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Nepenthes negros
A species that hid for nearly a century under another's name. The plants of the island of Negros were described in 1908 by Macfarlane as a variety of Nepenthes alata, the best-known pitcher plant of the Philippines. When Martin Cheek and Matthew Jebb worked out in 2013 what the name Nepenthes alata actually means, that species turned out to be far more narrowly bounded than thought, and the plants of Negros and the small island of Biliran received a name of their own: Nepenthes negros. It is a member of the alata group and one of the few pitcher plants of the Visayas, the island group between Luzon and Mindanao.
No photograph of this species under a Creative Commons licence or in the public domain is in the guide yet.
Identification
A climber four to five metres tall, with stems four to six millimetres thick which, like the underside of the midrib, are conspicuously densely hairy. The leaves are oblong-elliptic, mostly 11 to 15.5 cm long and 2.4 to 3.8 cm wide, narrowing into a winged, channelled petiole 3.4 to 5.7 cm long. The known pitchers are upper pitchers: almost cylindrical, 13 to 18.5 cm tall and 3.4 to 5 cm wide, broadest at the base and slightly narrowed above into a narrower cylinder that carries fringed wings. The mouth is ovate, the lid round, 2.2 to 4.3 cm long, with a well-developed hooked appendage beneath. The inner edge of the peristome bears distinct teeth and holes. Lower and intermediate pitchers are unknown from herbarium material, and the description gives no field colours.
Similar species
Within the alata group the species most resembles Nepenthes ramos from north-eastern Mindanao. That species has upper pitchers equally wide at base and top and slightly constricted in the middle, without fringed wings, and a lid appendage that is never hooked. From Nepenthes leyte, on the neighbouring island of Leyte, Nepenthes negros differs by its densely hairy stems (hairless in leyte), the fringed wings on the upper pitchers and the teeth on the inner edge of the peristome. It has been suggested that Nepenthes negros might fall within the natural variation of Nepenthes ramos; fieldwork will have to decide.
The trap and how it works
A pitfall trap with a slippery ribbed peristome as its rim. In this species the inner edge of the peristome carries conspicuous teeth, with the holes of nectar glands between them; such teeth prevent an animal that has slid over the rim from pulling itself back up the inside. The hooked appendage under the lid is typical of the alata group and bears nectar glands that lure insects to the spot above the opening. Since only upper pitchers are known, nothing can be said about the capture of crawling animals by lower pitchers. No specific study of prey or fluid has been published for this species.
Habitat and ecology
Submontane forest at about 1350 m (B1), the only altitude known from the available material. The description says little about soil, light requirement or associated vegetation. As in many relatives, one may expect the plant to do best in light gaps and along forest edges, where it climbs up through the surrounding vegetation, but that is a general expectation and not an observation. The elevation field gives the only documented collecting altitude.
Distribution and elevation
Endemic to the Philippines, in the Visayas: known from the island of Negros, after which it is named, and from the much smaller island of Biliran, north of Leyte. Our own list names only Negros; according to the description Biliran explicitly belongs to the range. The oldest material dates from May 1906. How the species is distributed on Negros, and whether it grows on several mountains there, cannot be gathered from the literature.
- Native
Forms and variation
No varieties or colour forms have been described. The old name Nepenthes alata var. biflora is a synonym, not a separate form. Because the species rests largely on herbarium material, virtually nothing is known of natural variation in colour and pitcher shape; the female inflorescence has never been collected. No natural hybrids have been reported. Whether Nepenthes negros and Nepenthes ramos are really different species is the main open question.
Where and when to see it
Visitors to Negros do best to search the mountain forests above 1000 m, where the climbing stems with their densely hairy, almost velvety surface and the narrow pitchers widened at the base stand out against the green. When you find a pitcher, look under the lid: a hooked appendage and teeth on the inner edge of the peristome point to this species. Good, dated photographs of the whole plant, including any lower pitchers, would genuinely add to what is known about it.
Conservation status
The species has not (yet) been assessed for the Red List. In 2013 the describers proposed treating it as Critically Endangered, chiefly because it is known from very few collections. Forest on Negros declined steeply during the twentieth century, and the remaining mountain forests are the last refuge of many endemic species. As a member of Nepenthes it is listed in CITES Appendix II, so international trade in wild plants requires a permit. New fieldwork is needed to know how it is really faring.
Scientific name
Nepenthes negros | Jebb & Cheek, 2013
Nepenthes negros was described in 2013 by Martin Cheek and Matthew Jebb, in "Typification and redelimitation of Nepenthes alata with notes on the N. alata group, and N. negros sp. nov. from the Philippines" (Nordic Journal of Botany 31(5): 616-622). The species occurs on the Philippine islands of Biliran and Negros; the type locality is associated with Negros Island, after which the species is named. The specific epithet refers directly to Negros, one of the two Philippine islands where this pitcher plant is found.
World Checklist of Vascular Plants (WCVP), via Plants of the World Online (POWO), Royal Botanic Gardens, Kew.