Nepenthes insignis — Vorstman's Guide to the Carnivorous Plants

Identification

An epiphytic shrub or climber of about 80 cm, with three-angled stems half a centimetre to nearly a centimetre thick. The leaves are thinly leathery and sessile, 20 to 35 cm long and 4 to 6 cm wide, the base running down the stem in two wings. Stems and leaves are hairless. Lower pitchers are ovoid below and cylindrical above, to 16 cm tall and 5 cm wide, with an expanded peristome of 6 to 12 mm. Upper pitchers are stout and funnel-shaped, sharply triangular in section at the base, 16 to 30 cm tall and 5 to 8 cm wide. The peristome is widest at the sides, to 3.5 cm. The lid is almost round, to 7.5 cm, without appendages. The pitchers are dark green in the lower half, yellow above with deep red spots, and the peristome is reddish brown.

Similar species

Until 2018 the plants of Biak island were also included in this species; they are now described as Nepenthes biak, with cylindrical upper pitchers and a peristome bearing stiff, pointed lobes. Within the Insignes group to which it belongs, it resembles Nepenthes sibuyanensis from the Philippines, but that species has one-flowered pedicels, an almost horizontal mouth, a short neck and much larger peristome teeth. In Papua itself the species often grows with Nepenthes ampullaria and Nepenthes maxima; the former has small, round ground pitchers, the latter slender cylindrical pitchers with a narrow peristome.

The trap and how it works

A large pitfall trap that appears remarkably specialised in one kind of prey. Field observations report that the catch consists almost entirely of large, winged cockroaches, nocturnal insects said to be attracted by a scent produced by the plant. The broad peristome, up to three centimetres wide at the sides, offers these large insects a roomy landing platform that becomes wet and slippery; once inside they fall into the digestive fluid. The inner wall carries many digestive glands, in upper pitchers up to several thousand per square centimetre. The difference between lower and upper pitchers in this species is mainly one of shape and colour: darker and more bulbous below, more yellow-green and funnel-shaped above.

Habitat and ecology

The canopy of evergreen lowland rainforest, where the plant grows as an epiphyte in thick layers of moss, especially in trees overhanging rivers; rarely terrestrial on river banks and sandbars, at 80 to 850 m (B2, W7). Humidity at these sites is constantly high. A striking observation is that the seeds of one plant near a small waterfall had germinated while still in the capsule. This preference for epiphytic sites high in trees also explains why the species escaped botanists' attention for so long.

Distribution and elevation

Endemic to the western, Indonesian part of New Guinea (the provinces of Papua and West Papua), with records from the south-west, the north-west and the lowland plain around the great lakes and rivers of the interior, and a few islands in Cenderawasih Bay. Our own species list gives 'New Guinea', which is correct. The 2001 Flora Malesiana also included Biak in the range, but since 2018 those plants have been treated as Nepenthes biak; Nepenthes insignis in the strict sense is now regarded as a species of the New Guinea mainland.

Recorded (one-degree cells)

Distribution based solely on records at GBIF (Global Biodiversity Information Facility), not on TDWG regions — those are often far larger than the actual range. The light halo is the area around a record, the dark core the record itself. The darker cells are 4 one-degree squares — roughly a hundred and ten kilometres — in which the species has been recorded, from all GBIF records. This is coarser than for most species because hardly any record of this plant carries an accurate coordinate: the locality of poached species is obscured at source. At this scale that obscuring disappears into the noise. The cells show where it has been seen, not where it occurs: an empty square means nothing.

Forms and variation

No varieties or forms have been described. One natural hybrid has been recorded, with Nepenthes mirabilis, at about 500 m. Although the species often grows alongside Nepenthes ampullaria and Nepenthes maxima, no hybrids with those species are known. Colour differences are mainly those between lower and upper pitchers: lower pitchers are usually dark green with red blotches around the dark reddish-brown peristome, upper pitchers yellowish green with fewer blotches. The smaller coastal plants once known as the 'Biak form' are now a species of their own.

Where and when to see it

The habitat lies in remote lowlands of Papua, usually reachable only by boat or light aircraft, and the plants often grow high in trees above the water. Your best chance is along rivers, from the boat: look for mossy branches overhanging the water and for large yellow funnels with a broad reddish-brown rim. Binoculars are indispensable. On sandbars and banks terrestrial plants sometimes grow within reach. Travel only with local guidance and with the necessary permits for the interior of Papua.

Conservation status

Assessed on the Red List as Least Concern. The range in the lowlands of Papua is large and largely undeveloped, and the epiphytic habit high in trees makes the plants hard for collectors to reach. As a member of Nepenthes it is listed in CITES Appendix II, so international trade in wild plants requires a permit. Logging, plantations and clearance of New Guinea's lowland forest are general long-term threats. The separation of Nepenthes biak probably changes the assessment for the mainland little.

Scientific name

Nepenthes insignis | Danser, 1928

Nepenthes insignis was described in 1928 by Benedictus Hubertus Danser in his monograph "The Nepenthaceae of the Netherlands Indies" (Bulletin du Jardin Botanique de Buitenzorg). The type material (Pulle 277, with male floral material) was collected on 9 November 1912 by August Adriaan Pulle at the border of the Beaufort River, south-western New Guinea, at 80 m elevation, and is held at the Bogor Botanical Gardens (Java) and the National Herbarium of the Netherlands (Leiden). The border of the Beaufort River, south-western New Guinea, at 80 m elevation. The specific epithet derives from the Latin "insignis" ("distinguished, remarkable"), reflecting the plant's notable characteristics.

World Checklist of Vascular Plants (WCVP), via Plants of the World Online (POWO), Royal Botanic Gardens, Kew.