Monanthotaxis mcphersonii 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 : 179

49. Monanthotaxis mcphersonii P.H.Hoekstra , sp. nov. — Fig. 22 ; Plate 5a, b; Map 28

Monanthotaxis mcphersonii is together with Monanthotaxis scamnopetala the only species in the genus with 3 sessile monocarps having seeds in 2 rows. It differs from M. scamnopetala in the long, erect hairs (vs short, appressed hairs) and the 3–5 cm long, supra-axillary flowering pedicels (vs 0.5–1.5 cm long axillary pedicels). — Type: G. D. McPherson 15708 (holo WAG ( WAG0031254 ); iso B100010096 , BR0000013211295 , LBV, MO, NY, P01982194 , US), Gabon, Ogooué-Ivindo, south of Ayem, western border of Lopé-Okanda Reserve , along lumber roads south of SEEF chantier, 200 m, 29 Dec. 1991. Paratypes : T. L. P. Couvreur et al. 528 ( WAG, YA), Gabon, Estuaire,forêts des conservateurs,near road to Cape Esterias , 35 m, 5 Nov. 2013 ; T. L. P. Couvreur et al. 862 ( LBV, WAG, YA), Gabon, Woleu-Ntem, c. 15 km south of Mitzic, in Foreex concession, c. 4 km after leaving main road ( N2 ), 543 m, 14 Nov. 2015 ; T. L. P. Couvreur et al. 881 ( LBV, WAG, YA), Gabon, Woleu-Ntem, on road from Mitzic to Lalara ( N2 ), just after the bridge over the Lara , c. 500 m in forest, 561 m, 15 Nov. 2015; J. M. Reitsma 2977 ( LBV, MO, NY, WAG), Gabon, Woleu-Ntem, c. 4 km NNE of Oveng , 887 m, 11 Feb. 1987 .

Etymology. This species is named after Gordon McPherson, collector of the type of this species, and of several other species of Monanthotaxis , including the type specimen of M. paniculata and the single paratype of M. aestuaria .

Liana, to 20 m long; young branches blackish, covered with erect, reddish brown hairs c. 2 mm long; old branches as young branches. Leaves: petiole 3–6 mm long, 0.8–1.2 mm diam, grooved, indument as on branches; lamina narrowly oblong-elliptic, 6.5–11.7 by 2.3–3.9 cm, 2.8–3.9 times longer than wide, chartaceous, not punctate, glaucous below, above sparsely covered with appressed hairs c. 1 mm long, more densely covered with erect hairs on primary vein, below sparsely covered with erect, yellowish hairs c. 2 mm long, base cuneate, rounded to subcordate, with slightly thickened margins, apex acute, primary vein reddish brown, secondary veins 8–14 per side, curving upwards, tertiary venation percurrent. Inflorescences supra-axillary, composed of solitary flowers or 2-flowered rhipidia; sympodial rachis 0–1 mm long; flowering and fruiting pedicels 31–48 mm long, 0.3–0.5 mm diam, covered with erect, reddish brown hairs; lower bracts absent; upper bract at c. one-third of the pedicel, ovate, 1–1.2 by 0.5–0.6 mm, densely covered with appressed hairs; flower buds ovoid. Flowers bisexual; sepals free, ovate to broadly ovate, 1.3–1.7 by 1.2–1.4 mm, apex acute, densely covered with appressed, yellowish hairs, persistent in fruit; receptacle 1.5–2 mm diam, convex; petals dull yellow at the outside, inside beige with white base, 6, in two whorls, outer petals ovate to broadly ovate, 5 –7 by 5 – 6 mm, densely covered with appressed, yellowish hairs, except for the glabrous base of the inside, inner petals rhombic, 5–6 by 2.5–3 mm, claw c. 2 mm long, outside and apex and base of the claw on the inside densely covered with appressed hairs; stamens 15, in two whorls, free, in groups of 5 opposite the outer petals, brown, obconical, 1–1.5 mm long, filaments 0.3–0.5 mm long, thecae extrorse, connective truncate, slightly prolonged inward, hiding thecae seen from above, glabrous, staminodes absent; carpels 3, ellipsoid, c. 3 by 1.4 mm, densely covered with yellow hairs, ovules 12–14, in two rows, lateral, stigma globose, c. 0.5 mm diam, slightly grooved, glabrous. Monocarps 1–3, yellowish brown, immature monocarps subglobose, c. 6.5 by 7 mm, stipes to 1 mm long. Seeds 2, immature, dark brown.

Distribution — Gabon (Estuaire, Ogooué-Ivindo, Woleu-Ntem).

Habitat & Ecology — In primary rain forest and old secondary forest. Altitude: 35– 887 m. Flowering: December; fruiting: February.

Preliminary IUCN conservation status — Endangered (EN): B2ab(iii). EOO: 15 157 km 2, AOO: 20 km 2. This species is known from 5 collections from 3 localities of which one in the Lopé National Park. However, the location in Woleu-Ntem is under pressure of habitat degradation by logging companies and the location in Estuaire by the expanding city of Libreville.

Note — Monanthotaxis mcphersonii can easily be recognized by the narrow oblong-elliptic leaves and the long erect hairs on the stems and leaves.

Figures

Map 28 Distribution of Monanthotaxis letestui Pellegr. (●, O means uncertain dets or aberrant specimens) and M. mcphersonii P.H.Hoekstra (■).

Fig. 22 Monanthotaxis mcphersonii P.H.Hoekstra. a. Flowering branch; b. fruiting branch; c. flower with one outer and one inner petal removed; d. outer petal, outside view; e. inner petal, outside view; f. stamen, inside view; g. stamen, outside view; h. stamen, side view; i. carpel (all: G.D. McPherson 15708). — Drawing by E. Winkel.