Dichapetalum timoriense (DC.) Boerl.

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Handleiding tot de Kennis der Flora van Nederlandsch Indie 1(1): 199 (1890).

Chailletia timoriensis DC., in Candolle, A.P. de (ed.), Prodromus Systematis Naturalis Regni Vegetabilis 2: 57 (1825). Type citation: “in ins. Timor. [insula Timoria]”. Type: Indonesia or Timor-Leste, s. dat., leg. ign. s.n. Probable syntypes: Timor, s. dat., leg. ign. s.n. (P-P04764482, P-P04764483, P-P04764485, P-P04764491); Timor, s. dat., Riedlé s.n. (P-P04764486); Timor, Voyage de Baudin, s. dat., leg. ign. s.n. (P-P04764487); Is Timor, s. dat., leg. ign. s.n. (G-G00476613); Timor, s. dat., leg. ign. s.n. (K-K000657824, K000657825); Timor, s. dat., leg. ign. s.n. (L-L0931088); Timor, s. dat., leg. ign. s.n. (NY-NY00000904).

Dichapetalum timorense W.E.Cooper, in W.E. Cooper & W.T. Cooper, Fruits of the Australian Tropical Rainforest: 150 (2004), orth. var.

For a more complete synonymy refer to Leenhouts (1957).

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Figure 5. Dichapetalum timoriense: A. Hermaphrodite inflorescence (Russell-Smith 10736 & Lucas [DNA]); B. Ripe fruit (Brennan 10298 [DNA]); C. Petiole showing short taper onto abaxial primary vein as well as glands on leaf blade (Russell-Smith 10736 & Lucas [DNA]). Photos: A & C J. Russell-Smith. B. K. Brennan

Monoecious shrub or scrambler becoming a vine, climbing with the aid of some backward-arching branches; twigs grey or purplish, tomentose becoming glabrous, lenticellate; indumentum white; stipules linear or very narrowly triangular, 4–6 mm long, sericeous; petioles 3–9 mm long (not including taper); taper along abaxial midrib extending for 1.8–2.5 mm long, truncate at junction with primary vein, tomentose, grey-brown. Leaves mostly oblong or oblanceolate, rarely elliptical or obovate, 70–180 mm long and 15–55 mm wide; coriaceous; adaxial surface with appressed hairs on primary and secondary veins, becoming glabrous; abaxial surface with appressed hairs on midrib and margin, becoming sparse on secondary veins; both surfaces usually with up to 15 glands near base and up to 20 may be scattered across the blade, discolourous; base sometimes asymmetrical, cuneate or slightly rounded; apex acute, often with a short soft apiculum c. 0.25 mm long or rarely narrowly rounded; margin repand; venation camptodromous proximally and brochidodromous distally; primary vein slightly raised adaxially and distinctly raised abaxially; secondary veins 7–9 pairs at 50º to midrib, slightly raised; tertiary venation reticulate, densely pitted within each reticulation on abaxial surface. Hermaphrodite inflorescence an axillary or terminal repeatedly dichotomously branched panicle or cyme, (often in pairs or rarely 3 arising from the same axil) up to 35 mm long; peduncle 8–11 mm long, tomentose; pedicels 2.5–5 mm long, tomentose; bracts at each junction along the rachis, linear, 2–3.5 mm long and c. 0.5 mm wide, tomentose. Flower fragrance not noted, diameter c. 5 mm and 2.5–2.75 mm long; calyx hemispherical at base; sepals elliptical, c. 2.5 mm long and 1.25 mm wide, abaxially tomentose throughout, adaxially tomentose in upper 1/2 to 2/3, green, white or cream; petals rhomboid, c. 2 mm long and 1.4–1.6 mm wide, glabrous, white or cream, apex emarginate to c. 0.6 mm; stamens 5, c. 1.5 mm long; filaments strap-shaped, glabrous; anthers introrse; staminodes spathulate or strap-shaped, apex 2-lobed with lobes rounded or mostly acute, glabrous, c. 0.75 mm long; ovary globose, 5-lobed, densely tomentose, 2-celled, c. 1.5 x 1.5 mm; style sparsely minutely hairy, c. 1.5 mm long; stigma 2-forked, rays c. 0.3 mm long. Fruit peduncle c. 2.5 mm long, tomentose; pedicel 0.5–2 mm long, clothed in erect velvety hairs interspersed with some longer hairs, drupe oblate or globular, 2-celled (unless one is aborted), 4-sutured, 15.5–17.5 x 22 x 14.5 mm, velvet-tomentose, yellowish-green, mesocarp c. 2 mm thick; seeds 1 or 2. Figs. 1 & 5

Specimens examined: Northern Territory: Bowerbird Gorge, Magela Creek, Aug 2018, Brennan 1373 (DNA); South Magela Gorge, April 2014, Brennan 10298 (DNA); Berry Springs, Russell-Smith residence, cultivated, Nov 2017, Cowie 14342 & Yee Wen Low (DNA); Magela Creek, upper catchment, April 1995, Brennan 5650 & Cowie (DNA); Upper Magela Creek valley, Arnhem Land, May 1991, Rusell-Smith 8471 & Brock (DNA); Lightening [Lightning] Dreaming, Arnhem Land, Feb 1984, Dunlop 6583 & Wightman (CNS, DNA); Magela Creek Falls, Kakadu National Park, March 2022, Dixon 1031 & Leach (DNA).

Diagnostic features. Dichapetalum timoriense is distinct by twigs grey or purplish; stipules linear or narrowly triangular; leaves mostly oblong or oblanceolate; glands numerous; inflorescences long-peduncled and often in pairs, repeatedly dichotomously branched; disk lobes glabrous; ovary tomentose; fruit a drupe without sutures, 2-celled, velvet-tomentose.

Phenology. Flowers have been recorded in December and February, and fruit in April and May.

Distribution & habitat. Within Australia, Dichapetalum timoriense is restricted to the Northern Territory in protected sandstone gorges with Allosyncarpia dominated vine forest in Kakadu National Park and Arnhem Land, especially the East Alligator River catchment, Lightening Dreaming and Magela Creek.

Conservation Status. Based on known localities, the Extent of Occurrence (EOO) of Dichapetalum timoriense is estimated to be between 113 km|^2^| (specimens) and 238 km|^2^| (observations) with an Area of Occupancy (AOO) of between 28 and 58 km|^2^| (calculated with GeoCat; Bachman et al. 2011). Sufficient information is not available to make good estimates of population size although it is likely that the NT population is <10 000 individuals. Regionally, the species is represented in conservation reserves (Kakadu National Park and Warddeken Indigenous Protected Area) although no targeted monitoring or management actions are known to have been undertaken for this species over the last decade.

Based on its EOO and AOO and a severely fragmented distribution or small number (estimated between 5 and 10) of localities (with severe wildfire as the most serious plausible threat) it continues to meet the thresholds for Criteria B1a + B2a (IUCN 2012).

The risk posed by recent megafires discussed under D. aurantiacum also applies to D. timoriense. Given this global phenomenon, it is plausible that an inferred or projected decline in habitat area, extent or quality could be reasonably expected into the future (Sub-criterion b(iii)). Given the most likely preferred habitat for this species is on monsoon forest margins, the area’s most sensitive to changed fire behaviours, it would also not be unreasonable to expect a corresponding projected decline in the number of mature individuals at known locations (Sub-criterion b(v)). Consequently, D. timoriense preliminarily satisfies the requirements for listing as VU B1a,b(iii) + B2(a,b(iii) under the IUCN criteria (IUCN 2012) at the National/regional scales.

Etymology. The species epithet refers to the type locality, the island of Timor.