| Nepenthes flava | |
|---|---|
 | |
| Lower pitchers ofNepenthes flava growing at an elevation of 1850–2000 m | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Order: | Caryophyllales |
| Family: | Nepenthaceae |
| Genus: | Nepenthes |
| Species: | N. flava |
| Binomial name | |
| Nepenthes flava | |
Nepenthes flava/nɪˈpɛnθiːzˈflɑːvə/ is a tropicalpitcher plantendemic to northernSumatra, where it grows inmontane forest at 1,800–2,200 mabove sea level.[1][2]
Thespecific epithetflava is derived from theLatin word for "yellow" and refers to the typical colouration of the plant's upper pitchers and other vegetative parts.[1]
Nepenthes flava entered cultivation several years prior to being described and was known from at least 2004 under the placeholder name "Nepenthes spec. nov. Sumatra".[3]
The species wasformally described byAndreas Wistuba,Joachim Nerz andAndreas Fleischmann in an issue ofBlumea[1] published on July 4, 2007.[4] The description was based on cultivated plant material;Wistuba cult. Wistuba 100201 was designated as theholotype. This specimen was collected at an altitude of 1,800 m and is deposited at theNational Herbarium of the Netherlands (L) inLeiden, together with anisotype.[1][4] The describing authors explained their choice of thespecific epithetflava as follows:[1]
The specific epithet ‘flava’ refers to the bright yellow colour of the upper pitchers and most of the lower pitchers. Climbing plants especially give the impression of a mainly yellow plant.
A detailed and slightly modified description ofN. flava appeared inStewart McPherson's 2009 monograph,Pitcher Plants of the Old World.[2] Whereas the type description mentions a basal crest on the underside of the lid,[1] McPherson writes that no appendages are present in either lower or upper pitchers.[2]
Nepenthes flava is a climbing plant growing to a height of 6 m.[2] It only remains in therosette stage for a short time before transitioning into a scramblingvine. Thestem, which may be branched,[2] is around 3 mm in diameter and has roughly cylindricalinternodes measuring up to 14 cm in length. The stem ranges in colour from green to dark red.[1]
Thelamina (leaf blade) is linear,[2] oblong, or narrowlyobovate, and measures up to 9 cm in length by 2.5 cm in width. Its apex is usually acute, but may also be obtuse.[2] The base of the lamina isattenuate[2] and clasps the stem for around half to three-quarters of its circumference. Three prominent longitudinal veins are present on either side of themidrib. Indistinctreticulate veins are also present. The lamina is yellowish-green in colour and the midrib may be reddish.[2]Tendrils reach 24 cm in length and may be green to red.[1][2]
Rosette and lower pitchers are eitherinfundibular throughout orovate and variably inflated.[2] They are small, measuring only up to 7 cm in height by 4 cm in width. A pair of wings (≤3 mm wide) often runs down the upper third of the pitcher's ventral surface, bearing fringe elements around 5 mm long. Occasionally, the wings may be absent altogether.[2] Theperistome varies from cylindrical to slightly expanded and has a wavy outer margin. It is up to 12 mm wide and bears fine ribs up to 0.6 mm high and spaced up to 1 mm apart.[2] On the inner margin of the peristome, these ribs terminate in teeth up to 1.5 mm long, with the largest located towards the rear.[2] The pitcher mouth is round and slightly elongated towards the rear, although it rarely exhibits a neck. The pitcher lid oroperculum is narrowly ovate or elliptic[2] and measures up to 3.5 cm in length by 2 cm in width. On its lower surface, the lid bears a basalglandular crest[1] or no appendages at all,[2] as well as numerous circularnectar glands (0.3 mm in diameter), which are concentrated around the midline and crest. An unbranched,filiformspur (≤4 mm long) is inserted near the base of the lid. Unlike their aerial counterparts, lower pitchers vary greatly in pigmentation. The pitcher cup may be yellow, orange, red, or even purple, whereas the inner surface may be light yellow, light orange, or whitish.[2] The peristome is usually darker than the rest of the pitcher, typically being dark orange to purple,[2] although it may be creamy white and occasionally exhibits red stripes. The lid has a similar colour to the pitcher cup, usually having a darker upper surface with dark red speckles.[1][2]
Upper pitchers are tubular to narrowly infundibular in the lower two-thirds, becoming broadly infundibular above.[2] Characteristically, the hollow pitcher tube often continues past the curved basal portion and for some distance up the tendril.[2] Upper pitchers are similar in size to their terrestrial counterparts, reaching 6 cm in height by 3.5 cm in width.[2] The peristome is flattened and expanded, reaching 15 mm in width. As in lower pitchers, its outer margin is undulate. The peristome ribs are up to 0.2 mm high and spaced up to 0.5 mm apart.[2] The lid is ovate or elliptic[2] and has a somewhattruncate apex. It measures up to 4 cm in length by 2.5 cm in width. A reduced basal crest may be present on the underside of the lid[1] or it may be absent entirely.[2] Other parts are similar to those found in terrestrial traps. Upper pitchers are typically yellow throughout, but some specimens may have a completely red or red-striped peristome and mature traps may be orange or reddish on the upper surface of the lid.[1][2]
Nepenthes flava has aracemoseinflorescence up to 15 cm long.[2] Male inflorescences are morefloriferous, bearing 15–40 flowers, compared to 15–25 in females. Thepeduncle measures up to 4 cm in males and up to 8 cm in females. Flowers are borne solitarily onpedicels that reach 6 mm in males and 11 mm in females. A basalbract is often present (≤4 mm long). The nectariferoustepals are ovate and measure up to 3 mm in length by 1 mm in width. Theandrophore is around 3 mm long and terminates in ananther head measuring 1–1.5 mm in diameter. Theovary is 3–4 mm long. The morphology of thefruits andseeds has not been documented. The inflorescence is yellowish throughout.[1]
All mature vegetative parts areglabrous, but acaducousindumentum is present on some developing structures. Young parts of the stem bear a sparse covering of reddish-brown, basally branched hairs (0.2–0.5 mm long). A dense indumentum of reddish-brown hairs (0.5–1 mm long) is present on developing pitchers and tendril ends. The inflorescence bears branched, yellowish-brown hairs measuring 0.5–1 mm in length. Tepals have a dense covering of curved, reddish-brown hairs (around 0.2 mm long) along their margins. Ovaries also have a dense covering of reddish-brown hairs, but these are longer, measuring 0.5–1 mm.[1]
Nepenthes flava is only known from a single mountain in theBarisan Mountains ofNorth Sumatra,Indonesia.[2] In the interests of conservation, the exact locality has not been disclosed.[1] The species has an altitudinal distribution of 1,800–2,200 mabove sea level.[1][5]
The typical habitat ofN. flava is upper montanemossy forest[2] dominated byRhododendron andLeptospermum plants.[1] It often grows terrestrially in more open areas of forest, where the vegetation rarely exceeds 4–5 m in height. The species is naturallysympatric withN. mikei,N. ovata,N. rhombicaulis, andN. spectabilis.[1]Natural hybrids withN. ovata andN. rhombicaulis have been recorded.[1]
The only known locality ofN. flava does not lie within the boundaries of anational park. Although it appears to be locally abundant,Stewart McPherson considers the species to be "at significant risk of being poached and over-collected" and cites the "rapid demise" ofN. aristolochioides, another highly sought-after Sumatran plant, as an example of the possible fate of this species.[2]
The pitcher fluid ofN. flava is highly viscous and coats the inner pitcher walls.[2] This is especially true of aerial traps, which must contend with the action of the wind.[2] The sticky inner walls have been observed to trap small flying insects above the surface of the fluid. The prey subsequently slide down into the fluid where they are digested.[2] It has been suggested that the pitchers of this species function not only aspitfall traps but also asflypaper traps. Indeed, this trapping method is employed by the closely relatedN. inermis, which also produces highly viscous pitcher fluid.[6][7]
Nepenthes flava is thought to be closely related to bothN. inermis andN. jacquelineae.[1] However, it cannot be anatural hybrid between these species as it does not occur sympatrically with them.[3]
The pitchers ofN. flava bear a close resemblance to those ofN. jacquelineae.[1][2]Nepenthes flava differs from this species in that its upper pitchers are markedly smaller and have a peristome that is significantly narrower, bears distinct ribs, and has an undulate margin. In addition, the upper pitchers ofN. jacquelineae are not yellow throughout, a colouration that is characteristic ofN. flava.[2]
WithN. inermis, this species shares similarlyinfundibular pitchers, a narrow lid, and the habit of rapidly transitioning from a rosette to a climbing plant (with associated sudden internode elongation).[1] Furthermore, the seedling pitchers of these two species can appear quite similar.[1]Nepenthes inermis differs most obviously in having upper pitchers that completely lack a peristome and in lacking conspicuous glands on the underside of the lid.[1]
The describing authors consideredN. flava to likely represent an evolutionary link between the pair ofN. inermis andN. jacquelineae and "common Sumatran species such asN. ovata".[1] They further speculated:[1]
Nepenthes flava might represent an intermediate betweenN. ovata of northern Sumatra and the unusualN. inermis of the western Sumatran mountains, and would confirmDanser’s hypothesis in which he united common species familiar to him, i.e.N. bongso,N. carunculata Danser andN. singalana, with the distinctive speciesN. inermis andN. dubia Danser into the subgenusMontanae Danser (Danser, 1928).Nepenthes ovata,N. jacquelineae and others were not known at this time, but it seems likely he would have included them in subgenusMontanae as well.
Other species that produce somewhat similarly shaped upper pitchers includeN. eymae,N. jamban,N. pitopangii,N. talangensis, andN. tenuis.[2]Nepenthes flava can be distinguished from all of these species on the basis of a combination of features: entirely yellow upper pitchers; a broad, wavy peristome; very small peristome teeth; and a narrowly ovate or elliptic lid that lacks appendages[2] (or has a small basal crest).[1] Furthermore, compared to many of these species, and particularlyN. eymae,N. flava is a diminutive plant.[2]
Twonatural hybrids involvingN. flava have been recorded; the describing authors found examples of crosses withN. ovataandN. rhombicaulis. Most of the observed hybrids were youngrosette plants. AlthoughN. flava is also sympatric withN. mikei andN. spectabilis, no natural hybrids with these species have been recorded.[1]
