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Nepenthes biak
A pitcher plant of limestone sea cliffs, on an island in Cenderawasih Bay north of New Guinea. The plants of Biak were long regarded as a small coastal form of Nepenthes insignis. In 2018 Matthew Jebb and Martin Cheek described them as a species of their own, Nepenthes biak, in a paper in Blumea with Murphy and Mambor. Remarkably, the type was based on a plant that had been in cultivation at Kew for years. The species belongs to the Insignes group, a group of about fourteen species found mainly in the Philippines.
No photograph of this species under a Creative Commons licence or in the public domain is in the guide yet.
Identification
A climber of at least three metres, dotted with scattered red glands. The leaves are linear to narrowly oblanceolate, glossy and leathery, with a rounded-acute tip; on the climbing stem mostly 16 to 18 cm long and 2 to 3 cm wide. Lower pitchers are known only from seedlings: small, ovoid-cylindrical, with fringed wings. Intermediate pitchers are 4.5 to 8.5 cm tall, sometimes with narrow wings. Most striking are the upper pitchers, which come in two forms and colours. Primary upper pitchers are 19 to 23 cm tall, cylindrical, heavily blotched purple on a green ground, with a glossy dark purple peristome of 5 to 7 mm bearing about five stiff, pointed lobes on each side. Secondary upper pitchers, higher on the stem, are smaller, 12.5 to 13.5 cm, and almost pure yellow, with a yellow peristome.
Similar species
According to the authors its closest relatives are Nepenthes insignis, now regarded as a species of the New Guinea mainland, and an as yet undescribed species from the Raja Ampat islands. Nepenthes insignis is an epiphyte of lowland rainforest with stout, funnel-shaped upper pitchers and a peristome up to 3.5 cm wide at the sides; Nepenthes biak has cylindrical upper pitchers with a narrower peristome bearing pointed lobes, and grows on coastal limestone cliffs. The two-coloured upper pitchers, purple-blotched and pure yellow on the same plant, are a good field character.
The trap and how it works
What sets this species apart is that the upper pitchers are dimorphic and two-coloured: the first upper pitchers on the climbing stem are large and blotched purple, the later ones smaller and yellow. What this difference means for capture has not been studied; the two colour forms may attract different prey. The peristome carries stiff, pointed lobes that fringe the mouth and may hinder escape. Nectar glands lie under the lid. As throughout the genus, insects slip off the wet peristome into the digestive fluid below. Nothing has been published on prey composition on Biak.
Habitat and ecology
Coastal limestone cliffs in the zone of evergreen lowland forest, at sea level, sometimes epiphytic on mangrove trees (R2, B2). That is an unusual combination for the genus: pitcher plants are mostly plants of acid, nutrient-poor soils, but limestone can also be a poor site where little soil lies on the rock and rainwater drains away quickly. Growth on mangrove trees, right beside salt water, is equally unusual. The plant grows in full sun or half shade on rocks above the surf.
Distribution and elevation
Endemic to the island of Biak, in the Schouten Islands in Cenderawasih Bay, Papua province, Indonesia. Our own species list gives 'New Guinea, Biak', which is correct: Biak lies off the north coast of New Guinea and belongs biogeographically to that island. The species is known only from sea level, along the coast. The mainland plants referred to Nepenthes insignis do not belong to it, and the undescribed relative from the Raja Ampat islands is a separate species as well.
- Recorded (one-degree cells)
Forms and variation
No varieties or forms have been described and no natural hybrids are known. The most striking variation lies within the plant: primary upper pitchers are green with heavy purple blotches and a dark purple peristome, secondary upper pitchers almost pure yellow with a yellow peristome. Anyone seeing only one of the two might think of two different plants. Inflorescences were still unknown at the time of description, so little can be said about the flowers of the species.
Where and when to see it
Biak has an airport and is relatively accessible from other parts of Indonesia. The species grows along the coast on limestone rocks and sometimes on mangrove trees, so search rocky stretches of coast with forest above. Watch for cylindrical, purple-blotched pitchers and for pure yellow pitchers on the same plant. Because the authors regard the species as critically endangered, restraint is called for: take no plants or seed and share no precise locations.
Conservation status
The species has not yet been assessed by the IUCN and therefore appears as 'Not Evaluated' (NE) in this guide. The authors considered it likely that a formal assessment would place it as Critically Endangered, given its occurrence on a single island and the threats they noted there. As a member of Nepenthes it is listed in CITES Appendix II, so international trade in wild plants requires a permit. Biak's coastal zone is inhabited and developing, which adds to its vulnerability.
Scientific name
Nepenthes biak | Jebb & Cheek, 2016
Nepenthes biak was described in 2018 by Martin Cheek, Matthew Jebb, Barbara Murphy and Ferdy Mambor, in "Nepenthes section Insignes in Indonesia, with two new species" (Blumea 62(3): 174-178). Biak Island, part of the Schouten Islands in Cenderawasih Bay (Biak Numfor Regency, Papua Province, Indonesia); the type material was collected from cultivated plants at Kew Gardens that originated from this island. The specific epithet derives from Biak Island, to which the species is endemic.
World Checklist of Vascular Plants (WCVP), via Plants of the World Online (POWO), Royal Botanic Gardens, Kew.