Nepenthes Sibuyanensis - Ecology

Ecology

Nepenthes sibuyanensis is endemic to Sibuyan Island in the Philippines, where it grows on Mount Guiting-Guiting, neighbouring Mount Mayo, as well as the ridge that connects these two mountains. The altitudinal distribution given for this species varies considerably between sources: Vlastik Rybka, Romana Rybková and Rob Cantley give a range of 1200–1800 m above sea level, while the authors of the describing paper and Stewart McPherson give narrower ranges of 1500–1800 m and 1250–1500 m, respectively. According to Rybka, Rybková and Cantley, the species is sympatric with the tiny N. argentii at around 1600–1770 m. A species resembling N. alata grows on Mount Guiting-Guiting at lower elevations of 800–1000 m; it was described as N. graciliflora by Adolph Daniel Edward Elmer. Other plant species endemic to the mountain include Lobelia proctorii and Rhododendron rousei. Nepenthes sibuyanensis has no known natural hybrids, although it may hybridise with N. argentii.

Nepenthes sibuyanensis occurs relatively sparsely on open slopes dominated by high grasses, small shrubs, and the fern Dipteris conjugata. Pitchers usually develop embedded in the substrate and are rarely exposed to direct sunlight. Nepenthes sibuyanensis exhibits modified seed morphology owing to its exposed, isolated habitat. The absence of seed wings in this species prevents strong winds carrying them away from suitable habitats and allows for dispersion by water (particularly rainfall and small streams).

Due to its localised distribution, the conservation status of N. sibuyanensis is listed as Vulnerable on the 2006 IUCN Red List of Threatened Species. Logging and mining operations are increasingly threatening Mount Guiting-Guiting and its national park.