Nepenthes stenophylla — Vorstman's Guide to the Carnivorous Plants

Nepenthes stenophylla — the trap in close-up — **The trap in close-up** · Photo: JeremiahsCPs — CC BY-SA 3.0 · Wikimedia Commons

Nepenthes stenophylla — the habitat — **The habitat** · Photo: JeremiahsCPs — CC BY-SA 3.0 · Wikimedia Commons

Identification

A climber of montane forest with, as the name says, narrow leaves. The pitchers are funnel-shaped and reach 25 cm tall. The lid is narrow, and that is the character by which, in the most widely used view, the species is distinguished from N. fallax, which has a round lid. No verifiable measurements of stem, leaves and separate lower and upper pitchers could be gathered for this guide; the size fields therefore hold only the pitcher height. Anyone wanting a firm identification should consult the monograph by Clarke (1997) or Phillipps, Lamb and Lee (2008).

Similar species

The species belongs to the N. maxima group, which on Borneo also includes Nepenthes fusca, N. faizaliana, N. chaniana, N. epiphytica, N. platychila and N. vogelii. N. faizaliana, which grows with N. stenophylla on the limestone mountains of Mulu, has more lanceolate leaves, larger inflorescences, a broader and more colourful peristome, one-flowered bracteate pedicels and lower pitchers bulbous at the base. N. fusca has a very narrow, triangular lid with down-curled margins. N. fallax is treated as a synonym by Danser and most later authors, but kept separate by Schlauer on account of its round lid.

The trap and how it works

A pitfall of the ordinary kind, with funnel-shaped upper pitchers aimed at flying insects: a funnel widening upwards gives an insect slipping on the smooth peristome little purchase. The narrow lid stands over the mouth and leaves the opening largely clear; it therefore offers the pitcher only limited protection from rain. No published data on the prey, or on the fine structure of peristome and glandular zone of this species, were found for this guide.

Habitat and ecology

Montane forest (B1), between 900 and 2100 m. The species grows in mossy montane forest and, according to the available literature, is often found with other montane species: with N. fusca, N. reinwardtiana and N. tentaculata, and at Gunung Mulu with N. faizaliana and N. vogelii. Its many natural hybrids point to a species that often grows alongside other Nepenthes.

Distribution and elevation

Endemic to Borneo. The species is widespread in the island's mountains, between 900 and 2100 m; the world checklist gives Borneo only. A finer breakdown over Sabah, Sarawak, Brunei and Kalimantan was not found in a verifiable source for this guide and is therefore not given. The area in our species list (Borneo) is correct.

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 12 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 are recognised, but the naming is untidy: the species has a long list of synonyms and misidentifications, and an invalid subspecies name under N. fusca belongs here. The biggest question is the status of N. fallax. Natural hybrids are known with N. fusca, N. lowii, N. rajah, N. reinwardtiana, N. tentaculata and N. veitchii.

Where and when to see it

Because the species is widespread in Bornean montane forest, there is a good chance of meeting it in the montane national parks, for example on the limestone mountains of Gunung Mulu or in the montane forest of Sabah. Confusion with related species and the many hybrids make field identification difficult; look at the funnel-shaped upper pitchers and the narrow lid, and compare with N. fusca and N. faizaliana. Photographs of lid, peristome and leaf shape allow later checking.

Conservation status

The Red List assesses the species as Least Concern; the taxon N. fallax, regarded by some as a separate species, has its own assessment as Vulnerable. The wide range and altitudinal span make the species as a whole little vulnerable; loss of montane forest to logging is the main threat. It is listed in CITES Appendix II.

Scientific name

Nepenthes stenophylla | Masters, 1890

Described by Maxwell T. Masters in 1890, in The Gardeners' Chronicle (series 3, volume 8, p. 240), under the heading "New or noteworthy plants". An unusual case: the type material was not a wild-collected plant but a specimen raised from seed in an English greenhouse. There is therefore no wild type locality in the protologue. The species is now known to be endemic to Borneo, at 900-2100 m elevation. From the Greek steno- ("narrow") and -phylla ("leaved") — "narrow-leaved", referring to this species' characteristically narrow leaves.

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