Nepenthes muluensis

Nepenthes muluensis is a climbing plant. The stem may attain a length of 4 m and is up to 5 mm in diameter. Internodes are cylindrical in cross section and up to 8 cm long.

The leaves of this species are coriaceous (leathery) and sessile. The lamina (leaf blade) is lanceolate in shape and up to 8 cm long by 1.5 cm wide. It usually has an acute apex and is gradually thinned towards the base, extending into an amplexicaul sheath, meaning the base of the leaf is dilated and clasping the stem. Up to 4 longitudinal veins are present on either side of the midrib. Pinnate veins are numerous but indistinct. Tendrils are up to 8 cm long. Rosette and lower pitchers are up to 7 cm high and 3 cm wide. They are ovate in the lower third, becoming cylindrical or conical above. The peristome, which is the ring of tissue surrounding the entrance to the plant's digestive tube, is approximately cylindrical and up to 5 mm wide. Its inner margin is lined with small but distinct 'teeth'. The pitcher mouth is round to ovate and has an oblique insertion. The lid or operculum is ovate and generally obtuse. It bears a number of filiform appendages (≤5 mm long) on its upper surface.

Upper pitchers are cylindrical for the most part, often with a bulbous basal quarter. Like their lower counterparts, they are relatively small, reaching only 10 cm in height and 2 cm in width. …

As its name suggests, N. muluensis was originally known only from Mount Mulu. Since its description it has also been found on several other mountains in Sarawak (including Mount Api, Mount Murud, and Bukit Batu Lawi) and one in southwestern Sabah. Nepenthes muluensis has not been recorded from the nearby summit of Mount Benarat, although this is a limestone peak and mostly lies outside the known altitudinal distribution of the species, which is 1,700 to 2,400 m above sea level.

Nepenthes muluensis grows in nutrient-deficient soils of the upper montane zone. It typically occurs in open areas of mossy forest amongst ridge-top vegetation. On Mount Mulu, the species seems to be restricted to the western ridge and occurs from an elevation of around 1,900 m to the summit at 2,376 m. The summit vegetation is greatly stunted, rarely exceeding a metre in height. It is dominated by rhododendrons (particularly Rhododendron ericoides), as well as species of the genera Diplycosia and Vaccinium. Nepenthes muluensis is most abundant in summit heath forest, where it forms dense stands with hundreds of white-speckled pitchers suspended over the sympatric shrubs. On Mount Murud, N. muluensis grows in shady mossy forest. This population produces darker pitchers than the one from Mount Mulu, possibly due to greater exposure to ultraviolet light at higher altitudes. …

Nepenthes muluensis was first collected by botanist Mitsuru Hotta on March 18, 1964, on Mardi between the third and fourth camps on the western ridge of Mount Mulu, Sarawak. The holotype, M.Hotta 14791d, is deposited at the Botany Department of Kyoto University (KYO). Hotta described the species in 1966, naming it after Mount Mulu, to which it was thought to be endemic. The description did not cover the lower pitchers of this species, which were unknown at the time. It was the first Nepenthes species to be described in 26 years (after N. densiflora in 1940) and the first since the end of World War II. At this time the genus was experiencing a revival in global interest, thanks largely to the work of Shigeo Kurata. Nepenthes muluensis has been misidentified at least once in the literature; Bertram Evelyn Smythies identified specimens of N. muluensis as belonging to N. gracillima, a species endemic to Peninsular Malaysia. This misidentification was published in 1965 in the proceedings of the UNESCO Humid Tropics Symposium, which was held in Kuching two years earlier.