Nepenthes diabolica — Vorstman's Guide to the Carnivorous Plants

Identification

A mountain species closely resembling Nepenthes hamata, but going a step further in almost everything. The lower pitchers are red and densely covered on the outside in woolly hairs. The peristome is exceptionally developed: the ribs are drawn out into large, curved teeth hanging over the mouth like a ring of hooks. The available summaries say little about the upper pitchers. As the full description was not consulted for this guide, no measurements are given; for field identification, the combination of woolly hairs, red lower pitchers and the extremely toothed peristome suffices.

Similar species

The only species on Sulawesi with a comparably extreme toothed peristome is Nepenthes hamata, which is also its closest relative. N. hamata, however, has less developed teeth, much less dense hairs, and is usually blotched rather than plain red. Plants offered in the trade as 'hamata' with red, hairy pitchers mostly turn out to be N. diabolica. Other members of the group, such as N. nigra and N. glabrata, have a much narrower and less toothed peristome.

The trap and how it works

A pitfall with a peristome built like a ring of hooks. As in N. hamata, the nectar glands lie along the inner edge, between the bases of the teeth, so a nectar-seeking insect must climb over and between the teeth towards the mouth. What the teeth actually contribute has not been studied experimentally; the explanation most often given is that they hinder escape or deter nectar thieves. The woolly hairs on the outside of the pitcher are unusual in pitcher plants and may give crawling animals a foothold on their way to the mouth, but that has not been studied either. No prey study has been published.

Habitat and ecology

Mossy cloud forest at about 2200 to 2300 m, on a single mountain in Central Sulawesi (B1). The site is cool and permanently damp, with thick moss and an acid, nutrient-poor soil. Further habitat details were not consulted for this guide. For a pitcher plant such a habitat is favourable: the constant humidity keeps the pitchers filled and the peristome slippery, while the poor soil supplies little nitrogen and phosphorus, so that the extra nutrition from prey is a real advantage.

Distribution and elevation

Endemic to Sulawesi and, as far as is known, confined to a single mountain in Central Sulawesi. This agrees with 'Sulawesi' in the guide's own species list, but the known range is very small. Since the species was formally described only in 2020 and the mountains of the island's centre are little explored, its occurrence elsewhere cannot be ruled out. Sulawesi lies east of Wallace's Line, in the transition zone between the Asian and Australian floras and faunas, and holds far fewer pitcher plants than Borneo; all the more striking, then, that a large share of the island's species is endemic.

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 2 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 wild forms have been described. The lower pitchers are generally red, varying in shade and in the density of the hairs. No natural hybrids have been published, but given the close relationship with N. hamata and other members of the group, crossing in the field is conceivable.

Where and when to see it

The site lies on a remote, high mountain in Central Sulawesi, reachable only on treks of several days with local guides. As the species is known from one mountain and has long been sought by collectors, restraint in sharing exact localities is appropriate. Anyone who sees the plant will recognise it by the red, woolly lower pitchers with a ring of long hooks around the mouth. In the mountains expect daily rain, cold nights and leeches on the trails, and allow plenty of time: most pitchers are found only by walking slowly and searching the vegetation systematically.

Conservation status

There is no IUCN assessment of this species (Not Evaluated). What is known: it is recorded from a single mountain and was sought after by collectors even before its formal description, being traded under informal names. A small range combined with collecting pressure makes the species vulnerable. As a member of Nepenthes it is listed in CITES Appendix II, so international trade in wild plants requires a permit. Newly described pitcher plants often quickly become sought after in the trade, and experience with other species shows that this can lead to the plundering of small populations before tissue culture meets the demand.

Scientific name

Nepenthes diabolica | Bianchi, Lee, Golos, Mey, Mansur & Robinson, 2020

Nepenthes diabolica was described in 2020 by Alberto Stefano Bianchi, Ch'ien C. Lee, Michael Golos, François Sockhom Mey, Deden Mansur and Alastair Robinson, in "Nepenthes diabolica (Nepenthaceae), a new species of toothed pitcher plant from Central Sulawesi" (Phytotaxa 464(1): 29-48). A single mountain in Central Sulawesi, Indonesia, at approximately 2,200-2,300 m elevation — known from nowhere else. The name comes from the Latin for "diabolical/devilish" and refers to both the typical red colouration of the lower pitchers and their greatly enlarged peristome teeth.

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