Nepenthes

Nepenthes

Synonymy

Nepenthes L., Sp. Pl.: 955. 1753 sec. Jebb & Cheek 1997
  • =Anurosperma (Hook.f.) Hallier f. in Beih. Bot. Centralbl., Abt. 2, 39(2): 162. 1921 syn. sec. Cheek & Jebb 2001

Other sources

Jebb, M. H. P. & Cheek, M. R. 1997: A skeletal revision of Nepenthes. – Blumea 42(1): 1-106: 5

Description

Carnivorous, dioecious, woody or subwoody climbers or subshrubs, terrestrial or epiphytic. Stems terete or 2-4-angled, or winged. Buds naked, lacking scales. Phyllotaxy spiral, 2/5 or 1/2. Leaves exstipulate; involute or convolute, marcescent, simple, chartaceous or coriaceous, petiolate or sessile; midrib extended into an unbranched tendril, the distal part of which expands into an elaborate, animal trapping receptacle (pitcher) containing digestive fluid. Pitchers dimorphic. Lower pitchers produced from rosettes or short stems, often resting on the ground, usually ovoid or globular, the mouth facing towards the stem, with two ventral fringed wings running from the base to the pitcher rim and with the tendril straight, not coiled. Upper pitchers (usually absent in N. argentii, N. ampullaria, and N. pectinata) usually more elongated and infundibuliform (funnel-shaped) than the lower pitchers, the mouth facing away from the stem, the wings reduced to ridges and not fimbriate, or absent, and the tendril coiled. Pitcher mouth apical or subapical, rimmed with a ribbed peristome (except N. inermis), the inner edge often toothed and bearing nectar glands, at the rear sometimes raised to form a column, supporting the lid; lid usually held over the mouth (reflexed e.g. in N. dubia), lower surface with a laterally flattened basal appendage, rarely an apical filiform appendage, or appendages absent; nectar glands usually abundant; spur inserted on dorsal surface at junction with lid, entire or variously divided, flattened or terete. Inflorescence terminal, appearing lateral by subsequent growth, a paniculoid thyrse or raceme, of 6-300 flowers, the main axis with indeterminate growth, the partial inflorescences 1-flowered (racemose) or 2-flowered, less usually 3-40-flowered, bracteate or ebracteate. Perianth imbricate, a single whorl of 4 (also interpreted as two whorls of 2) free or basally united, patent, nectariferous tepals. Female flowers with androecium lacking, ovary superior, 4-carpellate, incompletely 4-locular locules antitepalous, placentation lamellar, ovules erect, anatropous, bitegmic, crassinucellate, 200-500, stigmas sessile, as many as locules. Male inflorescence usually larger and more floriferous, perianth as in female; stamens 4-?12, filaments united into an androphore, anthers tetrasporangiate, in 1-3 dense whorls, united into a subspherical anther head, locules opening by longitudinal slits, extrorse; gynoecium lacking. Fruit sometimes stipitate, a loculicidally dehiscent capsule with 4 valves containing 50-500 seeds. Seeds filiform, 3-25 mm long, slender due to long basal and apical appendages. Testa reduced to an outer epidermis with thick outer walls to the cells and irregular thickenings on the radial and inner walls. Tegmen produced only around the embryonic cavity, crushed. Endosperm starchy or absent. Embryo minute, central, straight or U-shaped in a subellipsoid cavity, cotyledons and hypocotyl well-developed, though minute. Indumentum of simple, bifid, fasciculate, stellate, dendritic non-glandular and sunken, sessile or shortly stipitate glandular hairs. Colour of pitchers entirely green, or yellow or orange or white or purple or red, often marked with red streaks or blotches; peristome often glossy red; inflorescence with green, brown or red tepals. 2n = 80.A

Notes

Genus with 176 species and 9 natural hybrid described here (about 160 species according to Clarke & al. 2018). B

Conservation

Walters & Gillett (1997) in the IUCN Red list of threatened plant species treat 25% of the species of Nepenthes they recognise as ‘threatened’, and give IUCN ratings for 14 Malesian taxa as follows: Indeterminate 3 (N. burbidgeae, N. deaniana, N. philippinensis); Vulnerable 3 (N. edwardsiana, N. rajah, N. villosa); Rare 4 (N. burkei, N. lowii, N. paniculata, N. veitchii); Endangered 4 (N. gracillima, N. muluensis, N. northiana, N. neglecta).
However, apart from these species, there are several others which are probably more highly threatened. Nepenthes clipeata is believed to be reduced to only 2-6 plants in the wild owing to collection of plants for horticultural purposes at its only known wild locality. The type locality of N. campanulata was destroyed by fire and the species considered possibly extinct until it was rediscovered at a hitherto unknown, second locality in the last two years.
The species of Nepenthes are particularly vulnerable to threats because so many of them have highly restricted distributions. Many are known from a single locality or small area, such as a mountain. There are two main threats to Nepenthes: horticultural trade and habitat destruction.
The Horticultural Trade — The horticultural trade in Nepenthes is mostly international. The main markets are Western Europe, Japan, and the United States of America. Increasingly the supply of tissue-cultured plants is growing to meet the demand of purchasers. However, collection of plants from the wild for horticultural purposes continues.
All species of the genus Nepenthes are listed on CITES Appendix II, apart from N. khasiana (India) and N. rajah which appear on Appendix I (CITES is the Convention on International Trade in Endangered Species) (Knees & Cheek 1988; Cheek 1990). The average number of plants traded internationally in the period 1983-1989 (for which records were kept) was 1,168,000 plants per year (World Conservation Monitoring Centre 1991). Prices are generally highest in Japan, where a price of USD 304 per plant has been reported (World Conservation Monitoring Centre 1991). In Germany the highest price recorded has been USD 215 per plant, but plants can be bought for as little as USD 10, depending on rarity (Jenkins 1993).
Habitat Destruction — The species most threatened by habitat destruction are lowland species, particularly those of restricted distribution such as N. sumatrana and N. bicalcarata, and obligate ultramafic species, such as N. philippinensis and N. argentii. Lowland rain forest species are vulnerable to loss of habitat from non-sustainable logging, and the clearance of forest and scrub for agriculture, habitation, tourism, and associated house-building. Ultramafic-obligate species, and to a lesser extent species of limestone, are especially vulnerable to open-cast mining operations since ultramafic substrates have a super abundance of metals, such as manganese, nickel, and cobalt. Nepenthes danseri in particular, may be threatened by mining for nickel (Jebb, pers. obs.). Reference to mine-workings often appear on the collecting labels of such species. Underground workings are likely to have less impact than open-cast mining. Limestone-specific species may be under threat from mining if there are associated metal deposits (e.g. N. northiana: gold and antimony at Bau) or if the limestone itself is mined for cement production or other uses (N. northiana).
Montane species of Nepenthes, constituting most of the genus, are, generally, less threatened with habitat destruction than lowland species, although generally, of more interest to horticulturists. Lian (1995) sampled many of the montane localities in Peninsular Malaysia from which N. macfarlanei has been known historically, and found that it was still present at all the sites that she surveyed. However, there is concern that the expansion in number of touristic and leisure complexes situated in the mountains of Peninsular Malaysia has destroyed some populations of the endemic Nepenthes species there.

Distribution (General)

Mostly in Malesia, but with outlying species in: Madagascar, Seychelles, Sri Lanka, NE India, Indochina, Solomon Islands, New Caledonia and Australia. Most species are found in Borneo and Sumatra.A

Bibliography

A. Cheek, M. R. & Jebb, M. H. P. 2001: Flora Malesiana - Nepenthaceae, Series I, Volume 15. – Leiden: Nationaal Herbarium Nederland, Universiteit Leiden branch
B. Berendsohn, W. G. & al. 2018: Using the EDIT Platform for Cybertaxonomy to prepare and publish a treatment for the Caryophyllales Network: an online synthesis of the Nepenthaceae. – Willdenowia 48: 335-344. http://doi.org/10.3372/wi.48.48301

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