Nepenthes eustachya — Vorstman's Guide to the Carnivorous Plants

Identification

A climber with stems to 5 m long and 8 mm thick, with cylindrical internodes to 12 cm. The leaves are leathery and stalked, oblong-lanceolate, to 20 cm long and 5 cm wide, with a rounded to emarginate tip; the petiole is scarcely or not winged and the tendril reaches 15 cm. Lower pitchers are ovoid in the lowest quarter and cylindrical above, to 20 cm tall and only 4 cm wide, without wings but with a pair of ribs, a round mouth, a peristome to 5 mm with indistinct teeth and a nearly round lid without appendages; the spur is up to 4 mm and usually forked. Upper pitchers are similar, slightly larger and funnel-shaped in the upper quarter. Mature parts are hairless; only young parts carry some white hairs.

Similar species

The species was long treated as Nepenthes alata, but is readily distinguished: N. alata has lanceolate-ovate leaves with an acute tip, a broadly winged petiole, an undivided pointed spur and hairy mature parts, whereas N. eustachya has rounded leaf tips, a scarcely winged petiole, a forked spur and hairless mature parts. From N. mirabilis, which grows in the same area, it differs in wingless lower pitchers, fringed leaf margins on short shoots, and leathery rather than papery leaves. Where both occur, the slender, pale, red-speckled pitcher is the best field character.

The trap and how it works

A narrow pitfall, differing little between its two forms. Lower pitchers have no wings, only a pair of ribs, and the digestive glands lie only in the ovoid lower part. Upper pitchers become funnel-shaped towards the mouth, which steers flying insects slipping on the peristome downwards. The peristome is narrow, to 5 mm, and the lid is nearly round and without appendages; its underside is often darker than the rest of the pitcher. No specific data on the prey of this species have been published.

Habitat and ecology

Open, sunny sites at the forest edge: rock faces and steep slopes, almost always on sandstone or bare rock (B5, B2). Where the species occurs it forms dense clumps, growing alongside N. albomarginata, N. ampullaria, N. gracilis, N. longifolia and N. sumatrana, among others. Its altitudinal range is strikingly broad, from sea level to 1600 m, so it occurs both in the coastal hills and inland. Recent fieldwork in West Sumatra reports clustered populations on inland hills.

Distribution and elevation

Endemic to Sumatra, Indonesia, in the provinces of North and West Sumatra, from around Sibolga on the west coast to the highlands around Padang. The altitudinal range is 0 to 1600 m. Within this area the species is locally common, but its occurrence is tied to open rocky sites and therefore fragmented. The World Checklist (WCVP) gives Sumatra only. The area given in our species list (West and North Sumatra) agrees with the literature.

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 7 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. Pitcher colour varies: white to pale pink with many red speckles, a usually yellowish peristome sometimes striped red, and a lid with a darker underside. On its sites the species crosses with various neighbours: natural hybrids with N. albomarginata (with reddish leaves and pitchers) and N. longifolia are known, and hybrids with N. ampullaria, N. gracilis and N. sumatrana are suspected; the last was found around 1990 but reported then under the wrong parent names.

Where and when to see it

The species is easiest to find along roads through sandstone hill country in West and North Sumatra: look at open rock faces and steep, partly cleared slopes at the forest edge. From a distance the dense clumps give themselves away by their slender, pale pitchers, which stand out well against dark rock. Expect other lowland species in the same setting, and when in doubt check the spur under the lid (forked) and the petiole (almost wingless). Keep a safe distance from steep rock faces.

Conservation status

The Red List assesses the species as Least Concern. The range is long, the altitudinal span large, and the species grows on open rocky sites unsuited to agriculture. Locally, populations are lost to road building and slope excavation, and the surrounding forest is giving way to plantations, but the rock faces themselves are usually left alone. As a member of the genus it is listed in CITES Appendix II; international trade in wild plants requires a permit.

Scientific name

Nepenthes eustachya | Miquel, 1858

Nepenthes eustachya was described in 1858 by Friedrich Anton Wilhelm Miquel, in his work Flora Indiae Bataviae. The lectotype (Teijsmann 529) was collected in February 1856 by Johannes Elias Teijsmann near Sibolga, a port town on Sumatra's coast, and is held at the herbarium of the Bogor Botanical Gardens. Near Sibolga, a port town on the west coast of Sumatra, Indonesia. The specific epithet derives from Greek "eu" ("true") and "stachys" ("spike"), referring to the racemose structure of the inflorescence.

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