Orchids of extreme serpentinite (ultramafic) habitats in Kinabalu Park

Kinabalu Park has some of the most species-rich vegetation on ultramafic soils anywhere in the world with high levels of endemism among orchids. Some of the most remarkable habitats are those formed on serpentinite, an ultramafic soil type with extreme chemical properties. The vegetation of serpentinite soils in Sabah is generally characterised by the trees Gymnostoma sumatranum or Ceuthostoma terminale (Casuarinaceae), as well as the shrub Scaevola micrantha (Goodeniaceae). A number of orchids are known only or predominantly to occur in serpentinite habitats, including well-known species such as Apostasia wallichii, Crepidium metallicum, Paphiopedilum dayanum, P. rothschildianum, Paraphalaenopsis labukensis, Phalaenopsis maculata, Porpax borneensis, and Renanthera bella. The characteristic open stature of the forest on serpentinite soils is likely the main factor contributing to the richness in terrestrial and epiphytic orchids. However, for terrestrial orchids, adaptations to the adverse chemical conditions of serpentinite soils may be a contributing factor for the high level of endemisrn in this habitat.