A central issue of community ecology is finding rules that explain the composition and abundance of coexisting species. Environmental filtering and limiting similarity are the two major processes that determines species coexistence. Their relative importance under different environmental conditions, however, is still not properly clarified among aquatic plants. We study the effect of environmental filtering (causing trait convergence) and limiting similarity (causing trait divergence) to aquatic plant communities in lakes and ponds along a nutrient (oligotrophic to eutrophic) gradient, using a trait-based approach. The main environmental gradient is trophic status (i.e. productivity) was characterized by the concentration of total phosphorous and total nitrogen in water. The study is conducted in a large geographic scale; trait and environment data are collected from Finnland, Lithuania, Hungary, Italy and Spain. The cover of the plant species is estimated visually. Data of various plant traits (especiall leaf traits) collected by field measurements.