Monanthotaxis ochroleuca (Diels) 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 : 183-184

54. Monanthotaxis ochroleuca (Diels) P.H.Hoekstra , comb. nov. — Map 33

Popowia ochroleuca Diels, Bot.Jahrb.Syst. 53 (1915) 441. — Enneastemon ochroleucus (Diels) R.E.Fr. (1953) 41. — Lectotype (designated here): A.F. Stolz 170 (lecto B ( B100153045 ); isolecto B100153044 , BM000547360 , G00308344 , HBG-502504, K000198973 , K000198974 , L 0038041 , L 0188030 , M-0107926, MO, S, US, WAG0000091 ), Tanzania, Mbeya, Rungwe district, station Kyimbila , 1300 m, 2 Sept. 1907.

Popowia ochroleuca Diels var. keniensis R.E.Fr. in R.E.Fr. & T.C.E.Fr. (1925) 321. — Enneastemon ochroleucus (Diels) R.E.Fr. var. keniensis (R.E.Fr.) R.E.Fr. (1953) 41. — Lectotype (designated by Verdcourt 1971a: 94): R.E. Fries 1998 (holo UPS; iso B100460760 ), Kenya, Eastern, Chuca, 26 Feb. 1922.

Scandent shrub or liana, to 5 m long; young branches densely covered with appressed, reddish brown hairs 0.1–0.2 mm long or ascending hairs 0.2–0.3 mm long, becoming glabrous; old branches dark brown to grey-black. Leaves: petiole 4–8 mm long, 1.4–1.6 mm diam, slightly grooved, indument as on branches; lamina elliptic, obovate to oblanceolate, 6.4–14.5(–18.4) by 2.8–6.4(–7.5) cm, 2–3(–3.5) times longer than wide, chartaceous to subcoriaceous, not punctate, green above, glaucous below, above sparsely covered with appressed, whitish hairs c. 0.4 mm long, becoming glabrous, primary vein more densely covered with ascending, yellowish hairs, below sparsely covered with appressed, yellow-brown to reddish brown hairs 0.1–0.2 mm long, primary vein slightly more hairy, base cuneate to rounded, with thickened black margins or thick, black glands, apex acute to acuminate, acumen to 20 mm long, secondary veins 8–12 per side, slightly curving, tertiary venation percurrent, hardly visible. Inflorescences axillary, composed of solitary flowers or 2-flowered fascicle-like rhipidia; sympodial rachis absent or to 1 mm long; flowering pedicels 7.5–21 mm long, 0.3–0.4 mm diam, fruiting pedicels 14–35 mm long, 0.5–1.6 mm diam, densely covered with appressed or slightly ascending, reddish brown hairs; lower bract absent; upper bract in the lower half of the pedicel, halfway or sometimes slightly above the middle of the pedicel, ovate, 0.5–1.1 by 0.7–1 mm, indument as on pedicel; flower buds globose. Flowers bisexual; sepals slightly connate at the base, depressed ovate to shallowly triangular, 0.6–1.1 by 1–1.7 mm, apex acute, densely covered with hairs, persistent in fruit; receptacle 1.8–2 mm diam, flat; petals colour in vivo unknown, 6, in two whorls, base of inner petals visible in bud, outer petals ovate, 3.9–5.3 by 1.9–2.9 mm, outside densely covered with appressed, reddish brown hairs, inside covered with yellowish brown, very short hairs, sometimes glabrous at the base, inner petals rhombic to spathulate, 3.5–4.2 by 1.3–2.5 mm, outside and apical part of the inside densely covered with yellowish brown, very short hairs; stamens 7–9, in one whorl, free, obconical to clavate, 1.5–1.6 mm long, filaments 0.6–0.8 mm long, thecae extrorse, connective truncate, slightly prolonged inward or not, hiding the thecae, sparsely hairy on the inside or glabrous, staminodes absent; carpels 7–13, subcylindric, 1.7–2 by 0.5–0.7 mm, densely hairy, ovules 4–6, lateral, stigma elongate, 0.3–0.4 mm long, glabrous. Monocarps 1–10, colour in vivo unknown, moniliform, 12–50 by 7–9 mm, slightly verrucose, densely covered with appressed, reddish brown hairs 0.2–0.3 mm long, apiculate, apiculum 1–5 mm long, stipes 3–6 mm long. Seeds 1–4(–5), ellipsoid, 10–12 by 5 –7 mm, ochre-brown, rounded to short apiculate apex, raphe visible.

Distribution — South Sudan, Democratic Republic of the Congo, Uganda, Burundi, Kenya, Tanzania, Zambia, Malawi.

Habitat & Ecology — In evergreen forest, upland rain forest, gallery forest and secondary forest, on top of hills, in spray of waterfall; on grey sandy loam and on steep rocky slopes. Altitude: 850–1925 m. Flowering: February, March, May to November; fruiting: January to November.

Vernacular names — Democratic Republic of the Congo: Clu (Kilendu name) (A.S. Taton 156). Tanzania: Mbigiri (Nyakyusa name) (G.P. Leedal 5803).

Preliminary IUCN conservation status — Least concern (LC). EOO: 1 531 758 km 2, AOO: 176 km 2. This species is known from many locations, including several reserves.

Note — Monanthotaxis ochroleuca is the only species of Monanthotaxis in East Africa and Southern Africa with axillary inflorescences and reddish brown indument. Monanthotaxis ochroleuca belongs to the M. schweinfurthii complex ( Fig. 1 , clade B), but can be distinguished from the other species by the reddish brown indument and by having more than 6 carpels per flower. Furthermore, it can generally be recognized by the ellipsoid seeds and the leaf shape, however, some specimens from Zambia deviate from these 2 characters and can look similar to specimens from Angola of M. seretii . Those specimens can only be distinguished by the number of carpels. In the East of the Democratic Republic of the Congo some specimens can approach M. schweinfurthii , but that species has a yellow-brown indument.

Figures

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.