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Nepenthes zygon
A species discovered in a glasshouse. Nepenthes zygon was described in 2014 from a plant growing at Kew since 2004, raised from seed collected in 1997 on Mount Pasian in north-eastern Mindanao. Only on comparison with old herbarium material did it emerge that the same plant had been collected in 1912 on the summit of neighbouring Mount Masay and had lain in the cabinets for decades as Nepenthes alata. The name comes from Greek and means 'yoked, paired': a reference to its close tie with Nepenthes mindanaoensis.
No photograph of this species under a Creative Commons licence or in the public domain is in the guide yet.
Identification
A climber with terete stems 5.5 to 9.5 mm thick, set with brown, spreading 'dagger hairs'. Rosette leaves are oblanceolate, 14 to 18 cm long; leaves of the climbing stem are narrowly oblong-elliptic, 21 to 30 cm long and 2.8 to 7 cm wide, with a winged petiole whose wings spread flat. Lower pitchers are ellipsoid-cylindric, 9 to 14 cm tall, broadest in the lower half, with two fringed wings from base to mouth. Upper pitchers are larger, to 25 cm, with a swollen basal part seven or eight centimetres long and a narrower cylinder above. In life the swollen part is green and covered in a white waxy bloom, while the cylinder carries faint to marked red-purple stripes and flecks. In upper pitchers the wings are limited to a short fringed stretch just below the mouth. The peristome is green or reddish green.
Similar species
Its closest relative is Nepenthes mindanaoensis, and the two look much alike. That species, however, has ovate-lanceolate leaves, petiole wings so strongly rolled inward that the petiole looks cylindrical, and an inconspicuous or weak appendage under the lid. In Nepenthes zygon the petiole wings spread flat, and upper pitchers carry a distinct convex or hooked appendage under the lid. They also part ecologically: Nepenthes mindanaoensis grows in scrub on ultramafic soil at 200 to 300 m, this species in mossy cloud forest above 1500 m. The white waxy bloom on the lower part of the pitchers is a good field character within the group.
The trap and how it works
A pitfall trap with two clearly different pitcher forms. Lower pitchers stand on the ground, with fringed wings three or four millimetres wide along the whole front that guide crawling animals to the mouth. Upper pitchers hang from the tendrils and have only a short wing section below the mouth. The peristome is finely ribbed; its inner edge looks toothless, but dissection reveals small holes, the openings of nectar glands. Under the lid lie two types of nectar gland, concentrated mostly around the basal ridge, and the centre of the underside carries hairs, which the describers note as unusual. The white wax on the outside of the lower pitcher is remarkable; whether it plays a role in catching prey or deterring animals has not been studied. Nothing has been published on the prey.
Habitat and ecology
Submontane mossy forest along ridges, at 1500 to 1875 m, on ground the describers believe to be non-ultramafic (B1). That is a notable difference from many other pitcher plants of north-eastern Mindanao, which grow precisely on the serpentine-like soils of the region. The American botanist Elmer, who visited Mount Masay in 1912, saw three terrestrial pitcher plants side by side on the summit: Nepenthes surigaoensis, Nepenthes petiolata and this species, with the epiphytic Nepenthes truncata lower on the slopes.
Distribution and elevation
Endemic to the Philippines, in north-eastern Mindanao. Known for certain from two mountains: Pasian, source of the seed for the type plant, and Masay, where Elmer made his collection in the summit region at about 1900 m. Photographs suggest the species may also occur on the volcano Hibok-Hibok on Camiguin island, but this has not been confirmed by herbarium material. Our own list names only Mount Pasian; according to the description Mount Masay explicitly belongs to the range as well.
- Native
Forms and variation
The two known collections differ only in the density of hairs on stem and leaf and in the density of nectar glands under the lid; otherwise they are identical. No varieties or colour forms have been described. Strikingly, smaller lower pitchers of about 10 cm lack any ridge or appendage under the lid, while larger ones of about 15 cm already show the structure of the upper pitchers; the describers leave open whether this holds for the whole group. No natural hybrids have been reported.
Where and when to see it
The mountains of north-eastern Mindanao are rugged and hard to reach, and on Mount Pasian, according to the describers, forest has been clear-felled, possibly including the type population. A visit therefore needs local guides and permits, and much patience. Anyone walking the cloud forest on ridges above 1500 m should look for pitchers with a white-bloomed, swollen base and a red-striped cylinder above; lower pitchers lie in the moss on the ground. Since the species is already in cultivation, there is no reason to take material.
Conservation status
The species has not (yet) been assessed for the Red List. The describers themselves proposed Critically Endangered, because only two plants were known with certainty from the wild; Mount Masay appears secure around the summit, but on Mount Pasian the forest has been felled. As a member of Nepenthes it is listed in CITES Appendix II, so international trade in wild plants requires a permit. The describers count it as fortunate that the species is already in cultivation and available from nurseries; that lowers the pressure to collect wild plants, but does not replace protection of the cloud forest.
Scientific name
Nepenthes zygon | Jebb & Cheek, 2014
Described by Jebb & Cheek in 2014, in "Expansion of the Nepenthes alata group (Nepenthaceae), Philippines, and descriptions of three new species", Blumea, volume 59, no. 2, p. 144-154 — the same publication as N. tboli (golf 32). Mount Pasian, Mindanao, Philippines — an unusual case: the type material is a cultivated plant, grown from seed collected in the wild in 1997 by Robert Cantley (after whom N. robcantleyi, golf 30, is named) and subsequently cultivated at the Royal Botanic Gardens, Kew, where the formal type specimen was made from this cultivated plant. No elevation is known. The meaning of the name could not be established with certainty. "Zygon" is Greek for "yoke" and may plausibly refer to a paired structure (for example paired wings or lid appendages), but this remains a guess without confirmation from the original description.
World Checklist of Vascular Plants (WCVP), via Plants of the World Online (POWO), Royal Botanic Gardens, Kew.