Hydriastele longispatha (Becc.) Baker & Loo (2004: 65)

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

19. Hydriastele longispatha (Becc.) Baker & Loo (2004: 65) . Gulubia longispatha Beccari (1914: 25) . Type:— PAPUA NEW GUINEA. East Sepik Province: Sepik, Schultze 323 (holotype B†, isotype FI!)

Gulubia crenata Beccari (1923: 445) . Type:— PAPUA NEW GUINEA. East Sepik Province: Hunstein Mts., Ledermann 8449 (holotype B†).

Gulubia obscura Beccari (1923: 447) . Type:— PAPUA NEW GUINEA. East Sepik Province: Ettapenberg, Ledermann 9133 (holotype B†).

Gulubia brassii Burret (1935: 336) . Type :— PAPUA NEW GUINEA. Central Province : Bella Vista, Brass 5457 (holotype B†, isotypes A!, BRI!, NY!).

Hydriastele valida (Essig) Baker & Loo (2004: 68) . Gulubia valida Essig (1982: 169) . Type:— PAPUA NEW GUINEA. Sandaun Province: Torricelli Mts., Essig 55099 (holotype BH, isotypes CANB, L!, LAE), synon. nov.

Figure 42 (line drawing). Figure 43 (photo plate). Figure 35 (map).

Solitary, robust palm to 35 m tall bearing 15–17 leaves in crown. Stem 15–30 cm in diam.; internode 8–10 cm long. Leaf 2.5–3.6 m long including petiole; sheath 1–1.5 m long, covered with a thin layer of lanate, buff indumentum, crownshaft ca. 110–200 × 30 cm; petiole 10–40 cm long, flattened or slightly channelled adaxially; rachis usually strongly arcuate; leaflets (48–)57–70 per side, arranged regularly, ascending and sometimes drooping at their tips, linear; normally with ramenta on the abaxial, basal to middle portion of the midrib; basal leaflets single-fold, acuminate or truncately praemorse apically; middle leaflet 90–125 × 2–3 cm, single-fold, somewhat acuminate or truncately praemorse apically; terminal leaflets comprising 2 or 3 folds, truncately praemorse apically. Inflorescence 60–90 cm long including 10–15 cm peduncle, branched to 2 or 3 orders, apparently protogynous; rachillae ca. 28 (rarely 8–11); triads 4–10 mm apart, opposite and decussate; inflorescences 7–8 present. Staminate flower 13–20 × 3–6 mm in bud (when dry), cream; stamens 8–24. Pistillate flower 2–3 × 2–3 mm in bud (when dry), cream to brownish, with free sepals and free, low and ± rounded petals. Fruit 7–10 × 6–10 mm when ripe, subglobose to broadly ellipsoid, red, with a distinct, dark, sclerotic zone encircling apical stigmatic remains (up to ca. 3 mm in diam.). Seed ca. 6.5 × 5.5 mm, subglobose; endosperm homogeneous.

Distribution:— The central New Guinea highlands, Goodenough Island and the Torricelli Mountains of Papua New Guinea, and Yapen Island in western New Guinea.

Habitat:— Premontane and montane forest on slopes and ridgetops with volcanic soils and limestone, (300–) 500– 1450 m.

Uses:— Used in house construction, especially for flooring.

Vernacular names:— None recorded.

Conservation status:— Least Concern (LC). Hydriastele longispatha is widely distributed (EOO> 395,000 km 2) and the relatively low AOO (52 km 2) is most likely a low estimate resulting from under-collecting.

Specimens examined:— INDONESIA. Papua Province: Mimika, Timika, Mile 50, on road to Tembagapura , forest to west of container depot, Loc 36, 545 m, 4°17’S, 137°1’E, 26 February 1998, Baker et al. 882 (AAU, BH, BO, K!, L, MAN); Jalan trans Yapen, Yapen Island , 650 m, 1°45’S, 136°15’E, 26 October 1998, Maturbongs 614 (BO, FTG, K!, L, MAN, NY); 4 km SW of Bernhard Camp, Idenburg River, 900 m, 3°29’S, 139°6’E, March 1939, Brass 13099A (A!, BRI, L!,); Same locality as preceding, 3°29’S, 139°6’E, March 1939, Brass 13099 (A!, L) ; PAPUA NEW GUINEA. Central Province: Bella Vista , 1450 m, 8°33’S, 147°7’E, November 1933, Brass 5457 (B†, A!, BRI!, NY!) ; Milne Bay Province: Ridge above Mayu River near Mayu I camp ( Mt. Suckling Expedition ), 500 m, 9°38’S, 149°10’E, 15 July 1972, Essig LAE 55231 (BH, CANB, K, L!, LAE!); Subprovince Esa’ala, Goodenough Island , northern slopes of North peak, 1100 m, 9°19’S, 150°15’E, 26 December 1977, Croft LAE 71277 (BH, BRI, CANB!, L!); N of Bubuleta Agricultural Station, 30 km E of Alotau, 300 m, 10°20’S, 150°40’E, 18 December 1976, Croft et al. LAE 71094 (BH, L!, LAE) ; Sandaun Province: Miwaute, 950 m, 3°25’S, 142°7’E, 20 November 1996, Barfod 389 (AAU!, K!); Telefomon Subdist. , Frieda River , Kokomo Creek , 700 m, 4°42’S, 141°48’E, 28 June 1969, Henty NGF 42674 (LAE!); Lumi Subdistr. , Near Fatima , road from Lumi , 900 m, 3°20’S, 142°10’E, 26 November 1971, Essig 55099 (BH, CANB, L!, LAE); Telefomin Subdist. , Antap Mt. , Carpentaria Exploration Co., 1000 m, 4°45’S, 141°50’E, 1 May 1978, Essig LAE 74081 (LAE!); Same locality as preceding, 4°45’S, 141°50’E, 1 May 1978, Essig LAE 74083 (LAE!); Sepik: Nov 1910, Schultze 323 (B†, FI!) ; Southern Highlands Province: Mount Bosavi, Bona Village, WWF Integrated Conservation and Development Project Area , 700 m, 6°26’S, 142°47’E, 3 February 1996, Baker et al. 622 (BH, K!, LAE) .

Notes:— Hydriastele longispatha is a robust, emergent palm with arching leaves and ca. 57–70 ascending leaflets on each side of the rachis. It is distinct from other species treated here due to the combination of the apical leaflet pair with truncately praemorse tips and protogynous inflorescences. Other robust palms in New Guinea and Australia with truncately praemorse apical leaflets have protandrous inflorescences. Hydriastele longispatha is further distinguished by its high variation in stamen number (8–24 stamens) and relatively small (7–10 × 6–10 mm) subglobose to broadly ellipsoid fruits.

Hydriastele longispatha most closely resembles the five robust, protogynous species of Hydriastele that occur in east Melanesia. These taxa are described by Essig (1982) and Baker & Loo (2006), but, in brief, H. macrospadix and H. hombronii from the Solomon Islands have smaller proportions than H. longispatha with only 30–46 leaflets on each side of the rachis, while H. cylindrocarpa from Vanuatu, and H. vitiensis and H. boumae from Fiji, are all distinguished by their white to yellowish fruits.

Based on our study of the material cited here, we concur with Essig (1982) in broadening the circumscription of H. longispatha due to a continuum in stamen variation and homogeneity across other characters. In addition, due to several new collections, characters that were thought to be distinguishing for H. valida , e.g. slightly less arching leaves with stiff and erect leaflets, now fall within the continuum of variation that we accept for H. longispatha , resulting in H. valida being placed in synonymy.

Figures

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

FIGURE 42. Hydriastele longispatha. A. Leaf apex. B. Mid-leaf portion. C. Infructescence in part. D. Portion of rachilla with pistillate flowers. E. Pistillate flower whole and in longitudinal section. F. Portion of rachilla with fruit. G. Fruit whole and in longitudinal section. Scale bar: A–B = 8 cm; C = 6 cm; D, F = 1.5 cm; E = 2.5 mm; G = 7 mm. All from Baker et al. 882. Drawn by Lucy T. Smith.

FIGURE 43. Hydriastele longispatha. A. Habit. B. Inflorescence with pistillate flowers and infructescence with maturing fruit.All from Baker et al. 882. All photos: W.J. Baker.