Nepenthes rajah

Nepenthes rajah
Large lower pitcher of Nepenthes rajah. Mount Kinabalu, Borneo.
Conservation status
Endangered  (IUCN 2.3)[1]
CITES Appendix I (CITES)[2]
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Order:	Caryophyllales
Family:	Nepenthaceae
Genus:	Nepenthes
Species:	N. rajah
Binomial name
Nepenthes rajah Hook.f. (1859)
Borneo, showing natural range of Nepenthes rajah highlighted in green.
Synonyms
Heterochresonyms Nepenthes rajah auct. non Hook.f.: A.Slack (1986) [=Nepenthes × alisaputrana] Nepenthes rajah auct. non Hook.f.: G.Cheers (1992) [=Nepenthes × kinabaluensis]

Nepenthes rajah /nɪˈpɛnθiːz ˈrɑːdʒə/ is a carnivorous pitcher plant species of the family Nepenthaceae. It is endemic to Mount Kinabalu and neighbouring Mount Tambuyukon in Sabah, Malaysian Borneo.^[3]: 123 Nepenthes rajah grows exclusively on serpentine substrates, particularly in areas of seeping ground water where the soil is loose and permanently moist. The species has an altitudinal range of 1,500–2,650 m (4,920–8,690 ft) above sea level and is thus considered a highland or sub-alpine plant. Due to its localised distribution, N. rajah is classified as an endangered species by the IUCN and listed on CITES Appendix I.^[2]

The species was collected by Hugh Low on Mount Kinabalu in 1858, and described the next year by Joseph Dalton Hooker, who named it after James Brooke, the first White Rajah of Sarawak. Hooker called it "one of the most striking vegetable productions hither-to discovered".^[4] Since being introduced into cultivation in 1881, Nepenthes rajah has always been a much sought-after species. For a long time, the plant was seldom seen in private collections due to its rarity, price, and specialised growing requirements. However, recent advances in tissue culture technology have resulted in prices falling dramatically, and N. rajah is now relatively widespread in cultivation.

Nepenthes rajah is most famous for the giant urn-shaped traps it produces, which can grow up to 41 cm (16 in) high^[5] and 20 cm (7.9 in) wide.^[6] These are capable of holding 3.5 L (0.92 US gal) of water^[7] and in excess of 2.5 L (0.66 US gal) of digestive fluid, making them probably the largest in the genus by volume. Another morphological feature of N. rajah is the peltate leaf attachment of the lamina and tendril, which is present in only a few other species.

Nepenthes rajah traps vertebrates and even small mammals, with drowned rats having been observed in the pitcher-shaped traps.^[8] It is one of only three Nepenthes species documented as having caught mammalian prey in the wild, the others being N. rafflesiana and N. attenboroughii. N. rajah is also known to occasionally trap small vertebrates such as frogs, lizards, and even birds, although these cases probably involve sick animals and certainly do not represent the norm. Insects, and particularly ants, comprise the staple prey in both aerial and terrestrial pitchers.

Although Nepenthes rajah is most famous for trapping and digesting animals, its pitchers are also host to a large number of other organisms, which are thought to form a symbiotic association with the plant. Many of these animals are so specialised that they cannot survive anywhere else, and are referred to as nepenthebionts. N. rajah has two such mosquito taxa named after it: Culex rajah and Toxorhynchites rajah.

Another key feature of N. rajah is the relative ease with which it is able to hybridise in the wild. Hybrids between it and all other Nepenthes species on Mount Kinabalu have been recorded. However, due to the slow-growing nature of N. rajah, few hybrids involving the species have been artificially produced yet.