Areca churchii Heatubun, 2011

Heatubun, Charlie D., 2011, Seven New Species of Areca (Arecaceae), Phytotaxa 28, pp. 6-26 : 10-12

Areca churchii Heatubun , sp. nov.

Palma solitaria , caude gracillimo, inflorescentia fortiter effusa, floribus staminatis spiraliter dispositis, sepalis elongatis, staminibus 11−12, filamentis interdum tortilis et circinatis, floribus foemineis semper singulis in rachillis, 1−2 cm longioribus in rachillis basaliter dispositis, differt.

Type:–– INDONESIA. Borneo, West Kalimantan Province: Serawai , Sungai Merah , 2 km to W of camp along Gaharu trail towards Sungai Labang, surrounding ridges and valleys, February 1995, Church et al. 2083 (holotype K!, isotypes BO!, A) .

Solitary, slender, undergrowth palmlet. Stem up to 2 m tall, ca. 2 cm diam.; internodes 1−2 cm long. Leaves ca. 8 leaves in crown, pinnate, 95−115 × 65−90 cm long; sheath tubular, not fibrous, up to 20 cm long, striate; crown shaft well defined, 30−40 cm long, 3 cm diam.; petiole up to 65 cm long, channelled adaxially, rounded abaxially, 5−6 mm wide and 6−7 mm thick; rachis with adaxial longitudinal ridge, rounded abaxially; blade with irregularly arranged leaflets, 5−7 leaflets on each side, 3−11 cm spacing between leaflets, leaflets with 2−7 folds, leaflets near petiole ca. 46.5 × 1.5 cm, slightly sigmoid and tip oblique-lobed, middle leaflets 47−51 × 5−5.5 cm, and terminal leaflets about 33 × 7 cm, tips bifid with lobes 0.5−2 cm depth, papery, dark adaxially and pale abaxially when dried. Inflorescence infrafoliar, erect, 20−25 × 14−24 cm at anthesis, protandrous, branching to 1 order; peduncle 2−2.2 cm long, prophyll not seen; rachis pale yellow at the base and peach-coloured towards the apex and light brown when dried; rachis bracts caducous; rachillae 13−17, 12− 20 cm long, slender, spreading, covered by minute light brown to chocolate-brown indumentum, elongate, sinuous to slightly zigzag in appearance. Floral clusters spirally arranged on the rachillae, only one complete triad including a female flower occurring near the base of each rachilla. Staminate flowers relatively large, triangular, elongate, 8.5−10 × 2−2.5 mm, asymmetric, sessile; calyx cup-shaped, 1.5−2.3 mm wide and 2 mm high, 3-lobed, the lobes ca. 1.25 × 0.5 mm; petals 3, valvate, elliptic to slightly spathulate, ca. 7.7 mm long and 1.8 mm wide at anthesis, connate at the base, cream-coloured; pistillode lacking; stamens 11−12, 5− 6.5 mm long, elongate, basifixed; anthers 2.5−3.5 mm long and 0.3 mm wide after anthesis, cream-coloured; filaments 2−3.5 mm long and 0.2 mm wide, dark brown, sometimes twisted and coiled, free near corolla and connate at the centre. Pistillate flowers larger than the staminate, triangular, 11.8−15 × 6.7−7.1 mm, only one flower on each rachilla, positioned 1−2 cm from the base of rachilla; sepals 3, imbricate, triangular, striate, 7−9 mm long and 6 mm wide at anthesis; petals 3, imbricate, triangular, striate, ca. 10 × 5 mm; gynoecium 13 × 4 mm at anthesis, tubular shaped; stigma trifid, 4 × 4 mm; style 9 mm long, 4 mm wide; staminodes lacking. Fruits very young, dull green and yellow at the base, mature fruits not seen. ( Figure 3 ).

Distribution:––Only known from the type of locality in Sungai Merah, Serewai, West Kalimantan Province of Indonesia.

Habitat: ––This species grows on hill slopes above the perennial stream of Sungai Labang in Dipterocarp forest in association with Shorea , Dipterocarpus , species of Lauraceae and Sapotaceae .

Local name and uses:––Not recorded.

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 in Sungai Merah area in Serawai, Indonesian Province of West Kalimantan, Borneo and its area of occupancy is estimated to be less than 10 km 2. The area in which this palm grows faces major threats such as forest burning, land clearing for oil palm plantation and resettlement, logging and mining activities, and thus a decline in extent of occurrence, area of occupancy and quality of habitat is inferred.

Etymology: —The specific epithet of this species honours the collector of the type specimen, A. C. Church from Harvard University, USA.

Discussion: –– Areca churchii is similar to a number of other miniature Areca species , namely A. abdulrahmanii Dransfield (1980: 33) , A. andersonii Dransfield (1984: 6) , A. klingkangensis Dransfield (1984: 13) and A. mogeana in its slender-solitary habit and pinnate leaves in general, although there are still some distinctions in leaf segmentation and texture. Primarily, they differ in the inflorescence and flower structure, including number of stamens. Areca churchii has an inflorescence with 13−17 long-slender sinuous rachillae, with sessile staminate flowers with 11–12 stamens. A. abdulrahmanii has an inflorescence with 3 divaricatesinuous rachillae and stipitate staminate flowers with 16 stamens. Areca andersonii has an inflorescence with 3−4 very slender rachillae, and sessile staminate flowers with 6 stamens. Areca klingkangensis has an inflorescence with only 3 rachillae, and stipitate staminate flowers with 9 stamens. A. mogeana has an inflorescence with 5–8 slender rachillae, and sessile staminate flowers with 6 stamens.

The divaricate structure of the inflorescence and the sinuous to slightly zigzag rachillae of A. churchii are similar to those of A. abdulrahmanii , A. arundinacea Beccari (1877: 23) , A. furcata Beccari (1877: 23) , A. minuta Scheffer (1876: 146) , A. mogeana and A. ridleyana Beccari in Furtado (1933: 236). However, in addition to the important characters of staminate flowers already mentioned above, this new species can be easily distinguished from these by the presence of only one pistillate flower on each rachilla, this positioned 1−2 cm from the base of the rachilla.

The fused, twisted and coiled filaments that are found in this species have never been reported in the genus Areca or even in the subtribe Arecinae . In the tribe Areceae these characters have only been spotted in the monotypic and endemic genus Tectiphiala from Mauritius and also perhaps in the genus Calyptrocalyx and Chambeyronia ( Dransfield et al. 2008) .

Figures

FIGURE 3. Areca churchii. A. Apical portion of leaf. B. Middle and basal portion of leaf. C. Petiole, leaf sheath and crown shaft. D. Inflorescence with pistillate flowers still attached. E. Detail portion of rachilla showing staminate and pistillate flowers in bud. F, G. Staminate flower whole and in section. H, I. Pistillate flower whole and in section. Scale bar: A–C = 6 cm; D = 4 cm; E = 2 cm; F, G = 3 mm; H, I = 5 mm. A–E, H from Mogea 3452; F–G from Dransfield JD 7531; I from Heatubun 901. Drawn by Lucy T. Smith.