Angraecum borbonicum Bosser (1988: 20)

Pailler, Thierry, Verlynde, Simon, Bytebier, Benny, Florens, F. B. Vincent & Baider, Cláudia, 2020, Revision of Angraecum sect. Perrierangraecum (Orchidaceae; Epidendroideae; Vandeae) for the Mascarenes, with a description of a new endemic species for Mauritius, Phytotaxa 442 (3), pp. 183-195 : 187-188

2. Angraecum borbonicum Bosser (1988: 20) . ( Fig. 2D )

Type:— RÉUNION. Le Tremblet, sentier du volcan, 600–700 m, December 1971, Bosser 20805 (holotype P 00541650!).

Description:— Plants epiphytic, erect or pendulous with age; stem single, (15–) 20–50 mm long, covered with old leaf sheaths; internodes 1.1–2.1 mm. Roots many, basal, 2–3 mm diameter, smooth, silvery-grey. Leaves 4–8, rigid, (20)40–120 × 7–15 mm, linear-oblong, coriaceous, dark green, slightly V-shaped, sometimes recurved at the apex, unevenly bilobed. Inflorescences 1 to 2, single-flowered. Peduncle 5–8 mm long; covered by 2 to 3 imbricate sheaths; sheaths 3–10 mm, ovate, concave, obtuse, sometimes tip keeled, smooth, covered with small glands. Floral bracts (2–3–) 6–7 mm long, ovate. Flower resupinate, 25–50 mm diameter, white, fleshy, opening only rarely, odourless, nectariferous with only few drops of nectar present. Sepals narrowly-ovate, 20–23 × 5–6 mm, acuminate, 7-veined; median sepal slightly wider than the laterals, 9-veined, acute. Petals similar in shape to sepals, 22–26 × 3–4 mm, 5- veined. Labellum 20–23 × 15–20 mm, largely ovate, acuminate. Spur (55–) 65–70 mm long, filiform, pendulous, more or less curved, rarely straight. Column 1.5–2.0 mm high, fleshy; auricles truncate. Anther cap 1.5 mm diameter, keel gibbous. Rostellum abnormally developed. Pollinia 1.2 mm long, ovoid, in direct contact with stigma (autogamy). Ovary (including peduncle) 30–40 mm, narrowed at the base, triangulate. Capsule triquetrous, erect, 40–50 × 15–20 mm, long lasting; peduncle 10–15 mm long; thick.

Distribution:— Réunion.

Habitat and ecology:— Mid-elevation and mountainous moist forest, especially on ridges between 400–1500 m elevation. Often epiphytic on Ericaceae [ Erica Linnaeus (1753: 352) and Agarista D.Don ex Don (1834: 837–838) in particular], sometimes near to the ground in Acacia heterophylla ( Willdenow 1806: 1054–1055) forests (type ‘avoune’ - https://inpn.mnhn.fr/habitat/cd_hab/18671), where it forms dense colonies. Frequency of populations within its suitable habitat is quite high. It is an autogamous species with high fruit set.

Conservation status:— This is a common species, with large range and usually occurring in large density ( Jacquemyn et al. 2007), and has most of its distribution inside the Réunion National Park ( Fig. 3B ). With an Area of Occupancy of 108 km 2, and an Extent of Occurrence of 976 km 2, and its usual high population density, the species should be considered as Least Concern (LC).

Phenology:— Flowering in December and January. Flowers usually open for three days.

Additional specimens examined:— RÉUNION. Basse Vallée , 900 m, 12 Jaunary 1972, fr., fl., Cadet 3441 ( REU006098 , REU006310 , spirit REU008111 ) ; 600–700 m, 20 October 1972, fr., Bosser 21309 ( P00754460 ) ; 24 May 1978, fr., Bosser 22217 ( P00754461 ); (Kiosque 2) , 23 January 2008, Martos FM 195 ( REU010108 ); (Kiosque 2) , 23 January 2008, Martos & Pailler FM 196 ( REU010110 ) ; Bébour , 1300 m, 31 January 1973, fr., fl., Cadet 4070 ( REU006308 ) ; 12 December 2003, fl., Pailler TP 113 (spirit, REU008109 , REU008110 ) ; [ Sentier de la Rivière ], 07 June 2007, Martos FM 138 ( REU008008 ) ; 07 June 2007, Martos FM 139 ( REU008009 ) ; [ Sentier de Takamaka ], 16 January 2008, fl., Martos FM 184 ( REU010109 ) ; 1100–1400 m, 16 January 2008, fr., Martos FM 185 ( REU010111 ) ; Brûlé de St Denis , fr., 25 December 1971, Bosser 21008 ( P00754459 ) ; Le Brûlé, 1000 m, 10 December 1970, fr., Cadet 2953 ( REU006100 ) ; Les hauts du Boucan Launay, s.d., fr., Boivin 1048 ( P00754456 , P00754457 , P00754458 , REU006099 ) ; Hauts de Ste Marie , 1150 m, 05 October 1986, fr., Lavergne R 106 ( REU007840 ) ; Hauts de la Perrière , 8 December 2002, fl., Pailler TP 1189 (spirit, REU008114 ) ; Hauts du Tremblet, 500 m, 3 January 1979, fr., Cadet 5921 ( REU006301 ) ; Mare Longue , October 1985, Figier s.n. ( REU10621 ) ; path to Morne des Patates à Durand, 1000 m, 24 March 1973, fr., Lorence r4 ( P00754464 ) ; Plaine des Fougères , 1200 m, January 2008, fl., fr., Pailler & Juillet s.n. ( REU00822 ) ; Plaine des Palmistes , au-dessous du village, 850 m, 28 November 1982, fl., Cadet 6398 ( REU006101 ) ; 02 December 2003, fl., Pailler TP 101 (spirit, REU008115 ) ; Plaine des Palmistes , Gros Piton Rond, 1400 m, n.d., Martos & Pailler FM 395 ( REU006167 ) ; n.d., Martos & Pailler FM 396 ( REU006166 ) ; Ravine du Grand Bras Piton, 1250 m, 12 January 1972, fr., Cadet 3479 ( REU006309 , spirit REU008112 ) ; Sentier du Bras Cabot, Ilet de Patience , February 1971, fl., Bosser 20599 ( P00754463 ) ; Sentier Plaine des Fougères , 1160 m, 30 January 1986, fl., Lavergne R 548 ( REU007839 ) ; St Benoit , 24 January 2004, fl., Micheneau CM 1 (spirit, REU008113 ) ; Takamaka , Rivière des Marsouins, 17 November 1968, fr., Barclay CB 1205 ( MAU 0001934 ) ; s. loc., n.d., Thouars ( P00754462 ) ; s. loc., n.d., fr., Martin ( P00754710 ) ; s. loc., n.d., fl., Pailler TP 1178 (spirit, REU008116 ) .

Figures

FIGURE 2. Angraecum sect. Perrierangraecum of the Mascarenes.A. Angraecum cucullatum. B. Angraecum liliodorum. C. Angraecum cornigerum. D. Angraecum borbonicum. E. Angraecum baiderae. Photos: A, C, D. Frederic Henze; B. François Vandeschricke; E. F.B. Vincent Florens.

FIGURE 3. Distribution of the five species of Angraecum sect. Perrierangraecum on the islands of the Mascarenes. A. Angraecum baiderae (Mauritius). B. Angraecum borbonicum (Réunion). C. Angraecum cucullatum (Réunion). D. Angraecum cucullatum (Mauritius). E. Angraecum cornigerum (Réunion). F. Angraecum liliodorum (Réunion).