Soil phosphorus (P) availability is one of the major drivers of tree community in the tropics, suggesting that niche partitioning along soil P gradients could contribute to the maintenance of species diversity. It has been suggested that home-soil advantage in the growth of specialist tree species might be a mechanism underlying this pattern, yet evidence remains inconsistent.

Here, we tested this hypothesis on growth rate by analyzing the relationship between tree growth rate and soil P availability in neotropical tree species. In a shade house experiment we grew 10 species in five congeneric pairs under low and high-P conditions. The genera were Cecropia, Cordia, Inga, Psychotria, and Tabebuia, and the two species in each genus exhibit contrasting soil P affinities, being associated with either low or high P soils in central Panama. Overall, low-P specialists grew faster than high-P specialists at low P, whereas high P specialists grew faster than low-P specialists at high P. Furthermore, we compiled the tree growth data of 1-ha plots established along the Panama canal. Across the strong soil P gradient, growth rate of specialist species showed the consistent pattern with the experiment. Differences in growth at high and low P appear to explain species distribution patterns, and further analyses on P-use and uptake traits were conducted to identify the mechanisms underpinning this.