Nepenthes dubia
| Nepenthes dubia | |
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| An upper pitcher of Nepenthes dubia | |
Scientific classification 
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| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Order: | Caryophyllales |
| Family: | Nepenthaceae |
| Genus: | Nepenthes |
| Species: | N. dubia
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| Binomial name | |
| Nepenthes dubia Danser (1928)[2] | |
| Synonyms | |
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Heterochresonyms
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Nepenthes dubia
Botanical history
Nepenthes dubia was first collected on May 29, 1917
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
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,
In 1986, Mitsuru Hotta and Rusjdi Tamin included plant material belonging to N. dubia and N. inermis in their description of N. bongso.[3][8] 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.[5]
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.[8]
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.[2] Internodes are up to 10 cm long.[8]
Leaves are
Rosette and lower pitchers are rarely produced. They are narrowly
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.[2] 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;[2] it lacks a waxy zone.[10] The pitcher mouth is ovate, horizontal, and acute towards the lid.[2] It bears a cylindrical or involute peristome (≤4 mm wide) with indistinct teeth spaced 0.25 to 0.5 mm apart.[2] The inner portion of the peristome accounts for around 45% of its total cross-sectional surface length.[10] 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.[2] Characteristically, it is almost always reflexed beyond 180 degrees relative to the pitcher mouth.[8] In upper pitchers, the unbranched spur is 3 to 5 mm long.[2]
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. Pedicels are bracteolate and up to 8 mm long. Sepals are oblong-lanceolate and up to 3 mm long.[8]
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.[2][8]
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.[8] Danser described the colour of herbarium specimens as "fallow-dun, here and there blackish".[2]
Ecology
Nepenthes dubia was for a long time thought to be
In its natural habitat, N. dubia is sympatric with N. gymnamphora, N. izumiae, N. jamban, and N. lingulata.[8][12] The stunted upper montane forest which these species inhabit is dominated by ferns of the genera Dipteris and Dicranopteris. Trees rarely exceed 3 m in height and few Nepenthes plants emerge above the vegetation.[8]
Due to its extremely localised distribution, N. dubia is listed as Critically Endangered on the 2006 IUCN Red List of Threatened Species.[1] 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.[8]
Carnivory
Nepenthes dubia produces thick, mucilaginous 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.[8] Nepenthes like N. jamban also use this method with mucilaginous pitcher fluid.
Related species
Nepenthes dubia belongs to a group of closely related montane Sumatran species that includes N. flava,[13] N. inermis, N. jacquelineae, N. jamban,[12] 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.[8]
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:[14]
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,
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Natural hybrids
A single mature female plant of N. dubia × N. izumiae 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.[8] 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.[15]
In 2009, Adrian Y. Wartono observed a putative cross between N. dubia and N. jamban in an area where these two species grew with N. lingulata and N. rhombicaulis.[16]
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.[11][17]
Notes
- a.^ Bünnemeijer reached the base of Mount Talakmau and set up camp there on April 21, 1917, at 400 m altitude. This was followed by a stay at 1060 m on the mountain's northwestern slope on May 6, at 1300 m on May 11, at 1900 m on May 21, and finally on the plateau, at an elevation of 2780 m, between June 1 and June 4, during which he climbed the summit.[18][19]
Folia mediocria sessilia, lamina lanceolato-spathulata, nervis longitudinalibus utrinque c. 3, basi attenuata 1/3-2/3 caulis amplectente, vagina 0 ; ascidia rosularum et inferiora ignota ; ascidia superiora parva, parte inferiore tubulosa v. leviter ventricosa, supra medium infundibuliformia, costis 2 prominentibus ; peristomio fere horizontali, operculum versus acuto, applanato, 2-4 mm lato, costis 1/2-1/4 mm distantibus, dentibus 0 ; operculo anguste cuneato, facie inferiore plana ; inflorescentia ignota ; indumentum parcum, iuventute tomentum fuscum, denique deciduum.
References
- ^ .
- ^ a b c d e f g h i j k l m n o p q r Danser, B.H. 1928. 11. Nepenthes dubia DANS., spec. nova. In: The Nepenthaceae of the Netherlands Indies. Bulletin du Jardin Botanique de Buitenzorg, Série III, 9(3–4): 249–438.
- ^ Nepenthes di Sumatera: The genus Nepenthes of the Sumatra Island. In: M. Hotta (ed.) Diversity and Dynamics of Plant Life in Sumatra: Forest Ecosystem and Speciation in Wet Tropical Environments. Part 1: Reports and Collection of Papers. Kyoto University, Kyoto. pp. 75–109.
- ^ a b Kurata, S. 1973. Nepenthes from Borneo, Singapore and Sumatra. The Gardens' Bulletin Singapore 26(2): 227–232.
- ^ a b c Jebb, M.H.P. & M.R. Cheek 1997. A skeletal revision of Nepenthes (Nepenthaceae). Blumea 42(1): 1–106.
- Field Guide to the Pitcher Plants of Sumatra and Java. Redfern Natural History Productions, Poole.
- ^ Clarke, C.M. 2006. Introduction. In: Danser, B.H. The Nepenthaceae of the Netherlands Indies. Natural History Publications (Borneo), Kota Kinabalu. pp. 1–15.
- ^ a b c d e f g h i j k l m n o p q r Clarke, C.M. 2001. Nepenthes of Sumatra and Peninsular Malaysia. Natural History Publications (Borneo), Kota Kinabalu.
- ^ (in Japanese and English) Kurata, S. 2001. スマトラ島およびミンダナオ島産ウツボカズラの２新種(英文). [Two new species of Nepenthes from Sumatra (Indonesia) and Mindanao (Philippines).] The Journal of Insectivorous Plant Society 52(2): 30–34.
- ^
- ^ a b McPherson, S.R. 2009. Pitcher Plants of the Old World. 2 volumes. Redfern Natural History Productions, Poole.
- ^ a b Lee, C.C., Hernawati & P. Akhriadi 2006. Two new species of Nepenthes (Nepenthaceae) from North Sumatra. Blumea 51(3): 561–568.
- ^ Wistuba, A., J. Nerz & A. Fleischmann 2007. Nepenthes flava, a new species of Nepenthaceae from the northern part of Sumatra. Blumea 52(1): 159–163.
- ^ Nerz, J. & A. Wistuba 1994. Five new taxa of Nepenthes (Nepenthaceae) from North and West Sumatra Archived 2011-08-05 at the Wayback Machine. Carnivorous Plant Newsletter 23(4): 101–114.
- ^ Wartono, A.Y. 2011. Re: dubia hybrid ? ID opinions Archived 2012-07-22 at the Wayback Machine. Carnivorous Plants in the tropics, March 2, 2011.
- ^ Wistuba, A. N.d. Strange hybrid with Nepenthes jacquelineae? Archived 2007-09-28 at the Wayback Machine Wistuba.com.
- ^ Jacobson, E. 1919. In het oerbos van den Ophir. l.c. 8: 1–150.
- ^ van Steenis-Kruseman, M.J., et al. 2006. Cyclopaedia of Malesian Collectors: H. A. B. Bünnemeijer. Nationaal Herbarium Nederland.
Further reading
- Hernawati & P. Akhriadi 2006. A Field Guide to the Nepenthes of Sumatra. PILI-NGO Movement, Bogor.
- (in Indonesian) Mansur, M. 2001. Koleksi Nepenthes di Herbarium Bogoriense: prospeknya sebagai tanaman hias. In: Prosiding Seminar Hari Cinta Puspa dan Satwa Nasional. Lembaga Ilmu Pengetahuan Indonesia, Bogor. pp. 244–253.
- Meimberg, H., A. Wistuba, P. Dittrich & G. Heubl 2001. Molecular phylogeny of Nepenthaceae based on cladistic analysis of plastid trnK intron sequence data. Plant Biology 3(2): 164–175.
- (in German) Meimberg, H. 2002. Molekular-systematische Untersuchungen an den Familien Nepenthaceae und Ancistrocladaceae sowie verwandter Taxa aus der Unterklasse Caryophyllidae s. l.. Ph.D. thesis, Ludwig Maximilian University of Munich, Munich.
- Meimberg, H. & G. Heubl 2006. Introduction of a nuclear marker for phylogenetic analysis of Nepenthaceae. Plant Biology 8(6): 831–840.
- Meimberg, H., S. Thalhammer, A. Brachmann & G. Heubl 2006. Comparative analysis of a translocated copy of the trnK intron in carnivorous family Nepenthaceae. Molecular Phylogenetics and Evolution 39(2): 478–490.
External links
- Photographs of N. dubia at the Carnivorous Plant Photofinder