Nepenthes rigidifolia
Encyclopedia
Nepenthes rigidifolia is a tropical pitcher plant
endemic to Sumatra
, where it grows at elevations of 1000–1600 m above sea level.
The specific epithet rigidifolia is formed from the Latin
words rigidus (rigid) and folia (leaves). It refers to the stiff, coriaceous texture of the leaf blade. Tahul-tahul is a local vernacular name
for this species.
some time before 2001. The species was mentioned as an undescribed taxon
in Charles Clarke
's 2001 book, Nepenthes of Sumatra and Peninsular Malaysia
, under the name "Nepenthes species A". At the time, it was recorded as growing at an elevation of around 1600 m.
In 2004, Ch'ien Lee informally named the species N. alpicola and later N. aptera. Cultivated plants were sold under both of these names. Although intended to become scientific names, they were never published with an adequate description and are thus considered nomina nuda
. Instead, the species was formally described
later that year as N. rigidifolia by Pitra Akhriadi, Hernawati, and Rusjdi Tamin. The description was published on November 22, 2004. Two years later, Hernawati and Akhriadi covered the species in their book, A Field Guide to the Nepenthes of Sumatra, and assessed its conservation status
.
The holotype
of N. rigidifolia—Nepenthes Team (Hernawati, P. Akhriadi & I. Petra) NP 354—was collected on December 11, 2003, near Sidikalang
in Karo Regency
, North Sumatra
, at an elevation of 1000–1500 m. It is deposited at the Herbarium Universitas Andalas (ANDA) of Andalas University
in Padang
, West Sumatra
. An isotype
is held at Herbarium Bogoriense (BO) in Java
.
Stewart McPherson
observed N. rigidifolia at the type locality in 2007 and published an updated description of the species in his 2009 monograph, Pitcher Plants of the Old World
.
is cylindrical and up to 1.3 cm in diameter. It can attain a length in excess of 10 m. Internode
s are up to 5.1 cm long.
Leaves are sessile to broadly sub-petiolate and have a coriaceous texture. They are noted for being particularly thick and rigid. The lamina is usually spathulate-oblong, but may also be ovate in rosettes. It reaches a maximum recorded length of 20.8 cm and width of 7.8 cm. It is gradually attenuate towards the base, clasping the stem for half to two-thirds of its circumference. The apex of the lamina is usually obtuse-rounded in rosettes and obtuse-acute on leaves of the climbing stem, but may also be acuminate-acute. It may be sub-peltate in some specimens, with the tendril attachment being located subapically, up to 9 mm from the laminar apex. The midrib may be flattened or sunken on the upper surface and bulges outwards on the lower. Two to four longitudinal veins are present on either side of the midrib. Pinnate veins are distinct on the upper surface of the lamina and indistinct on its underside. Tendril
s are up to 32.1 cm long and may or may not have a loop.
Rosette and lower pitchers are broadly ovoid throughout, narrowing somewhat towards the orifice. They grow up to 15 cm in height by 6.4 cm in width. A pair of fringed wings (≤2 mm wide) extends up to 2 cm below the peristome, before narrowing to ribs. These wings may bear fringe elements up to 5 mm long. The pitcher mouth is elliptic-ovate and has an oblique insertion, measuring up to 6.7 cm by 4.7 cm. The peristome
is cylindrical, expanded, and up to 2.1 cm wide. It may be slightly raised at the front, forming a notch up to 1.1 cm long. It bears ribs up to 0.5 mm high and spaced up to 1 mm apart. The inner margin of the peristome is lined with very small but distinct teeth measuring 0.5–1 mm in length. The outer margin is recurved and may be sinuate to some degree. The peristome is elongated into a neck up to 6.7 cm long and 4.7 cm wide. The glandular zone covers the lower half of the inner surface. The pitcher lid is sub-orbicular to elliptic-ovate and may be up to 5.2 cm long by 3.5 cm wide. It often has a cordate base and acute-obtuse apex. Three longitudinal veins are present on either side of the lid. A number of circular or slightly ovate nectar glands (≤ 0.1 mm wide) are concentrated on the underside of the lid, but no appendages are present. A spur
measuring up to 12 mm in length is inserted around 2 mm below the apex of the neck. It may be simple (unbranched) or trifid.
Upper pitchers are similar in most respects to their lower counterparts. They are broadly infundibular in the lower third and ovoid above, narrowing below the pitcher opening. They are also larger, reaching 21.1 cm in height and 9.4 cm in width. Wings are reduced to narrow ribs that run the whole length of the pitcher cup. The peristome is cylindrical and up to 4.4 cm wide. As in lower pitchers, it bears ribs up to 0.5 mm high and spaced up to 1 mm apart. The lid is up to 7.9 cm long and 5.6 cm wide. The spur, reported to be bifid (with each branch being two-branched itself) and up to 16 mm long, is inserted near the base of the lid.
Nepenthes rigidifolia has a racemose
inflorescence
. Female inflorescences have not been recorded in the wild. In male inflorescences, the rachis
measures around 3.9 cm in length and the peduncle
around 4.2 cm. Bract
s are approximately 9 mm long by 4 mm wide. Flowers are produced on two-flowered partial peduncles bearing filiform basal bract
eoles up to 2 mm long. The unbranched portion of the partial peduncles is up to 5 mm long. The pedicels
themselves are up to 6 mm long. Tepal
s are ovate-oblong and measure up to 5 mm in length by 3 mm in width. The androphore is around 4 mm long and 1 mm in diameter. Nepenthes rigidifolia is one of the few Nepenthes species known to occasionally produce multiple inflorescences concurrently on a single stem. This unusual reproductive habit has also been observed in N. alba
, N. ampullaria
, N. attenboroughii
, N. benstonei
, N. philippinensis
, N. sanguinea
, and N. thai
.
The development of the indumentum
is variable in this species. Some plants are completely glabrous, while others bear a covering of orange to brown hairs (≤1 mm long) on the stem, pitchers, tendrils, and portions of the inflorescence. Developing rosette
pitchers and tendrils are often densely pubescent, while developing pitchers produced on the climbing stem are tomentose. The pitcher lid may be glabrous or pubescent. The peduncle is typically slightly pubescent, and the partial peduncles, pedicels, bracts, tepals, and androphores densely pubescent.
The laminae are green, whereas the stem, midribs and tendrils range from green, through yellow, to orange or even red. Terrestrial pitchers have a distinctive colouration: their outer surface is black, brown, or purple, with numerous large flecks of greenish-white, brown, or orange. The upper part of the inner surface ranges from white to light green or light yellow, with dark red to black blotches. Both the peristome and lid may be dark red, dark brown, or even black, although the latter is commonly lighter on its lower surface. The pigmentation of the upper pitchers is generally similar to that of the lowers, although typically lighter. The describing authors observed that rosette pitchers typically have a dark brown peristome, whereas that of upper pitchers is often orange to dark red. Herbarium specimens have an almost black stem. Dried leaves are light brown above with a dark brown underside, whereas pitchers are blackish-brown with dark brown blotches and an almost black lid.
No infraspecific taxa of N. rigidifolia have been described.
, where it has been recorded from a single small area near Sidikalang
in Karo Regency
, North Sumatra
province
. The only known population of this species grows on a road bank. The describing authors counted 24 mature plants at the type locality; subsequent field observations suggest that the population has since dwindled in number even more. Nepenthes rigidifolia grows terrestrially in lower montane forest and scrub
. It has an altitudinal distribution of 1000–1600 m above sea level. Nepenthes rigidifolia grows sympatrically
with N. spectabilis
and a natural hybrid between these species has been recorded.
Nepenthes rigidifolia is not included on the IUCN Red List
due to the recency of its description. In 2006, Hernawati and Pitra Akhriadi informally assessed N. rigidifolia as Critically Endangered
based on the IUCN criteria and using field data collected by the "Nepenthes Team" of Andalas University
. The species is threatened by habitat loss due to land clearing
, land conversion, road broadening, and clearing of road banks. Other threats include forest and shrub fires as well as poaching
by plant collectors.
If the type locality is the site of the last remaining population of this species then it is one of rarest Nepenthes known and "threatened with imminent extinction". In Pitcher Plants of the Old World
, Stewart McPherson
wrote that field studies are "urgently required" to properly assess its conservation status
. In 2010, the Rare Nepenthes Collection was established with the aim of conserving N. rigidifolia and three other critically endangered Nepenthes species: N. aristolochioides
, N. clipeata
, and N. khasiana
.
to a degree, although their colouration is closer to that of N. spectabilis
. Nepenthes rigidifolia differs from N. bongso, N. ovata
and related species in having mostly ovoid upper pitchers (compared to infundibular in the others), distinctly thick and coriaceous laminae, and a narrower, cylindrical peristome with very short teeth. In addition, the lower pitchers of N. bongso are considerably larger than those of N. rigidifolia.
Terrestrial pitchers of N. rigidifolia may superficially resemble those of N. spectabilis, but it can be distinguished from this species on the basis of its trap colouration, upper pitcher shape (largely ovate in N. rigidifolia versus predominantly cylindrical in N. spectabilis), thinner leaves, and branched spur.
Only one natural hybrid involving N. rigidifolia (with N. spectabilis
) is known. This cross, which is only known from a single open rocky outcrop, may now outnumber N. rigidifolia at the type locality (as observed by Stewart McPherson
in 2007). The hybrid differs from N. rigidifolia in having narrower pitchers with a strongly infundibular base and distinct hip around the middle. On the other hand, the pitchers of this hybrid are broader than those of N. spectabilis and have an expanded peristome, as well as a markedly shorter spur. Charles Clarke
wrote of this cross: "Unlike N. ovata × N. spectabilis (from Gunung Pangulubao
), this hybrid seems to combine the more attractive characteristics of both parent species, producing large, beautifully coloured pitchers".
The richly coloured lower pitchers of N. rigidifolia × N. spectabilis may superficially resemble those of N. macfarlanei
. However, since that species is confined to Peninsular Malaysia
, the two taxa
are not easily confused.
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...
, where it grows at elevations of 1000–1600 m above sea level.
The specific epithet rigidifolia is formed from 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...
words rigidus (rigid) and folia (leaves). It refers to the stiff, coriaceous texture of the leaf blade. Tahul-tahul is a local vernacular name
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
for this species.
Botanical history
Nepenthes rigidifolia was discovered by Ch'ien LeeCh'ien Lee
Ch'ien C. Lee is a photographer and botanist specialising in the carnivorous plant genus Nepenthes. Lee has described several new Nepenthes species, including N. chaniana, N. gantungensis, N. glandulifera, N. jamban, N. lingulata, N. palawanensis, N. pitopangii,...
some time before 2001. The species was mentioned as an undescribed taxon
Undescribed taxon
In taxonomy, an undescribed taxon is a taxon that has been discovered, but not yet formally described and named. The various Nomenclature Codes specify the requirements for a new taxon to be validly described and named. Until such a description has been published, the taxon has no formal or...
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 2001 book, 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...
, under the name "Nepenthes species A". At the time, it was recorded as growing at an elevation of around 1600 m.
In 2004, Ch'ien Lee informally named the species N. alpicola and later N. aptera. Cultivated plants were sold under both of these names. Although intended to become scientific names, they were never published with an adequate description and are thus considered nomina nuda
Nomen nudum
The phrase nomen nudum is a Latin term, meaning "naked name", used in taxonomy...
. Instead, the species was 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...
later that year as N. rigidifolia by Pitra Akhriadi, Hernawati, and Rusjdi Tamin. The description was published on November 22, 2004. Two years later, Hernawati and Akhriadi covered the species in their book, A Field Guide to the Nepenthes of Sumatra, and assessed its conservation status
Conservation status
The conservation status of a group of organisms indicates whether the group is still extant and how likely the group is to become extinct in the near future...
.
The holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
of N. rigidifolia—Nepenthes Team (Hernawati, P. Akhriadi & I. Petra) NP 354—was collected on December 11, 2003, near Sidikalang
Sidikalang
Sidikalang is a town in North Sumatra province of Indonesia and it is the seat of Dairi Regency....
in Karo Regency
Karo Regency
Karo Regency is a regency of North Sumatra, Indonesia. It is situated in the Bukit Barisan mountains. In 2000, the regency covered an area of 2,127.25 square kilometres and according to the 2000 census it had a population of 279,470. 60.99% of the regency is forested. Its regency seat is...
, North Sumatra
North Sumatra
North Sumatra is a province of Indonesia on the Sumatra island. Its capital is Medan. It is the most populous Indonesian province outside of Java. It is slightly larger than Sri Lanka in area.- Geography and population :...
, at an elevation of 1000–1500 m. It is deposited at the Herbarium Universitas Andalas (ANDA) of Andalas University
Andalas University
Andalas University is the oldest university in Indonesia outside of Java. The university consists of eleven faculties, with most located at the main campus Limau Manis, 12 km from the center of Padang, West Sumatra. This campus occupies 5 km², at an elevation of about 100 m. The Faculty...
in Padang
Padang, Indonesia
Padang is the capital and largest city of West Sumatra, Indonesia. It is located on the western coast of Sumatra at . It has an area of and a population of over 833,000 people at the 2010 Census.-History:...
, West Sumatra
West Sumatra
West Sumatra is a province of Indonesia. It lies on the west coast of the island Sumatra. It borders the provinces of North Sumatra to the north, Riau and Jambi to the east, and Bengkulu to the southeast. It includes the Mentawai Islands off the coast...
. An isotype
Isotype
Isotype can refer to:* In crystallography, an "isotype" is a synonym for isomorph* In biology, per the International Code of Botanical Nomenclature, the "isotype" is a duplicate of the holotype....
is held at Herbarium Bogoriense (BO) 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...
.
Stewart McPherson
Stewart McPherson (geographer)
Stewart R. McPherson is a British geographer.He studied at the University of Durham in England, the University of Tübingen in Germany and Yale University in the United States....
observed N. rigidifolia at the type locality in 2007 and published an updated description of the species in his 2009 monograph, Pitcher Plants of the Old World
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...
.
Description
Nepenthes rigidifolia is a climbing plant. The stemPlant 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...
is cylindrical and up to 1.3 cm in diameter. It can attain a length in excess of 10 m. Internode
Plant 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 5.1 cm long.
Leaves are sessile to broadly sub-petiolate and have a coriaceous texture. They are noted for being particularly thick and rigid. The lamina is usually spathulate-oblong, but may also be ovate in rosettes. It reaches a maximum recorded length of 20.8 cm and width of 7.8 cm. It is gradually attenuate towards the base, clasping the stem for half to two-thirds of its circumference. The apex of the lamina is usually obtuse-rounded in rosettes and obtuse-acute on leaves of the climbing stem, but may also be acuminate-acute. It may be sub-peltate in some specimens, with the tendril attachment being located subapically, up to 9 mm from the laminar apex. The midrib may be flattened or sunken on the upper surface and bulges outwards on the lower. Two to four longitudinal veins are present on either side of the midrib. Pinnate veins are distinct on the upper surface of the lamina and indistinct on its underside. 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 are up to 32.1 cm long and may or may not have a loop.
Rosette and lower pitchers are broadly ovoid throughout, narrowing somewhat towards the orifice. They grow up to 15 cm in height by 6.4 cm in width. A pair of fringed wings (≤2 mm wide) extends up to 2 cm below the peristome, before narrowing to ribs. These wings may bear fringe elements up to 5 mm long. The pitcher mouth is elliptic-ovate and has an oblique insertion, measuring up to 6.7 cm by 4.7 cm. 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, expanded, and up to 2.1 cm wide. It may be slightly raised at the front, forming a notch up to 1.1 cm long. It bears ribs up to 0.5 mm high and spaced up to 1 mm apart. The inner margin of the peristome is lined with very small but distinct teeth measuring 0.5–1 mm in length. The outer margin is recurved and may be sinuate to some degree. The peristome is elongated into a neck up to 6.7 cm long and 4.7 cm wide. The glandular zone covers the lower half of the inner surface. The pitcher lid is sub-orbicular to elliptic-ovate and may be up to 5.2 cm long by 3.5 cm wide. It often has a cordate base and acute-obtuse apex. Three longitudinal veins are present on either side of the lid. A number of circular or slightly ovate nectar glands (≤ 0.1 mm wide) are concentrated on the underside of the lid, but no appendages are present. A 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...
measuring up to 12 mm in length is inserted around 2 mm below the apex of the neck. It may be simple (unbranched) or trifid.
Upper pitchers are similar in most respects to their lower counterparts. They are broadly infundibular in the lower third and ovoid above, narrowing below the pitcher opening. They are also larger, reaching 21.1 cm in height and 9.4 cm in width. Wings are reduced to narrow ribs that run the whole length of the pitcher cup. The peristome is cylindrical and up to 4.4 cm wide. As in lower pitchers, it bears ribs up to 0.5 mm high and spaced up to 1 mm apart. The lid is up to 7.9 cm long and 5.6 cm wide. The spur, reported to be bifid (with each branch being two-branched itself) and up to 16 mm long, is inserted near the base of the lid.
Nepenthes rigidifolia 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...
. Female inflorescences have not been recorded in the wild. In male inflorescences, 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...
measures around 3.9 cm in length and 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...
around 4.2 cm. 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...
s are approximately 9 mm long by 4 mm wide. Flowers are produced on two-flowered partial peduncles bearing filiform basal 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...
eoles up to 2 mm long. The unbranched portion of the partial peduncles is up to 5 mm long. The pedicels
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....
themselves are up to 6 mm long. Tepal
Tepal
Tepals are elements of the perianth, or outer part of a flower, which include the petals or sepals. The term tepal is more often applied specifically when all segments of the perianth are of similar shape and color, or undifferentiated, which is called perigone...
s are ovate-oblong and measure up to 5 mm in length by 3 mm in width. The androphore is around 4 mm long and 1 mm in diameter. Nepenthes rigidifolia is one of the few Nepenthes species known to occasionally produce multiple inflorescences concurrently on a single stem. This unusual reproductive habit has also been observed in N. alba
Nepenthes alba
Nepenthes alba is a tropical pitcher plant endemic to Peninsular Malaysia. The specific epithet alba is derived from the Latin word albus, meaning "white", and refers to the colour of the upper pitchers.-Natural hybrids:...
, N. ampullaria
Nepenthes ampullaria
Nepenthes ampullaria , the Flask-Shaped Pitcher-Plant, is a very distinctive and widespread species of Nepenthes, present in Borneo, Sumatra, Thailand, Peninsular Malaysia, Singapore, the Maluku Islands, and New Guinea...
, N. attenboroughii
Nepenthes attenboroughii
Nepenthes attenboroughii is a montane species of insectivorous pitcher plant of the genus Nepenthes. It is named after the celebrated broadcaster and naturalist Sir David Attenborough, who is a keen enthusiast of the genus. The species is characterised by its large and distinctive bell-shaped...
, N. benstonei
Nepenthes benstonei
Nepenthes benstonei is a tropical pitcher plant endemic to Peninsular Malaysia, where it occurs at elevations of 450–600 m above sea level...
, N. philippinensis
Nepenthes philippinensis
Nepenthes philippinensis is a tropical pitcher plant endemic to the Philippines. It is known from Palawan and the Calamian Islands , where it grows at 0–600 m above sea level....
, N. sanguinea
Nepenthes sanguinea
Nepenthes sanguinea is a large and vigorous Nepenthes pitcher plant species, native to the Malay Peninsula, where it grows at 900–1800 m altitude. The pitchers are variable in size, from 10–30 cm tall, and range from green and yellow to orange and red. The insides of the pitchers are usually...
, and N. thai
Nepenthes thai
Nepenthes thai is a tropical pitcher plant endemic to peninsular Thailand. It grows on limestone hills at elevations of 500–600 m above sea level.Nepenthes thai has no known natural hybrids.-External links:*...
.
The development of the 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...
is variable in this species. Some plants are completely glabrous, while others bear a covering of orange to brown hairs (≤1 mm long) on the stem, pitchers, tendrils, and portions of the inflorescence. Developing rosette
Rosette (botany)
In botany, a rosette is a circular arrangement of leaves, with all the leaves at a single height.Though rosettes usually sit near the soil, their structure is an example of a modified stem.-Function:...
pitchers and tendrils are often densely pubescent, while developing pitchers produced on the climbing stem are tomentose. The pitcher lid may be glabrous or pubescent. The peduncle is typically slightly pubescent, and the partial peduncles, pedicels, bracts, tepals, and androphores densely pubescent.
The laminae are green, whereas the stem, midribs and tendrils range from green, through yellow, to orange or even red. Terrestrial pitchers have a distinctive colouration: their outer surface is black, brown, or purple, with numerous large flecks of greenish-white, brown, or orange. The upper part of the inner surface ranges from white to light green or light yellow, with dark red to black blotches. Both the peristome and lid may be dark red, dark brown, or even black, although the latter is commonly lighter on its lower surface. The pigmentation of the upper pitchers is generally similar to that of the lowers, although typically lighter. The describing authors observed that rosette pitchers typically have a dark brown peristome, whereas that of upper pitchers is often orange to dark red. Herbarium specimens have an almost black stem. Dried leaves are light brown above with a dark brown underside, whereas pitchers are blackish-brown with dark brown blotches and an almost black lid.
No infraspecific taxa of N. rigidifolia have been described.
Ecology
Nepenthes rigidifolia is endemic to SumatraSumatra
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...
, where it has been recorded from a single small area near Sidikalang
Sidikalang
Sidikalang is a town in North Sumatra province of Indonesia and it is the seat of Dairi Regency....
in Karo Regency
Karo Regency
Karo Regency is a regency of North Sumatra, Indonesia. It is situated in the Bukit Barisan mountains. In 2000, the regency covered an area of 2,127.25 square kilometres and according to the 2000 census it had a population of 279,470. 60.99% of the regency is forested. Its regency seat is...
, North Sumatra
North Sumatra
North Sumatra is a province of Indonesia on the Sumatra island. Its capital is Medan. It is the most populous Indonesian province outside of Java. It is slightly larger than Sri Lanka in area.- Geography and population :...
province
Provinces of Indonesia
The province is the highest tier of local government subnational entity in Indonesia. Each province has its own local government, headed by a governor, and has its own legislative body...
. The only known population of this species grows on a road bank. The describing authors counted 24 mature plants at the type locality; subsequent field observations suggest that the population has since dwindled in number even more. Nepenthes rigidifolia grows terrestrially in lower montane forest and scrub
Shrubland
Shrubland, scrubland, scrub or brush is a plant community characterized by vegetation dominated by shrubs, often also including grasses, herbs, and geophytes. Shrubland may either occur naturally or be the result of human activity...
. It has an altitudinal distribution of 1000–1600 m above sea level. Nepenthes rigidifolia grows sympatrically
Sympatry
In biology, two species or populations are considered sympatric when they exist in the same geographic area and thus regularly encounter one another. An initially-interbreeding population that splits into two or more distinct species sharing a common range exemplifies sympatric speciation...
with N. spectabilis
Nepenthes spectabilis
Nepenthes spectabilis is a tropical pitcher plant endemic to Sumatra, where it grows at elevations of between 1400 and 2200 m above sea level. The specific epithet spectabilis is Latin for "visible" or "notable".-Botanical history:...
and a natural hybrid between these species has been recorded.
Nepenthes rigidifolia is not included on the IUCN Red List
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...
due to the recency of its description. In 2006, Hernawati and Pitra Akhriadi informally assessed N. rigidifolia 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....
based on the IUCN criteria and using field data collected by the "Nepenthes Team" of Andalas University
Andalas University
Andalas University is the oldest university in Indonesia outside of Java. The university consists of eleven faculties, with most located at the main campus Limau Manis, 12 km from the center of Padang, West Sumatra. This campus occupies 5 km², at an elevation of about 100 m. The Faculty...
. The species is threatened by habitat loss due to land clearing
Deforestation
Deforestation is the removal of a forest or stand of trees where the land is thereafter converted to a nonforest use. Examples of deforestation include conversion of forestland to farms, ranches, or urban use....
, land conversion, road broadening, and clearing of road banks. Other threats include forest and shrub fires as well as poaching
Poaching
Poaching is the illegal taking of wild plants or animals contrary to local and international conservation and wildlife management laws. Violations of hunting laws and regulations are normally punishable by law and, collectively, such violations are known as poaching.It may be illegal and in...
by plant collectors.
If the type locality is the site of the last remaining population of this species then it is one of rarest Nepenthes known and "threatened with imminent extinction". In Pitcher Plants of the Old World
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...
, Stewart McPherson
Stewart McPherson (geographer)
Stewart R. McPherson is a British geographer.He studied at the University of Durham in England, the University of Tübingen in Germany and Yale University in the United States....
wrote that field studies are "urgently required" to properly assess its conservation status
Conservation status
The conservation status of a group of organisms indicates whether the group is still extant and how likely the group is to become extinct in the near future...
. In 2010, the Rare Nepenthes Collection was established with the aim of conserving N. rigidifolia and three other critically endangered Nepenthes species: N. aristolochioides
Nepenthes aristolochioides
Nepenthes aristolochioides is a tropical pitcher plant endemic to Sumatra, where it grows at elevations of 1800–2500 m above sea level. It has an extremely unusual pitcher morphology, having an almost vertical opening to its traps....
, N. clipeata
Nepenthes clipeata
Nepenthes clipeata , or the Shield-Leaved Pitcher-Plant, is a tropical pitcher plant known only from the near-vertical granite cliff faces of Mount Kelam in Kalimantan, Borneo...
, and N. khasiana
Nepenthes khasiana
Nepenthes khasiana |endemic]]) is a tropical pitcher plant of the genus Nepenthes. It is the only Nepenthes species native to India....
.
Related species
The pitchers of N. rigidifolia resemble those of N. bongsoNepenthes 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...
to a degree, although their colouration is closer to that of N. spectabilis
Nepenthes spectabilis
Nepenthes spectabilis is a tropical pitcher plant endemic to Sumatra, where it grows at elevations of between 1400 and 2200 m above sea level. The specific epithet spectabilis is Latin for "visible" or "notable".-Botanical history:...
. Nepenthes rigidifolia differs from N. bongso, N. ovata
Nepenthes ovata
Nepenthes ovata is a tropical pitcher plant endemic to Sumatra. The specific epithet ovata is Latin for "ovate" and refers to the shape of the lower pitchers.-Botanical history:...
and related species in having mostly ovoid upper pitchers (compared to infundibular in the others), distinctly thick and coriaceous laminae, and a narrower, cylindrical peristome with very short teeth. In addition, the lower pitchers of N. bongso are considerably larger than those of N. rigidifolia.
Terrestrial pitchers of N. rigidifolia may superficially resemble those of N. spectabilis, but it can be distinguished from this species on the basis of its trap colouration, upper pitcher shape (largely ovate in N. rigidifolia versus predominantly cylindrical in N. spectabilis), thinner leaves, and branched spur.
Natural hybrids
Nepenthes spectabilis
Nepenthes spectabilis is a tropical pitcher plant endemic to Sumatra, where it grows at elevations of between 1400 and 2200 m above sea level. The specific epithet spectabilis is Latin for "visible" or "notable".-Botanical history:...
) is known. This cross, which is only known from a single open rocky outcrop, may now outnumber N. rigidifolia at the type locality (as observed by Stewart McPherson
Stewart McPherson (geographer)
Stewart R. McPherson is a British geographer.He studied at the University of Durham in England, the University of Tübingen in Germany and Yale University in the United States....
in 2007). The hybrid differs from N. rigidifolia in having narrower pitchers with a strongly infundibular base and distinct hip around the middle. On the other hand, the pitchers of this hybrid are broader than those of N. spectabilis and have an expanded peristome, as well as a markedly shorter spur. 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...
wrote of this cross: "Unlike N. ovata × N. spectabilis (from Gunung Pangulubao
Mount Pangulubao
Mount Pangulubao or Pangulubau is a mountain near Lake Toba in Sumatra.Mount Pangulubao is notable for the relatively large number of tropical pitcher plant species that inhabit its forests. These include Nepenthes ampullaria, Nepenthes gymnamphora, Nepenthes mikei, Nepenthes ovata, Nepenthes...
), this hybrid seems to combine the more attractive characteristics of both parent species, producing large, beautifully coloured pitchers".
The richly coloured lower pitchers of N. rigidifolia × N. spectabilis may superficially resemble those of N. macfarlanei
Nepenthes macfarlanei
Nepenthes macfarlanei is a carnivorous pitcher plant species endemic to Peninsular Malaysia. It produces attractive red-speckled pitchers. Lower pitchers are ovoid to cylindrical and up to 20 cm high. The lower surface of the lid is densely covered with short, white hairs...
. However, since that species is confined to 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...
, the two taxa
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...
are not easily confused.
External links
- Photographs of N. rigidifolia at the Carnivorous Plant Photofinder