Pandanus, Parkinson

Callmander, Martin W., Keim, Ary P., Buerki, Sven & Phillipson, Peter B., 2015, The genus Pandanus Parkinson (Pandanaceae) on Halmahera Island (Moluccas, Indonesia) with descriptions of three new species and a key to the species on the island, Candollea 70 (2), pp. 179-195 : 181-182

The genus Pandanus in Halmahera

The coastal P. dubius Spreng., P. polycephalus and P. tectorius Parkinson are widespread in littoral and lowland forest in swampy or sandy ground. Pandanus dubius is distributed from the Andaman Sea (Andaman Nicobar islands) to the western Pacific region ( Kiribati, Federated states of Micronesia) and throughout Malesia. This ocean-dispersed species ( GALLAHER et al., 2015) is frequently cultivated in the tropics and the leaves are used for basketry and roof thatching. The albumen of the ripe fruit is edible and used in Micronesia as a source of starch ( LIM, 2012). It is easily recognizable by its habit (large tree with robust proproots at the base), its wide, coriaceous leaves (11-16 × 200 cm) with conspicuous longaristate apices and its large pendulous subspherical syncarp (20-30 cm in diam.), composed of pale bluish-green drupes ( Fig. 3D ). Pandanus tectorius , another well-known, ocean dispersed and frequently cultivated species has a broad distribution from Malesia to the Southern Pacific islands ( Fig. 2E ). This species, which is known to have various medicinal, nutritive and construction properties ( LIM, 2012), is taxonomically problematic and is currently regarded as a species complex in need of further study ( GALLAHER et al., 2015). Pandanus polycephalus is also a strand plant on seashores, it reaches its western-most distribution in the Moluccas and is found through New Guinea and as far east as the Solomon Islands. The species forms a slender treelet to 10 m tall and can be easily recognized by its small multispicate infructescence with the drupes becoming red on ripening ( Fig. 2H ). A fourth species is confined to coastal areas, P. kaernbachii Warb. It is a robust solitary tree reaching up to 10 m high and can be easily identified in the field by its spicate infructescence consisting of 2 to 4 syncarps with incompletely fused phalanges ( Fig. 3I ). Unlike P. tectorius , P. kaernbachii is always solitary or in scattered populations ( KEIM et al., 2009; Callmander, pers. obs.). The presence of this species in the Moluccas was firstly reported by KEIM et al. (2008) from Seram Island, 200 km south of Halmahera.

Pandanus krauelianus K. Schum. seems to be a common inland species at low to mid elevation on Halmahera ( Table 1 ). It is part of the morphologically homogenous Pandanus sect. Maysops H. St. John , in subgen. Lophostigma (Brongn.) H. St. John , characterised by a solitary, ovoid-ellipsoid syncarp hidden by persistent bracts, one-seeded drupes and a pileus generally topped apically with a small hardened turret bearing a lateral stigma ( Fig. 2F, 2G ) (see also STONE, 1974a). STONE (1992) published a review of the section for New Guinea, and accepted ca. 16 species and emphasised the need of further collections in this group in which species delimitation is difficult. In the latter revision, Pandanus amboinensis Warb. , the first valid publication of P. sylvestris Rumph. from Ambon, is considered to be different from P. krauelianus from New Guinea (West Papua, Indonesia). JEBB (1992) and KEIM (2009) did consider these two species as synonyms and this broader species concept is followed here. Pandanus krauelianus , thus delimited, is distributed from the Moluccas to the Bismark archipelago through New Guinea. Another species with a similar distribution is found in inland swamps at low elevation: P. papuanus Solms. It is a large tree species (to 20 m tall) with a large, impressive cone of proproots at the base and massive pendent syncarps ( Fig. 3G, 3H ). It is known from similar habitats at higher altitudes (ca. 900 m) in New Guinea ( STONE, 1982). Pandanus conoideus , first mentioned by RUMPHIUS (1741 -1755), has not yet been collected on Halmahera, but a photograph of it taken by one of us (PBP) during his first visit to the island in 2011 confirmed its presence on the island ( Fig. 3J ). Pandanus conoideus is widely cultivated in New Guinea for its edible fruits and may have originated from the Moluccas ( STONE, 1982).

The 55 Pandanus collections currently known from Halmahera are summarized in Table 1 .

Key to the Pandanus species on Halmahera

1. Carpels free in one-carpellate and one-seeded drupes (rarely bicarpellate in P. dubius Spreng. )............ 2

1a. Carpels connate into multicarpellate, several-seeded drupes..................................... 8

2. Stigma filiform or spinescent and linear........... 3

2a Stigma oblique, flat or on an apical turret, but not filiform or linear.................................... 4

3. Infructescence lateral, born just below the base of leaves; drupes with a yellow pileus; stigma filiform, appressed towards the apex of the syncarp, 15-20 mm long ( Fig. 2 A-D)............................................. P. benstoneiodes Callm., Buerki & Phillipson

3a Infructescence terminal, pendant; drupes with a red to purple shiny pileus; stigma spinescent, sharp, erect, 6-8 mm long ( Fig. 3E, 3F )............................................. P. halmaherensis Callm. & A. P. Keim

4. Syncarps spicately arranged, small (4 cm long), ovoid; stigma reniform and flat ( Fig. 2H )............................................... P. polycephalus Lam.

4a Syncarp solitary, much larger (10-40 cm long), ellipsoid to oblong; stigma with various shapes but not reniform and flat........................................ 5

5. Leaves wide (11-16 cm); drupes large (> 10 cm) at maturity ( Fig. 3D )..................... P. dubius Spreng.

5a. Leaves narrow (<8 cm); drupes smaller (<8 cm) at maturity........................................ 6

6. Small monocaulous shrub (3 m tall) with few slender proproots at the base; leaves (<110 cm long); and syncarp small (<15 cm); peduncle slender and short, c. 11 cm long ( Fig. 2 A-C)......... P. beguinii Callm. & A. P. Keim

6a. Tall ramified tree (8-15 m) with large cone of proproots at the base; leaves (> 180 cm long); and syncarp large (> 25 cm); peduncle stout and long,> 30 cm long.... 7

7. Syncarp yellow at maturity; pileus topped apically with a small hardened turret bearing a lateral stigma ( Fig. 2F, 2G )..................... P. krauelianus K. Schum.

7a. Syncarp red at maturity; pileus with central vertical stigma ( Fig. 3J )........................ P. conoideus Lam.

8. Syncarps spicately arranged ( Fig. 3I )......................................... P. kaernbachii Warb.

8a. Syncarp solitary.............................. 9

9. Large tree (to 20 m tall) with a large and impressive cone of proproots at the base; leaves large (200-600 cm × 10-15 cm); stigmas borne on the inner edge of the truncate carpel apices ( Fig. 3G, 3H )........ P. papuanus Solms

9a. Medium-sized tree (<15 m tall) with a narrow cone of proproots at the base; leaves smaller (mostly 60-150 × 3-6 cm); stigma borne on the top of each of the rounded carpel apices ( Fig. 2E ).......... P. tectorius Parkinson

Figures

Fig. 3. – Field pictures of Halmahera Pandanus Parkinson species. A, C. Pandanus beguinii Callm. & A. P. Keim (pistillate plant); B. Pandanus beguinii Callm. & A. P. Keim (staminate plant); D. Pandanus dubius Spreng.;E, F. Pandanus halmaherensis Callm. & A. P. Keim; G, H. Pandanus papuanus Solms; I. Pandanus kaernbachii Warb. [photo taken in Seram]; J. Pandanus conoideus Lam. [Photos: A: M. Merello; B-G: M. Callmander; H, J: P. Phillipson; I: A. Keim]

Fig. 2. – Field pictures of Halmahera Pandanus Parkinson species. A, D. Pandanus benstoneoides Callm., Buerki & Phillipson (pistillate plant); B, C. Pandanus benstoneoides Callm., Buerki & Phillipson (staminate plant); E. Pandanus tectorius Parkinson; F, G.Pandanus krauelianus K. Schum.;H. Pandanus polycephalus Lam. [Photos: A: E. Bidault; D, F-G: M. Callmander; B-C, E: P. Phillipson; H: M. Merello]