Areca dransfieldii Heatubun, 2011

Heatubun, Charlie D., 2011, Seven New Species of Areca (Arecaceae), Phytotaxa 28, pp. 6-26 : 12-13

Areca dransfieldii Heatubun , sp. nov.

Inflorescentiae structura A. tunku J.Dransf. & C.K. Lim affinis , sed caule caespitoso, inflorescentia cremea vel viride, floribus staminatis uniseriatim vel distichis, staminibus antheris dorsifixis, floribus foemineis solitariis in rachillis bene distincta.

Type:–– MALAYSIA. Borneo, Sarawak: Miri, Lambir National Park , Path from waterfall, 04º 12.209' N 114º 02.151' E , 1 April 2008, Heatubun & Rebi 901 (holotype K!, isotype SAR!) .

Small, slender, undergrowth palmlet, clustering (rarely solitary) with aerial branching, sometimes decumbent, stilt roots up to 40 cm. Stem 2−3 m tall, 1−2.5 cm diam.; internodes 1−4 cm long, green near tip and greyish at the base, nodal scars conspicuous, whitish brown. Leaves 5−7 in crown, pinnate, 100−165 cm long (including petiole); sheath tubular, 15−25 cm long, smooth, pale green to mid green; crown shaft well defined, 30−40 cm long and up to 2−2.5 cm diam.; petiole 25−81 cm long, channelled adaxially, rounded abaxially; rachis ascending but not arching, with adaxial longitudinal ridge, rounded abaxially; blade with regularly arranged leaflets, 9−23 leaflets on each side; leaflets somewhat descending, 1−2 main veins running parallel from the base to the tip, leaflets near petiole small, ca. 30 × 0.9 cm, slightly sigmoid, the middle leaflets about 46 × 2.1 cm and the terminal 27−29 × 1.1−1.8 cm, linear, pointed tip except for the terminal slightly oblique-lobed, papery, green adaxially and pale green abaxially. Inflorescence infrafoliar, erect, 10−14 cm long at anthesis, protandrous, branching to 1 order; peduncle 1−2.5 cm long, cream when young and turning green when mature; prophyll green, ca. 13 × 2 cm, elongate-triangular with pointed tip; rachis cream to green; rachis bracts not persistent; rachillae 4−7 and 7–11 cm long, very stiff and stout but not straight, flattened, elongate. Floral clusters distichous on rachillae, only one complete triad including female flower occurring at the base of each rachilla. Staminate flowers small, triangular, 3.5−6.3 × 1.8−2.2 mm, asymmetric, cream to pale green; sepals 3, low, about 1.5 × 1.5 mm; petals 3, triangular, 4.0−4.5 × 2.4−2.7 mm, striate; stamens 6, ca. 2.5 mm × 1.9 mm,; anthers dorsifixed, 2.1−3.0 × 0.5−1.0 mm, cream-coloured, elongate, longer than the filaments; filaments 1.2−1.5 × 0.4 mm, dark brown; pistillode low, ca. 0.5 × 0.5 mm, rounded. Pistillate flowers larger than the staminate, triangular, borne on the enlarged basal portion of rachillae, buds varying greatly in size depending on stage of development, just before anthesis 15.4−18.2 mm long and 10−11 mm wide, pale green to green; sepals 3, strongly imbricate, ca. 11.8 × 8 mm, triangular, asymmetrical; petals 3, imbricate, triangular, 5.5−12.6 × 2.5−5.2 mm; staminodes 3−4, irregular dentiform, 0.8 mm high. Fruits elongate, sickleshaped to ovoid, immature ca. 3.8 × 1 cm, apical stigmatic remains, perianth sometimes persistent; epicarp smooth, shiny, very thin, dark green when young; mesocarp fibrous, ca. 2.6 mm thick in immature fruit; endocarp very thin, adhering closely to seed. Seeds elongated with pointed tips, ca. 2.4 × 0.4 mm in immature fruits; endosperm ruminate; embryo basal. Eophyll bifid. ( Figures 4 & 6A ).

Distribution: —Central and Northern parts of Borneo (in Central Kalimantan of Indonesia, Sarawak and Brunei Darussalam).

Habitat: ––This palm grows in primary forest in mixed Dipterocarp forest. Other palms that occupy the same habitat are Areca insignis var. moorei (J.Dransf.) Dransfield (1984: 13) , Licuala sp. , and Pinanga spp.

Local Name: –– Pinang Nyaring and/or Pinang Bandang (local dialect in Central Kalimantan, Indonesia).

Uses:––Not recorded.

Conservation status: ––Near Threatened (NT). The extent of occurrence of this species is a large triangle that includes part of Central Kalimantan ( Indonesia), Lambir National Park ( Sarawak, Malaysia) and Ladan Hills Forest Reserve in Lamunin, Tutong ( Brunei Darussalam). However, it is known only from three wild localities, only two of which are protected. In Lambir, the species was observed to be rare. It is anticipated that this species will become increasingly threatened. Detailed population studies are needed to assess its conservation status more precisely.

Etymology: —The specific epithet to honour Dr. John Dransfield, former Head of Palm Research at the Royal Botanic Gardens, Kew, in recognition his great achievements in palm botany in general and to palm genus Areca in Borneo in particular.

Additional specimens examined: –– BRUNEI DARUSSALAM. Tutong, Lamunin, Ladan Hills Forest Reserve , 20 May 1995, Dransfield JD 7531 ( K!, BRUN) . INDONESIA. Borneo, Central Kalimantan Province: Upper Katingan River, ca. 60−80 km West of North West Tumbang Samba, Tumbang Merak , 20 November 1982, Mogea & de Wilde 3452 ( K!, L!, BO!) .

Discussion: –– Areca dransfieldii is similar to A. tunku Dransfield & Lim (1992: 81) in inflorescence structure, but it can be distinguished immediately by the clustering habit with aerial branching and sometimes decumbent stems. The inflorescence of A. dransfieldii is also cream when young, turning green when mature. The staminate flowers are mostly distichously arranged on the rachilla, with sepals free and stamens with dorsifixed anthers, and only one pistillate flower is borne on each rachilla. These features contrast with the purple inflorescence, uniseriate staminate flowers (spiral near the rachilla tip), and sepals united to form a cup-shaped calyx, sagittate anthers and more than one pistillate flower per rachilla in A. tunku . Moreover, this new palm is restricted to Borneo, whereas A. tunku is a species of Sumatra and the Malay Peninsula.

The swollen, flattened rachillae in the inflorescence structure suggest that A. dransfieldii has close relationships with A. bakeri and A. tunku . Dransfield & Lim (1992) mentioned that A. tunku is related to A. ahmadii Dransfield (1984: 4) and A. jugahpunya because of its swollen rachillae and purplish inflorescence, but in fact the rachillae of these two acaulescent species are long and cylindrical rather than truly flattened.

The differences between A. bakeri and A. dransfieldii have already discussed (see notes under A. bakeri ).

Figures

FIGURE 4. Areca dransfieldii. A. Stem, stilt roots and clustering habit. B. Middle portion of leaf. C. Apical portion of leaf. D. Inflorescence attached to stem just below the crown shaft. E. Detail portion of rachilla showing staminate and pistillate flowers in bud. F, G. Staminate flower whole and in section. H. Pistillate flower. I. Fruit still attached to rachilla. Scale bar: A–C = 6 cm; D = 3 cm; E = 1.5 cm; F, G = 2.5 mm; H = 7 mm; I = 2 cm. A–E, H from Mogea 3452; F–G from Dransfield JD 7531; I from Heatubun 901. Drawn by Lucy T. Smith.

FIGURE 6. A. Infructescence of Areca dransfieldii in Lambir National Park showing the stiff, straight rachillae with young fruits. B. Habit of Areca gurita with very few clustering stems and shoots, the palm cultivated at Semengoh Forest Arboretum near Kuching, Sarawak. C. Inflorescence of Areca gurita with the octopus tentacle-like rachillae. D. Young fruits of Areca gurita. Photos: A (John Dransfield), B–D (Charlie D. Heatubun).