Tricalysia achoundongiana Robbr., Sonké & Kenfack, 2002

Tricalysia achoundongiana Robbr., Sonké & Kenfack View in CoL , sp. nov.

Haec species subgeneris Tricalysiae propter fructus cum parietibus scleroticis et bracteolas in calyculis cupularibus connatas nullo dubio Tricalysia atherurae et T. vadensi proxima; a priori floribus sessilis, a posteriori foliorum laminis cuneatis et floribus 5-6-meris differt.

TYPUS. — Sonké 2315, Cameroon, Korup National Park , fl. 18 Nov. 1999 (holo-, BR!; iso-, BRLU!, K!, P!, SCA!, YA!) .

Shrub up to 10 m tall; young twigs puberulous. Leaves with interpetiolar stipules triangular, fused at base, protruded into an awn up to 10 mm long, puberulous outside; petioles up to 12 mm long, puberulous; leaf-blades elliptic or lanceolate, 14-18.5 × 5-9 cm, glabrous except for the midrib puberulous above and beneath, papyraceous, base cuneate, apex acuminate, acumen 9-11 mm long; lateral nerves 5-6 on each side of the midrib; intersecondaries few, difficulty visible, parallel and ± perpendicular to lateral nerves.

Inflorescences 3-flowered, sessile, congested; bracts and bracteoles fused into cups (‘‘calyculi’’), sitting in one another, the upper ones embracing the ovaries; 1-2(-4)-toothed or truncate cups per flower, and a basal 4-toothed cup embracing the flower triplet; calyculi puberulous outside and covered with colleters inside. Flowers 5-6-merous, sessile. Calyx puberulous outside and covered with colleters inside, tube 2.5 mm long and 1.5 mm wide, with (4-)5-6 short triangular teeth. Corolla white, sparsely hairy in- and outside; tube c. 4 mm long; lobes c. 3.5 mm long, with triangular tip. Stamens attached to throat; anthers subsessile with their bases included, c. 3.3 mm long, each with a shortly triangular, hairy, apical, sterile appendage. Ovary pubescent, more densely than the calyx, with two 4-ovulate placentas; style pubescent, c. 5 mm long except its lobes 1 mm long. Fruits ± spherical, 1.8 cm in diameter, sparsely pubescent, colour at complete maturity unknown; calyx withered, leaving a conspicuous scar on top; seeds four, ± having the shape of a quarter of a sphere, up to 8 mm long, with long comma-shaped hilum; coat glossy, chestnut brown. — Fig. 2. View Fig

PARATYPES. — Sainge & Mambo 277, Cameroon, Korup National Park , 05°03’N, 08°53’E, fr., 21 Jan. 2000 ( BR!, GoogleMaps MO!, GoogleMaps SCA!); GoogleMaps Thomas & Mambo 4239, Cameroon, Mundemba town, 05°58’N, 08°55’E, fl., June-July 1984 ( BR!, GoogleMaps MO!, GoogleMaps WAG!) GoogleMaps .

HABITAT. — The area in which Tricalysia achoundongiana occurs supports a closed-canopy evergreen forest with patches of secondary growth, classified by L ETOUZEY (1985) as Atlantic-Biafran evergreen forests, rich in Caesalpiniaceae . This forest has a well-defined structure with a high degree of local endemism (e.g. THOMAS & GEREAU 1993; GEREAU & KENFACK 2000). The area lies at 50-100 m above sea level and is flat to gently undulating with numerous small creeks in shallow valleys. Using the mean elevation, slope angle and convexity, the Korup Forest Dynamics Plot was divided into seven habitat categories, namely riverside, low gully, high gully, low flat areas, bench, ridge top, steep slopes. The new species obviously avoids steep slopes and swampy areas, and seems to be associated to low flat areas, river banks and bench.

D ISTRIBUTION. — The new species here described is endemic of the Lower Guinea Domain of the Guineo-Congolian Region, which is the centre of diversity of the genus Tricalysia and of the Tricalysia atherura group ( ROBBRECHT 1987, fig. 11).

CONSERVATION STATUS. — The species is widely distributed in the southern part of the Korup National Park, as shown by a field inventory in the 50 hectares Plot, but is not yet sufficiently documented by collections. Despite of past intensive botanical surveys of Cameroon coastal forest, the new species is known so far only from Korup and surrounding areas. This area is less than 20,000 km 2. Thus T. achoundongiana , following the Red Data criteria of IUCN (2001), should be classified as “VU B”.