Plukenetia kwangoensis L.J.Gillespie, 2023

Gillespie, Lynn J., 2023, Plukenetia kwangoensis sp. nov. (Euphorbiaceae, Acalyphoideae, Plukenetieae), a new species of Plukenetia L. sect. Hedraiostylus (Hassk.) Müll. Arg. from Democratic Republic of Congo, Adansonia (3) 45 (9), pp. 141-149 : 142-145

Plukenetia kwangoensis L.J.Gillespie , sp. nov.

( Figs 1 ; 2 ; 3 )

Plukenetia kwangoensis sp. nov. belongs to sect. Hedraiostylus based on the character combination of short styles (<2 mm long), small dry capsules (≤ 2 cm in diam.), small lenticular seeds, and foveolate pollen. It is distinguished from all other species in the section by its very short petioles (0.5-1.5 mm vs 2-60 mm long) and leaf blades with narrowly acute bases that are often attenuate along the petiole (vs obtuse to cordate, hastate, or sagittate), pinnate venation (vs palmate or 3-nerved venation except rarely appearing pinnate in P. africana Sond. ), and numerous secondary veins (10-16 vs 2-8). Additionally, it differs from P. africana and P. procumbens Prain by its shorter pistillate flower pedicels (1.4-1.8 mm vs ≥ 3 mm), from P. procumbens by its linear-oblong leaf blades (L/W = 6-10 vs elliptic or ovate and L/W <2), and from P. africana by its lack of stipels at the petiole apex.

TYPE. — Democratic Republic of the Congo. [Kwango Prov.]. Entre Kwango-Lufuna [Lufimi], savane herbeuse (incinérée) de la Ngambi, 4.VIII.1944 , R. G. A. Germain 2617 (holo-, BR [ BR0000015669865 ]!, iso-, MO!, P!) .

DISTRIBUTION AND ECOLOGY. — Plukenetia kwangoensis sp. nov. is known from a single collection made in Democratic Republic of the Congo, between the Kwango and Lufimi [Lufuna on label] rivers in westernmost Kwango Province (see Notes below) ( Fig. 4 ). The collection, with both flowers and fruit, was made in early August in herbaceous, seasonally burnt, open savanna.

ETYMOLOGY. — The specific epithet refers to Kwango, the province and region where the species is found, and also to the Kwango River and valley, which borders the savanna on the east.

DESCRIPTION

Monoecious perennial herbs, c. 30 cm high; caudex elongate, c. 1 cm diam., branched; stems erect to steeply ascending, older stems at base short, thick (3-6 mm diam.), woody, many-branched, leafy stems often purplish, especially basally and near leaf insertion, slender (1-1.4 mm diam.), pubescent.

Leaves

Alternate, simple; stipules linear-triangular to narrowly triangular, 1-2.3 mm long; petiole 0.5-1.5 mm long, pubescent; blade linear-oblong to linear-lanceolate, widest near or below the middle, 4-7 × 0.5-0.9 cm, L/W = 6-10, chartaceous, abaxial surface glabrate with pubescent midrib and scattered hairs on secondary veins, adaxial surface pubescent with major veins densely pubescent, base narrowly acute and often attenuate along the petiole, margins revolute, serrulate, teeth glandular, apex narrowly acuminate to narrowly acute; venation pinnate, often faintly 3-nerved at base, secondary veins 10-16 on each side of midrib, semicraspedodromous, sometimes brochidodromous, tertiary veins weakly percurrent or reticulate; stipels absent; adaxial basilaminar glands 2 (-6), often purplish, circular or elliptic, 0.1-0.6 mm in diam., on revolute margin, usually lateral- or sometimes abaxial-facing, basal pair 0.4-2 mm from blade base, sometimes additional 1-2 (-4) glands/side along margins on proximal 1/5of blade; abaxial laminar glands absent. Inflorescences

Bisexual, terminal (becoming leaf-opposed), narrow racemes, 2-7.5 cm long, axes moderately pubescent; peduncle 0.8-3.5 cm long; flowers 1/node, pistillate flower(s) 1 (2) at basal-most node(s), staminate flowers numerous above on axis 1-5 cm long; bracts triangular-ovate to lanceolate, 1.5-2.5 mm long, glabrate to sparsely pubescent.

Figures

FIG. 1. — Plukenetia kwangoensis L.J.Gillespie, sp. nov., Germain 2617 (MO): A, habit; B, pistillate flower; C, immature fruit; D, mature fruit; E, seed. Illustration by Jessica Cosham. Scale bars: A, 1 cm; B, C, E, 1 mm; D, 5 mm.

FIG. 2. — Plukenetia kwangoensis L.J.Gillespie, sp. nov., holotype specimen: R.G.A. Germain 2617 (BR0000015669865).

FIG. 3. — Plukenetia kwangoensis L.J.Gillespie, sp. nov., Germain 2617 (BR0000015669865): A, staminate flowers; B, pistillate flower; C, immature fruit. Scale bars: A, B, 1 mm; C, 2 mm.

FIG. 4. — Plukenetia kwangoensis L.J.Gillespie, sp. nov., Germain 2617 (MO): A, pollen grain, polar view; B, closeup of foveolate tectum. Scale bars: 5 µm.