The name of the species was chosen because of the capitate structure of its inflorescences.

Critical notes.

The distribution of C. capitatum is atypical because of its absence in the South of Cameroon and in Gabon. While rare, several other Rubiaceae species show distribution patterns with a similar macro-disjunction, notably Hymenocoleus rotundifolius (A. Chev. ex Hepper) Robbr. ( Robbrecht 1996) and Ixora brachypoda DC. ( De Block 1998). The reason of this atypical distribution is not yet clearly determined, but in this case, it is probable that the continuous humid forest in southern Cameroon and Gabon is not an ideal habitat for C. capitatum ,which occurs mostly in more semideciduous forests.

Additional specimens examined

(paratypes). CAMEROON: NE corner of Korup National Park, near Baro Village, 5°16'N, 9°11'E, 200 m, 24 March 1984 (fl), D.W. Thomas 3358 (MO, WAG). REPUBLIC OF THE CONGO: M’Boku-COFORIC, Forêt du Mayumbe, 4°15'S, 13°29'E, 8 October 1950 (fl), J. Trochain 8306 (P). NIGERIA: South-West, Shasha Forest Reserve, 1/ 4 mile SW of Osho enclave, 7°5'N, 4°30'E, 1 April 1946 (fl bud), A.D.P. Jones FHI 17233 (BM, K, P); Omo and Shara Forest Reserve, about 1/ 2 mile SW of Osho enclave, site of E.B. 3L., 7°0'N, 4°15'E, 3 April 1946 (fr), A.P.D. Jones & C.F. Onochie FHI 17352 (K, P); Omo Forest Reserve, 3 km S of Aberu, 10 km S of Omo Sawmill, 7°0'N, 4°15'E, 14 May 1980 (fl), E. Pilz 2455 (MO); Ogun, Omo Forest Reserve, 3 km S of Aberu, 10 km S of Omo Sawmill, 7°0'N, 4°15'E, 17 May 1980 (fl), E. Pilz 2530 (MO, WAG); Ijebu Province, Shasha Forest Reserve, 7°5'N, 4°30'E, 4 March 1935 (fl), P.W. Richards 3192 (BM, MO); Ijebu Province, Shasha Forest Reserve, 7°5'N, 4°30'E, 22 April 1935 (fr), P.W. Richards 3382, (BM, MO); Ijebu Province, Shasha Forest Reserve, 7°5'N, 4°30'E, 12 April 1935 (fr), R. Ross 210 (BM, MO); Oban, 5°19'N, 8°34'E, 1911 (fr), P.A. Talbot 208 (BM); South Eastern State, Ekinta River Forest Reserve, about 20 km ENE of Calabar, 5°0'N, 8°30'E, 1 April 1971 (fr), P.P.C. Van Meer 1113A (WAG); South Eastern State, Ekinta River Forest Reserve, about 20 km ENE of Calabar, 5°0'N, 8°30'E, 2 April 1971 (fl, fr), P.P.C. Van Meer 1124 (WAG); South Eastern State, Oban Group Forest Reserve, West block, between pillar 59 and 60, Kwa River, 5°9'N, 8°28'E, 150 m, 14 April 1971 (fr), P.P.C. Van Meer 1450 (WAG). DEMOCRATIC REPUBLIC OF THE CONGO: route Mabana km 3, terr. Maluku, 4°3'S, 15°33'E, 27 November 1970 (fr), H. Breyne 982 (BR); Sualempu, 12 km de Bita, 4°16'S, 15°48'E, 24 March 1971 (fr), H. Breyne 2125 (BR); sl, 1921 (fr), J. Claessens 644 (BR); Bokolongo-Djoa, terr. Bolomba, 0°12'N, 19°21'E, 27 February 1958 (fr), C. Evrard 3569 (BR); Djoa (territoire Bolomba), 0°8'N, 19°16'E, 17 May 1958 (fr), C. Evrard 4075 (BR); Djoa, terr. Bolomba, 0°8'N, 19°16'E, 15 October 1958 (fr), C. Evrard 5014 (BR); Bankaie, terr. Inongo 2°22'S, 18°25'E, 9 September 1953 (fr), G. Gilbert 14772 (BR); Yangambi, plateau de la Luweo, 0°46'N, 24°27'E, 470 m, 30 April 1938 (fr), J. Louis 9162 (BR).

Figures

Figure 1. Craterispermum capitatum. A Longistylous flower B Node with stipules and inflorescences (only one shown) C Node with infrutescence with young fruits D Young fruit. A from Trochain 8306 (P) B from Richards 3382 (MO) C, D from Louis 9162 (BR). Drawn by Antonio Fernandez.

Figure 2. Distribution map of Craterispermum capitatum.