Nepenthes fusca Danser (1928: 288

Robinson, Alastair S., Golos, Michal R., Barer, Marc, Sano, Yosuke, Forgie, Jennifer J., Garrido, Diego, Gorman, Chandler N., Luick, Adi O., Mcintosh, Nick W. R., Mcpherson, Stewart R., Palena, Gregory J., Pančo, Ivan, Quinn, Brian D. & Shea, Jeff, 2019, Revisions in Nepenthes following explorations of the Kemul Massif and the surrounding region in north-central Kalimantan, Borneo, Phytotaxa 392 (2), pp. 97-126 : 110-114

2. Nepenthes fusca Danser (1928: 288 , fig. 6) descr. emend. A.S.Rob. & Golos ( Figs. 7−8 )

Lectotype (designated by Jebb & Cheek 1997: 41):—Borneo, Kalimantan, W. Koetai, G. Kemoel, ± 1500 m, 12 October 1925, Endert 3955 (BO!, isotypes BO!, K!, L) [date incorrectly listed as 12 November in Jebb & Cheek (1997) and Cheek & Jebb (2001)] [lectotype BO—climbing stem with lidless upper pitchers, male inflorescence; iso- BO—separate lidless upper pitcher and intermediate pitchers, leaf and stem elements; K—climbing stem with upper pitcher, male inflorescence].

− Nepenthes veitchii? auct . non Hook.f. [ Endert (1927: 277)].

Other concepts of Nepenthes fusca s.lat.: —From our concept of Nepenthes fusca are to be excluded those of Kurata (1976: 48, pl. 13), Phillipps & Lamb (1988: 24, 3 figs.), Phillipps & Lamb (1996: 87, fig. 48), and Clarke (1997: 87, figs. 57–58), quae pro parte = N. fusca Danser & N. zakriana (J.H.Adam & Wilcock) J.H.Adam & Hafiza , as well as those of Jebb & Cheek (1997: 41), Cheek & Jebb (2001: 64), Phillipps et al. (2008: 121, figs. 149–156), and McPherson (2009: 346, figs. 183–185), quae pro parte = N. dactylifera A.S.Rob., Golos, S.McPherson & Barer , N. fusca Danser & N. zakriana (J.H.Adam & Wilcock) J.H.Adam & Hafiza.

Moreover, our concept of Nepenthes fusca does not include: − “ Nepenthes fusca subsp. apoensis ” J. H.Adam & Wilcock ex Jebb & Cheek (1997: 41), nomen nudum; quae = N. stenophylla Mast. , material at K!: S. 35939 (Chai), Borneo, Sarawak, 4th Div., Baram District, Kelabit Highland[s], summit of Apo Dari, 1550 m, 17 November 1974 [climbingstemwithupperpitchers,femaleinflorescence;annotatedas N.fusca var. apoensis (sic)byJ.H.Adam, 25/1/1991)]. − “ Nepenthes fusca subsp. kostermansiana ” J.H.Adam & Wilcock ex Jebb & Cheek (1997: 41), nomen nudum; quae ≡ N. epiphytica A.S.Rob., Nerz & Wistuba , material at L! and K! (type material of N. epiphytica —see under “Additional specimens examined”).

Description 1: —Terrestrial climbing or scrambling shrub, to 5 m tall. Stems of rosettes terete, 0.6–0.8 cm in diameter, internodes 0.4–1.5 cm long; vining stems 0.4–0.6 cm in diameter, internodes 8–15 cm long. Leaves of rosettes coriaceous, petiolate, obovate to sub-elliptic, 12–15 cm long, 4–5.5 cm wide, apex obtuse to emarginate, base gradually attenuate, petiole narrowly canaliculate, 2–3.5 cm long, base amplexicaul and sheathing stem for ca. 1/2 its circumference, rarely more. Longitudinal veins 4 on either side of midrib in outer third of lamina, where they run parallel to the laminar margin, originating at base of leaf, inconspicuous. Pinnate veins numerous, irregularly reticulate, indistinct. Tendrils more or less equal in length to lamina. Leaves of climbing stems scattered to subalternate, coriaceous, petiolate, rarely sub-petiolate, lamina elliptic, 10–16 cm long, 3.5–6 cm wide, apex obtuse, occasionally acute, base gradually attenuate, petiole 1.5–4.5 cm long, base amplexicaul and sheathing stem for ca. 1/2 its circumference, rarely more. Longitudinal veins 2 either side of midrib in outer third of lamina, parallel with laminar margin, indistinct. Tendrils equal or up to twice as long as lamina, typically curling once only. Lower pitchers sub-cylindric, narrowing slightly in the middle, with slight gibbosity below the mouth, 9–16 cm tall, 2.5–4.5 cm wide, with fringed wings 1–3 mm wide, fringe elements to 8 mm long, 3–5 mm apart; peristome strongly oblique, widening

1 This emended description is based on measurements made of N. fusca in situ in the Kemul Massif and on examination of the type material deposited at BO and K.

from midpoint of mouth towards raised and slightly recurved neck, 2.5–4 mm wide at front of pitcher, sub-cylindric in section, broadening and increasingly flattened towards neck and ≤ 12 mm wide, ribs ca. 0.3–0.5 mm apart, teeth fine, ≤ 0.4 mm long. Lid ovate, ±complanate, base sub-cordate, 3.5–5 cm long, 1.8–2.5 cm wide, adaxial surface typically channelled along midline, with abaxial midline rib only slightly pronounced, but with pronounced semi-circular basal keel 3–5 mm tall, bearing rounded glands and appearing bumpy, abaxial surface of lid with small, densely scattered pitted circular glands and fine brown hairs to 0.5 mm long, apex slightly retuse, no apical protuberance but frequently with a patch of sub-apical ocellate-crateriform glands. Spur filiform, simple, rarely branched at base into 2(–3) parts, 6–8 mm long. Upper pitchers narrowly infundibular throughout, 12–18 cm tall, 2.5–5.5 cm wide at mouth, wings reduced to prominent ridges, with slight ventral flattening in between; peristome robust, 4–6 mm wide at front of pitcher and flattened, usually slightly raised at front between wings, slightly oblique thereafter and increasingly cylindric, rising more or less vertically to form a slightly recurved neck and widening to ≤ 15 mm wide. Lid ovate, base cordate, ±complanate, margins sometimes sinusoid, longer and broader than in lower pitchers, 4.5–6.5 cm long, generally 1.8–2 times longer than wide, abaxial midline rib only slightly pronounced, but with a pronounced basal keel, keel semi-circular, 2–4 mm tall, bearing few inconspicuous to no glands and usually with brown, woolly hairs 0.8–1 mm long along lower margin, shorter and sparser on appressed surfaces either side, distal part of midline rib sometimes with longitudinally distended crateriform glands, apex usually diminished and without apical swelling, rarely with minute apical protuberance ca. 1 mm long, indumentum of short, simple, brown hairs on abaxial and adaxial surfaces of lid, to 0.5 mm long. Spur filiform, simple or branched at base into 2 parts, 0.8–1.2 cm long. Male inflorescence to 20 cm long, ca. 60–80 flowers, peduncle ca. 6–8 cm long, 4–5 mm in diameter at the base, rachis 8–12 cm long, partial peduncles 1- to (mainly) 2-flowered, bracts absent, bifurcating 0.5–1 mm from base, pedicels ca. 9 mm long; tepals green, distal 2/3 suffused with purple-red, elliptic, 3–3.5 mm long, 2 mm wide, apex acute, adaxial surface with 40–50 conspicuous glands, typically green; staminal column to 2–3 mm long, anther head 1.8 mm in diameter, consisting of 8 fused anthers, anthers red, pollen grains yellow. Female inflorescence to 18 cm long, peduncle 8–12 cm long, rachis 6–8 cm long, partial peduncles 2-flowered, pedicels 5–7 mm long, tepals narrowly elliptic, ca. 2.5 mm long, apex acute, fruit 1.5–2.2 cm long, seeds filiform, 7–9 mm long, pale brown. Indumentum of rufous simple and branching hairs present on stems, petioles, leaf margins and both surfaces of midrib, especially dense on emerging foliage and rachis, laminae with simple, minute white hairs on adaxial surface, becoming somewhat caducous in mature leaves, and simple, sparse, rufous hairs on abaxial surface and on pitchers. Colour of mature stems, leaves and tendrils green, developing foliage flushed red or bronze, pitchers pale green (lowers) to yellowish green (uppers) and spotted externally and internally (within the waxy zone only) with red to purple blotches, peristome colour as per pitchers with variable amounts of red striation.

Phenology: —Male and female plants were observed in flower and fruit in July 2018, while the type materials (all male) were collected in October. The region is not strongly seasonal and it is possible that flowering occurs spontaneously throughout the year.

Distribution and ecology: — Nepenthes fusca was observed from 1400–1600 m a.s.l. on narrow, rocky, freedraining ridges amidst relatively open ridge forest including small-trunked Elaeocarpus , Phyllocladus , and Tristaniopsis , alongside various grasses, shrubs and the resam fern Dicranopteris linearis (Burm.f.) Underw .. All observed plants were terrestrial in rocky humus banks or pockets of humus at the bases of trees, in breezy conditions that led to significant drying of surface moisture during the day. Although these observations do not rule out an epiphytic habit for N. fusca , no epiphytic plants were observed in damper forest away from the drying ridge-top conditions. This is in contrast with N. dactylifera and N. zakriana , which are occasionally found growing as epiphytes in sheltered situations close to where terrestrial plants are noted. In the absence of evidence to the contrary, N. fusca is regarded as a terrestrial species, as per Danser (1928).

Although Nepenthes tentaculata occurs close to the upper elevation limits of N. fusca , no hybrids between the two species were observed.

Conservation status: — Nepenthes fusca clearly has a restricted distribution, being thus far known only from the Kemul Massif, with no equivalent material being noted by this expedition on Mt. Bagong to the south, where N. dactylifera was present. However, in the absence of further explorations of the massif and adjacent mountains to the north and west, the species must be listed here as Data Deficient (DD; IUCN 2012). The remoteness of the massif and great expense of access present good barriers to unscrupulous collection; coupled with the low value of the plant, N. fusca is unlikely to be meaningfully threatened by the horticultural trade.

Notes: —The overall characteristics of Nepenthes fusca , but especially its flattened lid, peristome and its general colouration, resemble N. platychila and N. vogelii . Taking into account its basal lid appendage and mainly 2-flowered partial peduncles, it appears close to N. epiphytica Robinson, Nerz & Wistuba (2011: 36) , a species currently known from only two limestone peaks in East Kalimantan ( Robinson et al. 2011), which differs in being apparently exclusively epiphytic, producing lids bearing a greatly reduced but nonetheless glandular basal swelling, and for its very widely flaring upper pitchers. In common with N. mollis , the basal keels in the lids of the upper pitchers of N. fusca were found to be hairy, with few to no glands, contrasting with those of the N. fusca lower pitchers, which appear bumpy as they are covered with large, rounded glands.

Syrphid flies were observed on the male inflorescences of Nepenthes fusca , suggesting that they might represent a pollinator. Muscid flies were also observed feeding on the basal keels of upper pitchers, although ants were found to be the primary prey caught within the pitchers.

Additional specimens examined: — Nepenthes epiphytica :— KALIMANTAN: Kostermans 21495 (holotype L!, iso- K! [2 sheets]), Indon. E. Borneo [East Kalimantan], Berau, Mt. Njapa on Kelai R. limestone, 1000 m, 25 October 1963 [L—climbing stem with upper pitchers; annotated as N. fusca var. kostermaniana (sic) by J.H. Adam, 25/?/1991; K—climbing stem with upper pitchers, female inflorescence; climbing stem with upper pitchers, infructescence].

The following specimens were examined as part of the assessment of N. fusca s.lat., but are incompletely diagnosed: SARAWAK: Anderson 218 (K!), Gunong Rumput , no elevation data, August 1912 [stem with lower and upper pitchers] ; B. 2791 (Burtt & Woods) ( SAR! [2 sheets]), First Division, Poi [Pueh] Range , Gunong Berumput [= G. Rumput], 4870 ft [= 1484 m], 12 August 1962 [separate pitcherless stem, leaf, infructescence and male inflorescences; climbing stem with upper pitchers] ; Beccari 2386 (K!), locality given only as “ Sarawak ”, no elevation data, November 1871 [short stem with lower pitchers] ; Beccari 2387 (K!), locality given only as “ Sarawak, Borneo”, no elevation data, collected 1865–1868 [stems with upper pitcher]; (Clemens & Clemens) 20233 ( SAR!), Mt. Poi [=G. Pueh], 4500 ft [= 1372 m], September 1929 [climbing stem with upper pitcher] ; Jacobs 5115 (K!, L, SAR!), 1st div., N. slopes of Mount Penrissen (S. of Kuching ), approx. 1°5’N 110°15’E, 1000–1200 m, 7 August 1958 [K—climbing stem with upper pitcher, male inflorescence; SAR —short stem, separate leaf with upper pitcher] ; S. 513 (“ Museum Collector ”) ( SAR! [2 sheets]), foot of Mt Penrissen , no elevation data, 24 November 1909 [stem with intermediate pitchers; climbing stem with lidless upper pitcher] ; S. 12645 (Smythies) (K! [2 sheets], L, S, SAR!), Lundu District , G. Berumput [= G. Rumput], 4877 ft [= 1487 m], 25 August 1960 [K—leaf with upper pitchers; climbing stem with upper pitchers; SAR —climbing stem with upper pitchers] ; S. 15654 (Smythies) (K!, SAR!), Lundu District, G. Pueh Forest Reserve , S. Sebat Kechil / S. Tembaga ridge, 3700 ft [= 1128 m], 5 November 1961 [K—climbing stem with upper pitcher; SAR —short stem with lower pitchers] ; S. 42609 (Paie) ( SAR!), 2nd Division, S’ggang Road, 85th Mile , Silantek Kiri , Ulu Sg. , path to Gunong Silantek , 564 m, 27 August 1980 [climbing stem with upper pitchers]; ( Vogel ) 933190 ( L!), near Padawan, Gunung Penrissen , 800 m, October 1993 [two upper pitchers detached from leaves] .

Notes on specimens examined: — Anderson 218, Beccari 2386 and 2387, (Burtt & Woods) 2791, (Clemens & Clemens) 20233, Jacobs 5115, (“Museum Collector”) 513, (Paie) 42609, (Smythies) 12645 and 15654, and (Vogel) 933190 all represent an unusually robust form of Nepenthes fusca s.lat. with somewhat flattened lids that is periodically photographed in western Borneo from the mountains (> 900 m) S and W of Kuching, Sarawak, especially around the popular Borneo Highlands Resort and Mt. Rumput. Danser (1928) placed the Anderson, Beccari and “Museum Collector” specimens of this taxon within N. maxima , and Cheek’s notes on the first two accessions, as well Lee’s on the last, place them within N. fusca s.lat. We are unable to place this taxon within N. fusca s.str. owing to the atypical lid morphology, long-decurrent leaf bases, and particularly robust pitchers, while the form of the lid would also exclude it from N. dactylifera . In situ studies of this taxon are merited.

The isotype of Nepenthes fusca at L, cited by Cheek & Jebb (2001), is not found in the herbarium’s database and could not be located by MG during a visit in January 2018. According to Cheek & Jebb (2001), it and the isotype at K are the only two original sheets with intact upper pitcher lids.

Figures

FIGURE 7. Nepenthes fusca Danser. A—climbing stem with emerging inflorescence. B—lower pitcher. C—intermediate pitcher. D— base of lower/intermediate pitcher lid, showing detail of highly glandular keel. E—upper pitchers, top right ventral view, bottom left lateral view. F—base of upper pitcher lid showing distribution of indumentum. G—lower pitcher lid, top adaxial surface, bottom abaxial surface. H—peristome in cross-section. I—dehiscing seed capsules. J—male flowers. Scale bars:A, B, C, E, G = 1 cm, D, F, H, I, J = 5 mm. Based on Endert 3955 (isotype K) and supplemented with photographs and measurements made of in situ material. Illustrated by M. Barer.

FIGURE 8. Nepenthes fusca. A—lower pitcher. B–C—upper pitchers. D—detail of male partial peduncles showing red thecae. E—aerial camera view of the western flanks of the Kemul Massif.Approximate elevations for the main habitats of N. fusca (1400 m) and N. mollis (2000 m) are indicated. Photographs A, B by A.S. Robinson; C–E by M.R. Golos.