Angraecum cucullatum Du Petit-Thouars (1809

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 : 189-192

4. Angraecum cucullatum Du Petit-Thouars (1809 : tabl.). ( Fig. 2A )

Homotypic synonyms:— Angorkis cucullangis Du Petit-Thouars (1809 : tabl.); Aerobion cucullatum (Thouars) Sprengel (1826: 717) ; Angorkis cucullata (Thouars) Kuntze (1891: 651) ; Macroplectrum cucullatum (Thouars) Finet (1907: 23) ; Perrierangraecum cucullatum (Thouars) Szlach., Mytnik & Grochocka in Szlachetko et al. (2013: 19). Type :— RÉUNION. Thouars s.n. (holotype P00541648 !) .

Description:— Plants epiphytic, erect; stem single, up to 3(–5) cm long, covered with old leaf sheaths; internodes 0.4–0.7 mm. Roots few, basal, thick, smooth. Leaves 3–8, rigid, distichous, 20–60 × 5–9 mm, oblong, coriaceous, dark green, slightly V-shaped, apex unevenly bilobed, margins smooth. Inflorescences 1–6, single-flowered. Peduncle 7–9 mm long, covered by 3–5 membranous, imbricate sheaths; sheaths 3–8 mm long, oblong. Floral bracts 9 × 3 mm, oblong, amplexicaul. Flower resupinate, 20–35 mm in diameter, white, almost translucent, nectariferous, sweetly scented at dusk. Sepals 9–12 × 1.5–3.0 mm, linear-oblong, acute, 7-veined; median sepal slightly wider than the laterals, 9-veined. Petals 8–11 × 1.5–2.0 mm, lanceolate-oblong, 5-veined. Labellum 9–15 × 7–12 mm, widely ovate to sub-orbicular, cucullate, apiculate. Spur 8–20 mm long, conical, broad at the throat and abruptly narrowing near the middle, slightly diverging from the ovary. Column 2.5 × 2.5 mm, trapezoid. Rostellum with 2 oblong lobes along column, reaching far beyond the anther cap. Anther cap 1.5–2.0 mm diameter, without a prominent median furrow. Ovary 30–40 mm long, thin, pedicellate. Capsule slightly triquetrous, 10–15 × 6–8 mm; peduncle 20–30 mm long, thin.

Distribution:— Mauritius and Réunion.

Habitat and ecology:— Plants usually grow from the base of tree trunks in the shade to the top branches, where they are exposed to direct sunlight. On Réunion, this species occurs in low and mid-elevation wet forests, on the windward coast between 200–800 m elevation ( Fig. 3C ), where it is found in relatively few sites, but sometimes in high density. On Mauritius, the species has a more restricted distribution, found mostly in heath vegetation and in the low (<6 m tall) Sideroxylon ( Sapotaceae )-dominated forest on the higher grounds (550–700 m elevation) on the western side of the island ( Fig. 3D ), usually with few individuals in each locality. This species is pollinated by moths, and has fairly high fertility.

Conservation status:— The global Area of Occupancy for the species is of 108 km 2 and the Extent of Occurrence is 521 km 2 (after deducting unsuitable areas, e.g. sea between the two islands), and the species is present in more than 10 known localities (11 according to ConR version 1.2.4). Although occurring in low density, this species is relatively more widespread on Réunion compared to Mauritius. However, its habitat is getting less suitable on both islands because of invasion of alien species and urban development. Consequently, this species should be considered, at a global scale, as Near Threatened (NT). However, at the scale of individual islands, the species should be considered as Vulnerable (VU B1ab(iii)+2ab(iii)) on Réunion where its Area of Occupancy is 92 km 2, the Extent of Occurrence is 505 km 2, and the number of localities (using ConR version 1.2.4) is 10, whereas it should be considered Endangered (EN B1ab(iii,v)+2ab(iii,v)) on Mauritius as both the Area of Occupancy and the Extent of Occurrence are of 16 km 2, ConR version 1.2.4 gives two localities, and its native habitat is undergoing major loss of suitable host trees (half of the larger native trees lost in 68 years within protected areas) due to invasion by alien plants ( Florens et al. 2017).

Phenology:— Flowering from December to February(–May).

Additional specimens examined:— MAURITIUS. Les Mares , 4 January 1939, fl., Vaughan s.n. ( MAU 0001940 ), Les Mares road, 11 March 1965, fl., Vaughan s.n. ( MAU 0001941 , P00754591 ), Pétrin, 26 December 1951, fr., Vaughan 3265 ( MAU) ; Crown Land Leclerc , 07 December 1967, Vaughan s.n. ( MAU13162 ) ; Gouly Père,

11 January 2008, 638 m, fr., Pynee et al. s.n. (spirit, MAU 0016719 ) ; Plaine Champagne , 18 December 1971, fr., Lorence s.n. (spirit, MAU 0001948 ) ; Plaine Paul , Pigeon Wood, 671 m, 10 January 2013, fr., Pynee et al. s.n. (spirit, MAU 0016665 ). — RÉUNION. Basse Vallée, 3 April 1974, fr., Bosser 21805 ( P00754722 , P00754723 ) ; 24 May 1976, fr., Bosser 22262 ( P00754699 ) ; 27 May 1974, fl., Bosser 22072 ( P00754630 ) ; 24 February 2010, Dupéron 56 ( REU013311 ) ; Bras Panon , sentier Liberia, 500 m, 16 December 2003, fl., Pailler TP 111 ( REU10131 , REU10132 ) ; Bois de la Rivière de l’Est , s.d., fr., Boivin s.n. ( P00754592 ) ; Hauts de Sainte Marie , 600–700 m, fl., fr., 28 December 1971, Bosser 20998 ( P00754718 , P00754719 ) ; [Domaine de la Mare], 500 m, 28 December 1971, fl., Cadet 3365 ( REU08033 ) ; Le Tremblet, Sentier du volcan, 16 December 1971, fl., Bosser 20862 ( P00754583 ) ; Les Trois Bras , hauts de Sainte Anne, 30 May 1974, fl., Bosser 22080 ( P00754629 ) ; Saint Philippe , Mare Longue, 22 February 1971, fr., Bosser 20607 ( P00754580 ) ; 15 December 1971, fr., Bosser 20827 ( P00754582 ) ; 2 April 1974, fr., Bosser 21799 ( P00754588 ) ; 300 m, 15 December 1972, fl., Cadet 3954 ( REU08034 ) ; 500 m, 25 February 1975, fr., Cadet 5077 ( REU08032 ) ; October 1985, Figier s.n. ( REU10622 ) ; 01 January 2006, fl., Fournel J. Fo 336 (spirit, REU01350 , REU010351 ) ; Sainte Marguerite , 600–700 m, 6 June 2007, fl., Martos FM 114 ( REU008035 ) ; Ile Bourbon , s.d., fr., Delteil s.n. ( P00754593 ) .

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).