Benthamia vulcanorum Hervouet & Descourv., 2025

Hervouet, Jean-Michel, Descourvières, Pascal, Hermans, Johan & Longou, Ludivine, 2025, Revision of the genus Benthamia A. Rich. (Orchidaceae, Orchidioideae, Habenariinae), Adansonia (3) 47 (11), pp. 171-249 : 239-242

Benthamia vulcanorum Hervouet & Descourv. , sp. nov.

( Figs 98 ; 99 ; 100 )

DIAGNOSIS. — Similar to Benthamia africana but differing in the number and position of leaves (2-3 leaves in the middle of the stem vs 3-5 basal and cauline leaves in lower part of the stem), in the non-resupinate flowers, that are half closed and facing upwards (vs resupinate, opened and horizontal), the differently coloured flower parts (yellow tips of petals and lip, yellow spur, vs uniform green for Benthamia africana ) and the flattened spur (vs scrotiform). Similar to Benthamia perfecunda but flowers not in three rows, the ovary is vertical (vs perpendicular to the rachis in Benthamia perfecunda ), and the number and the position of the leaves are different (2-4 cauline leaves in lower part of the stem for Benthamia perfecunda ). TYPE MATERIAL. — France, La Réunion • sine loc.; 14.II.1969; T. Cadet 1963; holotype: P[P00738518]!.

ETYMOLOGY. — The species range lies in high altitude zones between the Fournaise volcano and the Piton des Neiges, hence the name vulcanorum , “of the volcanoes”.

PHENOLOGY. — From March to April, at the end of the rainy season. DISTRIBUTION AND ECOLOGY. — La Réunion.Collected between 1700 and 2300 m, growing on bare soil made of volcanic ash ( Fig. 101 ). CONSERVATION. — This species is known from more than ten localities but its AOO is very restricted, less than 20 km ², it could be threatened by the consequences of a volcanic eruption throwing ashes, it must therefore be considered Vulnerable (VU) according to criterion D2.

ADDITIONAL SPECIMENS EXAMINED. — France, La Réunion • Coteau Kervéguen; 21°07’27”S, 55°30’16”E; II.1971; J. Bosser 20737, 20740, 20744 and 20745; P [ P00738532 , and spirit, P00738371 , P00738372 , P00738524 ] ! • Sentier du Côteau Maigre, Plaine des Cafres ; 21°08’08”S, 55°31’40”E; II.1971; J. Bosser 20479; P [ P00738373 ] ! • Sentier du Côteau Maigre, Plaine des Cafres ; 21°08’08”S, 55°31’40”E; II.1971; J. Bosser 20481; P [ P00738523 and spirit] ! • Piton Mare à boue, Plaine des Cafres ; 21°07’56”S, 55°30’45”E; 30.III.1974; J. Bosser 21774; P [ P00738520 ] ! • Base du Piton Mare à Boue, Plaine des Cafres ; 21°09’35”S, 55°34’35”E; 30.III.1974; J. Bosser 21783; P [ P00738535 ] ! • Sentier du Piton des Neiges , Cilaos; 21°07’06”S, 55°29’12”E; alt. 1700-1800 m; 14.IV.1978; J. Bosser 22506; P [ P00738312 , P00738313 ] ! • Descente Plaine des sables le Tremblet; 21°17’14”S, 55°43’20”E; alt. 2000 m; 20.IV.1978; J. Bosser 22540; P [ P00738401 ] ! • sine loc.; alt. 2300 m; 1987; J. Renz 14774; RENZ ! • Sentier du Piton des Neiges par la Plaine des Cafres; 21°07’57”S, 55°32’36”E; alt. 1700 m; 24.IV.1988; J. Dupont 1; P [ P00738359 and spirit] ! • Sommet Kervéguen; 21°07’27”S, 55°30’16”E; alt. 2300 m; 24. V.2000; F. Martos FM706 ; REU [ REU007702 ] ! • Route forestière du volcan; 21°11’40”S, 55°38’36”E; alt. 2200 m; 1.III.2003; T. Pailler et al. TP70; REU [ REU006420 ] ! • Bébour, Piton des Neiges to Bélouve path; alt. 1900 m; 5.III.2003; V. Hoarau et al. 13 and 14; REU [ REU007941 , REU006426 ] ! • Saint-Joseph, Caverne de Cotte ; alt. 2240 m; 21°14’16”S, 55°38’18”E; III.2004; J. Férard et al. 1041 and 1042; CBNM ! • Saint-Joseph, Oratoire Sainte- Thérèse; 21°12’37”S, 55°39’15”E; 2300 m; II.2005; V. Grondin et al. 1564; CBNM ! • Maïdo, sentier du Grand Bénard; 21°04’09”S, 55°23’16”E; 21.III.2007; V. Lecomte s.n.; REU [ REU005135 ] ! • Route du Volcan, vers Le Piton de l’Eau ; 21°11’02”S, 55°40’28”E; 21. V.2008; F. Martos FM340 and FM341 ; REU [ REU007894 , REU007903 ] !• Puy Ramond; 21°17’41”S, 55°42’22”E; 22.II.2020; V. Lavergne; photographs .

NOTES

Although long overlooked, this species has distinctive features, such as the flat spur, the erect flowers and the leaves similar to those of the local Tylostigma , which shares the same altitude and habitat close to the top of the volcanoes Fournaise and Piton des Neiges. It was noted and briefly described by Bernet ( Bernet 2010) who provisionally labelled it Benthamia sp. 3 . It is likely that Jean Bosser also noticed this plant as he systematically noted on his specimens that the lip and petals were green with yellow tips. Another distinctive feature to look for is the erect ovary often prolonged by erect half-closed flowers. It is surprising that among 20 specimens found none were collected before 1969. However, it is unlikely that this is due to a recent arrival, since the plant is endemic to La Réunion. Given the number of very similar specimens and the absence of would-be parents in the same habitat, it is unlikely that this species is a hybrid. In the Benthamia africana complex in Madagascar, some plants (e.g. observation of first author on Sainte-Marie Island) may have two-colour erect flowers with a flattened spur, but in this case all the leaves are basal, as leaves in the drawing by Thouars ( Thouars 1822: t.9).

There is also in the spirit collection in P a sample corresponding to the type P00738518.

See also: Bernet (2010: 140, as Benthamia sp. 3 ), Szelengowicz & Tamon (2013: 248, as Benthamia misera ).

DESCRIPTION

Erect terrestrial herb 25-80 cm tall. Tubers 2-4, fusiform, 2 × 0.8 cm, roots 2-6, up to 7 cm long, 1-3 mm in diameter. Stem cylindrical, 1.2-3 mm in diameter, with leaves in the middle of or slightly lower. Leaves 2-3, 10-15 cm × 5-10 mm, erect, linear, longitudinally folded, rigid. Rachis terminal, 5-15 cm long, bearing 12-24 flowers roughly arranged in a spiral, 4-6 mm apart. Floral bracts lanceolate, acuminate, 8-10 mm long, slightly shorter to longer than the ovary. Ovary fusiform, not twisted, vertical, 5-5.5 mm long, with 3 longitudinal ridges sometimes coloured purple. Flowers not resupinate, hardly opening, 2-3 mm long, all floral parts except lateral sepals forming a loosely closed upward facing tube along the ovary, green with tips of petals, lip and spur yellow; dorsal sepal concave, oval, 2-2.5 × 1.2-1.3 mm; lateral sepals navicular, oblong, spreading, green, 2.8 × 1 mm; petals oblong, shorter than the lateral sepals, 2-2.2 × 0.9-1 mm, forming with the dorsal sepal a hood over the lip, green with a fleshy and yellow apex; lip 2.2-3 × 1.5 mm, without callus, concave in proximal part, trilobed at apex, calceolate, green with yellow apex, with central lobe 0.5-0.6 mm long, thickened, lateral lobes folded upwards, thickened, 0.3 mm long; spur 1 mm, flattened into a disc, not bilobed, slightly narrowed at the base. Column 0.9-1 mm high, 0.6 mm long, short, obtuse, without apiculus; auricles about as long as the column, sub-spathulate.

AMBIGUOUS OR INSUFFICIENTLY KNOWN SPECIES

Below we deal with species known only from a single specimen, that share similarities with other well-known species or could potentially be hybrids, and on which we are unable to make a taxonomic decision. We also mention undescribed species observed in the field, for which there are no specimens known. Finally, we list specimens which again share similarities but also differences with well-known species and for which additional data, especially observations in the field, are needed.

Figures

FIG. 98. — Benthamia vulcanorum Hervouet & Descourv.,sp.nov., Le Tremblet, La Réunion, 20 April 2018. Photograph by Jean-Michel Hervouet.

FIG. 99. — Benthamia vulcanorum Hervouet & Descourv.,sp.nov.,Le Tremblet, La Réunion, 20 April 2018. Photograph by Jean-Michel Hervouet.

FIG. 100. — Benthamia vulcanorum Hervouet & Descourv., sp. nov., drawing by Ludivine Longou after photographs and dried specimens: A, habit; B, part of rachis; C, front view of flower; D, side view of flower.. Scale bars: A, 12 mm; B, 2 mm; C, D, 1 mm.

FIG. 101. — Distribution map of Benthamia vulcanorum Hervouet & Descourv., sp. nov.