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Nepenthes samar
Samar, the third-largest island of the Philippines, was until 2013 practically a blank on the pitcher-plant map. That year Martin Cheek and Matthew Jebb described Nepenthes samar from a herbarium collection made on the island in August 1996 by Filipino collectors, which was kept in an American herbarium. The species is named after the island; the type collection, with pitchers and a fruiting inflorescence, was made under the Philippine Plant Inventory, a collaboration between the Philippine national herbarium and an American botanical institute. Unlike many recently described Philippine species it is not a mountain plant: it grows in lowland forest on ultramafic soil.
No photograph of this species under a Creative Commons licence or in the public domain is in the guide yet.
Identification
A robust climber with quadrangular stems five to seven, sometimes nine millimetres thick. The leaves are long and narrow, linear-oblong, 22 to 32 cm long but only 2.8 to 3.2 cm wide, with five or six pairs of longitudinal veins; they are arranged spirally along the stem. The known pitchers are upper pitchers: cylindrical to narrowly funnel-shaped, 12 to 25 cm tall and four to six, sometimes eight centimetres wide. The most striking feature is the peristome: rounded and broad, six to fourteen millimetres, with very low ribs. The mouth is ovate; the lid broadly elliptic, six to seven centimetres long. The pitchers are green with red spotting, and the inflorescence carries copper-coloured hairs. Lower pitchers have not been described.
Similar species
The describers name Nepenthes merrilliana as the closest relative. That species also grows low on ultramafic soil, but in north-eastern Mindanao and the islands above it, and is known for its very large upper pitchers with a broad peristome. On Samar itself confusion is possible mainly with the common and widespread Nepenthes mirabilis, which has leaves with a distinct petiole, a narrower peristome and a much less robust habit. The combination of square stem, long narrow leaves and broad rounded peristome makes Nepenthes samar recognisable on the island.
The trap and how it works
A pitfall trap with a broad peristome as its catching rim. A broad, slippery peristome enlarges the surface on which insects coming for nectar can lose their footing; the low ribs, only a tenth to a quarter of a millimetre high, carry a water film in humid weather that makes the rim impassable. The large lid shields the opening from inflowing rain. Since only hanging upper pitchers are known, the catch will consist mainly of flying insects and those climbing over the tendrils, but the prey of this species has not been studied. What the lower pitchers look like, and what they catch, is unknown.
Habitat and ecology
Lowland dipterocarp forest on ultramafic soil, at low elevation (B2, R3). Ultramafic soils, rich in magnesium, iron and heavy metals and poor in the usual nutrients, are a hotspot for pitcher plants in the Philippines; in the east of the archipelago they run in a chain from Samar via Dinagat to north-eastern Mindanao. The exact altitude of the site is not given and no altitudinal range has been published; the elevation field is therefore left empty.
Distribution and elevation
Endemic to the island of Samar in the eastern Visayas. The description deliberately withholds the exact site, and this guide follows suit. It is not known whether the species grows at more places on the island; much of Samar's ultramafic terrain has barely been explored botanically, and the chance of further populations is real.
- Native
Forms and variation
No varieties or colour forms have been described. With a single collection as its basis, nothing can be said about variation, other than that the pitchers of the type material are green with red spotting. No natural hybrids have been reported. Plants in the trade under this name have no documented wild origin and fall outside this account.
Where and when to see it
For visitors to Samar, the lowland forests on ultramafic soil are the terrain to explore, preferably with local conservationists or a university. Look for robust climbing stems with a square cross-section and long narrow leaves, and for pitchers with a conspicuously broad, rounded rim. The island has a very wet climate without a real dry season and is regularly struck by typhoons; plan a visit outside the typhoon season. Site details belong with conservationists and herbaria, not on social media.
Conservation status
The species has not (yet) been assessed for the Red List. The describers proposed Critically Endangered, on the basis of the very small number of known plants. Lowland forest on ultramafic soil in the eastern Philippines is under pressure from logging and above all from mining, since precisely these soils contain nickel and chromium. As a member of Nepenthes it is listed in CITES Appendix II, so international trade in wild plants requires a permit.
Scientific name
Nepenthes samar | Jebb & Cheek, 2013
Nepenthes samar was described in 2013 by Martin Cheek and Matthew Jebb, in Blumea 58(1): 82-84. The island of Samar, Philippines — the only known locality of this species. The specific epithet is named after the island of Samar, to which it is endemic.
World Checklist of Vascular Plants (WCVP), via Plants of the World Online (POWO), Royal Botanic Gardens, Kew.