Cyrtorchis submontana Stévart, Droissart & Azandi, 2016

Azandi, Laura, Stevart, Tariq, Sonké, Bonaventure, Simo-Droissart, Murielle, Avana, Marie-Louise & Droissart, Vincent, 2016, Synoptic revision of the genus Cyrtorchis Schltr. (Angraecinae, Orchidaceae) in Central Africa, with the description of a new species restricted to submontane vegetation, Phytotaxa 267 (3), pp. 165-186 : 183-184

15. Cyrtorchis submontana Stévart, Droissart & Azandi , sp. nov. Fig. 1 A–S

Diagnosis: Cyrtorchis submontana Stévart, Droissart & Azandi is close to Cyrtorchis guillaumetii but differs by having thinner leaves, fewer flowers, less curved and shorter inflorescences. Cyrtorchis submontana is also close to C. brownii but differs by having small elliptic leaves and shorter inflorescences with spaced bracts and flowers ( Fig. 3H ).

Type:— EQUATORIAL GUINEA (BIOKO). Engong, Parc National de Monté Alén, 5 km au NO de Engong, inselberg, 14 June 2001, Ndong Bokung & Stévart 273 (holotype BRLU!).

Epiphytic herb, suberect, non-branched with generally short stems, 1.5–18 cm long, internodes 2–5 mm long. Leaves elliptic to closely elliptic distichous, spaced closed together, fleshy, olive green, margins linear, unequally bilobed at the apex, with rounded lobes, 2.4–5.6 × 0.7–1.4 cm. Inflorescences axillary or below the leaves, 1–5 flowered, 1–4.4 cm long. Bracts broadly ovate, 4–7 mm long and 5–8 mm apart. Flowers white, fading to orange; sepals ligulate to lanceolate, acute to acuminate at the apex, 9–15 × 2–4 mm; petals similar but shorter and usually acuminate at the apex, 8–12 × 2–3 mm; lip sometimes closely triangular with acuminated fleshy apex, up to 10.5 mm long; spur straight sometimes sigmoid, 1.6–2.2 cm long; pedicel with ovary of 3.5–19.5 mm long; ovary triangular with two lobes on the two sides and one lobe on the “belly”, with a broad flat rib on each of the three sides; two ovoid pollinia, column stout and short of 1–1.5 mm long, viscidium with a uniformly hyalin texture.

Additional specimens examined:— CAMEROON. Akom II (route Kribi- Ebolowa), 1015 m, 905 m, 31 May 2006, Droissart 135 ( BRLU) ; ibid., 3 June 2006, Droissart 112 ( BRLU) ; ibid., 1,075 m, 4 June 2006, Droissart 129 ( BRLU) . EQUATORIAL GUINEA (RIO MUNI). Engong , Parc National de Monté Alén, dalle rocheuse (inselberg) d’Engong, à 5 km du Nord Ouest du village d’Engong, 1,095 m, 29 May 2002, Stévart 1593 ( BRLU) ; ibid., 1,200 m, 25 June 2000, Ndong Bokung et Stévart 185 ( BRLU) ; Montée de Monte Alén à Mirador, 1 August 1999, Ndong Bokung et Stévart 5 ( BRLU) . REPUBLIC OF THE CONGO, col de Bamba, 550 m, 2 October 1992, la Croix 1172 (K) .

Distribution:— Cyrtorchis submontana occurs in three countries ( Cameroon, Equatorial Guinea ( Rio Muni) and Republic of the Congo). This species is thus endemic to the Lower Guinea Domain.

Habitat and ecology:— Epiphyte, restricted to submontane vegetation in evergreen moist forest on mossy branches, and in saxicolous forests around inselbergs. Altitudinal range from 550 to 1,200 m.

Preliminary IUCN Red List category:— Endangered [EN]. The extent of occurrence (EOO) of Cyrtorchis submontana is estimated to be over 24,536 km 2, exceeding the 20,000 km 2 upper limit for Vulnerable status under the criterion B1), whereas its area of occupancy (AOO) is estimated to be 12 km 2 (which falls within the limits for Endangered status under the criterion B2). The species is now known from three subpopulations in Cameroon, Equatorial Guinea ( Rio Muni), and Republic of the Congo. These three subpopulations represent three different locations (sensu IUCN 2014), less than five locations, which is the upper limit for Endangered status under the subcriterion ‘a’ of criterion B2. Cyrtorchis submontana has been collected in protected areas in Equatorial Guinea (Monte Alén National Park) and Cameroon (Campo Ma’an National Park). None of these protected areas is under threat and they appear well managed, however the subpopulation in Republic of the Congo might be threatened. The available information suggests that the number of subpopulations and mature individuals, as well as its EOO and AOO, could decrease in the future. Cyrtorchis submontana is therefore assigned a preliminary status of EN B2ab(i,ii,iii,iv,v).

Notes:— This novelty is one of the smallest species of the genus. It belongs to the section Homocollecticon , within which it is close to C. crassifolia (stem 1.5–18 cm long; leaf 2.4–5.6 × 0.7–1.4 cm and flowers 2.2–3 cm long). Indeed, some specimens of the new taxa share some morphological similarities (stem length, flower size) with C. crassifolia but their leaves are not as succulent and not v-shaped. The new species resembles C. brownii (section Homocolleticon ) but it differs from it by its more spaced bracts, smaller leaves, short inflorescence (1–4 cm) and fewer flowers (1–5 flowers) ( Table 1). Cyrtorchis submontana is also close to C. guillaumetii (section Homocolleticon ). The two species share elliptic leaf form and stem length but should be distinguished by bract arrangement (imbricate vs. spaced), inflorescences length (6.4–8 cm vs. 1–4 cm), and number of flowers per inflorescence (6–12 flowers vs. 1–5 flowers).

Figures

FIGURE 1. Cyrtorchis submontana Stévart, Droissart & Azandi sp. nov. A. Habit. B. Inflorescence. C. Flower. D. Ovary, section. E. Dorsal sepal. F. Lateral petal. G. Lateral sepal. H. Labellum with spur, frontal. I. Labellum with spur, side view. J. Column with part of opened spur. K. Column, side view. L. Column, frontal. M. Column, side view. N.Anther cap, above. O.Anther cap, frontal. P.Anther cap, from below. Q. Stipe with pollinia. R. Stipe, frontal. S. Stipe, side view. Stévart & Ndong Bokung 273 (A, B, D, K, M, Q, R, S) Droissart 112 (C, E, F, G, H, I, N, O, P) Stévart 1593 (J, L) (Drawing by Hans de Vries, 6 November 2015).

FIGURE 3. Illustrative pictures of some central African taxa of the genus Cyrtorchis. A. C. arcuata. B. C. arcuata subsp. whytei. C. C. aschersonii. D. C. brownii. E. C. chailluana. F. C. hamata. G. C. henriquesiana. H. C. injoloensis. I. C. letouzeyi. J. C. monteiroae. K. C. ringens. L. C. submontana. Photographs ‘A–G’ & ‘I–L’ by Droissart Vincent and ‘H’ by Lourens Grobler.