Villose pitcher-plant

Appearance

"Nepenthes villosa" is a weak climber, rarely exceeding 60 cm in height, although the stem may grow to 8 m in length and 10 mm in diameter. Internodes are cylindrical and up to 10 cm long.

Leaves are coriaceous and petiolate. The lamina is spathulate to oblong and may be up to 25 cm long and 6 cm wide. The apex of the lamina is emarginate. The petiole is canaliculate, up to 10 cm long, and bears an amplexicaul sheath. One to three longitudinal veins are present on either side of the midrib. Tendrils may reach 50 cm in length.

Lower and upper pitchers are very similar. They are urceolate to ovate in shape. The pitchers grow up to 25 cm high and 9 cm wide. A pair of fringed wings runs down the front of the pitcher, although it may be reduced to ribs in aerial traps. The pitcher mouth is oblique and elongated into a neck at the rear. The glands on the inner surface are overarched and occur at a density of 200 to 1300 per square cm. The peristome is cylindrical in cross section and up to 20 mm wide. It bears well developed teeth and ribs. The lid or operculum is cordate and has a pointed apex. It has a pair of prominent lateral veins....hieroglyph snipped... An unbranched spur, ≤ 20 mm long, is inserted at the base of the lid.

"Nepenthes villosa" has a racemose inflorescence. The peduncle may be up to 40 cm long, while the rachis grows to 20 cm in length. Pedicels are filiform-bracteolate and up to 15 mm long. Sepals are round to elliptic and up to 4 mm long. A study of 490 pollen samples taken from two herbarium specimens ) found the mean pollen diameter to be 37.2 μm.

The species has a dense indumentum of long, brown hairs that covers all parts of the plant.

Naming

"Nepenthes villosa" is most closely related to "N. edwardsiana" and "N. macrophylla". There has been much taxonomic confusion surrounding the status of these three taxa.

Joseph Dalton Hooker, who described both "N. edwardsiana" and "N. villosa", noted the similarity between the two species as follows:

This most remarkable plant ["N. villosa"] resembles that of "edwardsiana" in so many respects, especially in the size, form and disposition of the distant lamellae of the mouth, that I am inclined to suspect that it may be produced by young plants of that species, before it arrives at a stage when the pitchers have elongated necks.

Günther Beck von Mannagetta und Lerchenau was the first to treat "N. edwardsiana" in synonymy with "N. villosa" when he published his monograph on the genus in 1895.

In his 1908 monograph, John Muirhead Macfarlane wrote the following with regards to the two species: "Examinatione microscopica probatur, illas species distinctas esse". This is probably "based on the old belief that plants, which differ anatomically, can not be forms of the same species".

B. H. Danser united the species "[w]ith some hesitation" in his 1928 monograph "The Nepenthaceae of the Netherlands Indies". He suggested that "N. villosa" is a stunted form of "N. edwardsiana" from higher elevations, which flowers at a "juvenile stage of development". Danser acknowledged that the indumentum of "N. villosa" is more dense than that of "N. edwardsiana", but noted that it "is a difference only of degree".

The two taxa differ considerably in their altitudinal distributions. "Nepenthes villosa" usually occurs at ultrahighland elevations, 2,300–3,240 m, whereas "N. edwardsiana" is found between 1,500–2,700 m. Where their altitudinal distributions overlap, they are still identifiable as distinct species.

"Nepenthes macrophylla" was originally described in 1987 as a subspecies of "N. edwardsiana" by Johannes Marabini. It was later elevated to species status by Matthew Jebb and Martin Cheek. This interpretation was supported by Charles Clarke, who noted that "N. edwardsiana" and "N. villosa" "have more in common" than "N. edwardsiana" and "N. macrophylla". Whereas "N. edwardsiana" and "N. villosa" are restricted to the Kinabalu area, "N. macrophylla" is only found near the summit of Mount Trus Madi.

Matthew Jebb and Martin Cheek suggest that "N. villosa" is related to "N. mira", a species endemic to Palawan in the Philippines. "N. villosa" also shows affinities to "N. peltata" of Mindanao.

Distribution

"Nepenthes villosa" is endemic to the upper slopes of Mount Kinabalu and neighbouring Mount Tambuyukon in Sabah, Borneo. It generally grows at 2300–3240 m above sea level, the highest elevation of all Bornean "Nepenthes" species; only "N. lamii" from New Guinea is found at greater elevations. On Mount Kinabalu, "N. villosa" is common along the Mesilau Trail and almost all the way up to the Laban Rata rest house; a particularly large population has been reported at around 3047 m. On Mount Tambuyukon, an altitudinal inversion has been noted, whereby "N. villosa" is more common at much lower elevations of 1600–1900 m, being replaced by "N. rajah" towards the summit. The exposed, uppermost slopes of Mount Tambuyukon can become very hot during the day and this might explain the inability of "N. villosa" to colonise them. Plants from Mount Tambuyukon generally produce slightly more elongated pitchers.

Habitat

"Nepenthes villosa" often grows in mossy forest and sub-alpine forest dominated by species of the genera "Dacrydium" and "Leptospermum", particularly "Leptospermum recurvum". It has also been recorded growing among shrubs, grass, and boulders in open areas. Here the soil may become relatively dry, although relative humidity is usually close to 100% as the slopes are often enveloped in clouds. Like many "Nepenthes" from the Mount Kinabalu area, it is endemic to ultramafic soils.

Although many plants grow along Mount Kinabalu's summit trail and are easily accessible to climbers, all known populations of the species grow within Kinabalu National Park and so their collection is illegal. In 1997, Charles Clarke suggested a revised assessment of Conservation Dependent based on this. Clarke writes that "N. villosa" "has a secure future", although he adds that climbers have had a significant impact on populations of the species growing along the summit trail, with the number of plants having declined in recent years. A 2002 study found 1180 individual "N. villosa" growing in 11 plots, each measuring 0.01 hectares, at elevations of between 2,610 m and 2,970 m on Mount Kinabalu. This number constituted 94% of the pitcher plants recorded from the plots, the rest being "N. × kinabaluensis".