Pandanus benstoneoides Callm., Buerki & Phillipson, 2015

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 : 187-193

Pandanus benstoneoides Callm., Buerki & Phillipson , spec. nova

( Fig. 2 A-D, 4 B, 6 , 7 ).

Typus: INDONESIA. Prov. North Maluku [Halmahera Isl.]: East Halmahera, Weda Bay, Pinto , 00°38’10”N 128°09’05”E, 340 m, 1.II.2013, Callmander et al. 1096 (holo-: G [ G00341588 ]! ; iso-: BO!, BM!, L!, MO-6465097 !, MO-6465098 !).

Haec species a congeneris inflorescentiis lateralibus axillaribus, staminibus liberis atque drupis unilocularibus stigma filiforme adpressum rectum undulatumve syncarpi apicem versus dirigens gerentibus distinguitur.

Treelet to 4-8(-15) m tall, stem c. 15 cm in diam., with a large cone of few proproots at base, up to 2 m high. Leaves linear-attenuate, mostly (110-)130-150(-160) cm long, 4.5-5.5 cm wide in the middle, apex gradually attenuate, ending with a flagellum (c. 7 cm long); sub-coriaceous, glaucous abaxially; longitudinal veins visible on both surfaces; marginal prickles borne 4-9 cm above base to apex, black near sheath, antrorse, erect, 0.8-1.5 mm long in the lower third, 0.5-2 mm apart, 0.5-1 mm long in the mid-third, 1-3 mm apart, to 0.2-0.5 mm long in the distal third, 0.2-1 mm apart, appressed in the distal third; midrib armed from 35-50 cm from base, prickles> 1 mm long towards the apex, irregularly spaced but mostly 2-4 mm apart in the middle and 1-2 mm towards the apex; prickles generally absent on apical ventral pleats, sometimes 5-10 minute prickles towards the apex; sheath straight, (4-)5-7(-8) cm long, 4.5-6 cm wide at apex, 5-8 cm at base. Infructescence lateral, comprising a solitary patent syncarp born in the axil of the leaves, several present in each fertile leaf rosette; each syncarp ovoid, obtuse at apex, 3-angled, 7-10 cm long, 5-7 cm wide, peduncle short, flattened dorso-ventrally, c. 7 cm long, 1-1.5 cm thick at apex, bearing multiple sub-coriaceous yellow bracts, broadly naviculate, the proximal ones c. 11 cm long, the distal one 7 cm long, crowded at peduncle apex, covering the syncarp. Drupes numerous, 500-800, 13- 15 mm long, 3-4 mm wide, 4-5 mm thick, 1-celled, 5-6-angled, linear, pileus short, 1-2 mm high, with a flat to slightly concave apex with a rugose surface, bearing an appressed, straight to wavy, filiform stigma on its upper edge; stigma towards the syncarp apex, (10-)15-20(-30) mm long, 1 mm wide at base, 0.5 mm at apex; stigmatic groove ventral (adaxial), running along the proximal two thirds of the stigma. Endocarp bony, median, c. 4 mm long, obovate, lateral walls> 0.4 mm thick, extending laterally toward the apex of the drupe; proximal mesocarp c. 3 mm long, fibrous, distal mesocarp c. 3-5 mm long, chambered, seed locule c. 1.5 × 3 mm, obovate to ovate. Staminate inflorescence c. 18 cm long (immature); with a single terminal spike on a peduncle c. 7 cm long, covered with narrowly navicular yellow bracts, proximal ones c. 14 × 3 cm; distal ones 8 × 2 cm; spike yellow, c. 7 × 1.5 cm, linear, composed of crowded and congested flowers, composed of free stamens; stamens c. 5.5 mm long; filament, 4 × 0.5-0.7 mm, oblong, often larger at apex (c. 1 mm wide); anther c. 1.5 × 1 mm, sometimes apiculate with a long slender apiculus c. 1 mm long.

Etymology. – This new species is named after its resemblance to species of the genus Benstonea , a genus characterized by single celled drupes with a spiniform stigma, a dorsal (abaxial) stigmatic groove with respect to the long axis of the syncarp and staminate flowers sessile, composed of free stamens ( CALLMANDER et al., 2012). When the first author collected it for the first time, he believed that he had discovered a new Benstonea species due to its typical single celled drupes with a spiniform stigma. Subsequently, more careful morphological study revealed that the stigmatic groove was ventral (adaxial) - unknown in Benstonea , and indicating the plant to be a remarkable new species of Pandanus . This conclusion has now been corroborated by molecular phylogenetic analysis. (Booth et al., unpubl. data) (see below).

Distribution and ecology. – Pandanus benstoneoides is found at lower to mid elevation (70-1030 m) in primary and disturbed evergreen tropical forest. The species is only known from our recent collections from the Eastern and Central Regencies of Halmahera ( Fig. 4B ).

Conservation status. – With an EOO of 66 km 2, an AOO of 45 km 2, and 4 subpopulations, none of which are situated within the protected area network, P. benstoneoides is assigned a preliminary status of “Endangered” [EN B1ab(iii)+2ab(iii)] based on the IUCN Red List Categories and Criteria ( IUCN, 2012). See P. beguinii for further justification of the IUCN Category. The conservation status is based on the currently available information on the geographical distribution of the species, and is justified because the extent of suitable habitat is expected to decrease in the coming years. However our remarks about the current inadequate knowledge of the flora of Halmahera and the possible establishment of conservation offset sites under P. beguinii above are applicable to P. benstoneoides .

Notes. – Pandanus benstoneoides is the only species of the genus known to have lateral inflorescences born in the axil of the leaves, with staminate flowers bearing free stamens and pistillate infrutescence with drupes holding elongate appressed long filiform stigma. The longest stigma in the family is known from the New Guinean Benstonea setistylus (Warb.) Callm. & Buerki , where it can reach 10-15 mm ( STONE, 1978). In the genus Pandanus , P. princeps B. C. Stone , a rare Malagasy endemic, is known to have long spiniform stigmas reaching 1 cm (STONE, 1972), but this magnificent tall monocaulous species has nothing else in common with our new species. Pandanus benstoneoides is morphologically isolated within the genus and cannot be placed in any of the infrageneric groups proposed by STONE (1974a). Further phylogenetic analyses will hopefully shed light into the evolution and systematics of this enigmatic and remarkable species.

Paratypi. – INDONESIA. Prov. North Maluku [Halmahera Isl.]: Central Halmahera, Weda Bay, Bukit Limber , 00°32’36”N 127°58’30”E, 942 m, 30.IV.2013, Bidault et al. 1184 ( BO, G, L, MO-6486429 , MO-6398420 carpo) ; Weda Bay , Km 3 from Lelilef on the road to Doromesmesan, 00°28’50”N 127°55’17”E, 70 m, 26.I.2013, Callmander, Haris, Lasut & Gushilman 1077 ( BO, G, L, MO-6451261 , MO-6451262 , PH) ; Weda bay, Bukit Limber , 00°33’14”N 127°59’17”E, 1031 m, 22.V.2013, Gushilman, Lasut & Haris 646 ( BO, G, K, MO-6489845 ) ; Weda Bay , Tarsan Camp , 00°31’41”N 127°56’18”E, 495 m, 2.VI.2013, Gushilman et al. 739 ( BO, G, L, MO-6486556 , MO-6399935 carpo) ; On road to Bukit Limber , 00°31’39”N 128°00’19”E, 712 m, 12.IX.2013, Phillipson et al. 6488 ( G, MO) ; ibid. loc., 00°31’44”N 128°00’21”E, 711 m, 12.IX.2013, Phillipson et al. 6489 ( BO, G, K, L, MO) .

Figures

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]

Fig. 4. –Distribution map of the three endemic new species of Halmahera.A. Pandanus beguinii Callm. & A. P. Keim; B. Pandanus benstoneoides Callm., Buerki & Phillipson;C. Pandanus halmaherensis Callm. & A. P. Keim.

Fig. 6. – Pandanus benstoneoides Callm., Buerki & Phillipson (pistillate). A.Tip of a leaf; B. Basal and medium sections of a leaf; C. Side view of a drupe; D. Cross section of a drupe; E. Syncarp on the peduncle; F. Top views of the pileus. [A-F: Callmander, Haris, Lasut & Mahroji 1096, G] [Drawing: R. L. Andriamiarisoa]

Fig. 7. – Pandanus benstoneoides Callm., Buerki & Phillipson (staminate). A. Staminate inflorescence; B. Section of tip of inflorescence showing arrangement of single stamens;C, D. Stamens. [A-G: Phillipson et al. 6488, G] [Drawing: R. L. Andriamiarisoa]