Bulbophyllum pauwelsianum Stévart & Droissart, 2014

Stévart, Tariq, Biteau, Jean Philippe, Cawoy, Valérie & Droissart, Vincent, 2014, Taxonomy of Atlantic Central African orchids 3. A new species of Bulbophyllum Thouars (Orchidaceae) from the Monts de Cristal, Gabon, Phytotaxa 177 (1), pp. 26-34 : 27-31

Bulbophyllum pauwelsianum Stévart & Droissart , sp. nov., Fig. 1 A–E .

Type:— GABON. Région de Ndjolé, 0.1869 S, 10.7573 E, 6 November 2009, Biteau & Stévart 120 (holotype: BRLU!, isotype: LBV!). Bulbophyllum pauwelsianum differs from B. saltatorium Lindl. (1837: t. 1970) in the leaves being pendulous, linear, semiterete with upper surface concave and v-shaped, fleshy, not planar in transverse section; sepals ciliate with hairs more than 0.5 mm.

Epiphytic herb. Roots up to 1 mm diam., creeping from the point of attachment to the substratum. Rhizome 1–3 mm diam., creeping, pendulous. Pseudobulbs up to 14 × 7 mm, spaced up to 3 cm apart, pendulous, ovoid, 3-angled, dark green, unifoliate, covered by a fibrous sheath from rhizome. Leaves up to 15.3 × 0.7 cm, one per pseudobulb, pendulous, petiolate; petiole up to 13 mm long, yellow-green, covered by a brown bract; blade linear, apex obtuse, base attenuate, upper surface with a narrow groove in the centre, lower surface convex, semiterete and v-shaped in cross section, glabrous, fleshy, green. Inflorescence up to 57.5 cm long, a lax raceme, pendulous, emerging from the base of pseudobulb. Peduncle 38 cm long, terete, glabrous, brown, with 5 tubular scales, up to 8 mm long, membranous, yellow-brown. Rachis 19.5 cm long, terete to flattened, puberulous, yellow-brown. Floral bracts broadly triangular, 4 × 2 mm, apex acute, membranous, keeled and puberulous, covering the ovary, yellow-brown to purple. Flowers up to 31, successive with no more than two open together, yellow-green with brown-purple spots; lip yellow-green with purple hairs. Pedicel and ovary 3–4 × 1 mm, puberulous, yellow-brown. Median sepal 7 × 2.2 mm, lateral sepals 6.5 × 2 mm, all strongly reflexed, narrowly triangular, adaxially 3-veined, abaxially slightly keeled at the acute apex, margin ciliate with long, linear, purple hairs up to 1 mm long, abaxially puberulous. Petals 3 × 0.52 mm, not reflexed, obliquely narrowly triangular, margins entire, glabrous, veined but not keeled abaxially at acuminate tip. Lip 6.3 × 1 mm, linear, apex acute, without lateral lobes at the base, base thickened, glabrous, adaxially divided in two ridges, with a median slit starting above the base and continuing over one third of the lip, abaxially with two weak ridges near the base, hairs along the margins of the adaxial side of the lip very fine, velvety and forming a rim around two thirds of the lip, in the top third they gradually become much longer, up to 4 mm long. Lip articulated with base of column. Column 2 mm long (from the free part up to the stelidia), with weak, rounded wings along its adaxial margins at the base of the stelidia, these up to 1.2 mm long, distinct, gradually tapering and more or less acuminate. Anther 1 × 0.8 mm, margin rounded, entire, slightly papillose, with a distinct ridge near the apex. Pollinia 2. Stigmas concave. Flowers smell not known.

Distribution:—Endemic to Gabon. Bulbophyllum pauwelsianum occurs in Atlantic Central Africa ( Fig. 2 ) and has been recorded to date from only the Ndjolé and the Kinguélé areas, both sites situated in the mountainous area of the Monts de Cristal. The distribution of this species corresponds to the Atlantic Sector of the Lower Guinea Domain ( Senterre 2005), which is the coastal part of the Lower Guinea Domain of the Guineo-Congolian Region ( White 1979).

Habitat and Ecology:— Bulbophyllum pauwelsianum is found in very humid forest. The elevation range of the species was estimated to be around 200 m.

Phenology:—Flowering in November.

Etymology:—We dedicate the new species to Olivier Pauwels, former Environmental Studies Coordinator of Shell Gabon and former Country Manager and Head Researcher for Gabon at the Smithsonian Institution, for his contribution to the knowledge of the Gabonese orchid flora.

Cultivation:—Two specimens of Bulbophyllum pauwelsianum are now being grown in the Garden of J.P. Biteau in Libreville. They are mounted on branches in a humid, semi-shaded environment. During dry seasons, the plants are misted over each morning and when needed also in the afternoon.

Conservation Status:—IUCN Red List Category. Many collectors have visited this area of Gabon, over recent years, to collect herbarium specimens. Yet despite this, Bulbophyllum pauwelsianum is known from only two localities. According to this long field experience in the Monts de Cristal, this species seems to be very uncommon in this habitat. However, given the distribution, it is likely that this species is also present in the Monte Alèn-Monte Mitra in Equatorial Guinea. While additional fieldwork may reveal more populations of this plant, one of the localities where it has been collected is situated in a protected area, the Monts de Cristal National Park in Gabon. The main threat to the species is the deforestation resulting from logging activities. In fact, the lowland vegetation where the species was found is currently highly threatened by this activity in Gabon, and only populations in National Parks will not be affected. Since the two known populations of Bulbophyllum pauwelsianum together occupy an area of less than 20 km 2, we assign the species a provisional status of Endangered: EN B2ab(iii) based on the IUCN (2001) Red List Categories and Criteria, at least until other populations are found.

Figures

FIGURE 1. Bulbophyllum pauwelsianum. A. Plant habit. B. Flower. C. Lip. D. Column only. E. (left to right) Dorsal sepal, petal, lateral sepal. Bars. 5 cm (A); 1 mm (B, C, D & E).

FIGURE 2. Distribution of Bulbophyllum pauwelsianum in Gabon (Central Africa).