Kylicanthe arcuata Descourvières, Stévart & Droissart, 2018

Descourvières, Pascal, Farminhão, João N. M., Dubuisson, Vincent Droissart Jean-Yves, Simo-Droissart, Murielle & Stévart, Tariq, 2018, A new genus of angraecoid orchids (Orchidaceae: Angraecinae) with highly distinctive pollinaria morphology, including three new species from tropical West and Central Africa, Phytotaxa 373 (2), pp. 99-120 : 104-106

Kylicanthe arcuata Descourvières, Stévart & Droissart , sp.nov. ( Figs. 2A , 4 )

Type :— CAMEROON. Southwest : Mt Kupe, Village de Nyasoso, arbre isolé au milieu d’un village sur Ficus sp. , 869 m, 4°49’57.66”N 9°41’5.28”E, 21 October 2009, Droissart & Stévart 695 (holotype: BRLU; isotype: YA) .

Kylicanthe arcuata is similar to K. quintasii but differs in its erect spur and substantially larger lip callus that is rectangular in front view.

Epiphytic herbs. Roots numerous, basal on the stem, unbranched, greyish, 3 mm in diameter. Stem with a few leaves in a fan, with internodes about 1 mm. Leaves less than 10, oblong, elliptic, sometimes slightly dissymmetric, margins entire, apex unequally bilobed without a notch, lobes of apex acute, difference between the two lobes 5–7 mm, 28–120 × 8–20 mm. Inflorescences usually 1 to 3, more or less pendent, emerging at the base of the stem, with up to 13 flowers, 45–190 mm long, floral internodes about 8–12 mm, rachis terete; bracts amplexicaul, about 2–3 mm long. Flowers resupinate, greenish, about 8 mm in diameter, veins inconspicuous; dorsal sepal elliptic sublinear, apex obtuse to subacute, margins entire, 5.0–4.0 × 1.2–2.0 mm; lateral sepals elliptic, slightly keeled dorsally, apex subacute, margins entire, 3.5–5.0 × 1.0–2.0 mm; angle between dorsal and lateral sepals about 120°; petals linear, apex subacute, margins entire, 3.5–4.1 × 1.0 mm; lip narrowly ovate, entire, margins entire, slightly deflected, triveined, with a callus, apex acute, 3.0–3.5 × 1.5–2.1 mm; callus rectangular in front view, hiding most of the mouth of the spur; spur tubular arcuate, curved but not pendent, raised upward, mouth slightly spreading, distal part slightly dilated, apex rounded, proximal part of the spur parallel to the ovary, 10–12 mm long; ovary/pedicel 4.0–4.5 × 1.0 mm. Column 1.2 × 1.0 mm; anther cavity approximately perpendicular to the axis of the column, margins winged; stigmatic cavity cup-shaped, margins winged, 3 veins generally visible; rostellum triangular and bifid with the 2 lobes fused, about 1 mm long; pollinia 2, spherical; 1 stipe, obcordate, prominently fringed, 0.8 mm × 0.5 mm, connected to a single pisiform viscidium. Fruits ventricose, pedicellate.

Distribution: —Recorded from West Africa ( Liberia, Guinea, Ivory Coast and Ghana) and Central Africa (Bioko) and in the mountains of southwestern and central Cameroon, at 700–1,000 m ( Fig. 3 ).

Habitat and ecology: —Epiphytic in submontane forest, occasionally growing in coffee plantations and orchards, in semi-shade to well-lit conditions.

Phenology: —Flowering August–November.

Conservation status: —The IUCN Red List category is Vulnerable [VU]. The extent of occurrence (EOO) of K. arcuata is estimated to be over 372,072 km 2 (far exceeding the 20,000 km 2 upper limit for vulnerable category under the criterion B1) whereas its minimal area of occupancy (AOO) is estimated to be 44 km 2, which falls within the limits for endangered category under the criterion B2. Kylicanthe arcuata is a Lower Guinea-Upper Guinea linking species and has been collected in one protected area (the Nimba Mountains World Heritage Site). This species is known from 16 specimens representing ten subpopulations. These ten subpopulations represent a total of ten “locations” (sensu IUCN 2017), exceeding the upper limit for endangered, but falling within the limits for vulnerable. We project that the on-going loss of its habitat will induce a continuous decline in the number of subpopulations and mature individuals in the next ten years as well as an important decline of its EOO and AOO. Kylicanthe arcuata is therefore assigned a status of VU B2ab(i,ii,iii,iv,v).

Etymology: —The species epithet refers to the distinctive shape of the lip spur, which is erect and arcuate.

Notes: —Records of Diaphananthe rohrii for Ivory Coast and Ghana ( Govaerts et al. 2018) correspond to this species. Records of D. rohrii for Togo also probably refer to this species, but we were unable to locate any specimens.We also failed to locate the single specimen of K. arcuata known from Liberia (Adams 28949), which is probably housed at IFAN in Dakar, Senegal. A line drawing of this specimen is provided by Adam (1981 pl. 922) who misidentified it as D. quintasii ( Adam 1981: 1692) . Kylicanthe arcuata is also depicted in the book of Pérez-Vera (2003 p. 267) under the name of Diaphananthe bueae with three pictures (flowers and plant in situ at Mount Tonkoui), with a description and a drawing (pp. 274–275). One can observe the arcuate spur clearly raised upward and prominent rectangular callus. One cited specimens, Pérez-Vera 696, is deposited at GDA, P and K. Additional duplicates of Pérez-Vera 696 and Pérez-Vera 236 from the same locality, Mont Tonkoui, might be at the herbarium of Abidjan (UCJ, ABI) but were not seen. Confusingly, K. arcuata in Ivory Coast had been previously identified as D. quintasii by Cribb & Pérez-Vera (1975), probably following Summerhayes (1968). The specimen of D. bueae mentioned by Cribb & Pérez-Vera (1975), Pérez-Vera 725 (K) actually corresponds to Diaphananthe lecomtei (Finet) Cribb & Carlsward (2012) , as determined by Droissart et al. (2009). We were unable to check the identity of the other specimen identified as D. bueae by the same authors, Aké Assi 9003 (UCJ). Finally, the recently reported record of D. rohrii from Equatorial Guinea ( Galán Cela et al. 2018) also corresponds to K. arcuata .

Additional specimens examined: — LIBERIA. Nimba: Kitoma à 25 km à l’ouest du Nimba, flowered August 1974, Adam 28949 (K-drawing) . GUINEA. Nzérékoré: Nimba, Seringbara 2, 1,123 m, 7°37’54”N 8°25’00”W, 15 September 2017, Stévart et al. 5057 (BRLU, MO, P, SERG) . IVORY COAST. Montagnes: Mont Tonkoui , January 1972 (flowered in Daloa August 1972), Pérez-Vera 696 (GDA, K, P) . GHANA. Eastern: Aburi , 31 October 1937, Cox 87 (K) ; Volta: Amedzofe, Rest House compound, 2 August 1954 (flowered September 1954), Westwood 31 (K) ; ibid. loc., 2 August 1954 (flowered September 1954) Westwood 31A (K) . EQUATORIAL GUINEA. Bioko: Basilé , old governor’s residence, 26 December 1966, Sanford 4016 (K) ; Pico Basilé , estrada km 2–3, 2 November 1989, Carvalho 4158 (MA) . CAMEROON. Southwest: Kupe-Manengouba, Engandong, 810 m, 5° 6’12.00”N 9°43’49.80”E, 22 October 2001, Simo SIP 011 (BRLU, YA) ; Mt Kupe , chemin (‘ Montane trail’) partant de Nyasoso jusqu’au sommet du Mont, 1,000 m, 4°49’37.08”N 9°41’47.34”E, 21 October 2009, Droissart & Stévart 682 (BRLU, YA) ; Mt Etindé (petit Mt Cameroun), Village d’ Ekondjo, 700 m, 4° 3’52.88”N 9° 9’6.55”E, 15 October 2013, Droissart et al. 1522 (BRLU, YA) ; ibid. loc., 643 m, 4° 3’47.37”N 9° 9’41.38”E, Yaoundé shadehouse series 4757 (BRLU, YA) ; Centre: Mbam-Minkom (région de, au NO de Yaoundé ), Village de Nye-Meyong , sommet de la colline située au N-NE du village, 1,165 m, 16 November 2007, Yaoundé shadehouse series 805 (BRLU, YA) ; ibid. loc., endroit ouvert sur sommet de la colline à l’E du village, 1,100 m, 3°55’23.34”N 11°21’59.64”E, 18 November 2007, Yaoundé shadehouse series 827 (BRLU, YA) .

Figures

FIGURE 2. Overview of Kylicanthe diversity. A. Kylicanthe arcuata, plants growing as twig epiphytes in Mt. Etindé (Cameroon) and detail of the flowers. B. Kylicanthe perezverae, seed capsules of a plant grown at the Nimba shadehouse (Guinea). C. Kylicanthe liae, habit and detail of a flower showing a prominent orange viscidium, in cultivation at Huye orchid garden of the University of Koblenz- Landau guest house (Rwanda). D. Kylicanthe bueae, habit of a plant grown at Yaoundé shadehouse (Cameroon) and detail of a flower. E. Kylicanthe quintasii, detail of inflorescence of a plant from São Tomé Island. F. Kylicanthe rohrii, detail of inflorescence of a plant from Tanzania. G. Kylicanthe cornuata, detail of flowers of a plant grown at Yaoundé shadehouse (Cameroon). Photographs by: A., D. and G. Vincent Droissart; B. Ehoarn Bidault; C. Eberhard Fischer; E. Tariq Stévart; F. W. Bachmann, facilitated by the World Orchid Iconography of the Swiss Orchid Foundation at the Herbarium Jany Renz (Botanical Institute, University of Basel, Switzerland).

FIGURE 3. Distribution of the seven species of Kylicanthe in tropical Africa.

FIGURE 4. Kylicanthe arcuata. A. Habit. B. Inflorescence. C. Flower. D. Dorsal sepal. E. Lateral sepal. F. Petals. G. Floral pedicel, ovary and column. H. Lip in lateral view. I. Lip in dorsal view. J. Column and lip spur in frontal view showing the callus. K. Spur, detail of the mouth in dorsal view. L. Column in frontal view. M. Column in lateral view with pollinaria still attached. N. Pollinaria in lateral view. N. Anther cap in frontal view. O.Anther cap in ventral view. P.Anther cap in lateral view. Q. Pollinaria in ventral view. R. Pollinaria in lateral view showing dorsal side of stipes with pollinia still attached. S. Pollinaria in lateral view showing ventral side of stipes with pollinia still attached. Drawn by Hans de Vries after a photograph of a living specimen (A) and after Droissart & Stévart 695 (B–S).