Areca mogeana Heatubun, 2011

Heatubun, Charlie D., 2011, Seven New Species of Areca (Arecaceae), Phytotaxa 28, pp. 6-26 : 18-20

Areca mogeana Heatubun , sp. nov.

Arecae abdulrahmanii J.Dransf. habitu et inflorescentia structura similis, sed staminibus 6, floribus foemineis plus quam uno (–10) semper in rhachis sitis ab imum usque ad apicem, differt.

Type:–– INDONESIA. Borneo, Kalimantan Barat Province: Kabupaten Hulu Kapuas , Bentuang Karimun National Park , Mogea ITTO / BA 0605 (holotype SAR!) .

Solitary, small palm. Stem to 2 m tall, 5−8 mm diam.; internodes 2−2.5 cm long. Leaves 5−7 in crown, pinnate, to 50 cm long (including petiole); sheath tubular, ca. 10 cm long and 1.2−2 cm wide, striate, dark green to tinged red, tomentose, and brown to dark brown when dried, covered by punctiform scales, sparse or very dense near the petiole; crown shaft well defined, up to 17 cm long and 1 cm diam.; petiole 4−10 cm long, channelled adaxially, rounded abaxially, covered with thick brown indumentum; rachis very slender with adaxial longitudinal ridge, rounded abaxially; blade with irregularly arranged leaflets, 5−6 leaflets on each side, spacing between leaflets 3−6 cm; leaflets from narrow to slightly broad, leaflets near petiole 21−26 × 1−1.2 cm, linear, tip oblique acuminate, the middle leaflets about 23−25 × 0.5−2.2 cm, linear with 1−3 veins, the terminal leaflets broad, sometimes less broad than middle leaflets or sometimes flabellate, 13−16 × 1−15 cm, somewhat lanceolate with small cleft, papery, discolorous when dried, slightly pale adaxially and dark abaxially, with sparse brown ramenta along the mid-ribs in abaxial surface. Inflorescence infrafoliar, erect, small and slender, 10−12 cm long and 4.5−6 cm wide, protandrous, always branching to 1 order; peduncle 2−5 mm long, covered by thick brown indumentum; prophyll not seen; rachis also covered by brown indumentum; rachis bracts persistent, low, triangular; rachillae 5−8 (including main axis), divaricate, 7−10 cm long and ca. 2 mm wide near base, elongate, very slender, sinuous. Floral clusters spirally arranged on the rachillae, only one complete triad including female flower occurring at the base of each rachilla, except for terminal rachilla with 1−10 complete triads distributed to the half of the terminal rachilla length. Staminate flowers small, triangular, sickle-shaped when young to elongate at anthesis, 3.5−4.8 × 1.2−2 mm, asymmetric, cream to pale brown, sessile; calyx fused, triangular cup-shaped, ca. 1.2 × 2 × 0.8 mm at anthesis, 3-lobed; petals 3, fused near base, obovate, 2.5−3.5 × 1.2−1.75 mm at anthesis, striate; stamens 6, 2− 2.5 mm × 0.5 mm, basifixed; anthers ca. 5.3 × 0.6 mm, cream-coloured, elongate, sagitatte, shorter than the filaments; filaments ca. 0.5 mm long, dark brown, connective furcate; pistillode absent. Pistillate flowers larger than the staminate, triangular, ca. 4.5 × 2.5 mm (young stage); sepals 3, strongly imbricate, ca. 4 × 2.5 mm (young stage), triangular, asymmetrical; petals 3, imbricate, triangular, ca. 4 × 2.6 mm (young stage); staminodes absent. Young fruits light orange at the base becoming red and darker red at the tip, elongate, sickle-shaped, ca. 1.5 cm long and 0.3 cm wide, apical stigmatic remains, mature fruits not seen. ( Figure 5 ).

Distribution: ––This species is known only from Bentuang Karimun National Park in Kabupaten Hulu Kapuas, Kalimantan Barat Province, Indonesian Borneo.

Habitat: ––This palm was recorded growing in submontane forest at an elevation 1100 m above sea level.

Local name and uses: ––Not recorded.

Conservation status: —Vulnerable (VU D2). Areca mogeana occurs in submontane areas in Bentuang Karimun National Park in the Indonesian province of West Kalimantan. The protected forest area extends across the border to Lanjak Entimau Wildlife Sanctuary in Sarawak, Malaysia. However, with only four records from two localities, we infer that the populations are highly restricted and potentially vulnerable to stochastic events or human activities. However, further population study is still needed to assess the conservation status of this palm more precisely.

Etymology: —The specific epithet honours the collector of the type specimen Professor Johanis P. Mogea, palm botanist from Herbarium Bogoriense —LIPI (Indonesian Institute of Science) in recognition of his contribution to our understanding of the palm flora of Indonesia.

Additional specimens examined: –– INDONESIA. Borneo, Kalimantan Barat Province: Kabupaten Hulu Kapuas, Bentuang Karimun National Park , trail to Bukit Condong , 17 September 1997, Chai et al. ITTO / BA 0368 ( SAR!); Mogea ITTO / BA 0585 ( BO, SAR!); Mogea ITTO / BA 0595 ( BO, SAR!) .

Discussion: –– Areca mogeana is similar to A. abdulrahmanii and A. churchii in its solitary habit, dissected-leaf blade with several leaflets and its inflorescence structure with elongated-sinuous rachillae. The first differs from the last two in the arrangement of floral clusters especially complete triads and the staminate flowers, including number of stamens. In A. mogeana , only one complete triad including female flower occurring at the base of each rachilla, although the terminal rachilla may bear up to 10 complete triads, distributed to half the length of the rachilla. The staminate flowers are sessile, spirally arranged and contain six stamens. In contrast, A. abdulrahmanii has complete triads including female flowers along the lower third of all rachilla and bears conspicuously stipitate staminate flowers with 16 stamens. Areca churchii has only one complete triad on all rachillae and sessile staminate flowers with 11-12 stamens.

Figures

FIGURE 5. Areca gurita. A. Habit. B. Leaf. C. Inflorescence showing staminate and pistillate flowers in bud and their arrangement on rachillae. D, E. Staminate flower whole and in section. F. Fruit still attached to rachilla. Scale bar: A = 31.5 cm; B = 3 cm; C = 3.6 cm; D, E = 1.2 mm; F = 1.3 cm. All from Heatubun 896. Drawn by Lucy T. Smith.