Monanthotaxis vulcanica P.H.Hoekstra, 2021

Hoekstra, P. H., Wieringa, J. J., Maas, P. J. M. & Chatrou, L. W., 2021, Revision of the African species of Monanthotaxis (Annonaceae), Blumea 66 (2), pp. 107-221 : 208-209

76. Monanthotaxis vulcanica P.H.Hoekstra , sp. nov. — Fig. 33 ; Map 42

Monanthotaxis vulcanica belongs to a group of species with a large leafy upper bract on the pedicel. It can be distinguished from the other species of this group by the combination of 15 stamens, c. 14 hairy carpels per flower and monocarps with large stipes of 6–10 mm long. — Type: R. G. Letouzey 15050 (holo P ( P01982551 ); iso WAG.1576469, YA0003005 ), Cameroon, South-West region, pentes NW du Mt Cameroun, vers Efolofo , 30 km W. S / Préfecture Muyuka (feuille IGN 1 /200.000 Buea – Douala ), 750 m, 1 June 1976. Paratypes : J. D. Chapman 3675 ( FHO, K), Nigeria, Taraba state, Sardauna prov. Kurmin Dodo, Chappal Waddi escarpment, 1800 m, 8 Feb. 1975 ; M. Etuge 4810 ( K, YA), Cameroon, North-west region, Bali Ngemba F. R. Mantum, 1600 m, 17 Nov. 2000 ; H. Jacques­Félix 3078 ( P), Cameroon, West region, Mt Nkogam , Feb. 1939 ; R. G. Letouzey 13046 ( P, YA), Cameroon, West region , Massif du Nkogam, 25 km W of Foumban, en lisière latérale, vallon au SW du sommet principal, 1600 m, 28 Oct. 1974 ; T. D.Maitland 1618 ( K), Cameroon, North-west region, Bamenda,af. Bambui , 1370 m, June 1931 .

Etymology. This species is named Monanthotaxis vulcanica as it is confined to the volcanic belt of Cameroon and Nigeria.

Liana, to 20 m long; young branches reddish brown, sparsely covered with appressed, yellowish hairs c. 0.2 mm long to almost glabrous; old branches reddish brown to blackish. Leaves: petiole 3–6 mm long, 0.6–1 mm diam, slightly grooved, indument as on branches; lamina oblong-elliptic to slightly oblanceolate, 5.6–11.8 by 2.3–3.9 cm, 2.3–3.6 times longer than wide, chartaceous, not punctate, glaucous below, above glabrous, primary vein covered with ascending, yellowish hairs 0.3–0.5 mm long, becoming glabrous, below sparsely covered with appressed to ascending, yellowish hairs 0.1–0.3 mm long, base rounded to slightly cuneate, with thickened black margin, apex acute to slightly acuminate, acumen to 20 mm long, secondary veins 8–12 per side, straight, halfway curving upwards, tertiary venation percurrent, slightly raised above, hardly visible below. Inflorescences extra-axillary or terminal, composed of solitary flowers; sympodial rachis absent; pedicels 19–25 mm long, 0.4–0.5 mm diam, fruiting pedicels 20–37 mm long, 0.5–1.1 mm diam, sparsely covered with appressed to ascending, yellowish hairs; lower bract absent; upper bract leaf-like, in the lower half of the pedicel, ovate, 7–15 by 5 –10 mm, sparsely covered with appressed-ascending, yellowish hairs; flower buds globose to slightly ovoid. Flowers bisexual; sepals connate at the base, depressed ovate to shallowly triangular, 1.5–2.3 by 3–3.4 mm, apex acute, densely covered with hairs, persistent in fruit; receptacle 3.2–3.5 mm diam, flat; petals colour in vivo unknown, 6, in two whorls, outer petals ovate to broadly ovate, 6.4–8 by 6–6.3 mm, outside and inside sparsely covered with yellowish hairs, base of inside glabrous, inner petals elliptic, 5.3–5.7 by 3.9–4.1 mm, indument as on outer petals; stamens 15, in two whorls, free, linear-obovoid, c. 2 mm long, filaments 0.8–0.9 mm long, thecae introrse in inner whorl, extrorse in outer whorl, connective truncate, prolonged outward in the inner whorl, and inward in the outer whorl, not hiding the thecae, glabrous, staminodes absent; carpels c. 14, subcylindric, c. 2.1 by 0.3–0.4 mm, densely hairy, ovules 5, lateral, stigma elongate, c. 0.8 mm long, glabrous. Monocarps 2–13, orange, moniliform, each part ellipsoid to subcylindric, 12 –50 by 4.5–6.5 mm, verrucose, covered with few hairs on the stipe, apex apiculate, apiculum to 2 mm long, stipes 6–10 mm long. Seeds 1–4, ellipsoid to subcylindric, 8–15 by 5–6 mm, apex rounded to apiculate, ochre-brown, raphe not visible.

Distribution — Nigeria (Taraba State), Cameroon (North-West Region, South-West Region, West Province).

Habitat & Ecology — In submontane forest and on forest edges. Altitude: 750–1800 m. Flowering: June; fruiting: February, June, October, November.

Preliminary IUCN conservation status — Endangered (EN): B2ab(iii). EOO: 18 794 km 2, AOO: 24 km 2. This species is known from 6 collections from 4 locations, of which only one in a nature reserve. The other 3 locations are under threat of habitat destruction.

Figures

Map 42 Distribution of Monanthotaxis submontana P.H.Hoekstra (■) and M. vulcanica P.H.Hoekstra (●).

Fig. 33 Monanthotaxis vulcanica P.H.Hoekstra. a. Fruiting branch; b. inflorescence with flower bud; c. flower bud with one outer and one inner petal removed; d. stamen,outside view; e. stamen,side view; f. carpel; g. longitudinal section of carpel (a: Chapman 3675, K; b–g: Letouzey 15050). — Drawing by E. Winkel.