Helicia woxvoldiana W.N.Takeuchi, 2014

Takeuchi, Wayne, 2014, A distinctive addition to the tree flora of Papua New Guinea: Helicia woxvoldiana sp. nov. (Proteaceae), a large-flowered myrmecophyte from the upper Sepik, Phytotaxa 172 (2), pp. 94-100 : 94-99

Helicia woxvoldiana W.N.Takeuchi , sp. nov. ( Figs. 2–5 )

Inter speciebus congeneribus Papuasiae floribus multo majoribus usque ad 39–46 mm longis statim distinguitur.

Type: — PAPUA NEW GUINEA. West Sepik Province: upper Sepik River basin, hill forest with scattered regrowth, 4°39.184’S, 141°43.456’E, 840 m, 5 December 2009, Takeuchi, Ama & Gambia 25095 (holotype A!; isotypes BO!, CANB!, K!, L!, LAE!, US!).

Canopy trees to 30 m tall. Branchlets compressed, conspicuously angulate, (4–) 6–10 mm wide near the top, hollow, marked by numerous ant-entry holes, straight-ascending, firm; indumentum strigulose, reddish-brown, lepidote or not, glabrescent; surfaces gray, fuliginous, or dull black, usually without lenticels; abscission scars lax, elliptic-crateriform, 8–14 × 4–8 mm; internodes to ca. 4 cm long. Leaves spirally inserted, crowded, obliquely spreading; petioles (4–)8–20 × 3–13 mm, swollen, cerebriform-wrinkled, black, not articulated; leaf-blades oblanceolate (or subelliptic), (24.5–)34–63 × (7–) 10–16.2 cm, firm, adaxially gray-fuliginous (or black), glabrous, abaxially dark reddish-brown, minutely appressed-hairy, indumentum persisting; lamina base attenuate; margins entire (lacking serrations even on the youngest blades and on juvenile plants); apex acute to acuminate; venation brochidodromous (or camptodromous); midrib prominently raised above, keeled beneath; secondaries (15–)20–27(–32) per side, at the lamina center with divergence angles of (40–)55–75°, 10–31 mm apart, gradually curved towards the margin, closing by inframarginal looping nerves or not, partial intersecondary veins often interposed between the main laterals; tertiary venation conspicuous, reticulate, tessellate, areoles irregular; all higher order nerves distinctly raised on both sides. Inflorescence below the leaves, racemiform, subsessile or with peduncle to 16 × 4 mm, solitary (rarely binate), (7–)10–20 × 8–11 cm, rufous-strigulose over all exterior surfaces; axis 7–15.8 × 0.3–0.7 cm, distally tapered, longitudinally lined or furrowed, inflated, ant-inhabited; bracts/bracteoles scalelike, linear-deltate, ca. 0.5–1 mm long, falling after anthesis. Flowers 4-merous, paired, glabrous on all interior surfaces, congested; floral peduncles 1.5–4 × 0.7–1.2 mm; pedicels cylindrical, 3.7–5.2 × 0.5–0.8 mm, not articulated; perianth initially tubular, 39–46 × 1.5–2 × 0.5–0.8 mm (i.e., length including limb × basal diameter × mid-tube diameter), limb ellipsoid-oblongoid in bud, 7–10 × 0.9–1.5 mm, tepals valvate, petaloid, free, strap-shaped, circinnately curled at anthesis; disk glands united, collectively cupuliform (1.5– 1.8 mm diameter), brunnescent, papery, crenate; stamens adnate to the limb base, sessile or nearly so, anthers 6–7 × 0.5–0.7 mm, introrse, ca. 0.5–1 mm apiculate at the top; ovary ovoid-conoid, 1.2–2 × 1–1.3 mm, glabrous, sulcate, jet black, style 29–32 × 0.2–0.3 mm exclusive of a discolorous 7–9 × 0.2–0.6 mm claviform apex, stigma obscure. Infructescence axis 8–24 × 0.6–1 cm, copiously marked by abscission scars, pedicels accrescent, to 9 × 2 mm. Fruits drupaceous, ellipsoid-globular, 5.5–6 × 4.6–5 cm when ripe, indehiscent.

Etymology: — Helicia woxvoldiana is named after ornithologist Iain Woxvold, team leader of the 2009–2010 Sepik surveys and the author’s frequent associate on multidisciplinary expeditions in New Guinea.

Field characters: —Canopy trees 15–30 m tall, buttressed or with basal swell, outer bark pale brown, wood straw; branchlets ant-inhabited, prominently ridged; leaf-blades coriaceous or firm, dry-textured, bifacially green, purple in flush; flowers white, very fragrant (recalling honeysuckle); fruits to 7 × 5.5 cm when ripe, resembling a potato in size and appearance, exocarp light brown, mesocarp purple.

Distribution: —Known from the foothill zone in West Sepik Province, near historical localities of the Kaiserin- Augusta-Fluss Expedition of 1912–13.

Habitat and ecology: —Hill and low-montane forest, sightings from 750–1200 m (collections from 810–880 m).

Phenology: —Flowering and fruiting from December to February.

Additional specimens examined (paratypes): — PAPUA NEW GUINEA. West Sepik Province: upper Sepik River basin, hill forest with scattered regrowth, 4°39.129’S, 141°43.362’E, 880 m, 2 December 2009, Takeuchi, Ama & Gambia 25028 (A!, LAE!) ; Takeuchi , Ama & Gambia 25031 (A!, BO!, CANB!, K!, L!, LAE!); hill forest, 4°41.895’S, 141°45.282’E, 810 m, 17 February 2010, Takeuchi, Ama & Gambia 25747 (A!, L!, LAE!) .

The new species is distinguished by a striking inflorescence composed of exceptionally-sized flowers to 46 mm long. The largest perianth (30–35 mm long) in New Guinea Helicia was previously found in H. insculpta Sleumer (1939: 141) . Although H. woxvoldiana keys (in Foreman 1995) to H. saurauioides Sleumer (1955a: 46) , the novelty can be easily separated from that congener with the following couplet:

1a Myrmecophytic canopy trees; leaf-blades to 63 × 16.2 cm, margins always entire; inflorescence below the leaves, pedicels 3.7–5.2 mm long; fruits ellipsoid-globular, 5.5–6 × 4.6–5 cm ........................................................................................ Helicia woxvoldiana

1b Non-myrmecophytic treelets; leaf-blades to 35 × 13 cm, margins serrate; inflorescence axillary, pedicels 1 mm long; fruits obovoid, 2.5 × 1.5 cm ........................................................................................................................................................ Helicia saurauioides

In H. woxvoldiana , ants are present in branches, petioles, midribs, and inflorescence axes, as evidenced by the numerous entry holes on those structures. Myrmecophily is uncommon among Papuasian congeners—only H. finisterrae Lauterbach (1913: 332) , H. macrostachya Lauterbach (1913: 332) , H. neglecta Diels ex Sleumer (1939: 135) , H. obtusata Sleumer (1939: 139) , and H. olivacea Sleumer (1939: 136) are known to exhibit such associations ( Foreman 1976, 1995).

Although numerous novelties have been revealed by recent botanical surveys, the modern discoveries are almost exclusively comprised of herbs, vines, or small shrubs ( Takeuchi 2009). Helicia woxvoldiana is one of the few canopy trees discovered by contemporary exploration. Judging from this documentation imbalance, tall arborescent taxa in New Guinea may be close to a complete accounting—primarily because of their visual apparency, but also due to the comprehensive inventories achieved by early forestry surveyors in New Guinea (e.g., the NGF- and Boswezen Neeuwgini-series collectors).

Notwithstanding its late discovery, H. woxvoldiana is a common species and is not presently susceptible to any conservation threat(s). Extensive sapling recruitment was evident in all the areas of observed occurrence, particularly in the regrowth resulting from natural agencies (e.g., windthrows, landslides) or from anthropogenic activities. The species is almost certainly more widespread than presently recognized. Extensions in geographic range can be expected as future investigators enter other upland environments within the Sepik basin.

Figures

FIGURE 2. Helicia woxvoldiana W.N.Takeuchi. Alois Gambia with a flowering branch from the type gathering (Takeuchi, Ama & Gambia 25095).

FIGURE 3. Helicia woxvoldiana W.N.Takeuchi. A, ant entry holes on branchlet; B, entry hole on abaxial midrib. A–B from Takeuchi, Ama & Gambia 25095.

FIGURE 4. Helicia woxvoldiana W.N.Takeuchi. A, mature fruit (7 × 5.5 cm in vivo); B, branch with pre-anthetic inflorescences; C, immature fructescence. A from Takeuchi, Ama & Gambia 25095; B from Takeuchi, Ama & Gambia 25028; C from Takeuchi, Ama & Gambia 25031.

FIGURE 5. Helicia woxvoldiana W.N.Takeuchi. Anthetic flowers from the attractive and fragrant inflorescence. Disk glands are clearly connate. From Takeuchi, Ama & Gambia 25095.