Nepenthes ( <!--The OED and Random House have [nɪ]; Merriam-Webster and the author of these pages have [nə]; other Webster's dictionaries have [ə̇] (written schwa-dot etc.)-->) is a genus of carnivorous plants, also known as tropical pitcher plants, or monkey cups, in the monotypic family Nepenthaceae. The genus includes about 170 species, and numerous natural and many cultivated hybrids. They are mostly liana-forming plants of the Old World tropics, ranging from South China, Indonesia, Malaysia, and the Philippines; westward to Madagascar (two species) and the Seychelles (one); southward to Australia (four) and New Caledonia (one); and northward to India (one) and Sri Lanka (one). The greatest diversity occurs on Borneo, Sumatra, and the Philippines, with many endemic species. Many are plants of hot, humid, lowland areas, but most are tropical, montane plants, receiving warm days but cool to cold, humid nights year-round. A few are considered tropical alpine, with cool days and nights near freezing. The name "monkey cups" refers to the fact that monkeys were once thought to drink rainwater from the pitchers.
Description
thumb|Nepenthes mirabilis at the [[Periyar Tiger Reserve, in Southern Western Ghats of India]]
Nepenthes species usually consist of a shallow root system and a prostrate or climbing stem, often several metres long and up to or more, and usually or less in diameter, although this may be thicker in a few species (e.g. N. bicalcarata). From the stems arise alternate, sword-shaped leaves with entire leaf margins. An extension of the midrib (the tendril), which in some species aids in climbing, protrudes from the tip of the leaf; at the end of the tendril the pitcher forms. The pitcher starts as a small bud and gradually expands into a globe- or tube-shaped trap. The trapping efficiency of this fluid remains high, even when significantly diluted by water, as inevitably happens in wet conditions.
The lower part of the trap contains glands that absorb nutrients from captured prey. Along the upper inside part of the trap is a slick, waxy coating, which makes the escape of its prey nearly impossible. Surrounding the entrance to the trap is a structure called the peristome (the "lip"), which is slippery and often quite colourful, attracting prey, but offering an unsure footing. The prey-capture effectiveness of the peristome is further enhanced in moist environments, where condensation may cause a thin water film to form on the surface of the peristome. When wet, the slippery surface of the peristome causes insects to "aquaplane", or slip and fall, into the pitcher. Above the peristome is a lid (the operculum); in many species, this keeps rain from diluting the fluid within the pitcher, the underside of which may contain nectar glands that attract prey. Records of cultivated plants trapping small birds have been made. Flowers occur in racemes or more rarely in panicles with male and female flowers on separate plants. Three species have symbiotic relationships with treeshrews, which eat the nectar produced by the plant and defecate into the pitchers, providing valuable nutrients.
Nepenthes are insect-pollinated, the primary agents being flies (including blow flies, midges, and mosquitoes), moths, wasps, and butterflies. Their smells can range from sweet to musty or fungus-like. This high number is thought to reflect paleopolyploidy (likely 8x or 16x).
Taxonomy
About 170 species of Nepenthes are currently recognised as valid. This number is increasing, with several new species being described each year. It references a passage in Homer's Odyssey, in which the potion "Nepenthes pharmakon" is given to Helen by an Egyptian queen. "Nepenthes" () literally means "without grief" ( nē = "not", penthos = "grief") and, in Greek mythology, is a drug that quells all sorrows with forgetfulness. Linnaeus explained:
<blockquote>If this is not Helen's Nepenthes, it certainly will be for all botanists. What botanist would not be filled with admiration if, after a long journey, he should find this wonderful plant. In his astonishment, past ills would be forgotten when beholding this admirable work of the Creator! [translated from Latin by Harry Veitch]</blockquote>
The plant Linnaeus described was N. distillatoria, called bāndurā (බාඳුරා), a species from Sri Lanka.
Nepenthes was formally published as a generic name in 1753 in Linnaeus's famous Species Plantarum, which established botanical nomenclature as it exists today. Nepenthes distillatoria is the type species of the genus.
thumb|400px|Nepenthes from Carolus Linnaeus's Species Plantarum of 1753
The name "monkey cups" was discussed in the May 1964 issue of National Geographic, in which Paul A. Zahl wrote:
<blockquote>The carriers called them "monkey cups", a name I had heard elsewhere in reference to Nepenthes, but the implication that monkeys drink the pitcher fluid seemed farfetched. I later proved it true. In Sarawak, I found an orangutan that had been raised as a pet and later freed. As I approached it gingerly in the forest, I offered it a half-full pitcher. To my surprise, the ape accepted it, and with the finesse of a lady at tea, executed a delicate bottoms-up.</blockquote>
The plants are often called kantong semar (Semar's pocket) in Indonesia and sako ni Hudas (Judas' money bag) in the Philippines.
Evolution and phylogeny
An absence of evidence of intermediate species, fossil or living (i.e. a missing link), does not allow forming a phylogenetic timeline for the development of the distinctive traits of modern Nepenthes, which include its relatively rare strict dioecy and carnivorous pitchers. Although Nepenthes is distantly related to several modern genera, among these, even the carnivorous relatives [the sundews (Drosera), Venus flytrap (Dionaea muscipula), waterwheel plant (Aldrovanda), and dewy pine (Drosophyllum)], all lack those traits. Among known Nepenthes, no protomodern characteristics or large variations are found, which suggests that all extant species radiated from a single close ancestor bearing all the modern traits. Phylogenetic comparisons of the chloroplast matK gene sequences between Nepenthes species and with related species support this conclusion, long genetic distance between Nepenthes and others, and abruptly diverging "pom-pon" grouping of the Nepenthes species .
Fossilized pollen of Nepenthes-like plants living on the northern Tethys Sea from 65 to 35 million years ago indicates that then-warmer Europe may have been where the proto-Nepenthes developed, and then escaped to Asia and India as Africa collided with Europe and the ensuing climate change wiped out the ancestral species in the original habitat. About 20 million years ago, Borneo, Sumatra, and Sulawesi and possibly even the Philippines were connected to mainland Asia, providing a bridge for the colonization of most sites of Nepenthes species radiation. The extensive land bridges in the area 20,000 years ago during the ice age would have provided access to the remaining sites of Nepenthes populations in Oceania. The main complication with this hypothesis is the presence of Nepenthes on the distant islands of Seychelles and Madagascar. The seeds were thought to have been transferred by seabirds and shorebirds, which rest during their migrations in swampy habitats and may have inadvertently picked up the seeds. This hypothesis is possibly reinforced by the success of the lowland swamp-dwelling N. distillatoria in colonizing so many locations. especially in the Borneo montane rain forests. The full range of the genus includes Madagascar (N. madagascariensis and N. masoalensis), the Seychelles (N. pervillei), Sri Lanka (N. distillatoria), and India (N. khasiana) in the west to Australia (N. mirabilis, N. rowanae, N. parvula, and N. tenax) and New Caledonia (N. vieillardii) in the southeast. Most species are restricted to very small ranges, including some found only on individual mountains. These limited distributions and the inaccessibility of the regions often means some species go decades without being rediscovered in the wild (e.g. N. deaniana, which was rediscovered 100 years after its initial discovery). About 10 species have population distributions larger than a single island or group of smaller islands. Nepenthes mirabilis has the distinction of being the most widely distributed species in the genus, ranging from Indochina and throughout the Malay Archipelago to Australia.
Because of the nature of the habitats that Nepenthes species occupy, they are often graded as either lowland or highland species, depending on their altitude above sea level, with the rough delineation between lowland and highland. Species growing at lower altitudes require continuously warm climates with little difference between day and night temperatures, whereas highland species thrive when they receive warm days and much cooler nights. Nepenthes lamii grows at a higher altitude than any other in the genus, up to .