Nepenthes fusca , or the dusky pitcher-plant,Phillipps, A. & A. Lamb 1996. Pitcher-Plants of Borneo. Natural History Publications (Borneo), Kota Kinabalu. is a tropical pitcher plant endemic to Borneo. It is found throughout a wide altitudinal range and is almost always epiphytic in nature, primarily growing in mossy forest.
The specific epithet fusca is derived from the Latin word fuscus, meaning "dark brown" or "dusky", and refers to the colour of the pitchers.
Botanical history The first known collection of N. fusca was made by Frederik Endert on October 12, 1925, from Mount Kemul in East Kalimantan, at an elevation of 1,500 m. It was discovered during an expedition to central Borneo by the Forest Research Institute of Bogor (then known as Buitenzorg), on which Endert also made the only known collection of N. mollis. The N. fusca specimen, designated as Endert 3955, includes male floral material and is deposited at Herbarium Bogoriense (BO), the herbarium of the Bogor Botanical Gardens.Schlauer, J. Nepenthes fusca . Carnivorous Plant Database. Endert wrote about this pitcher plant in a detailed 1927 account of the expedition, although he misidentified it as N. veitchii.
Nepenthes fusca was formally described in 1928 by Dutch botanist B. H. Danser in his seminal monograph "The Nepenthaceae of the Netherlands Indies". Danser based his description solely on Endert 3955, citing no other specimens. He wrote of N. fusca:
This new species is, together with N. Veitchii and N. stenophylla, very nearly related to N. maxima, but can not be confounded with any of these species. According to Endert it grew in the forest on a narrow, stony mountain ridge covered with humus, and was not rare.
Botanist Jan Schlauer has noted differences between the type specimen of N. fusca and Sabah plants referred to this species, even interpreting plants illustrated in Kurata's Nepenthes of Mount Kinabalu as representing N. stenophylla (as distinct from N. fallax).Clarke, C.M. 2006. Introduction. In: Danser, B.H. The Nepenthaceae of the Netherlands Indies. Natural History Publications (Borneo), Kota Kinabalu. pp. 1–15. Matthew Jebb does not consider these differences significant enough to merit distinction at the species level. He suggests that the type specimen consists of intermediate lower and upper pitchers as opposed to true forms of either, making them appear atypical.
Much of this taxonomic uncertainty stems from the fact that N. fusca has not been recollected from the type locality and many similar plants have been lumped under this taxon. Matthew Jebb and Martin Cheek attempted to resolve this confusion in their 1997 monograph by interpreting N. fusca as a widespread and variable species.
Subspecies Two subspecies of N. fusca have been described, neither of which is presently thought to represent the species:
Nepenthes fusca subsp. apoensis J.H.Adam & Wilcock ex Jebb & Cheek (1997)Jebb, M.H.P. & M.R. Cheek 1997. A skeletal revision of Nepenthes (Nepenthaceae). Blumea 42(1): 1–106. nom.nud. [=N. stenophylla] Nepenthes fusca subsp. kostermansiana J.H.Adam & Wilcock ex Jebb & Cheek (1997) nom.nud. [=N. epiphytica]
Both were originally coined by J. H. Adam and C. C. Wilcock and subsequently published in Jebb and Cheek's 1997 monograph, "A skeletal revision of Nepenthes (Nepenthaceae)". As these names were published without an adequate description, they are both considered nomina nuda. The former is likely based on Chai 35939, a specimen collected from Mount Apo. Schlauer considers it synonymous with N. fallax, a taxon that is in turn considered conspecific with N. stenophylla by most authors.
Nepenthes fusca subsp. kostermansiana was named from the herbarium material Kostermans 21495, which was collected by André Joseph Guillaume Henri Kostermans on October 25, 1963, at 1000 m altitude along the Kelai River on Mount Nyapa (Njapa), Berau Regency, East Kalimantan.Robinson, A.S., J. Nerz & A. Wistuba 2011. Nepenthes epiphytica, a new pitcher plant from East Kalimantan. In: McPherson, S.R. New Nepenthes: Volume One. Redfern Natural History Productions, Poole. pp. 36–51. It is deposited at the National Herbarium of the Netherlands in Leiden. This taxon was initially thought to fall within the variability of N. fusca, but in 2011 it was described as a distinct species, N. epiphytica, with Kostermans 21495 designated as its holotype.
Nepenthes maxima
Nepenthes maxima, a species native to Sulawesi, New Guinea, and the Maluku Islands, was once thought to extend to Borneo as well. Some authors even wrote that it was widespread on the island.Adam, J.H., C.C. Wilcock & M.D. Swaine 1992. The ecology and distribution of Bornean Nepenthes. Journal of Tropical Forest Science 5(1): 13–25. This confusion stemmed from the likeness of N. fusca and N. maxima, and from apparently mislabelled seeds collected by Charles Curtis. Curtis was not meticulous in recording where he located individual plants; although it was originally believed that he collected N. curtisii (now considered synonymous with N. maxima)Schlauer, J. Nepenthes curtisii . Carnivorous Plant Database. in Borneo, botanist Charles Clarke points out that he also visited Sulawesi on the same trip, and N. maxima is common there.
Matthew Jebb and Martin Cheek resolved this confusion in their 1997 monograph by referring a number of Bornean plants identified as N. maxima to N. fusca, thereby excluding the former from the island.
Nepenthes zakriana In 1996, J. H. Adam and C. C. Wilcock described Nepenthes curtisii subsp. zakriana. Ten years later, Adam and Hafiza A. Hamid elevated it to species status as Nepenthes zakriana (, not ). The authors described the taxon as a Sabah endemic growing at elevations of 1,200 to 1,500 m.
Adam and Hafiza wrote that N. zakriana "consistently differed from Nepenthes fusca by prominent raised midribs, extended beyond apex forming an apical glandular appendages on lower lid surface of both upper and lower pitchers; and basal half portion of the midrib developed in nail-shaped glandular crest". However, a number of authors soon voiced their doubts as to whether N. zakriana merited species statusRice, B.A. 2006. Do you want to tell me about a species I missed? The Carnivorous Plant FAQ. and in Pitcher Plants of Borneo by Anthea Phillipps, Anthony Lamb, and Ch'ien Lee, these features were considered to fall within the natural variability of N. fusca.Phillipps, A., A. Lamb & C.C. Lee 2008. Pitcher Plants of Borneo. Second Edition. Natural History Publications (Borneo), Kota Kinabalu. The taxon was reinstated in 2019 based on isolated distributions and morphology, and the previous synonymy was attributed to the frequent hybridization between members of Nepenthes.
Nepenthes dactylifera In his 1997 monograph, Nepenthes of Borneo, Charles Clarke lists the undescribed taxon "Nepenthes sp. A", which has been recorded from Gunung Mulu National Park in Sarawak. It bears a close resemblance to N. fusca and may be conspecific with it, although its colouration is unusual for the species. The pitchers of this plant match J. H. Adam and C. C. Wilcock's descriptionAdam, J.H. & C.C. Wilcock 1991. A new species of Nepenthes (Nepenthaceae) from Sarawak. Blumea 36(1): 123–125. of N. faizaliana, but the latter is now known to have a round lid (as opposed to narrowly triangular in N. fusca and "Nepenthes sp. A"), suggesting that these two taxa are not closely related. Clarke proposes that this taxon might fall under Jebb and Cheek's more inclusive concept of N. fusca, but retains it as an undescribed species because it remains poorly known.
"Nepenthes sp. A" was first illustrated in a 1988 article by Anthea Phillipps and Anthony Lamb, where it was considered an undescribed species.Phillipps, A. & A. Lamb 1988. Pitcher-plants of East Malaysia and Brunei. Nature Malaysiana 13(4): 8–27.
In 2019, "Nepenthes sp. A" was included as a synonym of the novel taxon Nepenthes dactylifera. Notably, several ecological distinctions were drawn between N. dactylifera and N. fusca, such as epiphytic habit observed in N. dactylifera as opposed to the terrestrial habit of N. fusca.
Description
Nepenthes fusca is a climbing plant. The stem may attain a length of 10 m and is up to 8 mm in diameter. Internodes are circular in cross section and up to 7 cm long.
The leaves of this species are petiolate and coriaceous in texture. The lamina or leaf blade is obovate-oblong in shape and measures up to 15 cm in length by 6 cm in width. Its apex is acute to obtuse and may even be slightly peltate. The base of the lamina is gradually attenuate towards the petiole. The petiole (≤4 cm long) is grooved lengthwise and bears a pair of narrow wings that form a semi-amplexicaul sheath around the stem. Up to 3 longitudinal veins are present on either side of the midrib, although they are indistinct. Pinnate veins are numerous. Tendrils measure up to 5 cm in length.
Rosette and lower pitchers are cylindrical throughout. They usually grow to 20 cm in height by 4 cm in width, although exceptional specimens up to 28 cm have been recorded. A pair of fringed wings (≤5 mm wide) runs down the ventral surface of the pitcher and bears fringe elements measuring up to 10 mm and spaced 6 mm apart. The glandular region is restricted to the lower portion of the pitcher's inner surface. The glands are small, overarched, and occur at a density of 600 to 650 per square centimetre. The waxy zone is reduced. The pitcher mouth is positioned horizontally at the front, becoming elongated into a neck at the rear. The peristome is flattened and expanded (≤12 mm wide), but bears only indistinct teeth (≤0.3 mm long). The inner portion of the peristome accounts for around 51% of its total cross-sectional surface length.Bauer, U., C.J. Clemente, T. Renner & W. Federle 2012. Form follows function: morphological diversification and alternative trapping strategies in carnivorous Nepenthes pitcher plants. Journal of Evolutionary Biology 25(1): 90–102. The pitcher lid or operculum is very narrowly ovate in shape and has a distinctive basal crest on its lower surface. An unbranched spur measuring up to 10 mm in length is inserted near the base of the lid.
Upper pitchers differ markedly in shape, being narrowly infundibular in the lower two-thirds and becoming widely infundibular above. They are similar in size to their lower counterparts, typically measuring up to 18 cm, with some larger forms reaching 26 cm. The tiny digestive glands are overarched and number 1,500 to 2,000 per square centimetre. The pitcher lid is very narrowly triangular with the margins and apex curved downwards. In aerial pitchers, the wings are reduced to ribs.
Nepenthes fusca produces a compact racemose inflorescence. The peduncle is up to 6 cm long, while the rachis is not known to exceed 10 cm. Partial peduncles are one- or two-flowered, up to 8 mm long, and lack a bract. Sepals are elliptic and up to 4 mm long. A study of 120 pollen samples taken from the type specimen (Endert 3955) found the mean pollen diameter to be 34.8 μm (SE = 0.6; CV = 9.1%).Adam, J.H. & C.C. Wilcock 1999. Palynological study of Bornean Nepenthes (Nepenthaceae). Pertanika Journal of Tropical Agricultural Science 22(1): 1–7.
Developing parts of the plant bear an indumentum of long, brown hairs. However, most of these disappear during the normal course of development, and mature parts only have a sparse covering of short, brown hairs.
Ecology