1.Global change triggers rapid alterations in the composition and diversity of plant communities which may change ecosystem functioning. Do changes in community diversity also change traits persistently, i.e. does coexistence with numerous or functionally or phylogenetically distinct species trigger, in a given focal species, trait shifts that persist? 2.We studied the grass Dactylis glomerata. Dactylis was grown in experimental plots with different species compositions for five years, sampled, cloned and grown in a common garden. We studied amines, regulators integrating growth responses of organisms to their environment. 3.We found that the mean levels and variances of most amines depended on the diversity of the source community, notably the species richness and the phylogenetic and functional distinctness from Dactylis, unbiased by species identity or biomass shifts. 4.Synthesis. Our results suggest that different levels of ambient diversity can, within a few years, select for different genotypes which have different compositions of growth regulators. Our study also suggests that a plant species can evolve in response to the diversity or distinctness of the surrounding plant community. Evolutionary changes of plant phenotypes might mediate an impact of past biological diversity on present ecosystem functioning.