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{{Short description|Species of pitcher plant from Borneo}}
{{Good article}}
{{Speciesbox
|image = Nepenthes rajah.png
|image_caption = Large lower pitcher of ''Nepenthes rajah''.  Mount Kinabalu, Borneo.
|status = EN
|status_system = IUCN2.3
|status_ref = <ref name="iucn status 19 November 2021">{{cite iucn |author=Clarke, C. |author2=Cantley, R. |author3=Nerz, J. |author4=Rischer, H. |author5=Witsuba, A. |date=2000 |title=''Nepenthes rajah'' |volume=2000 |page=e.T39690A10251581 |doi=10.2305/IUCN.UK.2000.RLTS.T39690A10251581.en |access-date=19 November 2021}}</ref>
|status2 = CITES_A1
|status2_system = CITES
|status2_ref = <ref name=CITES_A1/>
|genus = Nepenthes
|species = rajah
|authority = [[Joseph Dalton Hooker|Hook.f.]] (1859)
|range_map = Nepenthes rajah distribution.png
|range_map_caption = Borneo, showing natural range of ''Nepenthes rajah'' highlighted in green.
|synonyms = 
{{collapsible list|bullets = true
 |title=<small>[[Heterochresonym]]s</small>
 |''Nepenthes rajah''<br/><small>''auct. non'' [[Joseph Dalton Hooker|Hook.f.]]: [[Adrian Slack|A.Slack]] (1986)<br/>[<nowiki>=</nowiki>''[[Nepenthes x alisaputrana|Nepenthes × alisaputrana]]'']</small>
 |''Nepenthes rajah''<br/><small>''auct. non'' [[Joseph Dalton Hooker|Hook.f.]]: [[Gordon Cheers|G.Cheers]] (1992)<br/>[<nowiki>=</nowiki>''[[Nepenthes x kinabaluensis|Nepenthes × kinabaluensis]]'']</small>
 }}
}}

'''''Nepenthes rajah''''' {{IPAc-en|n|ᵻ|ˈ|p|ɛ|n|θ|iː|z|_|ˈ|r|ɑː|dʒ|ə}} is a [[carnivorous plant|carnivorous]] [[pitcher plant]] [[species]] of the [[family (biology)|family]] [[Nepenthes|Nepenthaceae]]. It is [[endemic (ecology)|endemic]] to [[Mount Kinabalu]] and neighbouring [[Mount Tambuyukon]] in [[Sabah]], [[Malaysia]]n [[Borneo]].<ref name="Clarke">{{cite book |last1=Clarke |first1=Charles |last2=Wong |first2=K. M. |title=Nepenthes of Borneo |date=1997 |publisher=Natural History Publications in association with Science and Technology Unit, Sabah |location=Kota Kinabalu |isbn=983-812-015-4 |url=https://archive.org/details/nepenthesofborne0000clar/mode/2up}}</ref>{{rp|123}} ''Nepenthes rajah'' grows exclusively on [[Serpentine group|serpentine]] [[Substrate (biology)|substrate]]s, particularly in areas of [[seepage|seeping]] [[ground water]] where the soil is loose and permanently moist. The species has an [[Altitude|altitudinal]] [[range (biology)|range]] of {{cvt|1500|–|2650|m|ft}} [[above sea level]] and is thus considered a [[Highland (geography)|highland]] or sub-[[Alpine climate|alpine]] plant. Due to its localised distribution, ''N. rajah'' is classified as an [[endangered species]] by the [[World Conservation Union|IUCN]] and listed on [[CITES|CITES Appendix I]].<ref name="CITES_A1" />

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".<ref name=Hooker1859>Hooker 1859.</ref> 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 {{cvt|41|cm|in}} high<ref name=largest>Hamilton, G. 2011. {{cite web |url= http://thesabahsociety.com/blog/wp-content/uploads/2011/04/TheSabahSocietyMesilauTrip.pdf |title= The Sabah Society Mesilau Trip, March 26–27, 2011. |access-date= 2011-07-02 |archive-url= https://web.archive.org/web/20180930031901/http://thesabahsociety.com/blog/wp-content/uploads/2011/04/TheSabahSocietyMesilauTrip.pdf |archive-date= 2018-09-30 |url-status= dead }} The Sabah Society.</ref> and {{cvt|20|cm|in}} wide.<ref name=McPherson>McPherson, S.R. 2009. ''[[Pitcher Plants of the Old World]]''. 2 volumes. Redfern Natural History Productions, Poole.</ref> These are capable of holding {{cvt|3.5|l|gal}} of water<ref name=Focus>{{cite web |url= http://www.arcbc.org.ph/arcbcweb/pdf/vol1no4/focus_pitcher_plant.pdf |title= Focus: Rajah Brooke's Pitcher Plant |url-status= dead |archive-url= https://web.archive.org/web/20060526141837/http://www.arcbc.org.ph/arcbcweb/pdf/vol1no4/focus_pitcher_plant.pdf |archive-date= 2006-05-26 }}</ref> and in excess of {{cvt|2.5|l|gal}} of digestive fluid, making them probably the largest in the [[genus]] by volume. Another [[morphology (biology)|morphological]] feature of ''N. rajah'' is the [[Leaf shape|peltate]] leaf attachment of the [[leaf|lamina]] and [[tendril]], which is present in only a few other species.

''Nepenthes rajah'' traps [[vertebrate]]s and even small [[mammal]]s, with drowned rats having been observed in the pitcher-shaped traps.<ref name=rats>Phillipps 1988, p. 55.</ref> It is one of only three ''Nepenthes'' species documented as having caught mammalian prey in the wild, the others being ''[[Nepenthes rafflesiana|N. rafflesiana]]'' and ''[[Nepenthes attenboroughii|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. [[Insect]]s, 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 [[Symbiosis|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]] [[taxon|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 [[Hybrid (biology)|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.

==Etymology==
[[Image:Sir James Brooke (1847) by Francis Grant.jpg|thumb|right|James Brooke]]
[[Joseph Dalton Hooker]] described ''Nepenthes rajah'' in 1859, naming it in honour of [[James Brooke|Sir James Brooke]], the first [[White Rajah]] of [[Sarawak]].<ref name=Kurata>Kurata 1976, p. 61.</ref>  In the past, the Latin name was written as ''Nepenthes Rajah'',<ref name=Hooker1859 /><ref>Masters 1881.</ref><ref>Reginald 1883.</ref><ref>Hemsley 1905.</ref><ref name=Danser>Danser 1928, 38.</ref> since it derives from a [[proper noun]]. However, this capitalisation is considered incorrect today. 'Rajah Brooke's Pitcher Plant'<ref name=P&L>Phillipps & Lamb 1996, p. 129.</ref> is an accurate, but seldom-used [[common name]]. ''N. rajah'' is also sometimes called the 'Giant Malaysian Pitcher Plant'<ref name=Gibson>Gibson 1983.</ref> or simply 'Giant Pitcher Plant', although the [[binomial nomenclature|binomial name]] remains by far the most popular way of referring to this species. The specific [[epithet]] ''[[raja]]h'' means "King" in [[Malay language|Malay]] and this, coupled with the impressive size of its pitchers, has meant that ''N. rajah'' is often referred to as the "King of ''Nepenthes''".<ref name=Steiner>Steiner 2002, p. 94.</ref>
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==Plant characteristics==
[[Image:Kinabalu Mesilau N. rajah upper pitcher plant 2.jpg|thumb|right|300px|Mature plants bearing both lower and upper pitchers]]
[[Image:nep rajah peltate.jpg|thumb|The characteristic peltate leaf attachment of ''N. rajah'']]

''Nepenthes rajah'', like virtually all species in the genus, is a scrambling vine. The [[Plant stem|stem]] usually grows along the ground, but will attempt to climb whenever it comes into contact with an object that can support it. The stem is relatively thick (up to {{cvt|30|mm|in}}) and may reach up to {{cvt|6|m|ft}} in length, although it rarely exceeds {{cvt|3|m|ft}}.<ref name="Clarke" />{{rp|10,120}} ''N. rajah'' does not produce [[Stolon|runners]] as some other species in the genus, but older plants are known to form [[Offshoot (plant)|basal offshoots]]. This is especially common in plants from [[tissue culture]], where numerous offshoots may form at a young age.

===Leaves===
[[Leaves]] are produced at regular intervals along the stem.  They are connected to the stem by sheathed structures known as [[Petiole (botany)|petioles]]. A long, narrow [[tendril]] emanates from the end of each leaf.  At the tip of the tendril is a small bud which, when [[physiology|physiologically]] activated, develops into a functioning trap.  Hence, the pitchers are modified leaves and not specialised [[flowers]] as is often believed.  The green structure most similar to a normal leaf is specifically known as the [[Leaf|lamina]] or leaf blade.

The leaves of ''N. rajah'' are very distinctive and reach a large size. They are leathery in texture with a wavy outer margin. The leaves are characteristically [[Leaf shape|peltate]], whereby the tendril joins the lamina on the underside, before the apex. This characteristic is more pronounced in ''N. rajah'' than in any other ''Nepenthes'' species, with the exception of ''[[Nepenthes clipeata|N. clipeata]]''. However, it is not unique to these two taxa, as mature plants of many ''Nepenthes'' species display slightly peltate leaves. The tendrils are inserted within {{cvt|5|cm|in}} below the leaf apex and reach a length of approximately {{cvt|50|cm|in}}.<ref name=Clarke />{{rp|120,122}} Three to five longitudinal veins run along each side of the lamina and [[pennate]] (branching) veins run towards the margin. The lamina is oblong to [[lanceolate]]-shaped, up to {{cvt|80|cm|in}} long and {{cvt|15|cm|in}} wide.

[[Image:Rajahpitcher3.jpg|left|thumb|upright|A typical terrestrial pitcher]]

===Pitchers===
All ''Nepenthes'' pitchers share several basic characteristics.  Traps consist of the main pitcher cup, which is covered by an [[Operculum (botany)|operculum]] or lid that prevents rainwater from entering the pitcher and displacing or diluting its contents. A reflexed ring of hardened tissue, known as the [[peristome]], surrounds the entrance to the pitcher (only the aerial pitchers of ''[[Nepenthes inermis|N. inermis]]'' lack a peristome).  A pair of fringed wings run down the front of lower traps and these presumably serve to guide terrestrial insects into the pitchers' mouth.  Accordingly, the wings are greatly reduced or completely lacking in aerial pitchers, for which flying insects constitute the majority of prey items.

''Nepenthes rajah'', like most species in the genus, produces two distinct types of traps. "Lower" or "terrestrial" pitchers are the most common. These are very large, richly coloured, and ovoid in shape. In lower pitchers, the tendril attachment occurs at the front of the pitcher cup relative to the peristome and wings. Exceptional specimens may be more than {{cvt|40|cm|in}} in length and hold {{cvt|3.5|l|gal}} of water<ref name=Focus/> and in excess of {{cvt|2.5|l|gal}} of [[digestive fluid]], although most do not exceed {{cvt|200|ml|U.S.oz}}.<ref name=ClarkeIV>Clarke 2001b, p. 7.</ref>

[[File:Nepenthes rajah 41 cm pitcher.jpg|thumb|The {{cvt|41|cm|in}} pitcher found on The Sabah Society's March 2011 trip to [[Mesilau]]]]

The largest recorded pitcher of ''N.&nbsp;rajah'', measuring {{cvt|41|cm|in}}, was found on March 26, 2011, during a trip to [[Mesilau]] organised by The Sabah Society.<ref name=largest /> The trap was discovered next to a steep sidepath of the [[Mesilau|Mesilau nature trail]] and was measured by Alex Lamb, son of [[Anthea Phillipps]] and [[Anthony Lamb (botanist)|Anthony Lamb]], who were also on the trip.<ref name=largest /> It was collected for preservation at Mesilau Headquarters.<ref name=largest /> Another trap measuring {{cvt|40|cm|in}} was spotted on the same day.<ref name=largest /> The previous record for a ''N.&nbsp;rajah'' pitcher was {{cvt|38|cm|in}}.<ref name=largest /><ref name=McPherson />

The lower pitchers of ''N. rajah'' are probably the largest in the genus by volume, rivaled only by those of ''[[Nepenthes merrilliana|N. merrilliana]]'', ''[[Nepenthes truncata|N. truncata]]'' and the giant form of ''[[Nepenthes rafflesiana|N. rafflesiana]]''. These traps rest on the ground and are often reclined, leaning against surrounding objects for support.  They are usually red to purple on the outside, whilst the inside surfaces are lime green to purple. This contrasts with all other parts of the plant, which are yellow-green. The lower pitchers of ''N. rajah'' are unmistakable and for this reason it is easy to distinguish it from all other Bornean ''Nepenthes'' species.<ref>Clarke 2001b, p. 26.</ref>

[[Image:Kinabalu Mesilau N. rajah upper pitcher 3.jpg|thumb|left|A rare aerial pitcher]]

Mature plants may also produce "upper" or "aerial" pitchers, which are much smaller, [[funnel]]-shaped, and usually more colourful than the lowers. The tendril attachment in upper pitchers is normally present at the rear of the pitcher cup. True upper pitchers are seldom seen, as the stems of ''N. rajah'' rarely attain lengths greater than a few metres before dying off and being replaced by off-shoots from the main rootstock.<ref>Clarke & Kruger 2005.</ref>

Upper and lower pitchers differ significantly in [[morphology (biology)|morphology]], as they are specialised for attracting and capturing different prey.   Pitchers that do not fall directly into either category are simply known as "intermediate" pitchers.

The peristome of ''N. rajah'' has a highly distinctive scalloped edge and is greatly expanded, forming an attractive red lip around the trap's mouth.  A series of raised protrusions, known as ribs, intersect the peristome, ending in short, sharp teeth that line its inner margin. The inner portion of the peristome accounts for around 80% of its total cross-sectional surface length in this species.<ref name=Baueretal2012>{{cite journal |last1=Bauer |first1=U. |last2=Clemente |first2=C. J. |last3=Renner |first3=T. |last4=Federle |first4=W. |title=Form follows function: morphological diversification and alternative trapping strategies in carnivorous Nepenthes pitcher plants |journal=Journal of Evolutionary Biology |date=January 2012 |volume=25 |issue=1 |pages=90–102 |doi=10.1111/j.1420-9101.2011.02406.x|pmid=22023155 }}</ref> Two fringed wings run from the tendril attachment to the lower edge of the peristome.

The huge, vaulted lid of ''N. rajah'', the largest in the genus, is another distinguishing characteristic of this species. It is ovate to oblong in shape and has a distinct [[keel]] running down the middle, with two prominent lateral veins.<ref>{{in lang|de}} Schmid-Hollinger, R. N.d. [http://www.bio-schmidhol.ch/site/index.cfm?id_art=54826&actMenuItemID=25460&vsprache/DE/Kannendeckel__lid_.cfm Kannendeckel (lid)] {{Webarchive|url=https://web.archive.org/web/20131206025936/http://www.bio-schmidhol.ch/site/index.cfm?id_art=54826&actMenuItemID=25460&vsprache%2FDE%2FKannendeckel__lid_.cfm |date=2013-12-06 }}. bio-schmidhol.ch. <!--https://www.webcitation.org/6La1Hg1xj--></ref> The [[spur]] at the back of the lid is approximately {{cvt|20|mm|in}} long and unbranched.<ref name=Clarke/>{{rp|122}}

''Nepenthes rajah'' is noted for having very large [[nectar]]-[[secretion|secreting]] [[glands]] covering its pitchers.  These are quite different from those of any other ''Nepenthes'' and are easily recognisable.  The inner surface of the pitcher, in particular, is wholly [[glandular]], with {{cvt|300 to 800|/cm2|/in2|disp=preunit|glands}}.<ref name=Danser/>

===Flowers===
[[Image:Nep rajah2 flower.jpg|thumb|A flowering plant of ''N. rajah'']]
''Nepenthes rajah'' seems to flower at any time of the year.  Flowers are produced in large numbers on [[inflorescences]] that arise from the apex of the main stem.  ''N. rajah'' produces a very large inflorescence that can be {{cvt|80|cm|in}}, and sometimes even {{cvt|120|cm|in}}  tall.<ref name=Focus/><ref name=Clarke/>{{rp|122}}  The individual flowers of ''N. rajah'' are produced on partial [[Peduncle (botany)|peduncles]] (twin [[scape (botany)|stalks]]) and so the inflorescence is called a [[raceme]] (as opposed to a [[panicle]] for multi-flowered bunches).  The flowers are reported to give off a strong sugary smell and are brownish-yellow in colour. [[Sepal]]s are elliptic to oblong and up to {{cvt|8|mm|in}} long.<ref name=Clarke/>{{rp|122}} Like all ''Nepenthes'' species, ''N. rajah'' is [[Plant sexuality|dioecious]], which means that individual plants produce flowers of a single sex.  Fruits are orange-brown and {{cvt|10 to 20|mm|in}} long (see [[:Image:Nep rajah28.jpg|image]]). A study of 300 [[pollen]] samples taken from a herbarium specimen (''J.H.Adam 2443'', collected at an altitude of {{cvt|1930–2320|m|ft}}) found the mean pollen diameter to be {{cvt|34.7|μm|in}} ([[Standard error (statistics)|SE]] = 0.3; [[coefficient of variation|CV]] = 7.0%).<ref>Adam, J.H. & C.C. Wilcock 1999. {{cite web|url= http://psasir.upm.edu.my/3779/1/Palynological_Study_of_Bornean_Nepenthes_%28Nepenthaceae%29.pdf |title=Palynological study of Bornean ''Nepenthes'' (Nepenthaceae). }} ''Pertanika Journal of Tropical Agricultural Science'' '''22'''(1): 1–7.</ref>

===Other characteristics===
The root system of ''N. rajah'' is notably extensive, although it is relatively shallow as in most ''Nepenthes'' species.

All parts of the plant are covered in long, white hairs when young, but mature plants are virtually [[Glossary of botanical terms#glabrous|glabrous]] (lacking hair).  This covering of hair is known as the [[indumentum]].

The colour of [[herbarium]] specimens is dark-brown in varying hues (see [[:Image:Nep rajah19.jpg|image]]).

Little variation has been observed within natural populations of ''Nepenthes rajah'' and, consequently, no forms or varieties have been described.  Furthermore, ''N. rajah'' has no true nomenclatural [[synonym (taxonomy)|synonyms]], unlike many other ''Nepenthes'' species, which exhibit greater variability.<ref name=Clarke />{{rp|120}}

==Carnivory==
{{See also|Carnivorous plant#Pitfall traps}}

[[Image:Rajahlizard.jpg|thumb|135px|Drowned lizard found in a freshly opened pitcher. The animal was pulled out of the digestive zone for the photograph.]]

''Nepenthes rajah'' is a [[carnivorous plant]] of the [[Carnivorous plant#Pitfall traps|pitfall trap]] variety. It is famous for occasionally trapping [[vertebrate]]s, even small [[mammal]]s. There exist at least two records of drowned rats found in ''N. rajah'' pitchers. The first observation dates from 1862 and was made by [[Spenser St. John]], who accompanied [[Hugh Low]] on two ascents of Mount Kinabalu.<ref name=Steiner/> In 1988, [[Anthea Phillipps]] and [[Anthony Lamb (botanist)|Anthony Lamb]] confirmed the plausibility of this record when they managed to observe drowned rats in a large pitcher of ''N. rajah''.<ref name=rats /><ref name=Steiner/> In 2011, the discovery of a drowned [[mountain treeshrew]] (''Tupaia montana'') in a ''N.&nbsp;rajah'' pitcher was reported.<ref name=Rattus2 />

''Nepenthes rajah'' is also known to occasionally trap other small vertebrates, including frogs, lizards and even birds, although these cases probably involve sick animals, or those seeking shelter or water in the pitcher, and certainly do not represent the norm.<ref name=Clarke />{{rp|33}} [[Insect]]s, and particularly ants, comprise the majority of prey in both aerial and terrestrial pitchers.<ref name=ClarkeIV/> Other arthropods, such as centipedes, also fall prey to ''N. rajah''.

''[[Nepenthes rafflesiana]]'' is one of the few other ''Nepenthes'' species reliably documented as having caught mammalian prey in its natural habitat. In [[Brunei]], frogs, [[gecko]]s and [[skink]]s have been found in the pitchers of this species.<ref name=Clarke/>{{rp|33}}<ref>Moran 1991.</ref> The remains of mice have also been reported.<ref>[https://archive.today/20031019180952/https://www.discover.com/issues/oct-01/features/featplants/ "I once found a perfect mouse skeleton in a pitcher of ''N. rafflesiana''"] &mdash; [[Ch'ien Lee]]</ref> On September 29, 2006, at the [[Jardin botanique de Lyon]] in France, a cultivated ''[[Nepenthes truncata|N. truncata]]'' was photographed containing the decomposing corpse of a mouse.<ref>[Anonymous] 2006.</ref>

[[File:Rattus baluensis visiting Nepenthes rajah.png|thumb|left|upright|''[[Rattus baluensis]]'' feeding on nectar from a pitcher of ''N.&nbsp;rajah'']]

===Mutualism with mammals===
''Nepenthes rajah'' has evolved a [[Mutualism (biology)|mutualistic relationship]] with [[mountain treeshrew]]s (''Tupaia montana'') in order to collect their droppings.  The inside of the reflexed lid exudes a sweet nectar. The distance from the pitcher mouth to the exudate is the same as the average body length of the mountain treeshrew.  These proportions also hold true for ''[[Nepenthes lowii|N.&nbsp;lowii]]'' and ''[[Nepenthes macrophylla|N.&nbsp;macrophylla]]''.  As it feeds, the treeshrew defecates, apparently as a method of marking its feeding territory.  It is thought that in exchange for providing nectar, the faeces provide ''N.&nbsp;rajah'' with the majority of the [[nitrogen]] it requires.<ref>Chin, L., J.A.  Moran & C. Clarke 2010. Trap geometry in three giant montane pitcher plant species from Borneo is a function of tree shrew body size. ''New Phytologist'' '''186''' (2): 461–470. {{doi|10.1111/j.1469-8137.2009.03166.x}}</ref><ref name=Walker>Walker, M. 2010. [http://news.bbc.co.uk/earth/hi/earth_news/newsid_8552000/8552157.stm Giant meat-eating plants prefer to eat tree shrew poo]. ''BBC Earth News'', March 10, 2010.</ref><ref>Clarke, C., J.A. Moran & L. Chin 2010. Mutualism between tree shrews and pitcher plants: perspectives and avenues for future research. ''Plant Signaling & Behavior'' '''5'''(10): 1187–1189. {{doi|10.4161/psb.5.10.12807}}</ref><ref>Clarke, C. & J.A. Moran 2011. Incorporating ecological context: a revised protocol for the preservation of ''Nepenthes'' pitcher plant specimens (Nepenthaceae). ''Blumea'' '''56'''(3): 225–228. {{doi|10.3767/000651911X605781}}</ref><ref>Davies, E. 2012. [https://www.bbc.co.uk/nature/20273855 David Attenborough's life lessons]. ''BBC Nature Features'', November 15, 2012.</ref> In ''N.&nbsp;lowii'', ''N.&nbsp;macrophylla'' and ''N.&nbsp;rajah'', the colour of the lower lid surface corresponds to visual sensitivity maxima of the mountain treeshrew in the [[visual spectrum|green and blue wavebands]], making the lid underside stand out against adjacent parts of the pitcher.<ref name=tuning>Moran, J.A., C. Clarke, M. Greenwood & L. Chin 2012. Tuning of color contrast signals to visual sensitivity maxima of tree shrews by three Bornean highland ''Nepenthes'' species. ''Plant Signaling & Behavior'' '''7'''(10): 1267–1270. {{doi|10.4161/psb.21661}}</ref> Of the three species, ''N.&nbsp;rajah'' shows the tightest 'fit', particularly in the green waveband.<ref name=tuning />

In 2011, it was reported that ''N.&nbsp;rajah'' has a similar mutualistic relationship with the [[summit rat]] (''Rattus baluensis'').<ref name=Rattus2>Wells, K., M.B. Lakim, S. Schulz & M. Ayasse 2011. Pitchers of ''Nepenthes rajah'' collect faecal droppings from both diurnal and nocturnal small mammals and emit fruity odour. ''Journal of Tropical Ecology'' '''27'''(4): 347–353. {{doi|10.1017/S0266467411000162}}</ref><ref name=Rattus>Greenwood, M., C. Clarke, C.C. Lee, A. Gunsalam & R.H. Clarke 2011. A unique resource mutualism between the giant Bornean pitcher plant, ''Nepenthes rajah'', and members of a small mammal community. ''PLoS ONE'' '''6'''(6): e21114. {{doi|10.1371/journal.pone.0021114}}</ref> Whereas the mountain treeshrew visits pitchers during daylight hours, the summit rat is primarily active at night; this may be an example of [[resource partitioning]]. Daily scat deposition rates were found to be similar for both mammalian species.<ref name=Rattus />
{{multiple image
 | align     = center
 | footer    = '''Left:''' Mammal visitation rates to ''N.&nbsp;rajah'' pitchers. White bars show visitation by ''T.&nbsp;montana'' and black bars by ''R.&nbsp;baluensis''. The horizontal bar below the x-axis indicates [[photoperiod]], white representing daylight hours and black nighttime.<ref name=Rattus /><br/>
'''Right:''' Scat deposition rates to ''N.&nbsp;rajah'' pitchers. Black squares show the mean number of ''T.&nbsp;montana'' droppings found within pitchers; white squares show the mean number found outside pitchers. Black and white diamonds show the same for ''R.&nbsp;baluensis''.<ref name=Rattus />
 | image1    = Mammal visitation rates to Nepenthes rajah pitchers.png
 | width1    = 357
 | image2    = Scat deposition rates to Nepenthes rajah pitchers.png
 | width2    = 350
}}

==Other interactions with animals==

===Pitcher infauna===
{{Main|Nepenthes infauna}}
[[Image:Culex rajah & Toxorhynchites rajah.PNG|thumb|250px|''Culex rajah'' (left) and ''Toxorhynchites rajah'' (right)]]
Although ''Nepenthes'' are most famous for trapping and digesting animals, their pitchers also play host to a large number of other organisms (known as [[Fauna (animals)#Infauna|infauna]]). These include [[fly]] and [[midge]] [[larva]]e, [[spider]]s ([[crab spider]]s such as ''[[Henriksenia labuanica]]''), [[mites]], [[ants]], and even a species of crab, ''[[Geosesarma malayanum]]''.  The most common and conspicuous predators found in pitchers are mosquito larvae, which consume large numbers of other larvae during their development.  Many of these animals are so specialised that they cannot survive anywhere else, and are referred to as [[nepenthebionts]].<ref>Beaver 1979, pp. 1–10.</ref>

The complex relationships between these various organisms are not yet fully understood.  The question of whether infaunal animals "steal" food from their hosts, or whether they are involved in a mutually beneficial ([[Symbiosis|symbiotic]]) association has yet to be investigated experimentally and is the source of considerable debate. [[Charles Clarke (botanist)|Clarke]] suggests that [[Mutualism (biology)|mutualism]] is a "likely situation", whereby "the infauna receives [[wikt:domicile|domicile]], protection and food from the plant, while in return, the infauna helps to break down the prey, increase the rate of digestion and keep bacterial numbers low".<ref name="Clarke" />{{rp|42-43}}

===Species specific===
As the size and shape of ''Nepenthes'' pitchers vary greatly between species, but little within a given taxon, it is not surprising that many infaunal organisms are specially adapted to life in only the traps of particular species.  ''N. rajah'' is no exception, and in fact has two mosquito taxa named after it.  ''[[Culex rajah|Culex (Culiciomyia) rajah]]'' and ''[[Toxorhynchites rajah|Toxorhynchites (Toxorhynchites) rajah]]'' were described by [[Masuhisa Tsukamoto]] in 1989, based on larvae collected in pitchers of ''N. rajah'' on Mount Kinabalu three years earlier.<ref>Tsukamoto 1989, p. 216.</ref> The two species were found to live in association with larvae of ''[[Culex jenseni|Culex (Lophoceraomyia) jenseni]]'', ''[[Uranotaenia moultoni|Uranotaenia (Pseudoficalbia) moultoni]]'' and an undescribed taxon, [[Tripteroides sp. No. 2|''Tripteroides (Rachionotomyia)'' sp. No. 2]]. Concerning ''C. rajah'', Tsukamoto noted that the "body surface of most larvae are covered in ''[[Vorticella]]''-like [[protozoa]]".<ref name=Tsukamoto>Tsukamoto 1989, p. 220.</ref> At present, nothing is known of this species with regards to its adult biology, habitat, or medical importance as a vector of diseases. The same is true for ''T. rajah''; nothing is known of its biology except that adults are not [[hematophagy|haematophagous]].

[[Image:Nep rajah27.jpg|thumb|180px|Damage caused by pests]]

Another species, ''Culex shebbearei'', has also been recorded as an infaunal organism of ''N. rajah'' in the past. The original 1931 record by [[F. W. Edwards]]<ref>Edwards 1931, pp. 25–28.</ref> is based on a collection by [[H. M. Pendlebury]] in 1929 from a plant growing on Mount Kinabalu. However, Tsukamoto notes that in light of new information on these species, "it seems more likely to conclude that the species [''C. rajah''] is a new species which has been misidentitied as ''C. shebbearei'' for a long time, rather than to think that both ''C. shebbearei'' and ''C. rajah'' n. sp. are living in pitchers of ''Nepenthes rajah'' on Mt. Kinabalu".<ref name=Tsukamoto/>

===Pests===
Not all interactions between ''Nepenthes'' and [[fauna]] are beneficial to the plant.  ''Nepenthes rajah'' is sometimes attacked by insects which feed on its leaves and damage substantial portions of the lamina.  Also, [[monkeys]] and [[tarsiers]] are known to occasionally rip pitchers open to feed on their contents.<ref>Burbidge 1880.</ref>

==History and popularity==
{{See also|#Timeline}}
{{cleanup|reason=Length of quotations is probably excessive; if kept, units should be translated to metric. "Click to show" section could be moved to "Further reading"?|date=April 2021}}
[[Image:Hugh Low.png|thumb|135px|Hugh Low]]

Due to its size, unusual morphology and striking colouration, ''N. rajah'' has always been a very popular and highly sought-after insectivorous plant.  However, despite its popularity amongst pitcher plant enthusiasts, ''N. rajah'' remains a little-known species outside the field of carnivorous plants.  Due to its specialised growing requirements, it is not a suitable candidate for a [[houseplant]] and, as such, is only cultivated by a relatively small number of hobbyists and professional growers worldwide. This being the case, ''N. rajah'' is nonetheless probably the most famous of all pitcher plants.  Its reputation for producing some of the most magnificent pitchers in the genus dates back to the late 19th century.<ref>Masters, M.T. 1872. [https://www.biodiversitylibrary.org/page/26129152 The cultivated species of ''Nepenthes''.] ''The Gardeners' Chronicle and Agricultural Gazette'' 1872(16): 540–542.</ref>

''Nepenthes rajah'' was first collected by [[Hugh Low]] on Mount Kinabalu in 1858.<ref name=P&L /> It was described the following year by [[Joseph Dalton Hooker]], who named it after [[James Brooke]], the first [[White Rajah]] of Sarawak. The description was published in ''The Transactions of the Linnean Society of London'':<ref name=Hooker1859 />

<blockquote>''Nepenthes Rajah'', H. f. (Frutex, 4-pedalis, ''Low''). Foliis maximis 2-pedalibus, oblongo-lanceolatis petiolo costaque crassissimis, ascidiis giganteis (cum operculo l-2-pedalibus) ampullaceis ore contracto, stipite folio peltatim affixo, annulo maximo lato everso crebre lamellato, operculo amplissimo ovato-cordato, ascidium totum æquante.—(''Tab.'' LXXII.)

''Hab.''—Borneo, north coast, on Kina Balu, alt. 5,000 feet (''Low''). This wonderful plant is certainly one of the most striking vegetable productions hitherto discovered, and, in this respect, is worthy of taking place side by side with the ''Rafflesia Arnoldii''. It hence bears the title of my friend Rajah Brooke, of whose services, in its native place, it may be commemorative among botanists. . . . I have only two specimens of leaves and pitchers, both quite similar, but one
twice as large as the other. Of these, the leaf of the larger is 18 inches long, exclusive of the petioles, which is as thick as the thumb and 7–8 broad, very coriaceous and glabrous, with indistinct nerves. The stipes of the pitcher is given off below the apex of the leaf, is 20 inches long, and as thick as the finger. The broad ampullaceous pitcher is 6 inches in diameter, and 12 long: it has two fimbriated wings in front, is covered with long rusty hairs above, is wholly studded with glands within, and the broad annulus is everted, and 1–1{{frac|1|2}} inch in diameter. Operculum shortly stipitate, 10 inches long and 8 broad.

The inflorescence is hardly in proportion. Male raceme, 30 inches long, of which 20 are occupied by the flowers; upper part and flowers clothed with short rusty pubescence. Peduncles slender, simple or bifid. Fruiting raceme stout. Peduncles 1{{frac|1|2}} inches long, often bifid. Capsule, {{frac|3|4}} inch long, {{frac|1|3}} broad, rather turgid, densely covered with rusty tomentum.</blockquote>

[[Image:Nepenthes rajah Life in the forests of the Far East.png|thumb|One of the earliest known illustrations of ''N. rajah'', published in ''Life in the Forests of the Far East'' in 1862.]]

[[Spenser St. John]] wrote the following account of his encounter with ''N. rajah'' on Mount Kinabalu in ''Life in the Forests of the Far East'' published in 1862:<ref>St. John 1862, pp. 324, 334.</ref>

<blockquote>Another steep climb of 800 feet brought us to the Marei Parei spur, to the spot where the ground was covered with the magnificent pitcher-plants, of which we had come in search. This one has been called the ''Nepenthes Rajah'', and is a plant about four feet in length, with broad leaves stretching on every side, having the great pitchers resting on the ground in a circle about it. Their shape and size are remarkable. I will give the measurement of one, to indicate the form: the length along the back nearly fourteen inches; from the base to the top of the column in front, five inches; and its lid a foot long by fourteen inches broad, and of an oval shape. Its mouth was surrounded by a plaited pile, which near the column was two inches broad, lessening in its narrowest part to three-quarters of an inch. The plaited pile of the mouth was also undulating in broad waves. Near the stem the pitcher is four inches deep, so that the mouth is situated upon it in a triangular manner. The colour of an old chalice is a deep purple, but that of the others is generally mauve outside, very dark indeed in the lower part, though lighter towards the rim; the inside is of the same colour, but has a kind of glazed and shiny appearance. The lid is mauve in the centre, shading to green at the edges. The stems of the female flowers we found always a foot shorter than those of the male, and the former were far less numerous than the latter. It is indeed one of the most astonishing productions of nature.

[...] The pitchers, as I have before observed, rest on the ground in a circle, and the young plants have cups of the same form as those of the old ones. While the men were cooking their rice, we sat before the tent enjoying our chocolate and observing one of our followers carrying water in a splendid specimen of the ''Nepenthes Rajah'', desired him to bring it to us, and found that it held exactly four pint bottles. It was 19 inches in circumference. We afterwards saw others apparently much larger, and Mr. Low, while wandering in search of flowers, came upon one in which was a drowned rat.</blockquote>

[[Image:First Nepenthes rajah cultivated in Europe.jpg|thumb|left|135px|Illustration of the first ''N. rajah'' plant to be cultivated in Europe, published in ''The Garden'', 1882.]]
''Nepenthes rajah'' was first collected for the [[Veitch Nurseries]] by [[Frederick William Burbidge]] in 1878, during his second trip to Borneo.<ref>Phillipps & Lamb 1996, p. 20.</ref> Shortly after being introduced into cultivation in 1881, ''N. rajah'' proved very popular among wealthy [[Victorian era|Victorian]] [[horticulturalists]] and became a much sought-after species. A note in ''[[The Gardeners' Chronicle]]'' of 1881 mentions the Veitch plant as follows: "''N. rajah'' at present is only a young Rajah, what it will become was lately illustrated in our columns...".<ref>[Anonymous] 1881.</ref> A year later, young ''N. rajah'' plants were displayed at the [[Royal Horticultural Society]]'s annual show for the first time.<ref name=P&L22>Phillipps & Lamb 1996, p. 22.</ref> The specimen exhibited at the show by the Veitch Nurseries, the first of this species to be cultivated in Europe, won a first class certificate.<ref>Phillipps & Lamb 1996, p. 21.</ref>  In Veitch's catalogue for 1889, ''N. rajah'' was priced at [[Pound sterling|£]]2.2[[shilling|s]] per plant.<ref>Phillipps & Lamb 1996, p. 18.</ref> During this time, interest in ''Nepenthes'' had reached its peak. ''[[The Garden (journal)|The Garden]]'' reported that ''Nepenthes'' were being [[plant propagation|propagated]] by the thousands to keep up with European demand.

However, dwindling interest in ''Nepenthes'' at the turn of the century saw the demise of the Veitch Nurseries and consequently the loss of several species and hybrids in cultivation, including ''[[Nepenthes northiana|N. northiana]]'' and ''N. rajah''.  By 1905, the final ''N. rajah'' specimens from the Veitch nurseries were gone, as the cultural requirements of the plants proved too difficult to reproduce.<ref name=P&L22 /> The last surviving ''N. rajah'' in cultivation at this time was located at the [[Irish National Botanic Gardens|National Botanic Gardens]] at [[Glasnevin]] in Ireland, however this soon perished also.<ref name=P&L22 /> It would be many years before ''N. rajah'' was reintroduced into cultivation.

{{hidden|ta1=left|Click [show] to view a list of early publications, illustrations, and collections of ''Nepenthes rajah''.|'''Early publications:''' Transact. Linn. Soc., XXII, p. 421 t. LXXII (1859); MIQ., Ill., p. 8 (1870); HOOK. F., in D.C., Prodr., XVII, p. 95 (1873); MAST., Gard. Chron., 1881, 2, p. 492 (1881); BURB., Gard. Chron., 1882, 1, p. 56 (1882); REG., Gartenfl., XXXII, p. 213, ic. p. 214 (1883); BECC., Mal., III, p. 3 & 8 (1886); WUNSCHM., in ENGL. & PRANTL, Nat. Pflanzenfam., III, 2, p. 260 (1891); STAPF, Transact. Linn. Soc., ser. 2, bot., IV, p. 217 (1894); BECK, Wien. Ill. Gartenz., 1895, p. 142, ic. 1 (1895); MOTT., Dict., III, p. 451 (1896); VEITCH, Journ. Roy. Hort. Soc., XXI, p. 234 (1897); BOERL., Handl., III, 1, p. 54 (1900); HEMSL., Bot. Mag., t. 8017 (1905); Gard. Chron., 1905, 2, p. 241 (1905); MACF., in ENGL., Pflanzenr., IV, 111, p. 46 (1908); in BAIL., Cycl., IV, p. 2129, ic. 2462, 3 (1919); MERR., Bibl. Enum. Born., p. 284 (1921); DANS., Trop. Nat., XVI, p. 202, ic. 7 (1927).<ref name=Danser/>

'''Early illustrations:''' Transact. Linn. Soc., XXII, t. LXXII (1859) optima; Gard. Chron., 1881, 2, p. 493 (1881) bona, asc. 1; Gartenfl., 1883, p. 214 (1883) bona, asc. 1; Wien. Ill. Gartenfl., 1895, p. 143, ic. 1 (1895) asc. 1; Journ. Roy. Hort. Soc., XXI, p. 228 (1897) optima; Bot. Mag., t. 8017 (1905) optima; BAIL., Cycl., IV, ic. 2462, 3 (1919) asc. 1; Trop. Nat., XVI, p. 203 (1927) asc. 1.<ref name=Danser/>

'''Early collections:''' North Borneo. Mt. Kinabalu, IX 1913, Herbarium of the Sarawak Museum (material without flowers or fruits); Marai-parai Spur, 1-4 XII 1915, Clemens 11073,  Herbarium Bogoriense, the Herbarium of the Buitenzorg Botanic Gardens (male and female material); 1650 m, 1892, Haviland 1812/1852, Herbarium of the Sarawak Museum (male and female material).<ref name=Danser/>}}

===Recent popularity===
[[File:Sheepstor Church Devon Nepenthes rajah.JPG|thumb|250px|A memorial stained glass window in St Leonard's Church, [[Sheepstor]], [[Devon]], [[England]], dedicated to those from Sarawak who died in [[World War II]]. It depicts a pair of pitcher plants, which the church guide describes as "a typical native pitcher plant - ''Naperthes Rajah''{{sic}}", although they appear to be ''[[Nepenthes edwardsiana|N. edwardsiana]]'']]
In recent years there has been renewed interest in ''Nepenthes'' worldwide. Much of the plants' current popularity can probably be attributed to [[Shigeo Kurata]], whose book ''[[Nepenthes of Mount Kinabalu]]'' (1976), which featured the best colour photography of ''Nepenthes'' to date, did much to bring attention to these unusual plants.

Not surprisingly, ''N. rajah'' is a relatively well known plant in Malaysia, especially its native Sabah. The species is often used to promote Sabah, and specifically Kinabalu National Park, as a [[tourist destination]], and features prominently on postcards from the region. ''Nepenthes rajah'' has appeared on the covers of several popular ''Nepenthes'' publications, including ''[[Nepenthes of Mount Kinabalu]]'' ([[Shigeo Kurata|Kurata]], 1976) and ''[[Nepenthes of Borneo]]'' ([[Charles Clarke (botanist)|Clarke]], 1997),<ref name="Clarke" /> both published in [[Kota Kinabalu]], Malaysia. On April 6, 1996, Malaysia issued a series of four postage stamps depicting some of its more famous ''Nepenthes'' species.  Two 30[[Malaysian ringgit|¢]] stamps, featuring ''[[Nepenthes macfarlanei|N. macfarlanei]]'' and ''[[Nepenthes sanguinea|N. sanguinea]]'', as well as two 50¢ stamps,  depicting ''[[Nepenthes lowii|N. lowii]]'' and ''N. rajah'', were released.<ref>Ellis 2000.</ref> The ''N. rajah'' stamp has been assigned a unique identification number in two popular [[stamp numbering system]]s: [[Scott catalogue|Scott]] #580 and [[Yvert et Tellier|Yvert]] #600. Curiously, the peltate leaf attachment that is so characteristic of this species is not shown. ''Nepenthes rajah'' was featured in the first episode of ''[[Kingdom of Plants 3D]]'', a natural history documentary series presented by [[David Attenborough]].<ref>[http://skyatlantic.sky.com/kingdom-of-plants/kingdom-of-plants-episode-1-life-in-the-wet-zone Kingdom of Plants: Episode 1 - Life in the Wet Zone]. Sky Atlantic HD.</ref>

==Classification==
{{See also|Nepenthes classification}}

{| class="wikitable" style="float: right; margin: 0em 0em 1em 1em;"
|+ ''Regiae'' Clade
|-
|''[[Nepenthes maxima|N. maxima]]''
|''[[Nepenthes pilosa|N. pilosa]]''
|''[[Nepenthes clipeata|N. clipeata]]''
|-
|''[[Nepenthes maxima|N. oblanceolata]]''&nbsp;*
|''[[Nepenthes burbidgeae|N. burbidgeae]]''
|''[[Nepenthes truncata|N. truncata]]''
|-
|''[[Nepenthes veitchii|N. veitchii]]''
|''N. rajah''
|''[[Nepenthes fusca|N. fusca]]''
|-
|''[[Nepenthes ephippiata|N. ephippiata]]''
|''[[Nepenthes boschiana|N. boschiana]]''
|''[[Nepenthes stenophylla|N. stenophylla]]''&nbsp;**
|-
|''[[Nepenthes klossii|N. klossii]]''
|''[[Nepenthes mollis|N. mollis]]''
|''[[Nepenthes lowii|N. lowii]]''
|-
| colspan="3" style="font-size: 90%;" | &nbsp;<nowiki>*</nowiki> Now considered a junior synonym of ''N. maxima''.<br/>&nbsp;<nowiki>**</nowiki> Danser's description was based on the type specimen of ''[[Nepenthes fallax|N. fallax]]''.
|-
| colspan="3" style="font-size: 90%;" | [[Image:Regiae distribution.svg|center|350px|Distribution of the ''Regiae'']] Distribution of the ''Regiae'', based on Danser (1928).<br/>Note: it is now known that ''N. maxima'' is absent from Borneo.
|}

''Nepenthes rajah'' is not generally considered to be closely related to any other species, due to its unusual pitcher and leaf morphology.  However, several attempts have been made to deduce natural groupings within the genus ''Nepenthes'', which have grouped ''N. rajah'' with other species thought to share certain traits with it.

The ''Nepenthes'' were first split up in 1873, when [[Joseph Dalton Hooker|Hooker]] published his [[monograph]] on the genus, titled "[[Nepenthaceae (1873 monograph)|Nepenthaceae]]". Hooker distinguished ''[[Nepenthes pervillei|N. pervillei]]'' from all other taxa based on its seeds, which lack the appendages typical of most ''Nepenthes''. He placed it in the [[monotypic]] [[subgenus]] ''Anourosperma''. All other species were subsumed in the second subgenus, ''Eunepenthes''.

A second attempt to establish a natural subdivision within the genus was made in 1895 by [[Günther Beck von Mannagetta und Lerchenau]] in "[[Die Gattung Nepenthes|Die Gattung ''Nepenthes'']]".<ref>Beck, G. 1895.</ref> Beck kept the two subgenera created by Hooker, but divided ''Eunepenthes'' into three subgroups: ''Retiferae'', ''Apruinosae'' and ''Pruinosae''.  ''Nepenthes rajah'' formed part of the ''Apruinosae '' (Latin: pl. of ''apruinosa'': not frosted).

''Nepenthes'' taxonomy was once again revised in 1908 by [[John Muirhead Macfarlane]] in his own monograph, "[[Nepenthaceae (1908 monograph)|Nepenthaceae]]".<ref>Macfarlane 1908, pp. 1–91.</ref> Oddly, Macfarlane did not name the groups he distinguished.  His revision is not generally considered to be a natural division of the genus.

In 1928, [[B. H. Danser]] published his seminal monograph, "[[The Nepenthaceae of the Netherlands Indies]]", in which he divided ''Nepenthes'' into six [[clades]], based on observations of herbarium material.<ref name="Clarke2001a">{{cite book |last1=Clarke |first1=Charles |title=Nepenthes of Sumatra and Peninsular Malaysia |date=2001 |publisher=Natural History Publications (Borneo) |location=Kota Kinabalu |isbn=983-812-050-2}}</ref>{{rp|81-82}} The clades were: the ''Vulgatae'', ''Montanae'', ''Nobiles'', ''Regiae'', ''Insignes'' and ''Urceolatae''.  Danser placed ''N. rajah'' in the ''Regiae'' (Latin: pl. of ''rēgia'': royal).  The ''Regiae'' clade as proposed by Danser is shown in the adjacent table.

Most of the species in this clade are large plants with [[Petiole (botany)|petiolate]] leaves, an [[indumentum]] of coarse reddish-brown hairs, raceme-like inflorescence, and funnel-shaped (infundibulate) upper pitchers.  All bear a characteristic appendage on the lower surface of the lid near the apex.  With the exception of ''N. lowii'', the ''Regiae'' all have a mostly flattened or expanded peristome. The majority of species comprising ''Regiae'' are [[Endemic (ecology)|endemic]] to Borneo. Based on current understanding of the genus, ''Regiae'' appears to reflect the relationships of its members quite well, although the same cannot be said for the other clades.<ref name="Clarke2001a" />{{rp|82}} Despite this, Danser's classification was undoubtedly a great improvement on previous attempts.

The taxonomical work of Danser (1928) was revised by [[Hermann Harms]] in 1936. Harms divided ''Nepenthes'' into three subgenera: ''Anurosperma'' Hooker.f. (1873), ''Eunepenthes'' Hooker.f. (1873) and ''Mesonepenthes'' Harms (1936) (Latin: ''meso'': middle; "middle" ''Nepenthes'').  The ''Nepenthes'' species found in the subgenera ''Anurosperma'' and ''Mesonepenthes'' differ from those in the ''Vulgatae'', where Danser had placed them.  Harms included ''N. rajah'' in the subgenus ''Eunepenthes'' together with the great majority of other ''Nepenthes''; ''Anurosperma'' was a [[monotypic]] subgenus, while ''Mesonepenthes'' contained only three species.  He also created an additional clade, the ''Distillatoriae'' (after ''[[Nepenthes distillatoria|N. distillatoria]]'').{{Citation needed|date=September 2024}}

In his 1976 book, ''[[Nepenthes of Mount Kinabalu]]'', [[Shigeo Kurata]] presented detailed photographs of lid [[nectar]] glands and the digestive glands of the trap interior. He divided the latter into the "lower", "upper" and "middle" parts.

===Biochemical analysis===
More recently, [[biochemical analysis]] has been used as a means to determine cladistical relationships between ''Nepenthes'' species.  In 1975, [[David E. Fairbrothers]] ''et al.''<ref>Fairbrothers, Mabry, Scogin & Turner 1975.</ref> first suggested a link between chemical properties and certain morphological groupings, based on the theory that morphologically similar plants produce chemical constituents with similar therapeutic effects.{{Citation needed|date=December 2019|reason=removed citation to predatory publisher content}}

In 2002, [[phytochemical|phytochemical screening]] and [[analytical chromatography]] were used to study the presence of [[natural phenol|phenolic]] [[Chemical compound|compounds]] and [[leucoanthocyanin]]s in several naturally occurring [[Hybrid (biology)|hybrids]] and their putative parental species (including ''N. rajah'') from Sabah and Sarawak.{{Citation needed|date=December 2019|reason=removed citation to predatory publisher content}}  The research was based on leaf material from nine dry herbarium specimens.  Eight spots containing [[phenolic acid]]s, [[flavonol]]s, [[flavone]]s, [[leucoanthocyanin]]s and 'unknown [[flavonoid]]' 1 and 3 were identified from chromatographic profiles. The distributions of these in the hybrid ''N. × alisaputrana'' and its putative parental species ''N. rajah'' and ''N. burbidgeae'' are shown in the adjacent table.  A specimen of ''N. × alisaputrana'' grown from [[tissue culture]] (''[[in vitro]]'') was also tested.

[[natural phenol|Phenol]]ic and [[ellagic acid]]s were undetected in ''N. rajah'', while concentrations of [[kaempferol]] were found to be very weak.  Chromatographic patterns of the ''N. × alisaputrana'' samples studied showed complementation of its putative parental species.{{Citation needed|date=December 2019|reason=removed citation to predatory publisher content}}

[[Myricetin]] was found to be absent from all studied taxa.  This agrees with the findings of previous authors ([[R. M. Som]] in 1988; [[M. Jay]] and [[P. Lebreton]] in 1972)<ref>Som 1988.</ref><ref>Jay & Lebreton 1972, pp. 607–613.</ref> and suggests that the absence of a widely distributed compound like myricetin among the ''Nepenthes'' examined might provide "additional diagnostic information for these six species".{{Citation needed|date=December 2019|reason=removed citation to predatory publisher content}}

Several [[protein]]s and [[nucleotide]]s of ''N. rajah'' have been either partially or completely [[Sequencing|sequenced]]. These are as follows:
* Translocated tRNA-Lys (trnK) pseudogene)<ref>{{cite journal |last1=Meimberg |first1=H |last2=Thalhammer |first2=S |last3=Brachmann |first3=A |last4=Heubl |first4=G |title=Comparative analysis of a translocated copy of the trnK intron in carnivorous family Nepenthaceae. |journal=Molecular Phylogenetics and Evolution |date=May 2006 |volume=39 |issue=2 |pages=478–90 |doi=10.1016/j.ympev.2005.11.023 |pmid=16414286|bibcode=2006MolPE..39..478M }}</ref> {{GenBank|DQ007139.1}}
* trnK gene & maturase K (matK) gene<ref name="MeimbergPlastid">{{cite journal |last1=Meimberg |first1=H. |last2=Wistuba |first2=A. |last3=Dittrich |first3=P. |last4=Heubl |first4=G. |title=Molecular Phylogeny of Nepenthaceae Based on Cladistic Analysis of Plastid trnK Intron Sequence Data |journal=Plant Biology |date=March 2001 |volume=3 |issue=2 |pages=164–175 |doi=10.1055/s-2001-12897|bibcode=2001PlBio...3..164M }}</ref> {{GenBank|AF315879.1}}
* trnK gene & maturase K (matK) gene <ref name=MeimbergPlastid/> {{GenBank|AF315880.1}}
* maturase K (chloroplast)<ref name=MeimbergPlastid/> {{GenBank|AAK56010.2}}
* maturase K (chloroplast)<ref name=MeimbergPlastid/> {{GenBank|AAK56011.1}}

===Related species===
In 1998, a striking new species of ''Nepenthes'' was discovered in the [[Philippines]] by [[Andreas Wistuba]].  Temporarily dubbed ''N.'' sp. Palawan 1, it bears a close resemblance to ''N. rajah'' in terms of pitcher and leaf morphology.<ref>{{cite web |title=Nepenthes spec. Philippines I |url=http://www.joachim-nerz.de/philippines1.htm |website=www.joachim-nerz.de}}</ref> In 2007, the species was described by Wistuba and [[Joachim Nerz]] as ''[[Nepenthes mantalingajanensis|N. mantalingajanensis]]''.<ref>{{cite journal |last1=Robinson |first1=Alastair S. |last2=Fleischmann |first2=Andreas S. |last3=Mcpherson |first3=Stewart R. |last4=Heinrich |first4=Volker B. |last5=Gironella |first5=Elizabeth P. |last6=PeñA |first6=Clemencio Q. |title=A spectacular new species of Nepenthes L. (Nepenthaceae) pitcher plant from central Palawan, Philippines |journal=Botanical Journal of the Linnean Society |date=February 2009 |volume=159 |issue=2 |pages=195–202 |doi=10.1111/j.1095-8339.2008.00942.x}}</ref>

==Ecology==

===Kinabalu===
[[Image:Mount kinabalu 01.png|thumb|180px|Mount Kinabalu, Borneo]]

''Nepenthes rajah'' has a very localised distribution, being restricted to [[Mount Kinabalu]] and neighbouring [[Mount Tambuyukon]], both located in [[Kinabalu National Park]], [[Sabah]], [[Malaysian Borneo]].<ref name=Clarke/>{{rp|123}} Mount Kinabalu is a massive [[granite|granitic]] dome structure that is geologically young and formed from the intrusion and uplift of a granitic [[batholith]]. At {{cvt|4095.2|m|ft}}, it is by far the tallest mountain on the island of Borneo and one of the highest peaks in [[Southeast Asia]].<ref>{{Cite web |url=http://www.sabah.gov.my/mocet/ |title=Sabah Ministry of Tourism, Culture and Environment Homepage |access-date=2006-05-02 |archive-url=https://web.archive.org/web/20060423041755/http://www.sabah.gov.my/mocet/ |archive-date=2006-04-23 |url-status=dead }}</ref> The lower slopes of the mountain are mainly composed of [[sandstone]] and [[shale]], transformed from marine sand and mud about 35 million years ago. Intrusive [[ultramafic]] ([[Serpentine group|serpentine]]) rock was uplifted with the core of the batholith and forms a collar around the mountain. It is on these ultramafic soils that the flora of Mount Kinabalu exhibits the greatest levels of [[Endemic (ecology)|endemicity]] and many of the area's rarest species can be found here.

[[Image:Kinabalu ultramafic soil.png|thumb|left|Ultramafic outcrops (yellow) in Kinabalu National Park (green)]]

===Substrate===
''Nepenthes rajah'' seems to grow exclusively on serpentine soils containing high concentrations of [[nickel]] and [[chromium]], which are toxic to many plant species.<ref name=Gibson/>  Its tolerance of these, therefore, means that it can grow in an ecological niche where it faces less competition for space and nutrients.<ref>Adlassnig, Peroutka, Lambers & Lichtscheidl 2005.</ref> The root systems of ''[[Nepenthes x alisaputrana|N. × alisaputrana]]''<ref>Clarke 2001b.</ref> and ''[[Nepenthes villosa|N. villosa]]''<ref>Kaul 1982.</ref> are also known to be resistant to the heavy metals present in serpentine substrates. These soils are also rich in [[magnesium]] and are slightly [[alkaline]] as a result. They often form a relatively thin layer over a base of ultramafic rock and are thus known as ultramafic soils. Ultramafic soils are thought to cover approximately 16% of Kinabalu National Park.  These soils have high levels of [[Endemic (ecology)|endemicity]] in many taxonomic groups, not least the ''Nepenthes''.  Four species in the genus, including ''N. rajah'', can only be found within the boundaries of the park.

[[Image:Nepenthes rajah climate.jpg|thumb|135px|Temperature and humidity readings taken along the "''Nepenthes rajah'' Nature Trail" (~2000 m a.s.l.) at around 10 am during an overcast sky]]

''Nepenthes rajah'' usually grows in open, grassy clearings on old land slips and flat ridge tops, particularly in areas of [[seepage|seeping]] ground water, where the soil is loose and permanently moist. Although these sites can receive very high rainfall, excess water drains away quickly, preventing the soil from becoming waterlogged. ''N. rajah'' can often be found growing in grassy undergrowth, especially among sedges.

===Climate===
''Nepenthes rajah'' has an [[Altitude|altitudinal]] [[range (biology)|distribution]] of {{cvt|1500–2650|m|ft}} above sea level<ref name=Kurata/><ref name=Clarke/> and is thus considered an (ultra) [[Highland (geography)|highland]] or [[mountain|Upper Montane]] plant.<ref>{{Cite web |url=http://homepage.univie.ac.at/christian.puff/AS_Borneo_Kinabalu.htm |title=Vegetation Zones on Mount Kinabalu |access-date=2006-04-14 |archive-url=https://web.archive.org/web/20050915121301/http://homepage.univie.ac.at/christian.puff/AS_Borneo_Kinabalu.htm |archive-date=2005-09-15 |url-status=dead }}</ref> In the upper limit of its range, night-time temperatures may approach freezing and day-time maxima rarely exceed {{cvt|25|C|F}}.<ref name="Clarke" />{{rp|2}} Due to the night-time temperature drop, [[relative air humidity]] increases significantly, rising from 65 to 75% to over 95%. Vegetation at this height is very stunted and slow-growing due to the extreme environmental conditions that prevail. Plants are often subjected to fierce winds and driving rain, as well as exposure to intense direct sunlight. The relatively open vegetation of the upper [[montane forest]] also experiences greater fluctuations in temperature and humidity compared with lower altitudes. These changes are largely governed by the extent of cloud cover. In the absence of clouds, temperatures rise rapidly, humidity drops, and light levels may be very high. When cloud cover returns, temperatures and light levels fall, while humidity levels increase.<ref name=Clarke />{{rp|29}}  Average annual [[Precipitation (meteorology)|precipitation]] in this region is around {{cvt|3000|mm|in}}.

==Conservation status==

===Endangered species===
''Nepenthes rajah'' is classified as [[Endangered species|Endangered]] (EN – B1+2e) on the [[World Conservation Union|IUCN]] [[IUCN Red List|Red List of Threatened Species]].<ref name="iucn status 19 November 2021" /> It is also listed on Schedule I, Part II of the [[Wildlife Conservation Enactment]] (WCE) 1997<ref>[http://www.internationalwildlifelaw.org/Malaysia.html Wildlife Conservation Enactment 1997]</ref> and [[CITES|CITES Appendix I]],<ref name=CITES_A1>{{cite web |url= http://www.cites.org/eng/cop/08/E-Appendices.pdf |title= APPENDICES I AND II as adopted by the Conference of the Parties |url-status= dead |archive-url= https://web.archive.org/web/20060214042229/http://cites.org/eng/cop/08/E-Appendices.pdf |archive-date= 2006-02-14 }}</ref> which prohibits commercial international trade in plants collected from the wild. However, due to its popularity among collectors, many plants have been removed from the wild illegally,<ref>Creek, M. 1990. {{cite web|url= http://www.carnivorousplants.org/cpn/articles/CPNv19n3_4p109_112.pdf |title=The conservation of carnivorous plants. }} ''[[Carnivorous Plant Newsletter]]'' '''19'''(3–4): 109–112.</ref> even though the species' distribution lies entirely within the bounds of Kinabalu Park. This led to some populations being severely depleted by over-collection in the 1970s and eventually resulted in the species' inclusion in CITES Appendix I in 1981.<ref>Clarke 2001b, p. 29.</ref>  Together with ''[[Nepenthes khasiana|N. khasiana]]'', it is one of only two species in the genus to feature on this list; all other ''Nepenthes'' species are covered by Appendix II.

The recent advent of artificial [[tissue culture]], or more specifically ''in vitro'', technology in Europe and the United States has meant that plants can be produced in large numbers and sold at relatively low prices (~US$20–$30 in the case of ''N. rajah''). ''In vitro'' [[plant propagation|propagation]] refers to production of whole plants from cell cultures derived from explants (generally seeds). This technology has, to a large extent, removed the incentive for collectors to travel to [[Sabah]] to collect the plant illegally, and demand for wild-collected plants has fallen considerably in recent years.<ref name="Clarke"/>{{rp|172}}

[[Rob Cantley]], a prominent [[conservation movement|conservationist]] and artificial propagator of ''Nepenthes'' plants, assesses the current status of plants in the wild as follows:<ref>{{Cite web |url=http://www.cites.org/common/com/ac/19/E19-10-1.doc |title=Nineteenth meeting of the Animals Committee. Geneva (Switzerland), 18–21 August 2003. |access-date=2006-05-15 |archive-url=https://web.archive.org/web/20060928183812/http://www.cites.org/common/com/ac/19/E19-10-1.doc |archive-date=2006-09-28 |url-status=dead }}</ref>

<blockquote>This species grows in at least 2 distinct sub-populations, both of which are well protected by Sabah National Parks Authority. One of the populations grows in an area public access to which is strictly prohibited without permit. However, there has been a decline in population of mature individuals in the better known and less patrolled site. This is largely due to damage to habitat and plants by careless visitors rather than organised collection of plants. Nepenthes rajah has become common in cultivation in recent years as a result of the availability of inexpensive clones from tissue culture. I believe that these days commercial collection of this species from the wild is negligible.</blockquote>

This being the case, however, it appears that the genetic variability of cultivated ''N. rajah'' plants is very small, as all commercially available tissue-cultured plants are thought to belong to just four clones originating from the [[Royal Botanic Gardens, Kew]] in London, England.

However, illegal collection is not the only threat facing plants in the wild. The [[El Niño]] [[climate|climatic]] [[phenomenon]] of 1997/98 had a catastrophic effect on the ''Nepenthes'' species on Mount Kinabalu.<ref name="Clarke2001a" />{{rp|236}} The dry period that followed severely depleted some natural populations. [[Wildfire|Forest fires]] broke out in 9 locations in Kinabalu Park, covering a total area of 25 square kilometres and generating large amounts of smog. During the El Niño period, many plants were temporarily transferred to the park nursery to save at least some individuals. These were later replanted in the "''Nepenthes'' Garden" in [[Mesilau]] (see below). In spite of this, ''N. rajah'' was one of the less affected species and relatively few plants perished as a result. Since then, Ansow Gunsalam has established a nursery close to the Mesilau Lodge at the base of Kinabalu Park to protect the endangered species of that area, including ''N. rajah''.

[[Image:Nepenthes rajah mountain garden.jpg|thumb|left|180px|Plant on display at the Kinabalu "Mountain Garden"]]

===Restricted distribution===
The newly opened [[Mesilau Nature Resort]], which lies near the golf course behind the village of [[Kundasang]], is now the only place where regular visitors can hope to see this species in its natural habitat.<ref name=ClarkeV>Clarke 2001b, p. 38.</ref> Here, several dozen ''N. rajah'' plants grow near the top of a steep landslide. Both young and mature plants are present, some with sizable pitchers that may occasionally exceed 40&nbsp;cm in height<ref name=largest /> (see [[:File:Nepenthes rajah.jpg|image]]). Daily guided tours are organised to the "''Nepenthes'' Garden" where these plants are located. The "''Nepenthes rajah'' Nature Trail" is subject to a fee and operates daily from 9:00&nbsp;am to 4:00&nbsp;pm. Almost all other natural populations of this species occur in remote parts of Kinabalu National Park, which are off-limits to tourists.<ref name=ClarkeV/> Visitors to the park can also see ''N. rajah'' on display in the nursery adjoining the "Mountain Garden" at Kinabalu Park Headquarters.<ref>Malouf 1995, p. 68.</ref>

Other known localities of wild ''N. rajah'' populations include the [[Marai Parai]] [[plateau]], [[Mesilau East River]] near [[Mesilau Cave]], the [[Kolopis River|Upper Kolopis River]], and the eastern slope of [[Mount Tambuyukon]].<ref>Kurata 1976, p. 64–65.</ref> On [[Pig Hill (Mount Kinabalu)|Pig Hill]], ''N.&nbsp;rajah'' grows at 1950–2320&nbsp;m<ref>Adam, J.H., C.C. Wilcock & M.D. Swaine 1992. {{cite web |url= http://myais.fsktm.um.edu.my/8918/1/10.pdf |title= The ecology and distribution of Bornean ''Nepenthes''. |url-status= dead |archive-url= https://web.archive.org/web/20110722233248/http://myais.fsktm.um.edu.my/8918/1/10.pdf |archive-date= 2011-07-22 }} ''Journal of Tropical Forest Science'' '''5'''(1): 13–25.</ref> and is sympatric with ''[[Nepenthes burbidgeae|N.&nbsp;burbidgeae]]'', ''[[Nepenthes tentaculata|N.&nbsp;tentaculata]]'', and the [[natural hybrid]] ''[[Nepenthes × alisaputrana|N.&nbsp;×&nbsp;alisaputrana]]''.<ref name=Thong2>Thong, J. 2006. {{cite web |url= http://www.vcps.au.com/journals/82_Dec_2006Public.pdf |title= Travels around North Borneo – Part 2. |access-date= 2011-07-04 |archive-url= https://web.archive.org/web/20110707185406/http://www.vcps.au.com/journals/82_Dec_2006Public.pdf |archive-date= 2011-07-07 |url-status= dead }} ''[[Victorian Carnivorous Plant Society Journal]]'' '''82''': 6–12.</ref>

==Natural hybrids==
{{See also|List of Nepenthes natural hybrids}}

[[Image:Nep rajah hybrid.jpg|thumb|135px|''N. rajah'' × ''N. tentaculata'']]


''Nepenthes rajah'' is known to hybridise with several other species with which it is [[Sympatric speciation|sympatric]]. It seems to flower at any time of year and for this reason it hybridises relatively easily. [[Charles Clarke (botanist)|Charles Clarke]] also notes that "''N. rajah'', more than any other species, appears to have been successful in having its pollen transported over considerable distances.  Consequently, a number of putative ''N. rajah'' hybrids exist without the parent plant growing nearby". However, it appears that the limit as to how far pollen can be transported is approximately {{cvt|10|km|mi}}.<ref name="Clarke"/>{{rp|143}} Hybrids between ''N. rajah'' and all other ''Nepenthes'' species on Mount Kinabalu have been recorded.<ref name=Clarke/><ref name=lowii>[http://lhnn.proboards.com/index.cgi?action=display&board=pforum&thread=3061&page=1 A rare find: ''N. rajah'' nat. hybrid]. Flora Nepenthaceae.</ref> Due to the slow-growing nature of ''N. rajah'', few hybrids involving it have been artificially produced yet.<ref>[Anonymous] 2012. {{cite web |url= http://www.borneoexotics.com/newsletters/Borneo_Exotics_Newsletter_Vol_1_Issue_2.pdf |title= BE-3518 ''Nepenthes rajah x mira''. |access-date= 2012-12-31 |archive-url= https://web.archive.org/web/20130510223136/http://www.borneoexotics.com/Newsletters/Borneo_Exotics_Newsletter_Vol_1_Issue_2.pdf |archive-date= 2013-05-10 |url-status= dead }} ''Nepenthes Growers Newsletter'' '''1'''</ref>

At present{{as of when?|date=September 2024}}, the following natural hybrids are known:<ref name=Clarke />

* ''[[Nepenthes burbidgeae|N. burbidgeae]]'' × ''N. rajah'' [=''[[Nepenthes × alisaputrana|N. × alisaputrana]]'' [[J. H. Adam|J.H.Adam]] & [[C. C. Wilcock|Wilcock]] (1992)]
* ''[[Nepenthes edwardsiana|N. edwardsiana]]'' × ''N. rajah''
* ''[[Nepenthes fusca|N. fusca]]'' × ''N. rajah''
* ''[[Nepenthes lowii|N. lowii]]'' × ''N. rajah''<ref name=Thong />
* ''[[Nepenthes macrovulgaris|N. macrovulgaris]]'' × ''N. rajah''
* ''N. rajah'' × ''[[Nepenthes stenophylla|N. stenophylla]]''
* ''N. rajah'' × ''[[Nepenthes tentaculata|N. tentaculata]]''
* ''N. rajah'' × ''[[Nepenthes villosa|N. villosa]]'' [=''[[Nepenthes × kinabaluensis|N. × kinabaluensis]]'' [[Shigeo Kurata|Sh.Kurata]] (1976) ''[[nomen nudum|nom.nud.]]'']

The "Mountain Garden" of Kinabalu National Park contains a number of well-grown ''Nepenthes'', including the rare hybrid ''N. rajah'' × ''N. stenophylla''.  This plant has leaves resembling those of ''N. stenophylla'', but the lid and wings are typical of ''N. rajah''.  The peristome is strongly influenced by ''N. stenophylla'' and bristles are present at the border of the lid, a unique characteristic of this hybrid.<ref>Steiner 2002, p. 124.</ref> It occurs at an altitude of 1500–2600&nbsp;m.

A single example of ''N.&nbsp;lowii'' × ''N.&nbsp;rajah'' grows along the [[Mesilau|Mesilau nature trail]].<ref name=lowii /><ref name=Thong>Thong, J. 2006. {{cite web |url= http://www.vcps.au.com/journals/81_Sep_2006Public.pdf |title= Travels around North Borneo – Part 1. |url-status= dead |archive-url= https://web.archive.org/web/20110707184733/http://www.vcps.au.com/journals/81_Sep_2006Public.pdf |archive-date= 2011-07-07 }} ''[[Victorian Carnivorous Plant Society Journal]]'' '''81''': 12–17.</ref>

Two hybrids of ''N. rajah'' have been [[Species description|formally described]] and given specific names: ''N. × alisaputrana'' and ''N. × kinabaluensis''. Both are listed on CITES Appendix II and the latter is also considered Endangered (EN (D)) under current IUCN criteria.<ref>Arx, Schlauer & Groves 2001, p. 44.</ref>

[[Image:Kinabalu N.× alisaputrana 10.jpg|thumb|left|''Nepenthes × alisaputrana'']]

===''Nepenthes × alisaputrana''===
''Nepenthes × alisaputrana'' (originally published as "''Nepenthes × alisaputraiana''")<ref>Adam & Wilcock 1992.</ref> is named in honour of [[Datuk Lamri Ali]], Director of [[Sabah Parks]]. It is only known from a few remote localities within [[Kinabalu National Park]] where is grows in stunted, open vegetation over serpentine soils at around 2000 m above sea level, often amongst populations of ''N. burbidgeae''. This plant is notable for combining the best characters of both parent species, not least the size of its pitchers, which rival those of ''N. rajah'' in volume (≤35&nbsp;cm high, ≤20&nbsp;cm wide).<ref>Clarke 2001b, p. 10.</ref> The other hybrids involving ''N. rajah'' do not exhibit such impressive proportions. The pitchers of ''N. × alisaputrana'' can be distinguished from those of ''N. burbidgeae'' by a broader peristome, larger lid and simply by their sheer size. The hybrid differs from its other parent, ''N. rajah'', by its lid structure, indumentum of short, brown hairs, narrower and more cylindrical peristome, and pitcher colour, which is usually yellow-green with red or brown flecking.  For this reason, Phillipps and Lamb (1996) gave it the common name ''Leopard pitcher-plant'', though this is rarely used. The peristome is green to dark red and striped with purple bands. Leaves are often slightly peltate.  The plant climbs well and aerial pitchers are frequently produced. ''N. × alisaputrana'' more closely resembles ''N. rajah'' than ''N. burbidgeae'', but it is difficult to confuse this plant with either. However, this mistake has previously been made on at least one occasion; a pitcher illustrated in ''Insect Eating Plants & How To Grow Them'' ([[Adrian Slack|Slack]], 1986) as being ''N. rajah'' was in fact ''N. burbidgeae × N. rajah''.<ref name="Clarke"/>{{rp|157}}<ref>Slack 1986.</ref>

===''Nepenthes × kinabaluensis''===
[[Image:Kinabalu N. × kinabaluensis 6.JPG|thumb|135px|''Nepenthes × kinabaluensis'']]
''Nepenthes × kinabaluensis'' is another impressive plant. The pitchers get large also, but do not compare to those of ''N. rajah'' or ''N. × alisaputrana''. It is a well-known natural hybrid of what many consider to be the two most spectacular ''Nepenthes'' species of Borneo: ''N. rajah'' and ''N. villosa''. ''Nepenthes × kinabaluensis'' is only found on Mount Kinabalu (hence the name) and nearby Mount Tambuyukon, where the two parent species are occur [[Sympatric speciation|sympatrically]].<ref name="Clarke"/>{{rp|165-167}} More specifically, plants are known from a footpath near Paka Cave and several places along an unestablished route on a southeast ridge, which lies on the west side of the Upper Kolopis River.<ref>Kurata 1976, p. 65.</ref> The only accessible location from which this hybrid is known is the Kinabalu summit trail, between [[Layang-Layang (Mount Kinabalu)|Layang-Layang]] and the [[helipad]], where it grows at about 2900&nbsp;m in a clearing dominated by ''[[Dacrydium gibbsiae]]'' and ''[[Leptospermum recurvum]]'' trees.  ''Nepenthes × kinabaluensis'' has an altitudinal distribution of 2420 to 3030&nbsp;m.<ref>Steiner 2002, p. 112.</ref> It grows in open areas in cloud forest. This hybrid can be distinguished from ''N. rajah'' by the presence of raised ribs that line the inner edge of the peristome and end with elongated teeth.  These are more prominent than those found in ''N. rajah'' and are clue as to the hybrid's parentage (''N. villosa'' has highly developed peristome ribs). The peristome is coarse and expanded at the margin (but not scalloped like that of ''N. rajah''), the lid orbiculate or reniformed and almost flat. In general, pitchers are larger than those of ''N. villosa'' and the tendril joins the apex about 1–2&nbsp;cm below the leaf tip, a feature which is characteristic of ''N. rajah''.<ref>Clarke 2001b, p. 19.</ref> In older plants, the tendril can be almost woody.  ''Nepenthes × kinabaluensis'' has an indumentum of villous hairs covering the pitchers and leaf margins, which is approximately intermediate between the parents. Lower pitchers have two fringed wings, whereas the upper pitchers usually lack these. The colour of the pitcher varies from yellow to scarlet. ''Nepenthes × kinabaluensis'' seems to produce upper pitchers more readily than either of its parents.  In all respects ''N. × kinabaluensis'' is intermediate between the two parent species and it is easy to distinguish from all other ''Nepenthes'' of Borneo. However, it has been confused once before, when the hybrid was labelled as ''N. rajah'' in ''Letts Guide to Carnivorous Plants of the World'' (Cheers, 1992).<ref>Cheers 1992.</ref>

''Nepenthes × kinabaluensis'' was first collected near [[Kambarangoh]] by [[Lilian Gibbs]] in 1910 and later mentioned by [[John Muirhead Macfarlane|Macfarlane]] as "''Nepenthes'' sp." in 1914.<ref>Kurata 1976, p. 64.</ref>  Although Macfarlane did not formally name the plant, he noted that "[a]ll available morphological details suggest that this is a hybrid between ''N. villosa'' and ''N. rajah''".<ref>Macfarlane 1914, p. 127.</ref> The name ''N.&nbsp;×&nbsp;kinabaluensis'' was first published in [[Shigeo Kurata]]'s 1976 book, ''[[Nepenthes of Mount Kinabalu]]'', but was a ''[[nomen nudum]]'' at the time as it lacked an adequate description and information on the [[Holotype|type specimen]]. The name was subsequently published validly by Kurata in 1984.<ref>Kurata, S. 1984. ''[[Journal of Insectivorous Plant Society]]'' '''35''': 65.</ref>

===Hybrid or species?===
[[Image:Nepenthesxkinabaluensis.jpg|thumb|Lower pitchers of ''N. × kinabaluensis'']]
''Nepenthes × alisaputrana'' and ''N. × kinabaluensis'' are often [[fertility|fertile]] and thus may [[breed]] among themselves. [[Clive A. Stace]] writes that we may speak of "stabilised hybrids when they have developed a distributional, morphological or genetic set of characters which is no longer strictly related to that of its parents, ... if the hybrid has become an independent, recognisable, self-producing unit, it is ''de facto'' a separate species".<ref>Stace 1980.</ref> ''[[Nepenthes hurrelliana]]'' and ''[[Nepenthes murudensis|N. murudensis]]'' are two examples of species that have a putative hybrid origin. ''Nepenthes × alisaputrana'' and ''N. × kinabaluensis'' are sufficiently stabilised that a species status has been discussed.<ref name=Steiner/> Indeed, ''N. kinabaluensis'' was described as a species by [[J. H. Adam|Adam]] & [[C. C. Wilcock|Wilcock]] in 1996.

Due to their [[dioecious]] nature, a hybrid involving a pair of ''Nepenthes'' species can represent one of two possible crosses, depending on which species was the female and which was the male. When the cross is known, the female (or pod) parent is usually referred to first, followed by the male (or [[pollen]]) parent.  This is an important distinction, as the hybrid will usually display different morphological features according to the type of cross; the pod parent is thought to be dominant in most cases and hybrid offspring usually resemble it more than the pollen parent.  Most wild plants of ''N. × kinabaluensis'', for example, show a greater affinity to ''N. rajah'' than ''N. villosa'' and are thus thought to represent the cross ''N. rajah'' × ''N. villosa''.  However, specimens have been found that seem to be more similar to ''N. villosa'', suggesting that they might be the reverse cross (see [http://www.scarnivores.com/showphotos.asp?id=N|~x~kinabuluensis]).  The same is true for other hybrids involving ''N. rajah''.

==Cultivation==
{{See also|Nepenthes#Cultivation}}

''Nepenthes rajah'' has always been considered to be one of the more difficult ''Nepenthes'' species to [[agriculture|cultivate]]. However, in recent years, it has become apparent that the plant may not be deserving of its reputation.

[[Image:2005-12-18 N rajah 034.jpg|thumb|left|135px|Cultivated ''N.rajah'' plant with large lower pitcher]]

===Environmental factors===
''Nepenthes rajah'' is a [[montane]] species or "highlander", growing at altitudes ranging from 1500 to 2650&nbsp;m. As such, it requires warm days, with temperatures ranging (ideally) from approximately 25 to 30&nbsp;°C,<ref name=rajah>[https://web.archive.org/web/20020811093531/http://www.cpzine.com/article.aspx?cid=13&y=2002&m=6&d=21 On the Cultivation of ''Nepenthes rajah'']</ref> and cool nights, with temperatures of about 10 to 15&nbsp;°C.<ref name=rajah/> The temperatures themselves are not vital (when kept within reasonable limits), but rather the temperature drop itself; ''N. rajah'' needs considerably cooler nights, with a drop of 10&nbsp;°C or more being preferable. Failure to observe this requirement will almost certainly doom the plant in the long term or, at best, limit it to being a small, unimpressive specimen.

In addition, like all ''Nepenthes'', this plant needs a fairly [[humidity|humid]] environment to grow well. Values in the region of 75% [[Relative humidity|R.H.]]<ref name=rajah/> are generally considered optimal, with increased humidity at night (~90% R.H.). However, ''N. rajah'' does tolerate fluctuations in humidity, especially when young, provided that the air does not become too dry (below 50% R.H.). Humidity can be easily controlled using an [[Ultrasound|ultrasonic]] [[humidifier]] in conjunction with a [[humidistat]].

[[Image:Nep rajah cultivated.jpg|thumb|180px|Cultivated ''N. rajah'' plant]]

In its natural habitat, ''N. rajah'' grows in open areas, where it is exposed to direct sunlight – it therefore needs to be provided with a significant amount of light in cultivation as well. To meet this need, many growers have used [[metal halide lamp]]s in the 500–1000&nbsp;watt range, with considerable success. The plant should be situated a fair distance from the light source, 1 to 2 m is recommended.<ref name=rajah/> Depending on location, growers can utilise natural sunlight as a source of illumination. However, this is only recommended for those living in [[equator]]ial regions, where light intensity is sufficient to satisfy the needs of the plant. A [[photoperiod]] of 12&nbsp;hours is comparable to that experienced in nature, since Borneo lies on the [[equator]].<ref name=rajah/>

===Potting and watering===
Pure long-fibre ''[[Sphagnum]]'' [[moss]] is an excellent potting medium, though combinations involving any of the following – [[peat]], [[perlite]], [[vermiculite]], [[sand]], [[lava rock]], [[pumice]], ''[[Osmunda]]'' fibre, [[orchid]] bark and horticultural [[charcoal]] – may be used with equal success. The potting medium should be well-drained and not too compacted. Moss is useful for moisture retention near the roots. The mix should be thoroughly soaked in water prior to potting the plant.

It has been noted that ''N. rajah'' produces a very extensive root system (for a ''Nepenthes'') and, for this reason, it is recommended that a wide pot be used to allow for proper development of the root system.<ref name=rajah/> This also eliminates the need for frequent re-potting, which can lead to [[transplant shock]] and the eventual death of the plant.<ref name=rajah/>

Purified water should be used for watering purposes, although '[[hard water]]' is tolerated. This is done to minimise the build-up of [[mineral]]s and [[chemical]]s in the soil. Water purity greater than 100&nbsp;[[parts per million|p.p.m.]] of [[total dissolved solids]] is often quoted as ideal.<ref>D'Amato 1998, p. 7.</ref> A [[reverse osmosis]] unit can be used to filter the water or, alternatively, bottled [[distilled water]] can be purchased. Watering should be done regularly. However, plants should not be allowed to sit in water, as this may lead to root rot.

[[Image:2008-1-1 cultivated Nepenthes rajah (126).jpg|thumb|135px|Cultivated ''N. rajah'' pitcher]]

===Feeding and fertilising===
''Nepenthes rajah'' is a carnivorous plant and, as such, supplements nutrients gained from the soil with captured prey (especially insects) to alleviate deficiencies in important elements such as [[nitrogen]], [[phosphorus]] and [[potassium]]. Just as in nature, a cultivated plant's 'diet' may include insects and other prey items, although this is not necessary for successful cultivation. [[Cricket (insect)|Crickets]] are recommended for their size and low cost. These can be purchased online or at specialist pet stores.  They can simply be dropped into the pitchers by hand or placed inside using metal [[tongs]] or similar, whether dead or alive.

From trials carried out by a commercial ''Nepenthes'' nursery,<ref name=BE>{{Cite web |url=http://borneoexotics.com/aspx/guides.aspx |title=''Nepenthes'' Cultivation and Growing Guides |access-date=2006-01-22 |archive-url=https://web.archive.org/web/20070721034030/http://www.borneoexotics.com/aspx/guides.aspx |archive-date=2007-07-21 |url-status=dead }}</ref> it appears that [[micronutrient]] solutions have "a beneficial effect on plants of improved leaf colouration, with no deleterious effects" as far as can be seen. However, more research is required to verify these results. Actual [[fertilizer|fertiliser]]s (containing [[Nitrogen|N]][[Phosphorus|P]][[Potassium|K]]) were, on the other hand, found to "cause damage to plants, promote [[pathogen]]s and have no observable benefits". Hence, the use of chemical fertilisers is usually not advised.

''Nepenthes rajah'' is a slow growing ''Nepenthes''. Under optimal conditions, ''N. rajah'' can reach flowering size within 10&nbsp;years of seed [[germination]].

==Common misconceptions==
[[Image:Kinabalu water fall N. rajah 11.JPG|thumb|220px|''N. rajah'' growing near a small waterfall]]

''Nepenthes rajah'' has been a well known and highly sought after species for over a century and, as a result, there are many stories woven around this plant. One such example is the famous legend that ''N. rajah'' grows exclusively in the spray zones of [[waterfall]]s, on [[ultramafic]] soils. Although it is true that they will grow in such places, ''N. rajah'' is certainly not found solely in the spray zones of waterfalls, and this statement seems to have little basis in fact.<ref name=Clarke/> It is likely that this misconception was popularised by [[Shigeo Kurata]]'s 1976 book ''[[Nepenthes of Mount Kinabalu]]'',{{Citation needed|date=November 2016}} in which he states that "''N. rajah'' is rather fond of wet places like swamps or the surroundings of a waterfall".<ref name=Kurata/>

This being the case, certain ''N. rajah'' plants do in fact grow in the ''vicinity'' of waterfalls (as noted by [[Hugo Steiner|H. Steiner]], 2002) "providing quite a humid microclimate",<ref name=Steiner/> which may indeed be the source of this particular misconception.

Another myth surrounding this species is that it occasionally catches small [[monkey]]s and other large animals in its pitchers. Such tales have persisted for a very long time, but can probably be explained as rodents being mistaken for other species.<ref>D'Amato 1998, XV.</ref> It is interesting to note that one common name for ''Nepenthes'' plants is '[[Monkey Cups]]'. The name refers to the fact that monkeys have been observed drinking rainwater from these plants.

==Timeline==
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  at:1858 text:"1858: Hugh Low collects Nepenthes rajah for the first time"
  at:1859 text:"1859: Joseph Dalton Hooker describes and names the new species"
  at:1862 text:"1862: Spenser St. John finds a drowned rat in a pitcher of N. rajah"
  at:1863 text:"1862: N. rajah appears in ''Life in the Forests of the Far East''"
  at:1869 text:"1869: Alfred R. Wallace mentions N. rajah in ''The Malay Archipelago''
  at:1873 text:"1873: Hooker places N. rajah in the Eunepenthes"
  at:1878 text:"1878: F. W. Burbidge collects N. rajah for the Veitch Nurseries"
  at:1881 text:"1881: N. rajah appears in ''The Gardeners' Chronicle''"
  at:1882 text:"1882: Plants are displayed at the RHS's annual show"
  at:1883 text:"1883: N. rajah appears in the botanical journal ''Gartenflora''"
  at:1892 text:"1892: Haviland collects specimens for the Sarawak Museum"
  at:1895 text:"1895: G. M. L. Beck places N. rajah in the Apruinosae"
  at:1897 text:"1897: N. rajah appears in the Journal of the RHS"
  at:1904 text:"1905: N. rajah appears in ''Curtis's Botanical Magazine''"
  at:1905 text:"1905: The final N. rajah plants of the Veitch Nurseries die"
  at:1906 text:"1906: N. rajah is lost from cultivation, as the last surviving plant dies"
  at:1908 text:"1908: John Muirhead Macfarlane revises the genus once more"
  at:1910 text:"1910: N. × kinabaluensis is collected for the first time by L. Gibbs"
  at:1914 text:"1914: Macfarlane suggests it might represent N. rajah × N. villosa"
  at:1915 text:"1915: Clemens collects specimens for the Buitenzorg Botanic Gardens"
  at:1921 text:"1921: N. rajah appears in the ''Bibl. Enum. Born.'' botanical journal"
  at:1927 text:"1927: N. rajah appears in the ''Tropical Nature'' botanical journal"
  at:1928 text:"1928: B. H. Danser places N. rajah within the Regiae clade"
  at:1929 text:"1929: H. M. Pendlebury makes the first collection of Culex rajah"
  at:1931 text:"1931: F. W. Edwards incorrectly identifies it as C. shebbearei"
  at:1936 text:"1936: H. Harms includes N. rajah in the Eunepenthes once more"
  at:1974 text:"1974: S. Kurata collects the holotype of N. × kinabaluensis (1984)"
  at:1976 text:"1976: N. rajah appears on the cover of ''Nepenthes of Mount Kinabalu''"
  at:1977 text:"1976: N. × kinabaluensis is described by Kurata"
  at:1981 text:"1981: N. rajah is placed on CITES Appendix I"
  at:1983 text:"1983: T. C. Gibson publishes the first cultivation guide for N. rajah"
  at:1984 text:"1984: Kurata describes N. rajah × N. villosa as N. × kinabaluensis"
  at:1986 text:"1986: A. Slack illustrates N. burbidgeae × N. rajah as N. rajah"
  at:1987 text:"1988: A. Phillipps and A. Lamb find a rat caught by N. rajah"
  at:1988 text:"1988: J. H. Adam collects the holotype of N. kinabaluensis (1996)"
  at:1989 text:"1988: Adam and A. Mahdi collect the holotype of N. × alisaputrana
  at:1990 text:"1989: M. Tsukamoto describes Culex rajah and Toxorhynchites rajah
  at:1991 text:"1992: G. Cheers illustrates N. × kinabaluensis as N. rajah"
  at:1992 text:"1992: Nepenthes × alisaputrana is described by Adam and Wilcock"
  at:1995 text:"1996: Malaysia releases a postage stamp depicting N. rajah"
  at:1996 text:"1996: Adam and Wilcock describe Nepenthes kinabaluensis"
  at:1997 text:"1997: N. rajah appears on the cover of  ''Nepenthes of Borneo''
  at:1998 text:"1997: N. rajah is listed on Schedule I, Part II of the WCE"
  at:2000 text:"2000: N. rajah is listed on the IUCN Red List as Endangered" 
  at:2001 text:"2001: N. × kinabaluensis appears on the cover of Clarke's guide
  at:2002 text:"2002: Biochemical analysis is conducted on N. rajah et al.

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{{hidden end}}

==Citations==
{{Reflist|30em}}

==References==
{{Refbegin|40em}}
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* [Anonymous] 1883. [https://www.biodiversitylibrary.org/page/26130371 Mr. A. E. Ratcliff's ''Nepenthes'']. ''The Gardeners' Chronicle'' '''20'''(497): 18–19.
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* [[Günther Beck von Mannagetta und Lerchenau|Beck, G.]] 1895. Die Gattung ''Nepenthes''. ''Wiener Illustrierte Gartenzeitung''.
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* Clarke, C. 2013. [http://flashstream1.jcu.edu.au/html/tess-13-seminar-sep25.html What Can Tree Shrews Tell Us about the Effects of Climate Change on Pitcher Plants?] {{Webarchive|url=https://web.archive.org/web/20160305062128/https://flashstream1.jcu.edu.au/html/tess-13-seminar-sep25.html |date=2016-03-05 }} [video] TESS seminars, 25 September 2013.
* [[Charles Clarke (botanist)|Clarke, C. M.]] & [[Rod Kruger|R. Kruger]] 2005. [http://www.carnivorousplants.org/cpn/Species/v34n2p36_41.html ''Nepenthes rowanae'' (Nepenthaceae), a remarkable species from Cape York, Australia.] ''[[Carnivorous Plant Newsletter]]'' '''34''' (2): 36–41.
* {{cite iucn|author= [[Charles Clarke (botanist)|Clarke, C.]]|author2= [[Rob Cantley|Cantley, R.]]|author3= [[Joachim Nerz|Nerz, J.]] |author4= [[Heiko Rischer|Rischer, H.]]|author5= [[Andreas Wistuba|Witsuba, A.]]|year= 2000|page= e.T39690A10251581 |title= ''Nepenthes rajah''|access-date= 4 February 2020}}
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* {{in lang|de}} Meimberg, H. 2002. {{cite web |url= http://edoc.ub.uni-muenchen.de/1078/1/Meimberg_Harald.pdf |title= Molekular-systematische Untersuchungen an den Familien Nepenthaceae und Ancistrocladaceae sowie verwandter Taxa aus der Unterklasse Caryophyllidae s. l.. }} Ph.D. thesis, Ludwig Maximilian University of Munich, Munich.
* Meimberg, H. & G. Heubl 2006. Introduction of a nuclear marker for phylogenetic analysis of Nepenthaceae. ''Plant Biology'' '''8'''(6): 831–840. {{doi|10.1055/s-2006-924676}}
* Mey, F.S. 2014. [http://carnivorousockhom.blogspot.fr/2014/02/joined-lecture-on-carnivorous-plants-of.html Joined lecture on carnivorous plants of Borneo with Stewart McPherson.] ''Strange Fruits: A Garden's Chronicle'', February 21, 2014.
* [[J. A. Moran|Moran, J. A.]] 1991. The role and mechanism of ''Nepenthes rafflesiana'' pitchers as insect traps in Brunei. Ph.D. thesis, [[University of Aberdeen]], [[Aberdeen]], [[Scotland]].
* [[Ernest Charles Nelson|Nelson, E. C.]] The waxing of glorious ''rajah''. ''Kew magazine'' [May 1991] '''8''' (2): 81–89.
* [[Joachim Nerz|Nerz, J.]] & [[Andreas Wistuba|A. Wistuba]] 2007. ''Nepenthes mantalingajanensis'' (Nepenthaceae), eine bemerkenswerte neue Spezies aus Palawan (Philippinen). ''[[Das Taublatt]]'' '''55'''(3): 17–25.
* {{in lang|ja}} Oikawa, T. 1992. ''Nepenthes Rajah'' Hook.f.. In: {{Nihongo||無憂草 – Nepenthes|[[List of Nepenthes literature|Muyū kusa – Nepenthes]]}}. [''The Grief Vanishing''.] Parco Co., Japan. pp.&nbsp;8–9.
* [[Anthea Phillipps|Phillipps, A.]] 1988. {{cite web |url= http://www.carnivorousplants.org/cpn/articles/CPNv17n2p55.pdf |title= A Second Record of Rats as Prey in ''Nepenthes rajah''. }} ''[[Carnivorous Plant Newsletter]]'' '''17''' (2): 55.
* [[Anthea Phillipps|Phillipps, A.]] & [[Anthony Lamb (botanist)|A. Lamb]] 1996. ''[[Pitcher Plants of Borneo]]''. [[Natural History Publications (Borneo)|Natural History Publications]] ([[Borneo]]), [[Kota Kinabalu]]. x + 171 pp.&nbsp;{{ISBN|983-812-009-X}}
* Reginald 1883. ''Nepenthes Rajah'' J. D. Hooker. ''[[Gartenflora]]'', XXXII, p.&nbsp;213.
* [[Spenser St. John|Saint-John, S.]] 1862. ''Life in the Forests of the Far East; or, Travels in northern Borneo''. 2 volumes. London: Smith, Elder & Co. (reprinted by [[Oxford University Press]], 1974)
* [[R. Simpson|Simpson, R.]] 1991. Plants in peril, 15: ''Nepenthes rajah''. ''Kew magazine'' [May 1991] '''8''' (2): 89–94.
* Slack, A. 1979. ''Nepenthes rajah''. In: ''Carnivorous Plants''. Ebury Press, London. p.&nbsp;85.
* [[Adrian Slack|Slack, A.]] 1986. ''Insect-Eating Plants and How to Grow Them''. Alphabooks, [[Dorset]], [[United Kingdom|UK]]. 172 pp.&nbsp;{{ISBN|0-906670-42-X}} (hardback) {{ISBN|0-906670-35-7}} (paperback)
* [[R. M. Som|Som, R. M.]] 1988. Systematic studies on ''Nepenthes'' species and hybrids in the Malay Peninsula. Ph.D. thesis, Fakulti Sains Hayat, [[Universiti Kebangsaan Malaysia]], UKM Bangi, Selangor Darul Ehsan.
* [[Clive A. Stace|Stace, C.A.]] 1980. ''Plant Taxonomy and Biosystematics''. Arnold, London. {{ISBN|0-521-42785-1}}
* [[Hugo Steiner|Steiner, H.]] 2002. ''[[Borneo: Its Mountains and Lowlands with their Pitcher Plants]]''. Toihaan Publishing Company, [[Kota Kinabalu]]. viii + 136 pp.&nbsp;{{ISBN|983-40421-1-6}}
* Thorogood, C. 2010. ''[[The Malaysian Nepenthes: Evolutionary and Taxonomic Perspectives]]''. Nova Science Publishers, New York.
* [[Masuhisa Tsukamoto|Tsukamoto, M.]] 1989. {{cite web |url= http://www.mosquitocatalog.org/files/pdfs/133700-0.pdf |title= Two New Mosquito Species from a Pitcher Plant of Mt. Kinabalu, Sabah, Malaysia: ''Culex rajah'' and ''Toxorhynchites rajah'' (Diptera: Culicidae) |access-date= 2009-12-01 |archive-url= https://web.archive.org/web/20110723204219/http://www.mosquitocatalog.org/files/pdfs/133700-0.pdf |archive-date= 2011-07-23 |url-status= dead }}. ''[[Japanese Journal of Tropical Medicine and Hygiene]]'', '''17''' (3): 215–228.
* Yeo, J. 1996. A trip to Kinabalu Park. ''[[Bulletin of the Australian Carnivorous Plant Society, Inc.]]'' '''15'''(4): 4–5.
<!--http://www.kew.org/uhtbin/cgisirsi.exe/?ps=d2AibDRwIU/PUBNS/195340009/9 = Wax model in glass case, 'Nepenthes Rajah, Hk.f BORNEO Modelled by Miss Blackman from a Plant Growing at Glasnevin' Blackman, Edith Delta (1868-1947)-->
{{Refend}}

==Further reading==
* Camilleri, T. 1998. ''Carnivorous Plants''. Kangaroo Press, [[Roseville, New South Wales|Roseville]], [[New South Wales]], [[Australia]]. 104 pp.
* [[Matthew Jebb|Jebb, M. H. P.]] & [[Martin Cheek|M. R. Cheek]] 1997. [[A skeletal revision of Nepenthes (Nepenthaceae)|A skeletal revision of ''Nepenthes'' (Nepenthaceae)]]. ''Blumea'' '''42''' (1): 1–106.
* [[Adrian Slack|Slack, A.]] 1979. ''Carnivorous Plants''. Alphabooks, [[Dorset]], [[United Kingdom|UK]]. 240 pp.

==External links==
{{Commons}}
{{Wikispecies}}
{{Wikisource|Description of Nepenthes rajah Hook.f. (1859)}}
{{Wikiquote}}
{{Wikispecies|Nepenthes x alisaputrana|Nepenthes × alisaputrana}}
{{Wikispecies|Nepenthes x kinabaluensis|Nepenthes × kinabaluensis}}

===General===
* [https://web.archive.org/web/20060526141837/http://www.arcbc.org.ph/arcbcweb/pdf/vol1no4/focus_pitcher_plant.pdf Focus: Rajah Brooke's Pitcher Plant]
* [http://www.fleischfressendepflanzen.de/db/species.ffp?id=435 Die Karnivoren-Datenbank: ''Nepenthes rajah''] {{in lang|de}}

===Images===
* [http://www.joachim-nerz.de/rajah.htm Photographs of ''N. rajah'' in its natural habitat]
* [https://web.archive.org/web/20051130055638/http://www.arkive.org/species/GES/plants_and_algae/Nepenthes_rajah/more_still_images.html Images of ''N. rajah'' in natural habitat and tissue culture]
* [https://web.archive.org/web/20050214195113/http://www.borneoexotics.com/Species%20Data/rajah.htm Borneo Exotics: ''Nepenthes rajah'']

===Cultivation===
* [https://web.archive.org/web/20160921065900/http://www.cpzine.com/displayarticle.asp?cid=13&y=2002&m=6&d=21 ''N. rajah'' Cultivation Notes]
* [https://web.archive.org/web/20060315190427/http://www.cpjungle.com/nucraj.htm Further Cultivation Notes]
* [http://www.coloradocarnivorousplantsociety.com/Nepenthes_rajah.htm Colorado Carnivorous Plant Society: ''Nepenthes rajah'']
* [http://home.arcor.de/j.danz/N_rajah_f.html Growth of plant in cultivation over several years] {{Webarchive|url=https://web.archive.org/web/20160303221643/http://home.arcor.de/j.danz/N_rajah_f.html |date=2016-03-03 }}
* [https://web.archive.org/web/20041226132950/http://www-cp.stech.co.jp/cp/nepe/rajah_e.html Large plants in cultivation]

===Other===
* [http://www.ipni.org/ipni/idPlantNameSearch.do?id=603791-1 The International Plant Names Index: ''Nepenthes rajah'']
* [http://www.omnisterra.com/botany/cp/pictures/nepenthe/dansermg/dans49.htm ''Nepenthes rajah'' entry from Danser's Monograph]
* [http://www.redlist.org/search/details.php?species=39690 IUCN Red List of Threatened Species: ''Nepenthes rajah'']
* [https://www.youtube.com/watch?v=trWzDlRvv1M Video about ''Nepenthes rajah''] from ''[[The Private Life of Plants]]''

{{Nepenthes}}
{{Taxonbar|from=Q132973}}

[[Category:Carnivorous plants of Asia]]
[[Category:Coprophagous plants]]
[[Category:Nepenthes|rajah]]
[[Category:Endemic flora of Borneo]]
[[Category:Flora of Sabah]]
[[Category:Threatened flora of Asia]]
[[Category:Plants described in 1859]]
[[Category:Articles which contain graphical timelines]]
[[Category:Flora of Mount Kinabalu]]
[[Category:Flora of the Borneo montane rain forests]]