''Nepenthes rhombicaulis'' is a tropical

pitcher plant Pitcher plants are several different carnivorous plants which have modified leaves known as pitfall traps—a prey-trapping mechanism featuring a deep cavity filled with digestive liquid. The traps of what are considered to be "true" pitcher p ...

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

Sumatra Sumatra is one of the Sunda Islands of western Indonesia. It is the largest island that is fully within Indonesian territory, as well as the sixth-largest island in the world at 473,481 km2 (182,812 mi.2), not including adjacent i ...

. The

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

''rhombicaulis'' is formed from the

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

words ''rhombicus'', meaning "rhomboid", and ''caulis'', "stem". It refers to the cross-sectional shape of the stem internodes.

Botanical history

''Nepenthes rhombicaulis'' was first collected by

Shigeo Kurata is a Japanese botanist and '' Nepenthes'' taxonomist whose work in the 1960s and 1970s contributed much to the current popularity of these plants.Clarke, C.M. & C.C. Lee 2004. ''Pitcher Plants of Sarawak''. Natural History Publications (Borneo), ...

on March 29, 1972, on

Mount Pangulubao Mount Pangulubao or Pangulubau ( id, Gunung Pangulubao) is a mountain near Lake Toba in Sumatra. Mount Pangulubao is notable for its large number of native tropical pitcher plant species. These include ''Nepenthes ampullaria'', '' Nepenthes gym ...

at an altitude of between 1700 and 1900 m above sea level. The species was mentioned by name in a 1972 issue (volume 26, number 10, page 44) of ''The Heredity''.Cheek, M.R. & M.H.P. Jebb 2001. Nepenthaceae. ''Flora Malesiana'' 15: 1–157. It was formally described by Kurata the following year in ''

The Gardens' Bulletin Singapore ''The'' () is a grammatical article in English, denoting persons or things already mentioned, under discussion, implied or otherwise presumed familiar to listeners, readers, or speakers. It is the definite article in English. ''The'' is the ...

''. One of the original specimens, ''Kurata 4300'', was designated as the

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

of the species and is deposited at the herbarium of the

Nippon Dental College Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

(NDC). An isotype is held at the National Herbarium of Singapore (SING).Clarke, C.M. 2001. ''

Nepenthes of Sumatra and Peninsular Malaysia ''Nepenthes of Sumatra and Peninsular Malaysia'' is a monograph by Charles Clarke on the tropical pitcher plants of Sumatra, Peninsular Malaysia, and their minor surrounding islands. It was published in 2001 by Natural History Publications (Borneo ...

''. Natural History Publications (Borneo), Kota Kinabalu. Kurata's illustration of the type specimen shows a small apical appendage on the underside of the pitcher lid. However,

Matthew Jebb Matthew Hilary Peter Jebb (born 1958) is an Irish botanist and taxonomist specialising in the ant plant genera ''Squamellaria'', ''Myrmecodia'', ''Hydnophytum'', ''Myrmephytum'' and ''Anthorrhiza'', as well as the carnivorous plant genus ''Nepe ...

and

Martin Cheek Martin Roy Cheek (born 1960) is a botanist and taxonomist at the Royal Botanic Gardens, Kew.Singapore Singapore (), officially the Republic of Singapore, is a sovereign island country and city-state in maritime Southeast Asia. It lies about one degree of latitude () north of the equator, off the southern tip of the Malay Peninsula, borde ...

.Jebb, M.H.P. & M.R. Cheek 1997. A skeletal revision of ''Nepenthes'' (Nepenthaceae). ''Blumea'' 42(1): 1–106. Kurata suggested that the appendage might be a developmental defect and of little significance. Observations made at the type locality by

Charles Clarke Charles Rodway Clarke (born 21 September 1950) is a British Labour Party politician, who was the Member of Parliament (MP) for Norwich South from 1997 until 2010, and served as Home Secretary from December 2004 until May 2006. Early life Th ...

and

Ch'ien Lee Ch'ien C. Lee (Chinese: 李乾; pinyin: Lǐ Qián) is a photographer and botanist specialising in the carnivorous plant genus ''Nepenthes''. Lee has described several new ''Nepenthes'' species, including '' N. baramensis''Clarke, C., J.A. Mora ...

seem to confirm this; while some wild plants exhibit this appendage, most do not. In the 1983 book ''Carnivorous Plants of the World in Colour'' by Katsuhiko and Masahiro Kondo, a photograph of '' N. gymnamphora'' is identified as ''N. rhombicaulis''.Schlauer, J. N.d.
''Nepenthes rhombicaulis''
Carnivorous Plant Database. In 1993,

Bruce Salmon The English language name Bruce arrived in Scotland with the Normans, from the place name Brix, Manche in Normandy, France, meaning "the willowlands". Initially promulgated via the descendants of king Robert the Bruce (1274−1329), it has been a ...

postulated that the lower pitchers of ''N. rhombicaulis'' are specially adapted to trapping subterranean insects. His observations were published in the ''

Carnivorous Plant Newsletter The ''Carnivorous Plant Newsletter'' is the official publication of the International Carnivorous Plant Society (ICPS), the largest such organization in the world. It is headquartered in Walnut Creek, California. History and editorship The newsle ...

''.Salmon, B. .1993. ''

'' 22(1–2): 11–12. Rudolf Schmid-Höllinger reported observing upper pitchers of ''N. rhombicaulis'' on Mount Pangulubao in 1993. He published his findings the following year in the ''

''.Schmid-Höllinger, R. 1994. ''

'' 23(3): 62–63.

also reported finding one small upper pitcher in 1995.Clarke, C. .1997
Another Nice Trip to Sumatra
''

'' 26(1): 4–10. Prior to this, it was thought that the upper stem of ''N. rhombicaulis'' was only used for climbing and did not produce pitchers. However, doubts have been raised about the identity of the upper pitchers observed by Schmid-Höllinger.

Description

''Nepenthes rhombicaulis'' climbs well and its stem is known to reach 35 m in length, making it one of the longest in the genus.

Internodes A stem is one of two main structural axes of a vascular plant, the other being the root. It supports leaves, flowers and fruits, transports water and dissolved substances between the roots and the shoots in the xylem and phloem, stores nutrien ...

are up to 20 cm long and 1 cm in diameter. They are usually rhomboid in cross section. The stem bears numerous sunken glands. The species has an extended

rhizome In botany and dendrology, a rhizome (; , ) is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from axillary buds and grow hori ...

which produces stems at irregular intervals. Leaves are

sessile Sessility, or sessile, may refer to: * Sessility (motility), organisms which are not able to move about * Sessility (botany), flowers or leaves that grow directly from the stem or peduncle of a plant * Sessility (medicine), tumors and polyps that ...

. The

lamina Lamina may refer to: Science and technology * Planar lamina, a two-dimensional planar closed surface with mass and density, in mathematics * Laminar flow, (or streamline flow) occurs when a fluid flows in parallel layers, with no disruption betwee ...

lanceolate The following is a list of terms which are used to describe leaf morphology in the description and taxonomy of plants. Leaves may be simple (a single leaf blade or lamina) or compound (with several leaflets). The edge of the leaf may be regular o ...

spathulate This glossary of botanical terms is a list of definitions of terms and concepts relevant to botany and plants in general. Terms of plant morphology are included here as well as at the more specific Glossary of plant morphology and Glossary o ...

, up to 25 cm long, and up to 4 cm wide. It has an acute to sub-

peltate The following is a list of terms which are used to describe leaf morphology in the description and taxonomy of plants. Leaves may be simple (a single leaf blade or lamina) or compound (with several leaflets). The edge of the leaf may be regular o ...

apex and an amplexicaul base. Two to three longitudinal veins are present on either side of the

midrib This glossary of botanical terms is a list of definitions of terms and concepts relevant to botany and plants in general. Terms of plant morphology are included here as well as at the more specific Glossary of plant morphology and Glossary o ...

Pinnate Pinnation (also called pennation) is the arrangement of feather-like or multi-divided features arising from both sides of a common axis. Pinnation occurs in biological morphology, in crystals, such as some forms of ice or metal crystals, and in ...

veins are oblique.

Tendril In botany, a tendril is a specialized stem, leaf or petiole with a threadlike shape used by climbing plants for support and attachment, as well as cellular invasion by parasitic plants such as ''Cuscuta''. There are many plants that have tendr ...

s may be up to 15 cm long. Rosette and lower pitchers are ovoid to

ventricose Ventricose is an adjective describing the condition of a mushroom, gastropod or plant that it is "swollen, distended, or inflated especially on one side". Mycology In mycology, ventricose is a condition in which the cystidia, lamella or stipe of a ...

in the lower parts and cylindrical above. They reach 12 cm in height and 4 cm in width. A pair of fringed wings (≤3 mm long) runs down the front of the pitchers. The

gland In animals, a gland is a group of cells in an animal's body that synthesizes substances (such as hormones) for release into the bloodstream (endocrine gland) or into cavities inside the body or its outer surface (exocrine gland). Structure De ...

ular region is restricted to the ovoid portion of the inner surface. Digestive glands occur at a density of 150 to 300 per square centimetre. The pitcher mouth is round and oblique. The

peristome Peristome (from the Greek ''peri'', meaning 'around' or 'about', and ''stoma'', 'mouth') is an anatomical feature that surrounds an opening to an organ or structure. Some plants, fungi, and shelled gastropods have peristomes. In mosses In mosses, ...

is sub-cylindrical to irregularly expanded and up to 5 mm wide. Its inner margin is lined with distinct, papery teeth up to 3 mm long. The lid or operculum is ovate and may bear a small apical appendage on its lower surface. Up to 100 nectar glands are present on the underside of the lid. A

spur A spur is a metal tool designed to be worn in pairs on the heels of riding boots for the purpose of directing a horse or other animal to move forward or laterally while riding. It is usually used to refine the riding aids (commands) and to back ...

(≤5 mm long), which may be unbranched,

bifid Bifid refers to something that is split or cleft into two parts. It may refer to: * Bifid, a variation in the P wave, R wave, or T wave in an echocardiogram in which a wave which usually has a single peak instead has two separate peaks * Bifid ci ...

, or trifid, is inserted near the base of the lid. Upper pitchers have not been reliably recorded in the field and measurements for them have not been published. Based on Schmid-Höllinger's observations, they are ventricose in the lower parts and elongated above, becoming tubiform or slightly infundibuliform towards the mouth. The peristome is greatly reduced and bears smaller teeth. Wings may or may not be reduced to ribs. Several hundred nectar glands are present on the underside of the lid, although they are smaller than in lower pitchers. ''Nepenthes rhombicaulis'' has a

racemose A raceme ( or ) or racemoid is an unbranched, indeterminate type of inflorescence bearing flowers having short floral stalks along the shoots that bear the flowers. The oldest flowers grow close to the base and new flowers are produced as the s ...

inflorescence An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed o ...

. The peduncle and

rachis In biology, a rachis (from the grc, ῥάχις [], "backbone, spine") is a main axis or "shaft". In zoology and microbiology In vertebrates, ''rachis'' can refer to the series of articulated vertebrae, which encase the spinal cord. In this c ...

both reach 20 cm in length, although the latter is usually shorter in female plants. Partial peduncles are two-flowered and lack

bract In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are usually different from foliage leaves. They may be smaller, larger, or of ...

eoles.

Sepal A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106 The term ''sepalum'' was coined b ...

s are elliptical and up to 4 mm long. Most parts of the plant are virtually

glabrous Glabrousness (from the Latin ''glaber'' meaning "bald", "hairless", "shaved", "smooth") is the technical term for a lack of hair, down, setae, trichomes or other such covering. A glabrous surface may be a natural characteristic of all or part of ...

. The margins of the lamina are often lined with short red hairs. Inflorescences may have a sparse

indumentum In biology, an indumentum (Latin, literally: "garment") is a covering of trichomes (fine "hairs") on a plant Davis, Peter Hadland and Heywood, Vernon Hilton (1963) ''Principles of angiosperm taxonomy'' Van Nostrandpage, Princeton, New Jersey, pa ...

of minute hairs. The stem and lamina are green. Lower pitcher range in colour from dull green throughout to light red with purple blotches. The peristome may be light green to dark purple and is often darker around its outer margin. According to Schmid-Höllinger, upper pitchers are yellowish-green with pale red spots in the upper part and pitchers produced on offshoots from the climbing stem have clear red speckles throughout.

Ecology

''Nepenthes rhombicaulis'' is known from a number of peaks in the

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...

n province of

North Sumatra North Sumatra ( id, Sumatra Utara) is a province of Indonesia located on the northern part of the island of Sumatra. Its capital and largest city is Medan. North Sumatra is Indonesia's fourth most populous province after West Java, East Java and ...

, particularly around

Lake Toba Lake Toba ( id, Danau Toba) ( Toba Batak: ᯖᯀᯬ ᯖᯬᯅ; romanized: ''Tao Toba'') is a large natural lake in North Sumatra, Indonesia, occupying the caldera of a supervolcano. The lake is located in the middle of the northern part of the ...

. Plants that appear to match the description of ''N. rhombicaulis'' have also been recorded from

Mount Bandahara Mount is often used as part of the name of specific mountains, e.g. Mount Everest. Mount or Mounts may also refer to: Places * Mount, Cornwall, a village in Warleggan parish, England * Mount, Perranzabuloe, a hamlet in Perranzabuloe parish, C ...

Aceh Aceh ( ), officially the Aceh Province ( ace, Nanggroë Acèh; id, Provinsi Aceh) is the westernmost province of Indonesia. It is located on the northernmost of Sumatra island, with Banda Aceh being its capital and largest city. Granted a s ...

. The species is known with certainty only from the

complex and

Mount Lubukraya Mount is often used as part of the name of specific mountains, e.g. Mount Everest. Mount or Mounts may also refer to: Places * Mount, Cornwall, a village in Warleggan parish, England * Mount, Perranzabuloe, a hamlet in Perranzabuloe parish, C ...

, although

suggested that it is likely to be more widespread in the Lake Toba region. ''Nepenthes rhombicaulis'' has an altitudinal distribution of 1600–2000 m

above sea level Height above mean sea level is a measure of the vertical distance (height, elevation or altitude) of a location in reference to a historic mean sea level taken as a vertical datum. In geodesy, it is formalized as ''orthometric heights''. The comb ...

.McPherson, S.R. 2009. ''

Pitcher Plants of the Old World ''Pitcher Plants of the Old World'' is a two-volume monograph by Stewart McPherson on the pitcher plants of the genera ''Nepenthes'' and ''Cephalotus''. It was published in May 2009 by Redfern Natural History Productions and covers all species kno ...

''. 2 volumes. Redfern Natural History Productions, Poole.McPherson, S.R. & A. Robinson 2012. ''

Field Guide to the Pitcher Plants of Sumatra and Java This list of ''Nepenthes'' literature is a listing of major published works dealing with the tropical pitcher plants of the genus ''Nepenthes''. It includes specialised standalone publications and taxonomic monographs released as part of larger ...

''. Redfern Natural History Productions, Poole. ''Nepenthes rhombicaulis'' grows terrestrially in dense, shady

montane forest Montane ecosystems are found on the slopes of mountains. The alpine climate in these regions strongly affects the ecosystem because temperatures fall as elevation increases, causing the ecosystem to stratify. This stratification is a crucial f ...

. It is usually found in lower montane forest above steep slopes, but has also been recorded from upper montane forest. It is one of the few ''Nepenthes'' species that are common in the

understory In forestry and ecology, understory (American English), or understorey (Commonwealth English), also known as underbrush or undergrowth, includes plant life growing beneath the forest canopy without penetrating it to any great extent, but abov ...

. Lower pitchers frequently develop embedded in

detritus In biology, detritus () is dead particulate organic material, as distinguished from dissolved organic material. Detritus typically includes the bodies or fragments of bodies of dead organisms, and fecal material. Detritus typically hosts commun ...

and leaf litter on the forest floor, resulting in their often deformed appearance.

noted that lower pitchers which develop in this way grow around twice as large as those which develop completely above ground. He postulated that the species is adapted to trapping subterranean insects, although he did not examine the contents of these pitchers to test the hypothesis.Hopkins, M., R. Maulder & B. .Salmon 1990. ''

'' 19(1–2): 19–28. In its natural habitat, ''N. rhombicaulis'' occurs sympatrically with '' N. flava'',Wistuba, A., J. Nerz & A. Fleischmann 2007
flava'', a new species of Nepenthaceae from the northern part of Sumatra
''Blumea'' 52(1): 159–163. '' N. ovata'', '' N. spectabilis'', and '' N. tobaica''. Natural hybrids with all of these species have been recorded. On Mount Pangulubao, '' N. gymnamphora'' ('' N. xiphioides'') and '' N. mikei'' grow around 100 m above populations of ''N. rhombicaulis''.Salmon, B.R. & R.G. Maulder 1995
Two New Species of ''Nepenthes'' from North Sumatra, Indonesia
''

'' 24(3): 77–85. Due to its somewhat restricted distribution, ''N. rhombicaulis'' is listed as Vulnerable on the 2006 IUCN Red List of Threatened Species.

Related species

''Nepenthes rhombicaulis'' is very similar to '' N. gymnamphora'' in both morphology and growth habit. It is sympatric with this species on

. ''Nepenthes rhombicaulis'' also bears a close resemblance to '' N. hirsuta'' from

Borneo Borneo (; id, Kalimantan) is the third-largest island in the world and the largest in Asia. At the geographic centre of Maritime Southeast Asia, in relation to major Indonesian islands, it is located north of Java, west of Sulawesi, and eas ...

. In 2001,

performed a

cladistic analysis Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived chara ...

of the ''Nepenthes'' species of Sumatra and

Peninsular Malaysia Peninsular Malaysia ( ms, Semenanjung Malaysia; Jawi: سمننجڠ مليسيا), or the States of Malaya ( ms, Negeri-negeri Tanah Melayu; Jawi: نڬري-نڬري تانه ملايو), also known as West Malaysia or the Malaysian Peninsula, ...

using 70 morphological characteristics of each taxon. The resultant

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...

placed ''N. rhombicaulis'' in an unresolved

polytomy An internal node of a phylogenetic tree is described as a polytomy or multifurcation if (i) it is in a rooted tree and is linked to three or more child subtrees or (ii) it is in an unrooted tree and is attached to four or more branches. A tr ...

at the base of the '' Montanae/Nobiles''

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

, together with '' N. benstonei''.

Natural hybrids

At least four

natural hybrid In biology, a hybrid is the offspring resulting from combining the qualities of two organisms of different breeds, varieties, species or genera through sexual reproduction. Hybrids are not always intermediates between their parents (such as in ...

s involving ''N. rhombicaulis'' have been recorded and at least three of the parent species (excluding ''N. rhombicaulis'') occur on Mount Pangulubao. *'' N. flava'' × ''N. rhombicaulis'' *? '' N. gymnamphora'' × ''N. rhombicaulis'' *'' N. ovata'' × ''N. rhombicaulis'' *''N. rhombicaulis'' × '' N. spectabilis'' *''N. rhombicaulis'' × '' N. tobaica''

References

External links

''Nepenthes rhombicaulis'' in its natural habitat
{{Taxonbar, from=Q5460419 Carnivorous plants of Asia rhombicaulis Endemic flora of Sumatra Threatened flora of Asia Plants described in 1973 Vulnerable plants