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Nepenthes halmahera
A small pitcher plant of open places on ultramafic rock in the lowlands of Halmahera, the largest island of the North Moluccas. The type material was collected as early as August 1949 by De Haan, but was long regarded as an aberrant form of Nepenthes danseri from the island of Waigeo. Only in 2015 did Martin Cheek of Kew describe the plants as a separate species, in the same paper in which he also described Nepenthes weda. The name is that of the island, used as a noun in apposition.
Identification
A climber of two to five metres, with terete stems dotted with small, depressed-globose glands. Leaves of the short shoots are elliptic to lanceolate, 16.5 to 22.5 cm long and 4 to 6 cm wide; those of the climbing stem are smaller, elliptic, mostly 8 to 15 cm long and 1.5 to 3.5 cm wide, on a channelled, winged petiole of 1.5 to 3.4 cm. Lower pitchers are ellipsoid to cylindrical, about 11 cm tall and 3.6 cm wide, with fringed wings about seven millimetres broad and a narrow peristome of 1.5 to 2 mm. Upper pitchers are ovoid-cylindrical, mostly 8 to 10.5 cm tall and 2.4 to 3.3 cm wide, with a peristome of 1.5 to 2.5 mm with fine ridges a third of a millimetre apart, and a small lid of about two centimetres.
Similar species
The species was formerly included in Nepenthes danseri, which on current understanding is confined to Waigeo, where it is an entirely yellowish plant with small pitchers and a very narrow, barely ribbed peristome. On Halmahera itself Nepenthes weda is the main other species on ultramafic rock; it is much larger, with upper pitchers of 24 to 25 cm, lower pitchers with 2 to 3 mm teeth on the peristome and an underground network of stems, and grows higher up, in montane forest. On the island Nepenthes halmahera can thus be recognised by its small pitchers, narrow peristome and preference for open lowlands.
The trap and how it works
A small pitfall trap of the usual kind. Lower pitchers stand at the foot of the plant and have fringed wings that serve as a ramp for crawling animals. Upper pitchers hang from the tendrils of the climbing stem, are ovoid to cylindrical and have a narrow, finely ribbed peristome. Notably, the inner wall of both pitcher types is waxy: a layer of wax scales on which insects find no purchase and which, together with the wet peristome, hinders escape. Digestive fluid stands at the bottom. No prey study of this species was found in the literature consulted.
Habitat and ecology
Open places in lowland forest, rarely in lower montane forest, on ultramafic substrate, from about 10 to 500 m and exceptionally to 760 m (R3, B5, B2). Ultramafic soils, derived from weathered peridotite and serpentinite, are poor in the main nutrients and rich in nickel, chromium and magnesium. The forest on them is often low and open, with patches where bare soil comes to the surface. These are the places where this species can grow in sufficient light. Halmahera has extensive ultramafic areas, especially in the centre and east.
Distribution and elevation
Endemic to Halmahera in the province of North Maluku, Indonesia. Our own species list gives 'Moluccas, Halmahera', which is correct. At its description in 2015 the species was known only from the area of a nickel project at Weda Bay, in the centre of the island; the author then estimated the occupied area at 32 square kilometres. Later surveys showed the species to be common in the Weda Bay area. Whether it also occurs on other ultramafic terrain on the island is not stated in the sources consulted.
- Recorded (one-degree cells)
Forms and variation
No varieties or forms have been described, and no natural hybrids are known, not even with Nepenthes weda, which grows on ultramafic rock on the same island but higher in the mountains. The size of the upper pitchers varies considerably, from about 6 to 11 cm tall, probably reflecting the age and light conditions of the plant. Little on colour variation is recorded in the sources consulted.
Where and when to see it
The known sites lie in and around a nickel mining concession at Weda Bay, where access is restricted. Outside concessions, search on Halmahera in open lowland vegetation on red or brown, bare-looking ultramafic soil, where the vegetation is low and light reaches the ground. Look for small, cylindrical pitchers with a narrow peristome on plants climbing into the scrub. Confusion with Nepenthes weda is ruled out once you see pitcher size: upper pitchers of more than 20 cm belong to that species.
Conservation status
Assessed on the Red List as Least Concern. That is noteworthy, as the author proposed in 2015 that the species be treated as critically endangered, because all known populations lay within a single nickel mining area. The formal Red List assessment of 2018 reached a more favourable verdict after the species proved to be common in the Weda Bay area. As a member of Nepenthes it is listed in CITES Appendix II, so international trade in wild plants requires a permit. Expansion of nickel mining on Halmahera remains the main risk to its habitat.
Scientific name
Nepenthes halmahera | Cheek, 2015
Nepenthes halmahera was described in 2015 by Martin Cheek, in Blumea 59: 215-225. The island of Halmahera, North Maluku, Indonesia, at the time (2015) confined to the Weda Bay Nickel Project concession area, on ultramafic substrates between 10 and 760 m elevation. The specific epithet refers directly to the island of Halmahera, to which the species is endemic.
World Checklist of Vascular Plants (WCVP), via Plants of the World Online (POWO), Royal Botanic Gardens, Kew.