Explaining rarity of the narrowly endemic dipterocarpus cf. condorensis by in situ physiological measurements

Comparative physiological attributes, obtained by chlorophyll fluorescence and gas exchange techniques, of restricted Dipterocarpus cf. condorensis and widespread Shorea roxburghii species that are actually co-located in Ta Kou Nature Reserve - Binh Thuan Province, provided essential information for understanding rarity of D. condorensis. The narrowly endemic D. condorensis had similar photosynthetic performance to the locally abundant S. roxburghii in more common habitats in which ground water tables are deep (>20m), but had significantly higher photosynthetic activities in its specific habitat, where the ground water level is shallow (<10m). These differences are probably the consequence of evolutionary trade-offs, and represent specializations of the endemic D. condorensis which is only successful in habitat where the ground water is accessible. However, while adaptive in this habitat, these traits may reduce success in other more common habitats in this region.