Nepenthes muluensis

Tropical pitcher plant endemic to Borneo

Nepenthes muluensis /n//ᵻ/'/p//ɛ//n//θ//iː//z// /,/m//ʊ//l//u/'/ɛ//n//s//ɪ//s/, or the Mulu pitcher plant, is a tropical pitcher plant endemic to Borneo. It grows in highland habitats at elevations of 1700

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, 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. The pitcher mouth is round and bears a cylindrical peristome up to 3 mm wide. The lid is orbicular and lacks appendages. An unbranched spur is inserted near the base of the lid. The species completely lacks an indumentum, with all parts of the plant being glabrous. Plants from Mount Murud produce darker coloured pitchers.

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) 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,

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. 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. The conservation status of N. muluensis is listed as Least concern on the IUCN Red List based on a 2018 assessment. and in 1995 as Endangered. In 1997, Charles Clarke informally classified the species as Endangered based on the IUCN criteria, noting that it is Conservation Dependent if populations in protected areas are taken into account. More recently, N. nigra has joined this group of related taxa. Nepenthes muluensis is most easily confused with N. tentaculata. The lower pitchers of these species are almost identical, but those of N. muluensis have a rounder mouth. The climbing stem, growth habit and leaves are also similar, although N. muluensis usually has a narrower lamina. However, the upper pitchers of N. muluensis are distinctive; they usually have a white lid, a round mouth, and their wings are either greatly reduced or absent altogether.

Nepenthes muluensis × N. tentaculata was described as N. × sarawakiensis in 1993 by J. H. Adam, C. C. Wilcock, and M. D. Swaine. The authors distinguished the taxon from N. muluensis on the basis of its branched spur and the presence of fringe hairs on the top of the lid. They also compared the distribution of phenolic compounds in the leaves of N. muluensis and the hybrid, although they did so without specifying the number of plants studied or the number of repetitions performed. Charles Clarke writes that the authors described N. × sarawakiensis "in such a way that their work cannot be easily repeated". and suggests that the absence of a widely distributed compound like myricetin among the Nepenthes examined might provide additional diagnostic information for these taxa.