Psychotria defretesiana (Takeuchi) Takeuchi

Takeuchi, Wayne, 2011, Additional notes on Psychotria (Rubiaceae) from the southern karst of Papua New Guinea: P. defretesiana comb. et stat. nov., P. dieniensis var. banakii var. nov., and P. stevedarwiniana sp. nov., Phytotaxa 24, pp. 19-27 : 20-22

Psychotria defretesiana (Takeuchi) Takeuchi , comb. et stat. nov. ( Fig. 1 )

Basionym: Psychotria leptothyrsa Miq. var. defretesiana Takeuchi, Harvard Pap. Bot. 14: 176. 2009. Type:— INDONESIA. Papua Province: Baitanisa (Kwaneha), margin of swampy forest, 2°13'53"S, 137°19'10"E, 20 m, 10 May 2007, Takeuchi & Mogea 21645 (holotype: BO; isotypes: A, K) .

Unbranched subshrubs, 10–60 cm tall, glabrous. Stems erect, terete, 1–8 mm diam.; surfaces longitudinally (to transversely) wrinkled, brownish black, prominently marked by discoid abscission scars or not, lacking lenticels, periderm usually not flaking; internodes 4–20(–60) mm long. Leaves cauline, 4–10 per stem, equal, horizontally spreading; stipules ovate-deltate, 3.5–6.5 × 2–4 mm, often attenuate, caducous; petioles 5–35(–55) × 0.5–2 mm, planoconvex; leaf-blades oblanceolate-obovate (or elliptic), 5.4–15(–22) × (2.2–) 4.2–12.5 cm, chartaceous; base cuneate; margin entire, reflexed or not; apex acuminate, obtuse or truncate; lamina surfaces brown or fuliginous, dull; raphides pusticulate; domatia absent; venation usually camptodrome, secondaries (5–)8–13 per side, arcuate, (3–) 7–31 mm apart, at the lamina center with divergence angles of (50–)60–85°; reticulum irregular, coarsely areolate; midribs prominulous on both sides; higher order nerves weakly raised (or impressed) above, more raised beneath. Inflorescence terminal, narrowly paniculate, ca. 10.5 × 6 cm, solitary (rarely 2–3 together), erect, axes compressed or angulate, nigrescent; peduncle 30–63 × 0.4–1.5 mm; primary axis 9–37(–53) × 0.2–0.7 mm; lateral branches 3–4- verticillate, 5.5–15(–22) × 0.3–0.6 mm; primary bracts early-falling, the scarious base or its abscission scar persisting; floral bracts (if present) scalelike, triangular; pedicels 1–2.5 mm long, not articulated. Flowers 4(– 5)-merous, heterostylous, black; calyx discoid-cupuliform, 0.5–1 × 1.5–2 mm, truncate or obscurely denticulate; corolla infundibular, tube length 2.5–3 mm, proximal tube diameter 0.7–1.2 mm, distal tube diameter (1.2–) 2–2.5 mm, pilose at the throat (hair-band 0.6–1.1 mm wide) otherwise glabrous, lobes triangular-ovate, ca. 1 × 1 mm, reflexed; stamens antesepalous, filaments 0.5–0.6 mm long, inserted within the hair-band, anthers oblongoid, 0.6–0.7 × 0.1–0.2 mm; disk dome-shaped, ca. 0.5 mm across, fleshy; style cylindrical, ca. 1.5 mm long, with stigma below the hair-band (short-styled form), or ca. 2.5 mm long and exserted (long-styled form); stigma 2-lobed, the lobes longer in the long-styled flower. Infructescence ca. 15.5 × 9 cm; pedicels ca. 3 × 0.3 mm. Fruits arranged in loose cymules, obovoid, (6–)8–10 × 5.5–8 mm; exocarp black, usually furnished with pale raphides; calyx residue 4–5-toothed; pyrenes 2, conspicuously (2–)3–4- ridged on the back; preformed germination slits 2, marginal, extending ca. 1/2 the pyrene length starting from the base; seed coat without ethanol soluble pigments; endosperm not ruminate.

Field characters: —Monocaulous dwarfs to 60 cm tall; stems often contorted-torulose, firm, black; leafblades chartaceous to fleshy-subcoriaceous, adaxially dark dull green, abaxially pale green or yellow-green; panicles terminal, erect, axes green or brownish green, verticillately branched; corolla barrel-shaped, obtuse in bud, white, lobes 4–5, reflexed at anthesis, white-hairy at the throat; styles dimorphic; fruits obovoidsubglobose, ca. 6 x 7 mm (Muller Range only—living drupes apparently larger in Mamberamo populations), green turning red when ripe; pyrenes (2–)3–4-ridged on the back, each ridge abruptly narrowed to a linear crest extending to the exocarp.

Distribution: —Originally discovered in the lower Mamberamo drainage of Papua Province ( Indonesia) and more recently recorded from the Muller Range of PNG ( Fig. 2 ).

Habitat and ecology: —Alluvial swamp understories at 20–50 m (Mamberamo), and lowland hill forest from 420–535 m (Muller Range). Occurring on seasonally inundated substrates, often rooted in mud, but also distributed across well-drained slopes. Restricted to densely shaded understories.

Phenology: —Fruiting in May (Mamberamo drainage); flowering and fruiting in September (Muller Range).

Additional specimens examined: — PAPUA NEW GUINEA. Western Province: Muller Range , Gugusu (Expedition Camp 1), lowland hill forest, 5°43.947'S, 142°15.973'E, 450 m, 7 September 2009, Takeuchi, Ama & Gamui 24504 ( A, LAE) ; 5°43.786'S, 142°15.669'E, 420 m, 8 September 2009, Takeuchi et al. 24525 ( A, K, LAE) ; 5°43.575'S, 142°15.630'E, 535 m, 9 September 2009, Takeuchi et al. 24560 ( A, K, LAE) ; 5°43.780'S, 142°15.813'E, 505 m, 10 September 2009, Takeuchi et al. 24571 ( A, LAE) .

When P. defretesiana was first described as a variety of P. leptothyrsa , only fruiting collections were available for study. The stipules and inflorescence were unknown. With recent acquisition of complete specimens from the Muller Range, the former assignment to the leptothyrsa complex has been reassessed. In the material now in hand, the short pedicels (1–2.5 mm long) and small flowers (corolla 2.5–3 mm long) are incompatible with any presumed relationship to P. leptothyrsa . Because of the differences now accruing, the former variety should stand as a separate species (see Table 1 ).

a. entries from Sohmer (1988: 157–168).

Psychotria is currently represented in New Guinea by at least seven monocaulous species, usually growing as subshrubs less than 1 m tall. The monocaulous-dwarf habit is less common among east Malesian Psychotria —for example in the Philippines there is only one species of similar stature and aspect to P. defretesiana and its allies ( P. pygmaea Merr. ; in Sohmer & Davis 2007: 94). Architectural reduction and simplification are frequently seen in other Papuasian genera (e.g., Ardisia hymenandroides [ Takeuchi 2009a], Cyathea lamoureuxii [ Takeuchi 2007b], Dysoxylum middletonianum [ Takeuchi 2009c], Harpullia mabberleyana [ Takeuchi 2011 in press], Zanthoxylum novoguineensis [ Hartley 1975], etc.) and are nearly always associated (though perhaps only coincidentally) with restricted geographic distributions.

Figures

FIGURE 1. Psychotria defretesiana. A, fruiting stem with galled vegetative structures; B, immature fruits; C, pyrene (9.5 × 7 mm) in proximal-oblique view, the preformed germination slits appearing as a mouthlike orifice. Each of the (2–)3–4 dorsal ridges is abruptly narrowed to a linear crest extending to the exocarp. A–B from Takeuchi et al. 24571; C from Takeuchi & Mogea 21578.

FIGURE 2. Island of New Guinea. Collection localities. A, Baitanisa (lower Mamberamo basin), type locality for Psychotria leptothyrsa var. defretesiana; B, Muller Range, type locality for P. dieniensis var. banakii and P. stevedarwiniana. Overlay (shaded area) shows distribution of the southern karst formations.