Angraecum lanceolatum Jecmenica , Stevart & Droissart, 2016

Jecmenica, Vladimir, Droissart, Vincent, Noret, Nausicaa & Stevart, Tariq, 2016, Taxonomy of Atlantic Central African orchids 5. A new species of Angraecum sect. Conchoglossum (Orchidaceae, Angraecinae) from Gabon and Cameroon, PhytoKeys 61, pp. 61-71 : 63-66

Angraecum lanceolatum Jecmenica, Stevart & Droissart sp. nov. Figs 1 , 2

Diagnosis.

Angraecum lanceolatum is close to Angraecum stolzii Schltr. (1915) but differs from it by shorter narrowly ovate leaves that convolute in the distal half, by a shorter zig-zag stem and by a rhombic lip shape. The species also resembles Angraecum cultriforme Summerh. (1958) but differs from it by smaller flower size and slightly curved spur. Angraecum lanceolatum is also close to Angraecum pyriforme Summerh. (1936) in the shape of floral parts, but differs from it by previously stated vegetative characters, hanging habit, single-flowered inflorescence and smaller flower.

Type.

Cameroon. South Region of Cameroon, Campo-Ma’an National Park, nearby villages of Ebianemeyong and Nyabissan, 02°29.2488'N, 010°19.9026'E, 14 Feb 2015, V. Droissart, T. Couvreur & N. Kamdem 1874 (holotype: BRLU!; isotype: YA!).

Description.

Small epiphytic herbaceous plant. Stem hanging, slightly zig-zag in form, unbranched, up to 8.5 cm long. Leaves alternate, spaced, narrowly ovate to lanceolate, sometimes slightly falcate and always convolute in the distal part, margins entire; distinct midvein forming slight channel, accompanied with 2 or 3 nerves on each side merging into one throughout; small stomata spots visible in young leaves; leaf apex unequally bilobed, acuminate, with the larger lobe 1.5-2.8 mm long and the smaller 0.3-1.2 mm long, leaf blade 2.3-4.1 × 0.6-0.9 cm; leaf internode about 5-6 mm long. Inflorescence single flowered, eventually two-flowered; peduncle elongated 13-23 mm long, opposite to the leaf at the node. Bracts acute, 2 mm long. Flowers white, opening diameter about 12.5 mm. Ovary and pedicel not resupinate, 8 mm long. Dorsal sepal 6.2-8.5 × 3 mm, elliptic, acute, thick, with entire margins. Lateral sepals 6-7 × 2-2.2 mm, elliptic, acute, thick, with entire margins. Petals 5-6.5 × 2-2.2 mm, obliquely elliptic, acute, entire margins, similar in shape to lateral sepals. Lip 5-6 × 4.5-5 mm, concave, rhombic when flattened, widest between first third and the half, acute; spur 16-19.5 mm, cylindric, slender, straight, somewhat elliptically inflated and greenish at the apex. Column 1.5 × 2 mm. Pollinia 2, pyriforme . Fruit capsule, 18-24 × 3.5-5 mm.

Additional specimens.

Gabon. Monts de Cristal National Park. Mont Seni, 13 Sept 2001, Nguema Miyono 2037 (LBV, BRLU!); Ivindo National Park, near Langoué Bai, 17 Sept 2005, D. Nguema s.n. (BRLU!); ibid., J.P. Biteau 263 (BRLU!); ibid., J.P. Biteau 244 (BRLU!).

Distribution and habitat.

Endemic to the Lower Guinea Domain (Cameroon and Gabon, Fig. 3 ). The specimen collected in Cameroon was found at 850 m elevation in submontane forest with Gilbertiodendron unijugum (Pellegr.) J. Léonard ( Fabaceae ). The plant was epiphyte at about 1.5 m from the ground, on the trunk of a shrub with a diameter less than 10 cm.

Phenology.

Flowering occurs in June and September.

Conservation.

IUCN Red List category: Least Concern [LC]. The extent of occurrence (EOO) of Angraecum lanceolatum is estimated to be over 23,884 km2, exceeding the 20,000 km2 upper limit for Vulnerable status under the criterion B1, whereas its area of occupancy (AOO) is estimated to be 12 km2 (which falls within the limits for Endangered status under the criterion B2). The species is now known from three subpopulations in Gabon and Cameroon. These three subpopulations represent three different locations (sensu IUCN 2014), less than five locations, which is the up per limit for Endangered status under the subcriterion ‘a’ of criterion B2. Angraecum lanceolatum has only been collected in protected areas (Monts de Cristal and Ivindo National Parks in Gabon and Campo-Ma’an National Park in Cameroon). None of these protected areas is under threat and they appear well managed. Angraecum lanceolatum is thus not threatened. The available information suggests that the number of subpopulations and mature individuals, as well as its EOO and AOO, will not decrease noticeably in 10 years or 3 generations the future. Application of the IUCN criteria therefore indicates that it cannot be regarded as Endangered despite the fact that its AOO is limited. Angraecum lanceolatum is therefore assigned a preliminary status of LC.

Etymology.

The specific epithet of the new species owes to the particular leaf shape. Even though there are several interpretations of “lanceolate” shape according to different authors (Linnaeus, Lindley), we relied on the current depiction from Beentje (2010) that describes it as narrowly ovate and tapering to a point at the apex.

Figures

Figure 1. Photographs of living specimen of Angraecum lanceolatum (A, C, D V. Droissart et al. 1874 B J. P. Biteau 263): A habit and top view of the flower B half front view of the flower (from spirit material) C inflorescence and flower D habit and peduncle with fruit. Photographs taken by: A, D V. Droissart; B V. Jecmenica; C G. Kamdem.

Figure 2. Angraecum lanceolatum: A Sepals B Petal C Lip, column, ovary and pedicel, spur D Lip, flattened, overhead view E Column without anther cap F Anther cap G Pollinia. Bars represent 1 mm. Illustration of specimen D. Nguema s. n. by Danka Jecmenica and Vladimir Jecmenica.

Figure 3. Distribution of Angraecum lanceolatum in tropical Africa.