Areca bakeri Heatubun, 2011

Heatubun, Charlie D., 2011, Seven New Species of Areca (Arecaceae), Phytotaxa 28, pp. 6-26 : 6-10

Areca bakeri Heatubun , sp. nov.

A ceteris speciebus Borneensibus habitu acaule–caespitoso, petiolis longis 100–105 cm, inflorescentia erecta rigida, floribus staminatis distichisis, floribus foemineis singulariter dispositis distincta.

Type :––CULTIVATED. Borneo , Sarawak: Cultivated at the Semengoh Forest Arboretum , 22 April 1996, Baker et al. 716 (holotype K!, isotypes KEP, SING, SAR!) .

Undergrowth palmlet densely clustering with ca. 20 stems in a clump to 1 m in height. Stem subterranean to very short (to 1 cm), ca. 2 cm diam.; internodes very close (0.5−1 cm long), not conspicuous, covered by marcescent leaf sheaths. Leaves 4−6 in crown, litter trapping, pinnate, 140−200 cm long (excluding petiole); sheath tubular, 20−31 cm long and 3−4 cm wide, smooth, not fibrous, yellowish green; crown shaft not well defined, up to 40 cm long and up to 4 cm diam.; petiole 100−105 cm long, channelled adaxially, rounded abaxially; rachis ascending but not arching, with adaxial longitudinal ridge, rounded abaxially; blade with slightly irregularly arranged leaflets, 7−8 leaflets on each side; basal leaflets ca. 52 × 6.4−14 cm, with 7−9 folds, sigmoid, the middle leaflets 57−59 × 4.5−10 cm, with 5−9 folds, slightly sigmoid and the terminal leaflets ca. 42 × 11 cm, with up to 11 folds, slightly sigmoid, tips pointed except for the terminal leaflets slightly oblique-lobed, papery, discolorous, darker adaxially than abaxially. Inflorescence infrafoliar, erect, bursting out among marcescent sheaths, 20−26 cm long and 4.5−12.5 cm wide, protandrous, branching to 1 order; prophyll elongated, up to 26 cm long, ca. 3 cm wide, two-keeled, leathery, cream, light green near the apex; peduncle 6−10 cm long, pale yellowish green; rachis yellowish green; rachis bracts caducous; rachillae 11−13, 8.5−14 cm long and 3.5−5.6 mm wide, very stiff, stout and straight, slightly swollen and flattened near the base, pale green, elongate. Floral clusters distichous on rachillae, only one complete triad including female flower occurring at the base of each rachilla. Staminate flowers small, sessile, triangular, ca. 6.2 × 3.1 mm, asymmetric; sepals 3, low; petals 3, triangular, small, striate; stamens 6, small, anthers shorter than the filaments; filaments slender, elongate; pistillode ca. 2.5 × 1.0 mm, pointed. Pistillate flowers larger than the staminate, triangular, borne on the enlarged basal portion of rachillae, only one flower on each rachillae, buds varying greatly in size depending on stage of development, ca. 17 mm long and 8 mm wide in late anthesis; sepals 3, strongly imbricate, ca. 7 × 7 mm, triangular, asymmetrical, striate; petals 3, imbricate, triangular, ca. 12.5 × 6.5 mm, striate; gynoecium ca. 10.5 mm long and 4 mm wide at the base; stigma ca. 8 mm long, pointed with 3 lobes, split 8 mm to the base; style ca. 1.5 mm long; staminodes ca. 6, irregularly dentiform, 0.5−1 × 0.25−0.5 mm. Fruits elongate, sickle-shaped, 6.0−6.5 × 1.3−1.45 cm (young fruits), beak 1.4−1.5 mm; epicarp smooth, shiny, dark green (young), mature fruits not known. Seed very young; endosperm sparsely ruminate. ( Figures 1 & 2 ).

Distribution: —Only known from very limited collections from Miri (4 th) Division of Sarawak in northern Borneo and from a plant cultivated in Semengoh Forest Arboretum near Kuching.

Habitat: ––This species grows in primary mixed dipterocarp forest in river valleys at about 42 m above sea level.

Local names: —Not recorded.

Uses: —Traditional uses are not known. However, the palm has potential as an ornamental.

Conservation status: —Critically Endangered (CR B2ab). This palm meets the criteria for the threat category “Critically Endangered” ( IUCN 2001) because it is known only from one locality at Ulu Anap, Tatau, Miri , Sarawak and its area of occupancy is estimated to be less than 10 km 2. In addition, rain forest is highly threatened in general in Sarawak, for example due to logging activities and oil palm plantation, and thus a decline in extent of occurrence, area of occupancy and quality of habitat is inferred. One clump of this palm has been successfully established and fruits in Semengoh Forest Arboretum as part of the ex situ conservation program run by Biodiversity Research Centre, Sarawak Forestry Corporation (previously known as Sarawak Forestry Institute).

Etymology: —This new Areca is named after Dr. William J. Baker, the Head of Palm Research at the Royal Botanic Gardens, Kew and the collector of the type specimen.

Additional specimens examined: –– MALAYSIA. Borneo, Sarawak: Miri (4 th) Division, Tatau , Ulu Anap , 22 June 1982, Mokhtar & Othman S 44726 (K!, L!, KEP, SAN, SAR!). CULTIVATED. Borneo, Sarawak: Semengoh Forest Arboretum, 01º 24.059ʹ N 110º 19.423ʹ E, 31 March 2008, Heatubun & Kuda 903 (K!, SAR!).

Discussion: –– Areca bakeri is similar to A. jugahpunya Dransfield (1984: 13) in its acaulescent, clustering habit and broad leaflets, but can immediately be distinguished by the densely clustering habit with ca. 20 stems in the clump, very long and slender petioles, leaflets more papery and the tips of terminal leaflets slightly obliquely lobed. The inflorescence of A. bakeri is more similar to A. dransfieldii than to A. jugahpunya , especially with its swollen-flattened rachillae and only one pistillate flower on each rachilla. However, A. bakeri is easily distinguished from A. dransfieldii by its acaulescent litter-trapping habit, leaves with very long petioles (100–105 cm) and broad leaflets, and infrafoliar inflorescences borne among marcescent leaf sheaths with somewhat long peduncles. In contrast, A. dransfieldii has conspicuous stems with aerial branching, leaves with long petioles (25–81 cm) and numerous finely-regular leaflets, and infrafoliar inflorescences with short peduncles.

Figures

FIGURE 1. Areca bakeri. A. Apical portion of leaf. B. Middle portion of leaf. C. Basal portion of leaf and petiole attached to crown shaft. D. Inflorescence attached to stem just below the crown shaft and showing acaulescent habit. E, F. Staminate flower whole and in section. G. Pistillate flower. Scale bar: A, B = 8 cm; C, D = 3 cm; E, F = 2.2 mm; G = 7 mm. A–D from Baker et al. 716; E–G from Mokhtar & Othman S 44726. Drawn by Lucy T. Smith.

FIGURE 2. Areca bakeri. A. Acaulescent habit with densely suckering clump; the palm was mis-identified as A. jugahpunya, as shown on the label. B. Infructescence bursting out from the marcescent leaf sheaths. C. Prophyll, inflorescence, infructescence and seedling. All photos were taken from the specimen cultivated at Semengoh Forest Arboretum near Kuching, Sarawak, Malaysia. Photos: A (Charlie D. Heatubun), B–C (John Dransfield).