Hydriastele calcicola W.J.Baker & Petoe, 2018

Petoe, Peter, Heatubun, Charlie D. & Baker, William J., 2018, A monograph of Hydriastele (Areceae, Arecaceae) in New Guinea and Australia, Phytotaxa 370 (1), pp. 448-450 : 448-450

15. Hydriastele calcicola W.J.Baker & Petoe , sp. nov. Type:— PAPUA NEW GUINEA. Gulf Provine: Kikori Distr. , bank of Kikori River near to Kopi , 13 km N of Kikori, 40 m, 7°22’S, 144°14’E, 19 November 2000, Baker et al. 1096 (holotype K!, isotypes AAU!, BRI, L, LAE, NY)

Diagnosis:— Distinguished by its gregarious habit, the non-ventricose and moderately robust, solitary stem with pithy inner wood, the leaf with a deeply adaxially channelled petiole and multi-fold basal leaflets, and the inflorescence with a short peduncle.

Figure 33 (line drawing). Figure 34 (photo plate). Figure 35 (map).

Solitary and gregarious, moderately robust canopy palm to 30 m tall, bearing 15–20 leaves in crown. Stem ca. 15 cm in diam., inner wood very soft and pithy; internode 4–5 cm long. Leaf ca. 2.7 m long including petiole; sheath ca. 100 cm long, not seen close up, crownshaft ca. 130 × 14 cm; petiole ca. 60 cm long, deeply channelled adaxially; rachis strongly arcuate; leaflets ca. 46 per side, arranged regularly, ascending, linear, with short, widely spaced ramenta on the abaxial, basal portion of the midrib; basal leaflets comprising ca. 4 folds; middle leaflets ca. 80 × 3 cm, single-fold, obliquely to truncately praemorse apically; terminal leaflets comprising ca. 2 folds, truncately praemorse apically. Inflorescence ca. 70 cm long including 3–5 cm peduncle, branched to 2 orders, protandrous; rachillae ca. 26; triads on average 11 mm apart, opposite and decussate. Staminate flower 17–19 × 3–6 mm in bud, cream; stamens ca. 13. Pistillate flower ca. 6 × 2.5–3 mm in bud, cream, with free sepals and free petals with conspicuous, triangular and valvate tips. Fruit ca. 15 × 9 mm when ripe, obovoid to broadly ellipsoid, bright red, with a distinct, dark, sclerotic zone encircling apical stigmatic remains (up to ca. 3.5 mm in diam.). Seed ca. 10–11 × 7.5 mm, obovoid to ellipsoid; endosperm homogeneous.

Distribution:— The type locality north of Kikori (Gulf Province) and sight records on the Mubi River (Southern Highlands Province; Baker 1997) of Papua New Guinea.

Habitat:— Lowland tropical rainforest river margins, on karst limestone crags, 40–500 m.

Uses:— None recorded.

Vernacular names:— None recorded.

Conservation status:— Data deficient (DD). More data are needed about the range and abundance of this species.

Specimens examined:— PAPUA NEW GUINEA. Gulf Province: Kikori Distr., bank of Kikori River near to Kopi , 13 km N of Kikori, 40 m, 7°22’S, 144°14’E, 19 November 2000, Baker et al. 1096 (AAU!, BRI, K!, L, LAE, NY) .

Notes:— Hydriastele calcicola is a moderately robust, tall palm with arching leaves and ascending leaflets. It occurs in large numbers in the Kikori River catchment (Baker, pers. obs.), where it crows gregariously on limestone outcrops (hence the species epithet). Sometimes the palm emerges directly from near-vertical limestone cliffs. We note that it also occurs at relatively low elevation compared to similar species. Hydriastele calcicola is distinguished by its pithy, non-ventricose stem, ca. 15 cm in diameter, by its leaves with deeply adaxially channelled petioles and multi-fold basal leaflets, and inflorescences with 3–5 cm long peduncles. Hydriastele calcicola is most similar to H. gibbsiana but that species is strongly ventricose and has leaves with adaxially flattened petioles and single-fold basal leaflets.

Figures

FIGURE 33. Hydriastele calcicola. A. Leaf apex. B. Mid-leaf portion. C. Inflorescence with pistillate flowers. D. Portion of rachilla with pistillate flowers. E. Triad. F. Staminate flower in longitudinal section. G. Pistillate flower whole and in longitudinal section. H. Portion of rachilla with fruit. I. Fruit in longitudinal section. Scale bar:A–B = 8 cm; C = 6 cm; D, H = 1.5 cm; E, I = 1 cm; F = 7 mm; G = 4 mm. All from Baker et al. 1096. Drawn by Lucy T. Smith.

FIGURE 34. Hydriastele calcicola. A–B. Habit. C. Portions of rachillae with triads. D. Portion of rachilla with fruit. All from Baker et al. 1096. All photos: W.J. Baker.

FIGURE 35. Distribution map of the Longispatha group of Hydriastele in New Guinea and adjacent islands.