Nepenthes mapuluensis is a rare tropical pitcher plant endemic to East Kalimantan, Borneo, first described in 1990 by J.H. Adam and C.C. Wilcock. The species is named after Mount Ilas Mapulu, its type locality. Known for its elegant pitchers and limestone habitat specialization, it is considered Endangered on the IUCN Red List due to habitat degradation and fire threats.
Habitat Overview: Climate and Soil
This species grows terrestrially on limestone cliffs and escarpments, typically at elevations between 50 and 850 meters above sea level. The habitat is characterized by pristine vegetation, high humidity, and continuous moisture, often in dense shade. The soil is thin and rocky.
Natural Range and Distribution
Nepenthes mapuluensis is endemic to Northeast Kalimantan, specifically the Sambaliung range and karst outcrops in the Kerangan River Basin. Its distribution is patchy, as it is confined to steep limestone formations. The original population on Mount Ilas Mapulu was destroyed, and no known populations currently lie within protected areas, increasing its vulnerability to fire and land clearing.
Physical Characteristics
This species is a mostly glabrous climbing plant, with stems up to 6 mm in diameter and internodes up to 4 cm long. Leaves are coriaceous, oblanceolate-linear, up to 26 cm long and 5 cm wide, with sub-petiolate, semi-amplexicaul bases. Tendrils can reach 50 cm.
The lower pitchers are ellipsoidal, up to 21 cm tall and 8.5 cm wide, with fringed wings up to 10 mm wide. The peristome is moderately developed, folded or wavy, and up to 12 mm wide, bearing distinct but not pronounced teeth. Upper pitchers are infundibular or cylindrical, smaller, and may have reduced wings or ribs.
The inflorescence is racemose, with peduncles up to 7 cm and pedicels up to 8 mm. Pollen grains average 28.9 μm in diameter.
Similar Species and Differentiation
Nepenthes mapuluensis is very similar to N. northiana, and there has been debate over its species status. While both share pitcher shape and peristome structure, N. mapuluensis differs in:
- Pitcher proportions
- Peristome folding
- Habitat preference (more montane and patchy limestone outcrops)
These stable morphological differences support its recognition as a distinct species.