Nepenthes dubia
Encyclopedia
Nepenthes dubia is a tropical pitcher plant
endemic to Sumatra
. The specific epithet dubia is the Latin
word for "doubtful".
, at an altitude of around 1900 m above sea level. Eleven years later, B. H. Danser
formally described
N. dubia in his seminal monograph "The Nepenthaceae of the Netherlands Indies
". Danser noted similarities between N. dubia and the closely related N. inermis
and suggested that it might represent a natural hybrid involving this species. He wrote:
Danser based his description on the specimen collected in 1917, Bünnemeijer 938. It consists of a portion of a climbing stem with upper pitchers. The specimen is deposited at the Bogor Botanical Gardens
(formerly the Herbarium of the Buitenzorg Botanic Gardens) in Java
and Herbarium Lugduno-Batavum in Leiden, Netherlands
. Bünnemeijer 938 was later designated as the lectotype
of N. dubia by Matthew Jebb
and Martin Cheek
.
Renewed interest in Nepenthes in the latter half of the 20th century saw N. dubia become the subject of both confusion and taxonomic revision.
In an article published in 1973 on the Nepenthes of Borneo, Singapore, and Sumatra, botanist Shigeo Kurata
incorrectly identified specimens of a natural cross between N. inermis and N. talangensis
as belonging to N. dubia. Kurata would later describe this hybrid as a new species, N. pyriformis.
In 1986, Mitsuru Hotta
and Rusjdi Tamin included plant material belonging to N. dubia and N. inermis in their description of N. bongso
. However, N. bongso differs considerably in pitcher morphology from these species and is not easily confused with them.
In 1997, Matthew Jebb
and Martin Cheek
published their monograph "A skeletal revision of Nepenthes (Nepenthaceae)
", in which they referred to N. dubia specimens from Mount Talang
(Kurata s.n. SING) and the mountains of the Tjampo region near Payakumbuh
(Meijer 6949 L). The latter specimen is the holotype of N. tenuis
, which Jebb and Cheek treated in synonymy with N. dubia.
However, subsequent authors have rejected this interpretation. Charles Clarke
restored N. tenuis to species rank in Nepenthes of Sumatra and Peninsular Malaysia
(2001), citing differences in pitcher morphology. Clarke also identified Kurata s.n. as the natural hybrid N. × pyriformis, which is similar to N. dubia, but can be distinguished on the basis of several stable characters. The hybrid has a wider pitcher lid that is never relfexed beyond 90 degrees and the pitcher cup is not appressed in the lower parts as in N. dubia. In addition, the mouth of N. × pyriformis is raised towards the back as opposed to being horizontal.
s are up to 10 cm long.
Leaves are sessile and coriaceous. The lamina is lanceolate-spathulate in form. It may be up to 10 cm long and 2 cm wide. It has an acute apex and is gradually attenuate towards the base, which clasps the stem for one third to a half of its circumference. Around three pairs of longitudinal veins are present on the lamina, originating from the basal third of the midrib. Pinnate veins are oblique and irregularly reticulate, although they are not easily distinguishable. Tendril
s can be up to 15 cm long and may or may not have a curl.
Rosette and lower pitchers are rarely produced. They are narrowly infundibular in the lower two-thirds, becoming ovoid above, and are sharply contracted below the rim. Terrestrial pitchers are relatively small, reaching 5 cm in height and 3.5 cm in width. A pair of fringed wings (≤3 mm wide) runs down the upper third of the pitcher beneath the rim. The glandular region covers the lower two-thirds of the inner surface. The pitcher mouth is round and slightly raised at the back. The peristome
is cylindrical, up to 3 mm wide, and bears indistinct teeth. The lid or operculum
is ovate and slightly raised in the middle. It bears no appendages. An unbranched spur
(≤4 mm long) is inserted at the base of the lid.
Upper pitchers are generally larger, growing to 8 cm in height and 4 cm in width. They gradually arise from the ends of the tendrils, forming a 5 to 10 mm wide curve. They are tubular to infundibular in the lower parts with laterally appressed pitcher walls. As in N. inermis, there is almost no gap between the walls in mature pitchers. The upper part of the pitcher is widely infundibular throughout. Wings are reduced to ribs in upper pitchers. The inner surface of the pitcher is covered with numerous small, slightly depressed glands, occurring at a density of 600-900 per square centimetre. The pitcher mouth is ovate, horizontal, and acute towards the lid. It bears a cylindrical or involute peristome (≤4 mm wide) with indistinct teeth spaced 0.25 to 0.5 mm apart. The lid is narrowly cuneate, without appendages, and up to 4 cm long and 0.7 cm wide. It is rounded at the apex, gradually attenuate towards the base, and bears numerous small round or elliptical glands on its undersurface. Characteristically, it is almost always reflexed beyond 180 degrees relative to the pitcher mouth. In upper pitchers, the unbranched spur is 3 to 5 mm long.
Nepenthes dubia has a racemose
inflorescence
that is distinctly short and compact. The peduncle
may be up to 8 cm long. The rachis
grows to 10 cm in length, although it is usually shorter in female inflorescences. Pedicel
s are bract
eolate and up to 8 mm long. Sepal
s are oblong-lanceolate and up to 3 mm long.
Most parts of the plant are virtually glabrous. Inflorescences sometimes bear a sparse indumentum
of simple hairs. Caducous brown hairs are present on developing pitchers.
The stem, inflorescence and tendrils are characteristically purplish-red in most plants. The lamina is green, often with a red midrib. Pitchers generally range in colour from light green to yellow throughout, although orange and red forms are also known to exist. Danser described the colour of herbarium specimens as "fallow-dun, here and there blackish".
Nepenthes dubia was for a long time thought to be endemic to Mount Talakmau
, but it was recently found on a second mountain, where it grows at lower elevations of around 1600 m above sea level. On Mount Talakmau, the species occurs at an altitude of 1800–2700 m. At lower elevations on Talakmau, it grows epiphytically
in montane forest. However, above around 2400 m, vegetation is very stunted and here N. dubia also grows terrestrially on clumps of moss.
In its natural habitat, N. dubia is sympatric with N. gymnamphora
, N. izumiae
, N. jamban
, and N. lingulata
. The stunted upper montane forest which these species inhabit is dominated by fern
s of the genera Dipteris and Dicranopteris. Trees rarely exceed 3 m in height and few Nepenthes plants emerge above the vegetation.
Due to its extremely localised distribution, N. dubia is listed as Critically Endangered
on the 2006 IUCN Red List of Threatened Species
. N. dubia occurs at several locations along the only permanent trail up Mount Talakmau. However, the upper pitchers of this species bear a peristome, and so are not as desirable as those of N. inermis. Because of this, wild populations of N. dubia have not suffered from over-collection.
pitcher liquid similar to that found in related species such as N. inermis
. The pitchers of N. inermis function not only as pitfall traps but also as flypaper traps, with the sticky inner walls trapping flying insects above the surface of the fluid. A similar trapping method may be employed by N. dubia.
Nepenthes dubia belongs to a group of closely related montane Sumatran species that includes N. flava
, N. inermis
, N. jacquelineae
, N. jamban
, N. talangensis
, and N. tenuis
. These species are characterised by infundibular upper pitchers and highly viscous pitcher fluid.
Nepenthes dubia is thought to be most closely related to N. inermis. It shares with this species the general morphology of its pitchers and leaves. It differs in having a well-developed peristome, more glands on the underside of the lid, and the lid being reflexed by more than 180 degrees. The lid of N. dubia is unique in this respect and is almost always reflexed beyond this angle, unless surrounding objects prevent it from assuming such a position.
In their description of N. tenuis, Joachim Nerz
and Andreas Wistuba
included a table of morphological characteristics that distinguish it from related species, including N. dubia:
In 2001, Charles Clarke
performed a cladistic analysis of the Nepenthes species of Sumatra and Peninsular Malaysia
using 70 morphological characteristics of each taxon
. The following is part of the resultant cladogram
, showing "Clade 1", which has 51% bootstrap support. Its most strongly supported subclade is the sister pair of N. inermis and N. dubia, having 95% support.
grows along the summit trail on Mount Talakmau
. It produces infundibular upper pitchers that are yellowish-green in colouration. The pitchers are relatively small, reaching only around 10 cm in height. As in N. dubia, the stem and tendrils are purplish-red. The lamina is green with a red midrib. Nepenthes dubia × N. izumiae differs most obviously from N. dubia in having an ovate lid that is never reflexed beyond 180 degrees. This hybrid is listed as N. dubia × N. singalana in Charles Clarke
's Nepenthes of Sumatra and Peninsular Malaysia
, since N. izumiae is very closely related to N. singalana
and was only described as a distinct species in 2003.
Among natural populations of N. jacquelineae
, botanist Andreas Wistuba
observed a single plant that appears to represent a natural cross between N. dubia and N. jacquelineae.
Pitcher plant
Pitcher plants are carnivorous plants whose prey-trapping mechanism features a deep cavity filled with liquid known as a pitfall trap. It has been widely assumed that the various sorts of pitfall trap evolved from rolled leaves, with selection pressure favouring more deeply cupped leaves over...
endemic to Sumatra
Sumatra
Sumatra is an island in western Indonesia, westernmost of the Sunda Islands. It is the largest island entirely in Indonesia , and the sixth largest island in the world at 473,481 km2 with a population of 50,365,538...
. The specific epithet dubia is the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
word for "doubtful".
Botanical history
Nepenthes dubia was first collected on May 29, 1917 by H. A. B. Bünnemeijer on Mount TalakmauMount Talakmau
Talakmau is a volcano in West Sumatra, Indonesia. Its elevation is 2,919 m .-External links :*...
, at an altitude of around 1900 m above sea level. Eleven years later, B. H. Danser
B. H. Danser
Benedictus Hubertus Danser , often abbreviated B. H. Danser, was a Dutch taxonomist and botanist...
formally described
Species description
A species description or type description is a formal description of a newly discovered species, usually in the form of a scientific paper. Its purpose is to give a clear description of a new species of organism and explain how it differs from species which have been described previously, or are...
N. dubia in his seminal monograph "The Nepenthaceae of the Netherlands Indies
The Nepenthaceae of the Netherlands Indies
"The Nepenthaceae of the Netherlands Indies" is a seminal monograph by B. H. Danser on the tropical pitcher plants of the Dutch East Indies, North Borneo, the Malay Peninsula, and eastern New Guinea...
". Danser noted similarities between N. dubia and the closely related N. inermis
Nepenthes inermis
Nepenthes inermis is a tropical pitcher plant endemic to Sumatra. The specific epithet inermis is Latin for "unarmed" and probably refers to the upper pitchers of this species, which are unique in that they completely lack a peristome....
and suggested that it might represent a natural hybrid involving this species. He wrote:
N. dubia strongly resembles the striking N. inermis, but the difference is too large to unite these two species. N. inermis, like N. Lowii has only a rudiment of a peristome. N. dubia has a broad and flat one. There are, however, also differences in the other parts: the pitchers are less widely infundibuliform and the lid is not so narrow as in N. inermis. Perhaps N. dubia is a hybrid of N. inermis and another species with normal peristome and in that case N. Bongso could be the other parent species, the more so as the vegetative parts of N. inermis, N. dubia and N. Bongso are very similar, and between the other species of the gymnamphora-group intermediate forms often occur.
Danser based his description on the specimen collected in 1917, Bünnemeijer 938. It consists of a portion of a climbing stem with upper pitchers. The specimen is deposited at the Bogor Botanical Gardens
Bogor Botanical Gardens
The Bogor Botanical Gardens are located 60 km south of the capital of Jakarta in Bogor, Indonesia. The botanical gardens are situated in the city center of Bogor and adjoin the Istana Bogor...
(formerly the Herbarium of the Buitenzorg Botanic Gardens) in Java
Java
Java is an island of Indonesia. With a population of 135 million , it is the world's most populous island, and one of the most densely populated regions in the world. It is home to 60% of Indonesia's population. The Indonesian capital city, Jakarta, is in west Java...
and Herbarium Lugduno-Batavum in Leiden, Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...
. Bünnemeijer 938 was later designated as the lectotype
Lectotype
In botanical nomenclature and zoological nomenclature, a lectotype is a kind of name-bearing type. When a species was originally described on the basis of a name-bearing type consisting of multiple specimens, one of those may be designated as the lectotype...
of N. dubia by Matthew Jebb
Matthew Jebb
Dr. Matthew H. P. Jebb is an Irish taxonomist and botanist specialising in the ant plant genera Squamellaria, Myrmecodia, Hydnophytum, Myrmephytum and Anthorrhiza, as well as the carnivorous plant genus Nepenthes....
and Martin Cheek
Martin Cheek
Dr. Martin Roy Cheek is a taxonomist and botanist specialising in the carnivorous plant genus Nepenthes.-Research:Cheek has described several new Nepenthes species, mostly with Matthew Jebb, including: N. argentii, N. aristolochioides, N. danseri, N. diatas,...
.
In an article published in 1973 on the Nepenthes of Borneo, Singapore, and Sumatra, botanist Shigeo Kurata
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. Of particular note is his 1976 guide, Nepenthes of Mount Kinabalu....
incorrectly identified specimens of a natural cross between N. inermis and N. talangensis
Nepenthes talangensis
Nepenthes talangensis is a tropical pitcher plant endemic to Sumatra, where it grows in upper montane forest at elevations of 1800–2500 m above sea level....
as belonging to N. dubia. Kurata would later describe this hybrid as a new species, N. pyriformis.
In 1986, Mitsuru Hotta
Mitsuru Hotta
is a Japanese botanist best known for his research on Araceae.Hotta was born in Osaka, Japan in 1937. He graduated from the Agricultural Department of Osaka Prefecture University in 1960. The same year, he took part in the Tonga and Fiji Expedition organised by Kyoto University...
and Rusjdi Tamin included plant material belonging to N. dubia and N. inermis in their description of N. bongso
Nepenthes bongso
Nepenthes bongso is a tropical pitcher plant endemic to Sumatra, where it has an altitudinal distribution of 1000–2700 m above sea level. The specific epithet bongso refers to the Indonesian legend of Putri Bungsu , the spirit guardian of Mount Marapi.The species was formally described by Pieter...
. However, N. bongso differs considerably in pitcher morphology from these species and is not easily confused with them.
In 1997, Matthew Jebb
Matthew Jebb
Dr. Matthew H. P. Jebb is an Irish taxonomist and botanist specialising in the ant plant genera Squamellaria, Myrmecodia, Hydnophytum, Myrmephytum and Anthorrhiza, as well as the carnivorous plant genus Nepenthes....
and Martin Cheek
Martin Cheek
Dr. Martin Roy Cheek is a taxonomist and botanist specialising in the carnivorous plant genus Nepenthes.-Research:Cheek has described several new Nepenthes species, mostly with Matthew Jebb, including: N. argentii, N. aristolochioides, N. danseri, N. diatas,...
published their monograph "A skeletal revision of Nepenthes (Nepenthaceae)
A skeletal revision of Nepenthes (Nepenthaceae)
"A skeletal revision of Nepenthes " is a monograph by Matthew Jebb and Martin Cheek on the tropical pitcher plants of the genus Nepenthes. It was published in the May 1997 issue of the botanical journal Blumea. The work represented the first revision of the entire genus since John Muirhead...
", in which they referred to N. dubia specimens from Mount Talang
Mount Talang
Mount Talang is an active stratovolcano in West Sumatra, Indonesia. Talang has two crater lakes on its flanks, the largest of which is 1 x 2 km wide and is called Lake Talang....
(Kurata s.n. SING) and the mountains of the Tjampo region near Payakumbuh
Payakumbuh
Payakumbuh is a city north-east of Bukittinggi , Indonesia. It has an area of 80.43 km² and a population of over 99,300 people. Literally translated, the city name means "grassy swamp"....
(Meijer 6949 L). The latter specimen is the holotype of N. tenuis
Nepenthes tenuis
Nepenthes tenuis is a tropical pitcher plant endemic to Sumatra. The species was first collected in 1957, from a remote mountain in the western part of the island. It remained undescribed until 1994, and was only rediscovered in the wild in 2002. Prior to this, N...
, which Jebb and Cheek treated in synonymy with N. dubia.
However, subsequent authors have rejected this interpretation. Charles Clarke
Charles Clarke (botanist)
Dr. Charles M. Clarke is a botanist and taxonomist specialising in the carnivorous plant genus Nepenthes. Clarke has an honours degree in Botany from Monash University in Melbourne, and a Ph.D. in Ecosystem Management at the University of New England, in Armidale, New South Wales.Clarke first...
restored N. tenuis to species rank in Nepenthes of Sumatra and Peninsular Malaysia
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...
(2001), citing differences in pitcher morphology. Clarke also identified Kurata s.n. as the natural hybrid N. × pyriformis, which is similar to N. dubia, but can be distinguished on the basis of several stable characters. The hybrid has a wider pitcher lid that is never relfexed beyond 90 degrees and the pitcher cup is not appressed in the lower parts as in N. dubia. In addition, the mouth of N. × pyriformis is raised towards the back as opposed to being horizontal.
Description
Nepenthes dubia is a climbing plant. The stem can reach 3 m in length and is 3 to 4 mm in diameter. It is cylindrical or slightly angular. InternodePlant stem
A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , conifer cones, roots, other stems etc. The internodes distance one node from another...
s are up to 10 cm long.
Leaves are sessile and coriaceous. The lamina is lanceolate-spathulate in form. It may be up to 10 cm long and 2 cm wide. It has an acute apex and is gradually attenuate towards the base, which clasps the stem for one third to a half of its circumference. Around three pairs of longitudinal veins are present on the lamina, originating from the basal third of the midrib. Pinnate veins are oblique and irregularly reticulate, although they are not easily distinguishable. Tendril
Tendril
In botany, a tendril is a specialized stem, leaf or petiole with a threadlike shape that is used by climbing plants for support, attachment and cellular invasion by parasitic plants, generally by twining around suitable hosts. They do not have a lamina or blade, but they can photosynthesize...
s can be up to 15 cm long and may or may not have a curl.
Rosette and lower pitchers are rarely produced. They are narrowly infundibular in the lower two-thirds, becoming ovoid above, and are sharply contracted below the rim. Terrestrial pitchers are relatively small, reaching 5 cm in height and 3.5 cm in width. A pair of fringed wings (≤3 mm wide) runs down the upper third of the pitcher beneath the rim. The glandular region covers the lower two-thirds of the inner surface. The pitcher mouth is round and slightly raised at the back. The peristome
Peristome
The word peristome is derived from the Greek peri, meaning 'around' or 'about', and stoma, 'mouth'. It is a term used to describe various anatomical features that surround an opening to an organ or structure. The term is used in plants and invertebrate animals, such as in describing the shells of...
is cylindrical, up to 3 mm wide, and bears indistinct teeth. The lid or operculum
Operculum (botany)
An operculum, in botany, is a term generally used to describe a structure within a plant, moss, or fungus acting as a cap, flap, or lid. In plants, it may also be called a bud cap.Examples of structures identified as opercula include:...
is ovate and slightly raised in the middle. It bears no appendages. An unbranched spur
Spur (biology)
A spur in botany is a spike, usually part of a flower.In certain plants, part of a sepal or petal develops into an elongated hollow spike extending behind the flower, containing nectar which is sucked by long-tongued animals . Plants with such structures include Delphinium, Aquilegia, Piperia, and...
(≤4 mm long) is inserted at the base of the lid.
Nepenthes dubia has a racemose
Raceme
A raceme is a type of inflorescence that is unbranched and indeterminate and bears pedicellate flowers — flowers having short floral stalks called pedicels — along the axis. In botany, axis means a shoot, in this case one bearing the flowers. In a raceme, the oldest flowers are borne...
inflorescence
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. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...
that is distinctly short and compact. The peduncle
Peduncle (botany)
In botany, a peduncle is a stem supporting an inflorescence, or after fecundation, an infructescence.The peduncle is a stem, usually green and without leaves, though sometimes colored or supporting small leaves...
may be up to 8 cm long. The rachis
Rachis
Rachis is a biological term for a main axis or "shaft".-In zoology:In vertebrates a rachis can refer to the series of articulated vertebrae, which encase the spinal cord. In this case the rachis usually form the supporting axis of the body and is then called the spine or vertebral column...
grows to 10 cm in length, although it is usually shorter in female inflorescences. Pedicel
Pedicel (botany)
A pedicel is a stem that attaches single flowers to the main stem of the inflorescence. It is the branches or stalks that hold each flower in an inflorescence that contains more than one flower....
s are bract
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 often different from foliage leaves. They may be smaller, larger, or of a different color, shape, or texture...
eolate and up to 8 mm long. Sepal
Sepal
A sepal is a part of the flower of angiosperms . Collectively the sepals form the calyx, which is the outermost whorl of parts that form a flower. Usually green, sepals have the typical function of protecting the petals when the flower is in bud...
s are oblong-lanceolate and up to 3 mm long.
Most parts of the plant are virtually glabrous. Inflorescences sometimes bear a sparse indumentum
Indumentum
The indumentum is a covering of fine hairs or bristles on a plant or insect.In plants, the indumentum types are:*pubescent*hirsute*pilose*villous*tomentose*stellate*scabrous*scurfy...
of simple hairs. Caducous brown hairs are present on developing pitchers.
The stem, inflorescence and tendrils are characteristically purplish-red in most plants. The lamina is green, often with a red midrib. Pitchers generally range in colour from light green to yellow throughout, although orange and red forms are also known to exist. Danser described the colour of herbarium specimens as "fallow-dun, here and there blackish".
Ecology
Mount Talakmau
Talakmau is a volcano in West Sumatra, Indonesia. Its elevation is 2,919 m .-External links :*...
, but it was recently found on a second mountain, where it grows at lower elevations of around 1600 m above sea level. On Mount Talakmau, the species occurs at an altitude of 1800–2700 m. At lower elevations on Talakmau, it grows epiphytically
Epiphyte
An epiphyte is a plant that grows upon another plant non-parasitically or sometimes upon some other object , derives its moisture and nutrients from the air and rain and sometimes from debris accumulating around it, and is found in the temperate zone and in the...
in montane forest. However, above around 2400 m, vegetation is very stunted and here N. dubia also grows terrestrially on clumps of moss.
Nepenthes gymnamphora
Nepenthes gymnamphora is a tropical pitcher plant native to the Indonesian islands of Java and Sumatra. There is much debate surrounding the taxonomic status of this species and the taxa N. pectinata and N. xiphioides....
, N. izumiae
Nepenthes izumiae
Nepenthes izumiae is a tropical pitcher plant endemic to Sumatra, where it grows in montane forest at 1700–1900 m above sea level. It appears to be most closely related to N. lingulata and N...
, N. jamban
Nepenthes jamban
Nepenthes jamban is a tropical pitcher plant endemic to northern Sumatra. The specific epithet jamban is the Indonesian word for "toilet" and refers to the shape of the pitchers.-Botanical history:...
, and N. lingulata
Nepenthes lingulata
Nepenthes lingulata is a tropical pitcher plant endemic to northern Sumatra. The species is characterised by the highly developed appendage present on the underside of the lid...
. The stunted upper montane forest which these species inhabit is dominated by fern
Fern
A fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...
s of the genera Dipteris and Dicranopteris. Trees rarely exceed 3 m in height and few Nepenthes plants emerge above the vegetation.
Due to its extremely localised distribution, N. dubia is listed as Critically Endangered
Critically Endangered
Critically Endangered is the highest risk category assigned by the IUCN Red List for wild species. Critically Endangered means that a species' numbers have decreased, or will decrease, by 80% within three generations....
on the 2006 IUCN Red List of Threatened Species
IUCN Red List
The IUCN Red List of Threatened Species , founded in 1963, is the world's most comprehensive inventory of the global conservation status of biological species. The International Union for Conservation of Nature is the world's main authority on the conservation status of species...
. N. dubia occurs at several locations along the only permanent trail up Mount Talakmau. However, the upper pitchers of this species bear a peristome, and so are not as desirable as those of N. inermis. Because of this, wild populations of N. dubia have not suffered from over-collection.
Carnivory
Nepenthes dubia produces thick, mucilaginousMucilage
Mucilage is a thick, gluey substance produced by most plants and some microorganisms. It is a polar glycoprotein and an exopolysaccharide.It occurs in various parts of nearly all classes of plant, usually in relatively small percentages, and is frequently associated with other substances, such as...
pitcher liquid similar to that found in related species such as N. inermis
Nepenthes inermis
Nepenthes inermis is a tropical pitcher plant endemic to Sumatra. The specific epithet inermis is Latin for "unarmed" and probably refers to the upper pitchers of this species, which are unique in that they completely lack a peristome....
. The pitchers of N. inermis function not only as pitfall traps but also as flypaper traps, with the sticky inner walls trapping flying insects above the surface of the fluid. A similar trapping method may be employed by N. dubia.
Related species
Nepenthes flava
Nepenthes flava is a tropical pitcher plant endemic to northern Sumatra, where it grows in montane forest at 1800–2200 m above sea level....
, N. inermis
Nepenthes inermis
Nepenthes inermis is a tropical pitcher plant endemic to Sumatra. The specific epithet inermis is Latin for "unarmed" and probably refers to the upper pitchers of this species, which are unique in that they completely lack a peristome....
, N. jacquelineae
Nepenthes jacquelineae
Nepenthes jacquelineae is a tropical pitcher plant endemic to Sumatra. Due to its unique pitcher morphology, it is considered to be one of the most spectacular Nepenthes species native to the island.-Botanical history:...
, N. jamban
Nepenthes jamban
Nepenthes jamban is a tropical pitcher plant endemic to northern Sumatra. The specific epithet jamban is the Indonesian word for "toilet" and refers to the shape of the pitchers.-Botanical history:...
, N. talangensis
Nepenthes talangensis
Nepenthes talangensis is a tropical pitcher plant endemic to Sumatra, where it grows in upper montane forest at elevations of 1800–2500 m above sea level....
, and N. tenuis
Nepenthes tenuis
Nepenthes tenuis is a tropical pitcher plant endemic to Sumatra. The species was first collected in 1957, from a remote mountain in the western part of the island. It remained undescribed until 1994, and was only rediscovered in the wild in 2002. Prior to this, N...
. These species are characterised by infundibular upper pitchers and highly viscous pitcher fluid.
Nepenthes dubia is thought to be most closely related to N. inermis. It shares with this species the general morphology of its pitchers and leaves. It differs in having a well-developed peristome, more glands on the underside of the lid, and the lid being reflexed by more than 180 degrees. The lid of N. dubia is unique in this respect and is almost always reflexed beyond this angle, unless surrounding objects prevent it from assuming such a position.
In their description of N. tenuis, Joachim Nerz
Joachim Nerz
Dr. Joachim Nerz is a taxonomist and botanist specialising in the carnivorous plant genera Heliamphora and Nepenthes. Nerz has described several new species, mostly with Andreas Wistuba.-Publications:...
and Andreas Wistuba
Andreas Wistuba
Dr. Andreas Wistuba is a German taxonomist and botanist specialising in the carnivorous plant genera Heliamphora and Nepenthes. More than half of all known Heliamphora species have been described by Wistuba.-Publications:...
included a table of morphological characteristics that distinguish it from related species, including N. dubia:
Character N. bongso N. dubia N. talangensis N. tenuis Shape of upper pitchers tubulate - infundibulate tubulous in the lower part, infundibulate above the middle tubulous to narrow infundibuliform in the lower half, ovate in the upper half wide infundibulate, contracted below the mouth Lid orbiculate narrow cuneate broad-ovate very narrow elliptical Length/width ratio of upper pitchers 3.3 1.9 2.3 1.75
In 2001, Charles Clarke
Charles Clarke (botanist)
Dr. Charles M. Clarke is a botanist and taxonomist specialising in the carnivorous plant genus Nepenthes. Clarke has an honours degree in Botany from Monash University in Melbourne, and a Ph.D. in Ecosystem Management at the University of New England, in Armidale, New South Wales.Clarke first...
performed a cladistic analysis of the Nepenthes species of Sumatra and Peninsular Malaysia
Peninsular Malaysia
Peninsular Malaysia , also known as West Malaysia , is the part of Malaysia which lies on the Malay Peninsula. Its area is . It shares a land border with Thailand in the north. To the south is the island of Singapore. Across the Strait of Malacca to the west lies the island of Sumatra...
using 70 morphological characteristics of each taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
. The following is part of the resultant cladogram
Cladogram
A cladogram is a diagram used in cladistics which shows ancestral relations between organisms, to represent the evolutionary tree of life. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational...
, showing "Clade 1", which has 51% bootstrap support. Its most strongly supported subclade is the sister pair of N. inermis and N. dubia, having 95% support.
Natural hybrids
A single mature female plant of N. dubia × N. izumiaeNepenthes izumiae
Nepenthes izumiae is a tropical pitcher plant endemic to Sumatra, where it grows in montane forest at 1700–1900 m above sea level. It appears to be most closely related to N. lingulata and N...
grows along the summit trail on Mount Talakmau
Mount Talakmau
Talakmau is a volcano in West Sumatra, Indonesia. Its elevation is 2,919 m .-External links :*...
. It produces infundibular upper pitchers that are yellowish-green in colouration. The pitchers are relatively small, reaching only around 10 cm in height. As in N. dubia, the stem and tendrils are purplish-red. The lamina is green with a red midrib. Nepenthes dubia × N. izumiae differs most obviously from N. dubia in having an ovate lid that is never reflexed beyond 180 degrees. This hybrid is listed as N. dubia × N. singalana in Charles Clarke
Charles Clarke (botanist)
Dr. Charles M. Clarke is a botanist and taxonomist specialising in the carnivorous plant genus Nepenthes. Clarke has an honours degree in Botany from Monash University in Melbourne, and a Ph.D. in Ecosystem Management at the University of New England, in Armidale, New South Wales.Clarke first...
's Nepenthes of Sumatra and Peninsular Malaysia
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...
, since N. izumiae is very closely related to N. singalana
Nepenthes singalana
Nepenthes singalana is a highland Nepenthes pitcher plant species native to the island of Sumatra. It is most closely related to N. diatas and N. spathulata.-Taxonomy:...
and was only described as a distinct species in 2003.
Among natural populations of N. jacquelineae
Nepenthes jacquelineae
Nepenthes jacquelineae is a tropical pitcher plant endemic to Sumatra. Due to its unique pitcher morphology, it is considered to be one of the most spectacular Nepenthes species native to the island.-Botanical history:...
, botanist Andreas Wistuba
Andreas Wistuba
Dr. Andreas Wistuba is a German taxonomist and botanist specialising in the carnivorous plant genera Heliamphora and Nepenthes. More than half of all known Heliamphora species have been described by Wistuba.-Publications:...
observed a single plant that appears to represent a natural cross between N. dubia and N. jacquelineae.
External links
- Photographs of N. dubia at the Carnivorous Plant Photofinder