Localized ultramafic outcrops in Kinabalu Park (encompassing Mount Kinabalu and Mount Tambuyukon) in Sabah (Malaysia) are known for high levels of plant diversity and endemism, which have been stimulated by extreme soil chemistry and biogeographic factors, such as isolation. Characteristic of these outcrops are edaphic endemics of insectivorous pitcher plants from the Nepenthaceae-family including Nepenthes burbidgeae, N. edwardsiana, N. macrovulgaris, N. rajah and N. villosa, all of which (except N. macrovulgaris) are confined solely to the protected area of Kinabalu Park. Although the various aspects of plant taxonomy and nutrition of this genus have been extensively studied, the habitat of these rare species has to date not been studied in detail. It was hypothesized that while the Nepenthes of Mount Kinabalu and Mount Tambuyukon are excluders of excess trace elements, soil chemistry is nevertheless a major driver for creating the specific habitats in which ultramafic edaphic endemic Nepenthes occur, and that this is reflected in vegetation physiognomy and co-occurring species composition as well as in the foliar chemistry of Nepenthes. The results show that the characteristics of the physical environment and soil chemistry 'induces' a vegetation physiognomy that varies among sites and produces a series of different niches that are colonised by different Nepenthes-species. Although other plant species associated with these niches do not directly influence the distributions of the Nepenthes-species, some are characteristic. The unusual ultramafic soil chemistry is not reflected in the foliar chemistry of Nepenthes and they appear to be 'Excluders' of potentially toxic soil trace element concentrations. The populations of Nepenthes burbidgeae, N. edwardsiana, N, rajah, N. villosa are small (in particular, N. burbidgeae) and these species are thus likely to be vulnerable to the potential effects of climate change-induced drought and fire.
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