There are quantitative variations in many plant traits among and within species. Part of the variations may be explained by local adaptation; an adaptive value of some trait maximizing the fitness differs depending on environmental conditions and species or genotypes that are selected in a habitat differ among habitats.  Comparison of variations in traits and genome between populations occurring in different environmental conditions within a species may provide us a deeper understanding of evolutionary adaptation to respective environment. We have studied trait variations among ecotypes of several species. Brassicaceae species may be advantageous to relate phenotypic variations to genetic differentiations because of abundant knowledges from molecular studies. In this talk, I show trait variations in Arabidopsis halleri ecotypes and our on-going attempts to analyze molecular basis of the variation.