Macaranga esseriana W.N.Takeuchi, 2012

Takeuchi, Wayne, 2012, Floristic discoveries from the LNG Pipeline in Papua New Guinea: Macaranga esseriana sp. nov. (Euphorbiaceae), and noteworthy records for twelve taxa from the southern provinces, Phytotaxa 56 (1), pp. 35-58 : 36-40

Macaranga esseriana W.N.Takeuchi , sp. nov. ( Figs. 1–6 )

Affinis M. caudatae Pax & K. Hoffm. sed foliis multo majoribus usque ad 89 × 54 cm, nervis lateralibus 15–20-jugis (nec 7–8-jugis), staminibus 5–7 (nec 3), inflorescentiis femineis condensatis minoribus usque ad 3.5–8.2 cm longis (nec ad 30 cm longis) differt.

Type: — PAPUA NEW GUINEA. Western Province: Strickland drainage, Juha North (LNG Bivouac 1), survey track 1, perhumid hill forest, 5°48.473'S, 142°18.672'E, 240 m, 30 March 2008, Takeuchi, Gambia & Jisaka 23540 (holotype M! [2 sheets]; isotypes A! [2 sheets], L!, LAE!) .

Dioecious shrubs 3–5 m tall. Branchlets compressed, angular, 10–15 mm diameter near the top, firm, blackresinous, exudate vernicose; surfaces reddish-brown to fuliginous, longitudinally lined, glaucous or not, without lenticels; stipule scars conspicuous, annulate, raised, slanted or horizontal; hairs 1–4 mm long, setiform, appressed, irritant, easily dislodged by casual handling, light brown or tawny; scale-glands peltatediscoid, ca. 0.1 mm diameter, dark brown with pale-translucent margins, sparse, early-falling. Leaves spirally inserted; stipules connate, narrowly conoid, (6–)10–22 × 1.5–5.5 cm, sheathing, terminal, erect, ferruginous turning black, tearing irregularly with age, the residue persisting through 5 or more nodes, papery, crispate, indument as the branchlets; petioles (20–)26–40 × (0.3–) 0.6–1.2 cm, planoconvex, stiff, not articulated, proximally pulviniform, distally geniculate, surfaces light brown to black, pustulate, laxly scaly, glabrescent; leaf-blades cordate, (38–)53–89 × (27–) 33–54 cm, coriaceous; adaxially gray, olivaceous (or fuliginous); abaxially orange brown; lamina base with sinuses 5–9.5(–13.5) × 9–15 cm, inflexed-auriculate at the petiole insertion, the auricles patelliform-pluriglandular; margins reflexed or not, callose-denticulate; apex acuminate, acumen (12–)20–37 × (1–) 4–10 mm; hair indument: upper surface without hairs (except when immature); lower surface with appressed hairs on veins, puberulent or long-setiform; scales: densely lepidote on upper surfaces; scales on lower surfaces lax, white (or brownish-black), dimorphic, the major scales 0.1– 0.2 mm in diameter, scored by radiating lines, minor scales much smaller, punctiform, hardly visible; venation craspedodromous; secondaries 15–20 per side above a basal nervation, (1–) 3–8.5 cm apart, at the lamina center straight-diverging (55–)60–70° from midribs; tertiary nerves scalariform, reticulum tessellate, areoles regular or not; midribs and laterals bifacially prominent, all higher order nerves distinctly raised on both sides. Staminate inflorescence paniculate, pyramidal, to 18 × 13 cm, axillary, divaricately branched through 3 orders, hirtellous on all exterior surfaces; axes compressed, black; peduncle 10–25 × 3.5–4 mm; lateral branches opposed or not, to 70 × 1.5 mm; primary (axial) bracts linear-deltate, 6–9 × 1.5–2 mm, membranous, persisting; bracteoles expanded-cupuliform at the base, abruptly tapering to a 0.5–1.5 mm long acumen, adaxially set with a single disk-gland near the summit. Staminate flowers (measurements from spiritpreserved material) clustered in ± evenly-spaced glomerules, globose in bud; pedicels ca. 0.5 mm long; sepals 3, ovate, 0.3–0.5 × 0.3–0.5 mm; stamens 5–7; anthers apparently 2-locular, opening like a clamshell. Pistillate inflorescence spiciform, 3.5–8.2 × 2–3.3 cm at anthesis, axillary, condensed, erect, appressed-hairy on all exterior surfaces; peduncle 1.5–3 × 0.3–1 cm; primary bracts elongate-cuneate, (10–)15–43 × (1.5–) 4–15 mm, persisting, papery, obscuring surfaces; bracteoles 4.5–7 mm stipitate, distally widened to a spathulate limb 6– 9 × 1.5–4 mm, adaxially furnished with ca. 20–25 discoid glands. Pistillate flowers subsessile, congested; calyx globose-ovoid, (3.5–)5–6 × 3–5.5 mm, entire, completely enclosing the ovary except for the styleostiole, chartaceous, rupturing irregularly at anthesis, deciduous, inner surfaces glabrous; ovary depressedly globose, sessile, densely furfuraceous, scurfy; locules 3–5, ovules 1 per cell, axile; styles 3–5, spreading, curved, plumosely lobed. Infructescence to 14 cm long; pedicels accrescent, 5–8 × 1–2 mm. Fruits capsular, 10–12 × 12–14 mm; exocarp jet black, glandular-lepidote, encircled by 2 longitudinal sutures; spines subulate, 2–6 × 0.1–0.5 mm, strigulose.

Etymology: — Macaranga esseriana is named after Hans-Joachim Esser (Botanische Staatssammlung München), a specialist in Malesian Euphorbiaceae .

Field characters: —Pole shrubs 3–5 m tall, dioecious; stipules pink turning black with age; petioles widely spreading, often inserted at right angles to the stem; leaves reddish-purple in flush, blades hanging obliquely or vertically, papyraceous, adaxially dark green, abaxially light green with red venation; staminate panicles bright red all parts excepting the whitish-yellow anthers; pistillate flowers congested in a conical mass, ovary black, shining, styles red; fruits brownish-green, spines subulate, red.

Distribution: —Known with certainty only from the type locality in the Strickland basin of Papua New Guinea ( Fig. 7 ). Sterile plants, possibly of this species, have also been seen on limestone karst in the Muller Range, 8 km northwest of Juha North (pers. obs.).

Habitat and ecology: —Early successional communities in anthropogenic or windthrown clearings, perhumid hill forest, common, 240– 275 m.

Phenology: —Flowering and fruiting in March.

Additional specimens examined (paratypes): — PAPUA NEW GUINEA. Western Province: Strickland drainage, Juha North (LNG Bivouac 1), survey track 2 A, perhumid hill forest, 5°48.450'S, 142°18.660'E, 275 m, 29 March 2008, Takeuchi, Gambia & Jisaka 23528 ( A!, LAE!); same data, Takeuchi, Gambia & Jisaka 23531 ( A!, L!, LAE!, M!) .

Macaranga esseriana is the latest addition to the Longistipulata Group (19 species), the most distinctive of the informal groups recognised by Whitmore (1980b, 2008) from New Guinea. Within this alliance, the new species is closest to M. caudata Pax & Hoffman (1919: 30) but is easily distinguished by the characters specified in the diagnosis, particularly by the macrophyllous foliage and condensed pistillate inflorescence.

East Malesian Macaranga Du Petit Thouars (1806: 26) is usually found in heliophytic habitats associated with anthropogenic disturbance or ecologically comparable processes (e.g., landslips, windthrows, vulcanism). Because of their visual prominence in open environments, the light-demanding taxa are generally well-represented in Papuasian collections—the local conspectus was thus suspected of being close to a complete enumeration ( Takeuchi 2007a). However the discovery of another new Macaranga , the second in recent years from the southern ranges, suggests that a comprehensive inventory is probably still beyond our reach.

Figures

FIGURE 1. Macaranga esseriana W.N.Takeuchi. Severed top from a pistillate plant (Takeuchi et al. 23531).

FIGURE 2. Macaranga esseriana W.N.Takeuchi. A, typical form and size of mature leaves; B, basal auricles. A from Takeuchi et al. 23528; B from Takeuchi et al. 23531.

FIGURE 3. Macaranga esseriana W.N.Takeuchi. A, connate stipules, a defining characteristic of the Longistipulata Group (two stipules shown, the apical one sheathing, the one below with a developing rupture); B, stipule residues are long-persisting through 5 or more nodes. A from Takeuchi et al. 23531; B from Takeuchi et al. 23540.

FIGURE 4. Macaranga esseriana W.N.Takeuchi. Staminate panicle (Takeuchi et al. 23528).

FIGURE 5. Macaranga esseriana W.N.Takeuchi. Pistillate structures. A, anthetic inflorescence; B, submature inflorescence with sheathing basal bracts. A–B from Takeuchi et al. 23531.

FIGURE 6. Macaranga esseriana W.N.Takeuchi. A, immature infructescence; B, mature fruits. A–B from Takeuchi et al. 23540.

FIGURE 7. Island of New Guinea. Collection localities from recent expeditions to the Southern Fold Mountains. A, Muller Range; B, Juha North; C, Juha South; D, Baia River; E, Tualapa and Umgé; F, South Karius; G, Hides; H, Benaria; I, Deviation. The southern limestone is a melange of spatially fragmented environments extending from Kikori in the east to the Star Mountains in the west. Overlay (shading): distribution of the principal karst formations.