Plukenetia brevistyla, Cardinal-McTeague & Gillespie, 2020

10. Plukenetia brevistyla Card. -McTeag. & L.J.Gillespie sp. nov. TYPE: BRAZIL. Amazonas, km 320 on Manaus- Humaitá road, 16 September 1980, S.R. Lowrie, B. Lowy, D. Coelho, M. Morreira & V.M. de Souza 30 (holotype: MO! [accession 2926690, barcode MO-1381795]; isotypes: CAN!, NY!, RB [accession 564286, barcode RB00749078, image!], US!).

Similar to P. brachybotrya Müll.Arg. and P. megastyla Card. -McTeag. & L.J.Gillespie, but with a short depressed-subglobose stylar column, 0.3–1 mm long.

Monoecious slender lianas; stems erect or twining; older stems dull light grey-brown or straw-coloured, to; 5 mm in diam, striate or weakly striate, glabrate with patches of exfoliating cuticle; younger stems smooth to striate, sparsely puberulous. Leaves alternate, evergreen; stipules narrowly triangular to deltoid, 0.4–1.1 mm long, persistent; petioles generally of uniform thickness and colour, 0.4–3 cm long, glabrate except sparsely puberulous when young, often with exfoliating cuticle; blades simple, narrowly elliptic to elliptic or oblanceolate, sometimes oblong-elliptic, 4.2–19.9 3 1.9–7.4 cm, subcoriaceous, both surfaces glabrate except sparsely puberulous on abaxial major veins when very young, base cuneate or obtuse, sometimes attenuate, margins remotely serrulate, apex usually cuspidate, sometimes acuminate, tip 0.4–1.4 cm long; venation pinnate, primary vein 1, secondary veins (4) 5–6(7) on each side of the midrib, brochidodromous, tertiary veins percurrent and somewhat reticulate near the midrib; stipels and glandular knobs absent adaxially at petiole apex; adaxial basilaminar extrafloral nectaries 2, narrowly oblong-elliptic to elliptic, oblong-obovate to broadly obovate, or round-deltoid (rarely circular or irregularly obovate), 1.3–3 3 0.4–1.8 mm; abaxial laminar extrafloral nectaries (2–)4–7(–14) per side, 0.2–0.6 mm in diam, near the margins on distal 2/3rds of the blade, adaxial laminar nectaries absent. Inflorescences axillary, bisexual racemose thyrses (often appearing unisexual due to protogynous development), 0.5–3.5 cm long, 1–2/axil; peduncle absent; axes glabrate to sparsely puberulous; staminate bracts ovate to broadly ovate, 0.5–0.9 mm long, glabrate to puberulous (sometimes only on the central vein and margin); pistillate bracts ovate, 0.6–0.9 mm long, glabrate to puberulous (sometimes only along the margin); staminate flowers numerous, distal, 1–2(3)/node in reduced and condensed cymules (rarely proximal cymules bisexual with a terminal pistillate flower); pistillate flowers 1, basal (may appear to arise from the leaf axil), or rarely 2–3, 1/node in proximal bisexual cymules, usually fallen or in fruit when staminate flowers are at or near anthesis. Staminate flowers: pedicel (2.5) 9–13 mm long at anthesis, sparsely to densely puberulous; bud subglobose to ovoid, apex rounded; sepals 3, often recurved at anthesis, ovate, 1.2–1.5 3 0.8–1 mm, apex obtuse, abaxial surface sparsely to moderately puberulous (sometimes only near the apex); receptacle globose, fully covered with anthers; nectary an extrastaminal annular ring, sometimes appearing lobed or 3-segmented, or not evident; androecium subglobose, 0.5–0.6 3 0.6–0.8 mm, stamens 16–20, filaments absent (rarely present, stout,, 0.5 mm long, on;3 basal-most stamens), anther sacs ellipsoid, dehiscing longitudinally. Pistillate flowers: pedicel (comprising cyme axis and true pedicel) 3–12.5 mm long, glabrate to sparsely puberulous; sepals 4, triangular to broadly triangular, sometimes lanceolate, 0.5–0.7 3 0.3–0.6 mm, glabrate to sparsely puberulous; ovary 4–lobed, 0.8–2 3 1.3–3.4 mm, lobes rounded and laterally compressed, glabrate except often puberulous along midline of the lobe, conspicuous wings or horns absent; styles 4, entirely connate into a depressed-subglobose column, wider than long, sometimes donut-shaped, with a central dimple when young, 0.3–1 3 0.6–1.8 mm, unlobed distally, glabrate; stigmas 4, pale yellow or goldenbrown when dry, round-deltoid (appearing clover-shaped as a group), 0.3–0.5 mm long each, smooth. Fruits 4–lobed capsules, 0.5–0.8 3 0.9–1.3 cm, surface verrucose, glabrate to very sparsely puberulous, each carpel subglobose, usually unornamented, sometimes with a short tubercle, 0.9–1.1 mm long; stylar columns persistent, depressed-subglobose with conspicuous clover-shaped stigmas, glabrate; pedicels 8.5–15 mm long. Seeds not seen. Figure 5 View FIG .

Pollen —Tricolpate, oblate spheroidal (P/ E 5 0.88 –1.0), polar axis 29.1–32.7 m m, equatorial axis 29.1–37.1 m m; amb subcircular; colpi broad, margins uneven and jagged; tectum coarsely reticulate (voucher: Lowrie et al. 6161 MO).

Etymology —The specific epithet is derived from brevi - (Latin, short or small) and - styla (Latin, -styled), and refers to the short stylar column that differentiates it from other neotropical species.

Distribution, Habitat, and Phenology —This species is known from the Rio Jar´ı region of northern Pará and a single collection from east-central Amazonas, Brazil ( Fig. 6 View FIG ), suggestive of a more widespread distribution in the central and eastern Amazon basin. They are slender lianas climbing 3–6 m in terra firme rainforest, with elevations not recorded (estimated, 100 m), and flowering and fruiting specimens collected from July to October.

Discussion — Plukenetia brevistyla is morphologically similar to P. megastyla but differs by having short depressed-subglobose stylar columns, 0.3–1 mm long ( Fig. 5 View FIG ), petioles with more or less uniform thickness (sometimes darker in colour at the base and apex), and subcoriaceous leaf blades, compared to thick oblong-obovoid stylar columns, 2.6–4.4 mm long, petioles with thickened, often purplish, pulvinus-like regions at the base and apex, and thick-chartaceous leaf blades in P. megastyla . Both species are distributed in the Amazon basin with P. brevistyla near the main stem of the Amazon River and P. megastyla along the southern boundary of the region ( Fig. 6 View FIG ). The ETS phylogeny resolved P. brevistyla as an early diverging lineage in sect. Penninerviae, distinct from P. megastyla ( Fig. 4 View FIG ). Both P. brevistyla and P. megastyla are vegetatively similar to P. brachybotrya , but the latter differs in its short massive globose stylar columns, 2–2.5 mm long ( Fig. 3C View FIG ), staminate flowers 1/node (compared to 1–3(4)/ node), and primarily western Amazon distribution.

Staminate flowers of P. brevistyla show variation that falls within the typical range of sect. Penninerviae. All have sessile anthers densely packed on a globose or subglobose receptacle; however, variation was noted in the presence of a nectary and outer whorl of stamens with short filaments. An annular nectary was either consistently ( Lowrie et al. 30) or variably present ( Silva 2392). A third collection (Oliveira 4513) had a distinctly 3-lobed annular nectary and an outer whorl of;3 stamens with very short filaments. Additional collections are needed to understand this variation in staminate flower morphology.

The NY sheet of Lowrie et al. 30 is unusual for having inflorescences with 2–3 pistillate flowers arising from the basal-most node, as well as for having proximal bisexual cymules that terminate with a pistillate flower. Remaining sheets of the same collection (CAN, MO, US) have a single pistillate flower per inflorescence, which is typical for the species.

The collection Oliveira 3603 (NY01461552) co-occurs with P. brevistyla near Monte Dourado, Pará, but differs by having oblong-elliptic leaf blades and petioles with slightly thickened pulvinus-like regions at the base and apex, which is more typical of P. megastyla . There is insufficient floral material to confidently determine its identification, but we tentatively place this collection with P. brevistyla based on its location.

Specimens Examined — Brazil. — PARÁ: Rio Jar´ı, Monte Dourado, ao lado do Campo de Aviaç ~ ao, 14 June 1968, Oliveira 4513 ( NY) ; Rio Jar´ı, Monte Dourado, 4 October 1968, Silva 1105 ( CAN, NY, US) ; Jari, Estrada do Munguba , km 10, 10 July 1969, Silva 2392 ( NY) .