Areca triginticollina Heatubun, 2011

Heatubun, Charlie D., 2011, Seven New Species of Areca (Arecaceae), Phytotaxa 28, pp. 6-26 : 24-26

Areca triginticollina Heatubun , sp. nov.

Species nova Sumatrana A. tunku habitu et A. jugahpunya inflorescentiae structura similis, sed floribus staminatis spiraliter dispositis, differt.

Type:–– INDONESIA. Sumatra, Riau Province: Indragiri Hulu Regency, Seberida District , Bukit Tiga Puluh National Park , 10 km North of Jambi border, 5 May 1991, Gundersen et al. 15 (holotype K!, isotype BO) .

Solitary, understorey tree palm. Stem 2−5 m tall, 3−4 cm diam.; internodes 3−6 cm long. Leaves 11−12 in crown, pinnate, 95−110 cm long (including petiole); sheath tubular, 20−25 cm long and 6−10 cm wide, smooth, yellowish-green to grey brown, covered in punctiform brown indumenta, sparse or very frequent near the petiole; crown shaft well defined, up to 50 cm long and 15 cm diam., sometimes swollen; petiole very short or lacking, channelled adaxially, rounded abaxially; rachis with adaxial longitudinal ridge, rounded abaxially; blade with irregularly arranged leaflets, 6−12 leaflets on each side, spacing between leaflets 6−7 cm; leaflets variable from narrow to broad, leaflets near petiole shorter than others, ca. 32 × 5 cm, slightly sigmoid, the middle leaflets about 47−55 × 4.5−8 cm, with up to 4 folds, the terminal leaflets broad, 22−33 × 7.5−14 cm, linear, tips pointed except for the terminal leaflets with notched tips, papery, slightly dark adaxially and pale abaxially. Inflorescence infrafoliar, erect, 15−22 cm long and 5−6 cm wide, protandrous, branching to 1 order (sometimes 2 at basalmost rachilla); peduncle 2−5 cm long, cream to warm yellow; prophyll 14−24 × 2.5−7 cm, borne about 1/2 way up the peduncle, lanceolate, 2-keeled, boat shaped, papery, cream to light brown, entirely enclosing the inflorescence, then splitting longitudinally and disintegrating into numerous fibres, still persistent after staminate anthesis; rachis cream-coloured; rachis bracts not persistent; rachillae ca. 13, 10−13 (−15) cm long, very stiff, flattened, wide or swollen near base, zigzag, slightly congested. Floral clusters distichous on the rachillae, complete triads including female flowers occurring from the base to half the length of each rachilla, 3–6 complete triads per rachilla. Staminate flowers small, triangular, sickle-shaped when young to elongate at anthesis, 6.9−9.3 × 2.5−4 mm, asymmetric, cream to pale brown; calyx fused, cup-shaped, ca. 2.3 × 2.5 mm at anthesis, 3-lobed, the lobes triangular about 1.6 × 1 mm; petals 3, fused near base, lanceolate, 5.1−6.7 × 1.3−2 mm at anthesis, striate; stamens 6, ca. 6.7 mm × 0.6 mm, elongated, basifixed; anthers ca. 5.3 × 0.6 mm, creamy, elongated, sagittate, shorter than filaments; filaments ca. 6.7 × 0.3 mm, joined to anther from base to tip, dark brown; pistillode absent. Pistillate flowers larger than the staminate, triangular, buds varying greatly in size depending on stage of development, 10−13 mm long and 5−6 mm wide at anthesis; calyx with 3 sepals; sepals free, strongly imbricate, ca. 7.2 × 6.4 mm at anthesis, triangular, asymmetrical; petals 3, imbricate, triangular, ca. 13 × 5 mm at anthesis; staminodes lacking. Fruits (young) green, elongate, apical stigmatic remains, mature fruits not seen. ( Figure 10 ).

Distribution: —This species is only known very few collections from Bukit Tiga Puluh National Park in Riau Province in South Western of Sumatra, Indonesia.

Habitat: ––Recorded growing on a ridge crest on primary forest at 120−250 m above sea level.

Local Name and uses: —Not recorded.

Conservation status: ––Endangered (EN B1ab, B2ab). Areca triginticollina occurs in a restricted area within Bukit Tiga Puluh National Park, Riau, Sumatra. This protected area is small and adjacent to forest production areas. Thus, despite its protected status, the habitat of this lowland palm area is at risk.

Etymology: ––The specific epithet refers to the type locality of this new palm in Taman Nasional Bukit Tiga Puluh in Riau, Sumatra, Indonesia. Triginticollina in latin mean thirty hills or bukit tiga puluh in Indonesian.

Adiditional specimens examined: –– INDONESIA. Sumatra, Riau Province: Indragiri Hulu Regency, Seberida District, Bukit Tiga Puluh National Park , 5 km West of Kelesa, 15 May 1991, Gundersen et al. 32 ( K!, BO); Talang Langkat village , 9 August 1991, Witono et al. 146 ( K!, BO!); 10 August 1991, Witono et al. 150 ( K!, BO!) .

Discussion: –– Areca triginticollina is similar to A. tunku in many respects, including the litter-trapping crown and the inflorescence sometimes bursting out from the persistent prophyll. However, they can be distinguished by inflorescence structure. Areca triginticollina has swollen-flattened rachillae, which are folded in a zigzag fashion, this corresponding to the position of the pistillate flowers; also the triads are distributed along half of the length of the rachilla. Areca tunku has erect, stiff and rigid rachillae and triads with female borne at the base of the rachillae only. Although the inflorescence structure is slightly similar to A. jugahpunya , the species are totally different in habit.

Figures

FIGURE 10. Areca triginticollina. A. Apical portion of leaf. B. Middle and basal portion of leaf. C. Basal portion of leaf and leaf sheath showing absence of petiole. D. Prophyll with disintegrating fibrous mass. E. Inflorescence. F. Details of rachilla showing staminate and pistilate flowers in bud and their arrangements. G. Pistillate flowers at anthesis on rachillae. H, I. Staminate flower whole and in section. J. Pistillate flower in section. Scale bar: A–C = 6 cm; D, E = 3 cm; F = 1.5 cm; G = 2.5 cm; H–J = 4 mm. A–F, H–J from Witono et al. 150; G from Gundersen et al. 15. Drawn by Lucy T. Smith.