Drought sensitivity shapes species distribution patterns in tropical forests

Although patterns of tree species distributions along environmental gradients have been amply documented in tropical forests, mechanisms causing these patterns are seldom known. Efforts to evaluate proposed mechanisms have been hampered by a lack of comparative data on species’ reactions to relevant axes of environmental variation. Through combining extensive experimental data with quantitative assessments of species occurence, we show that differential drought sensitivity shapes plant distributions in tropical forests at both regional and local scales. Our results suggest that niche differentiation with respect to soil water availability is a direct determinant of both local and regional scale distributions of tropical trees. Changes in soil moisture availability caused by global climate change and forest fragmentation are therefore likely to alter tropical species distributions, community composition and diversity.