Psychotria ternatifolia Takeuchi, 2010

Takeuchi, Wayne, 2010, Additions to the rubiaceous flora of Papua New Guinea: Psychotria stolonifera and P. ternatifolia, two remarkable species from the Muller limestone, Phytotaxa 7, pp. 25-34 : 29-33

Psychotria ternatifolia Takeuchi , sp. nov. ( Figs. 6–8 )

Ab omnibus speciebus Psychotriae Papuasiae foliis ternatis differt.

Type: — PAPUA NEW GUINEA. Western Province: Muller Range, Expedition Camp 2, Nothofagus - emergent montane forest on doline karst, 5°39.610'S, 142°18.018'E, 1450 m, 13 September 2009, Takeuchi, Ama & Gamui 24621 (holotype LAE; isotypes A, BO, K, L, MO) .

Understory shrubs 1–3(–5) m tall, glabrous on all parts (stipules excepted). Branchlets terete, apically compressed or planate, 1–3(–4) mm across, furrowed, pithy; surfaces nigrescent (or light brown), dull, longitudinally wrinkled, without lenticels; internodes 1.8–8.5(–12.5) cm. Leaves ternately whorled, obliquely spreading; stipules cylindrical, 2.5–4.0 × 4.5–5.0 mm, denticulate, ciliate, adaxially appressed-hairy, abaxially glabrous, the upper part (ca. 2/3) caducous, base persisting as a collariform ring, later disintegrating irregularly; petiole 4–17(–21) × 0.7–1.0 mm, planoconvex, proximally articulate or not; leaf-blades chartaceous, elliptic-oblanceolate, (5.9–)8.0–17.4(–20.1) × (2.3–)3.0– 7.1 cm; base cuneate-decurrent, often poorly delimited from the petiole; margin reflexed; apex acuminate-cuspidate, acumen to ca. 2.5 × 0.5 cm; lamina surfaces bifacially olivaceous or fuliginous, copiously black-puncticulate, cystoliths white, numerous; domatia absent; venation camptodromous or brochidodromous, secondary veins 7–11(–14) per side, (3–)8– 20(–26) mm apart, arcuate, at the lamina center with divergence angles of (50–)70–85°; reticulum irregular, coarsely areolate, conspicuous; midrib and lateral veins channeled above, prominent beneath; tertiary nervation slightly raised on both sides. Inflorescence (known only from immature fruiting stage) terminal, paniculate, to ca. 10 × 7 cm, subpyramidal, verticillately branched, diffuse, ascending; axial surfaces black, striate; peduncle 17–35(–46) × 0.5–1.2 mm; axis to ca. 28 × 1 mm; lateral branches to ca. 24 × 1 mm; pedicels cylindrical, (2.5–)4.0–8.0(–9.5) × 0.4–0.7 mm, not articulate; bracts scalelike, cuneate-deltate, persisting, diverging; primary (axis) bracts (1.5–)2.0–3.0 × 0.6–1.2 mm; higher order bracts (0.6–)1.0–1.5 × 0.2–0.5 mm. Flowers unknown. Fruits globose-obovoid, 7–10 × 6.5–9.5 mm, compressed or not, exocarp black, set with pale raphides; calyx residue annulate or 5-dentate; pyrenes 2, sharply ridged on the back, crests linear (in cross-sectional view), 1–2 mm high; endocarp crustaceous, inconspicuously furrowed on the commissural face; preformed germination slits 2, marginal, extending 1/3–1/2 the pyrene length; endosperm not ruminate.

Field characters: —Branchlets cylindrical, fleshy, smooth, green or pinkish-brown; leaf-blades rugose, undulate, firm, dry-textured, adaxially mid-green, abaxially pale green to glaucescent; panicles erect, axial surfaces green; immature drupes dark green with white longitudinal lines.

Distribution: —Known thus far only from the type locality ( Fig. 5 ).

Habitat and ecology: — Nothofagus -emergent montane forest on doline karst, 1450–1660 m.

Phenology: —Fruiting in September.

Additional specimens examined: — PAPUA NEW GUINEA. Western Province: Muller Range, Expedition Camp 2, Nothofagus -emergent montane forest on doline karst, 5°39.610'S, 142°18.018'E, 1450 m ,

13 September 2009, Takeuchi, Ama & Gamui 24619 ( A, K, L, LAE); 5°39.385'S, 142°18.294'E, 1660 m , 17 September 2009, Takeuchi, Ama & Gamui 24710 ( A, K, LAE) ; Takeuchi, Ama & Gamui 24716 ( A, K, L, LAE) ; Takeuchi, Ama & Gamui 24723 ( A, BO, K, L, LAE) .

The 3-whorled leaves of P. ternatifolia are manifestly distinguishing, but the undulate leaf-blades and their stiffly-dry texture (in vivo) are also unusual for this genus. Even sterile plants can be easily recognized. Scores of individuals were seen on the limestone in spatial association with P. stolonifera .

Although the flowers of Psychotria ternatifolia are unknown, there is little doubt that the species is a Psychotria in the contemporary sense (sensu Davis & Bridson 2001, 2004, Davis et al. 2001). The terminal panicles, double pyrenes with sharply raised ridges, and marginal germination slits (2) on endocarps, are salient characteristics consistent with the assigned genus.

The CI Muller Range Expedition delivered extraordinary biological results from all participating disciplines (Richards in prep.). Bivouac 2 (type locality for Psychotria stolonifera and P. ternatifolia ) was an exceptional site, yielding novelties in Barringtonia , Begonia , Octamyrtus , and a remarkable four new species of Psychotria –-all with singular qualities permitting immediate determination as nova. The multidisciplinary discoveries now in hand are a convincing corroboration of conservation estimates regarding limestone environments in the southern ranges (e.g., Beehler 1993, Sekhran & Miller 1994).

Figures

FIGURE 5. Island of New Guinea. A, Muller Range, Bivouac 2, type locality for Psychotria stolonifera and P. ternatifolia. Shaded circle for visual emphasis only (not indicative of observed or potential distribution).

FIGURE 6. Psychotria ternatifolia. Habit, 1.5–2.0 m shrub in limestone forest (Takeuchi et al. 24716).

FIGURE 7. Psychotria ternatifolia. A, cylindrical stipule and two developing leaf whorls; B, stipule at lower node, basal part of cylinder persisting. A–B from Takeuchi et al. 24716.

FIGURE 8. Psychotria ternatifolia. A, fruiting branchlets, drupes immature; B, pyrene (9 × 8 mm, shown inverted), adaxial surface with germination slits on margins; C, pyrene, ridged abaxial surface. A–C from Takeuchi et al. 24621.