Nepenthes hirsuta — Vorstman's Guide to the Carnivorous Plants

Nepenthes hirsuta — the trap in close-up — **The trap in close-up** · Photo: NepGrower — CC BY-SA 2.5 · Wikimedia Commons

Nepenthes hirsuta — the habitat — **The habitat** · Photo: en:User:NepGrower — Public domain · Wikimedia Commons

Identification

A climber with a stem densely set with long brown hairs. The leaves are leathery, channelled-spathulate to obovate, to 20 cm long, with an acute to rounded tip and a narrowed base passing into a laterally flattened, half-clasping sheath; the longitudinal veins are inconspicuous. The hairs are 1 to 2 mm long and brown. The pitchers are mostly green, some with red blotches inside. Verifiable measurements of the pitchers and of stem length were not available to this guide; the trap size field is therefore left empty.

Similar species

Its closest relatives are Nepenthes hispida and N. macrovulgaris; a relationship with N. philippinensis of Palawan has also been suggested. The distinction from N. hispida matters most: that species has a very dense indumentum of bristly, purplish-grey hairs 1.5 to 4 mm long and a clasping, decurrent leaf base, whereas N. hirsuta has brown hairs of 1 to 2 mm and no decurrent leaf base. In the flower, N. hirsuta has a longer staminal column, 3.5 to 6 mm against 1.5 to 2 mm. N. macrovulgaris is a species of ultramafic soils.

The trap and how it works

A pitfall of the ordinary kind, with lower and upper pitchers that are inconspicuous in this species: mostly green, sometimes with red blotches on the inner wall, and hairy outside like the rest of the plant. Whether the hairs play a part in capture, for example as a walkway for ants, has not been studied. Capture works, as throughout the genus, through the slippery peristome and a digestive fluid at the bottom of the pitcher. No specific prey data have been published.

Habitat and ecology

Poor, acid soils, mainly on sandstone, from 200 to 1100 m. The species grows in kerangas, the heath forest on poor sandy soil (B3), on mossy banks and slopes in lower montane forest (B1), and in open places and disturbed vegetation on lower ridges (B5). That it persists in disturbed, open vegetation too makes it less vulnerable at island scale than many montane species.

Distribution and elevation

Endemic to Borneo. The world checklist gives Borneo only; a finer breakdown over states and provinces was not found in a verifiable source for this guide and is therefore not given. Altitude: 200 to 1100 m. 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 20 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

Three varieties were described in the nineteenth and early twentieth centuries: var. glabrescens (1882), and var. glabrata and var. typica (1908); they are not recognised as separate taxa today, but show that the density of the indumentum varies. N. leptochila, described by Danser in 1928, is regarded as a synonym. Natural hybrids are known with N. albomarginata and N. ampullaria, and a cross with N. lowii is suspected.

Where and when to see it

Search heath forest and open, poor slopes on sandstone in the hill country, between 200 and 1100 m. The species stands out not for its pitchers but for its hairs: a climber with brown-haired stems and leaf margins on poor ground in Borneo is already a strong clue. Check hair colour and length to rule out N. hispida. Because it also grows along trails and in disturbed vegetation, it can often be found without long treks.

Conservation status

The Red List assesses the species as Least Concern. It tolerates disturbance, spans a broad altitudinal range and occurs in several vegetation types. Loss of kerangas and hill forest to clearing, plantations and fire does affect part of its habitat. As a member of the genus it is listed in CITES Appendix II.

Scientific name

Nepenthes hirsuta | J.D. Hooker, 1873

Nepenthes hirsuta was described in 1873 by Joseph Dalton Hooker, in "Ordo CLXXV bis. Nepenthaceae" (Prodromus Systematis Naturalis Regni Vegetabilis 17: 90-105). The precise type locality could not be established with certainty; the species is endemic to Borneo, growing at 200-1,100 m elevation in kerangas forest, on mossy banks and on sandstone substrates. The name derives from the Latin "hirsūtus" ("hairy, bristly"), referring to the plant's indumentum of thick brown hairs, which is even present on the inflorescence.

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