Monanthotaxis bidaultii 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 : 130-133

7. Monanthotaxis bidaultii P.H.Hoekstra , sp. nov. — Plate 1 ; Map 6

Monanthotaxis bidaultii has unisexual flowers and is closely related to M.cauliflora , but it is differentiated from all species of Monanthotaxis by the staminate flowers with 3 stamens and 3 staminodes. It is differentiated from M. mortehanii and M. glomerulata for which no staminate flowers are known by the pistillate flowers with <60 carpels and 2–4 ovules per carpel,while the latter two species have> 80 carpels and 6 or 7 ovules per carpel. — Type: T. L. P. Couvreur et al.918 (holo WAG (consisting of 2 sheets: WAG.1576038, WAG.1576039); iso LBV not seen, YA not seen), Gabon, Moyen-Ogooué, 30 km ESE of Lambaréné, 3–4 km on road after Mabounié ‘camp de vie, 103 m, 22 Nov. 2015. Paratypes : E. Bidault et al. 551 ( LBV, MO), Gabon, Moyen-Ogooué, Mabounié ,forest west of camp, 100 m, 13 May 2012 . E. Bidault & Akouangou 1528 ( BR, BRLU, LBV, MO, P), Gabon, Moyen-Ogooué, zone de Mabounié, à 45 km au sud-ouest de Lambaréné , rive nord de la rivière Ngounié, 80 m, 16 May 2014 . E. Bidault & Akouangou 1632 ( BR, BRLU, LBV, MO), Gabon, Moyen-Ogooué, zone de Mabounié, à 45 km au sud-ouest de Lambaréné , rive nord de la rivière Ngounié, 80 m, 19 June 2014 . E. Bidault et al. 1641 ( BRLU, LBV, MO), Gabon, Moyen-Ogooué,zone de Mabounié, à 45 km au sud-ouest de Lambaréné, rive nord de la rivière Ngounié, 77 m, 20 June 2014 . E. Bidault et al.1647 ( BR, BRLU, LBV, MO, P, WAG), Gabon, Moyen-Ogooué,zone de Mabounié,à 45 km au sud-ouest de Lambaréné, rive nord de la rivière Ngounié, 94 m, 21 June 2014 . E. Bidault et al. 1876 ( BRLU, LBV, MO), Gabon, Moyen-Ogooué, Mabounié, à 35 km au sud-est de Lambaréné,en bordure du site de la Base Vie 2, 22 m, 31 Oct. 2014 . F. J. Breteler 9756 ( LBV, WAG), Gabon, Ogooué-Maritime, Rabi , Di- vangui road, 3 Apr.1990 . T. L. P. Couvreur et al. 914 ( LBV, WAG, YA), Gabon, Moyen-Ogooué, 30 km E SE of Lambaréné ,on main road to Mabounié mine exploitant ‘camp de vie’, c. 9 km the Ngounié, 62 m, 21 Nov. 2015 .

Etymology. Monanthotaxis bidaultii is named after Ehoarn Bidault, the discoverer of the population in Mabounié and collector of the majority of specimens of this species.

Small shrub or liana, to 20 m long, to 1 cm diam; young branches densely covered with appressed to slightly ascending or erect, reddish brown hairs 0.1–0.3 mm long, becoming glabrous; old branches dark brown to blackish. Leaves: petiole 5–8 mm long, 1.2–1.6 mm diam, grooved, indument as on branches; lamina narrowly oblong-elliptic to oblanceolate, 9–19 by 3–6.1 cm, 2.4–3.3 times longer than wide, chartaceous, slightly punctate, discolorous, dark glossy green above, glaucous below, above with appressed to ascending, yellowish hairs 0.1–0.3 mm long, becoming glabrous except for the primary vein, below densely covered with ascending to erect, yellowish hairs 0.1–0.3 mm long, base cuneate to rounded, with thickened black margin at the base, apex acute to slightly acuminate, acumen to 10 mm long, secondary veins 10 –15 per side, straight to slightly curving upwards towards the margin, tertiary venation percurrent. Flowers unisexual. Staminate inflorescences cauliflorous, ramiflorous or axillary, composed of 2–5-flowered fascicles or rhipidia; sympodial rachis 1–3 mm long, densely covered with erect hairs 0.1–0.2 mm long; pedicels 1–2 mm long, c. 0.4 mm diam, fruiting pedicels 10–15 mm long, 1.2–1.9 mm diam, densely covered with appressed hairs; bracts ovate, c. 0.8 by 0.5 mm, indument as on rachis; flower buds depressed globose; sepals free, ovate, c. 0.8 by 0.6 mm, densely covered with appressed, short hairs; receptacle 0.8–1.2 mm diam, flat; petals beige, 3, in one whorl, broadly ovate, 1.9–2.2 by 1.8–2.1 mm, outside covered with appressed, short hairs, inside covered with appressed, very short hairs to papillate; stamens 3, in one whorl, free, alternating with the petals, oblong, 0.6–0.7 mm long, filaments very short, less than 0.1 mm long, thecae latrorse, connective truncate, hairy on the inside, staminodes 3, alternating with the stamens, 0.2–0.3 mm long, sparsely hairy, hairs <0.1 mm long. Young pistillate inflorescences cauliflorous, few-flowered glomerules to 2 cm long; sympodial rachis densely covered with erect, reddish brown hairs 0.1–0.2 mm long; flowering pedicels c. 11 mm long, 0.5–0.7 mm diam; bracts ovate, c. 0.7 by 0.5 mm, indument as on rachis; flower buds globose to ovoid; sepals ovate to broadly ovate, 1.1–1.4 by 0.8–1.4 mm, densely covered with hairs, not persistent in fruit; receptacle unknown; petal colour in vivo unknown, at least 3 in at least one whorl, outer petals depressed ovate, at least 2–2.2 by 2.7–2.8 mm, outside densely covered with dark brown hairs, inside densely covered with yellowish hairs c. 0.05 mm long, inner petals absent or not yet developed; carpels c. 52, ellipsoid, c. 1 by 0.4 mm, densely hairy, ovules 2(–4), lateral, stigma subglobose, c. 0.4 mm long, glabrous. Monocarps 4–23, brown, ellipsoid or moniliform, each part ellipsoid to narrowly ellipsoid, 12–28 by 6.5–7.5 mm, slightly verrucose, densely covered with hairs, apex apiculate, apiculum 1–1.5 mm long, stipes 3.5–5 mm long. Seeds 1–2(–4), ellipsoid, 12–13 by c. 6.5 mm, ochre-brown, apex rounded, raphe slightly visible.

Distribution — Gabon (Moyen-Ogooué, Ogooué-Maritime).

Habitat & Ecology — In terra firme forest, swamp forest and secondary forest. Altitude: 22– 180 m. Flowering: April to June; fruiting: June, October, November.

Preliminary IUCN conservation status — Endangered (EN): B2ab(iii). EOO: 336 km 2, AOO: 8 km 2. This species is only known from 2 localities, both outside protected reserves.

Notes — 1. Monanthotaxis bidaultii can be distinguished from other species as indicated in the diagnosis.

2. F.J. Breteler 9756 from Ogooué-Maritime has a slightly different facies caused by more dense and slightly more ascending/erect hairs than the specimens from Moyen-Ogooué. This specimen is identified here as M. bidaultii because of the similarity in leaf shape, inflorescence and DNA-sequences ( Fig. 1 , clade I). The description of the pistillate inflorescence is based on that specimen.

Figures

Plate 1 Monanthotaxis bidaultii P.H.Hoekstra. a–c. Leafy branches; d–e. staminate inflorescences; f–g. staminate flower; h. fruit (a: cultivated specimen, same plant as Bidault 1528; b–c, f: Bidault 1528; d, g: Bidault 551; e: Bidault 1632; h: Bidault 1647). — Photos: a: P.H. Hoekstra; b–h: E. Bidault.

Map 6 Distribution of Monanthotaxis bidaultii P.H.Hoekstra (■, D means uncertain det) and M. bokoli (De Wild. & T.Durand) Verdc. (●, O means uncertain dets).

Fig. 1 Bayesian 50 % majority rule consensus tree of the genus Monanthotaxis. Asterisks at nodes indicate node support, i.e., *** Strong node support, ** moderate node support, * weak node support, see Hoekstra et al. (2018). The letters A to K with adjacent black bars indicate the clades. The triangles, circles and squares represent morphological characters of the species which are of some use to distinguis the clades. Green triangles = staminodes absent, red triangles = staminodes present. Green circles = petals in one whorl, red circles = petals in two whorls, yellow circles = petals in bud basally in one whorl, at the top outer petals overlapping the inner ones. Green squares = inflorescences extra-axillary or if cauliflorous also extra-axillary inflorescences present, red squares = inflorescences axillary, supra-axillary or cauliflorous, red and green squares = both extra-axillary and axillary inflorescences present.