Urbanization drives genetic and plastic responses of the spotted jewelweed flower morphology

The spectacular diversity of flowers is strongly driven by pollinator-mediated selection that favors attractive flowers and effective pollen transfer. We tested how urbanization affected the genetic and plastic components of flower morphology of Impatiens capensis across four Canadian cities, accounting for changes in abiotic conditions and pollinator communities. Urbanization altered the species composition of pollinator communities and bumblebee size – the main pollinator, but the size effect varied among cities. Urbanization also impacted flower size through both genetic and plastic responses. In particular, the genetic component of the sepal size – a tubular floral organ in which pollinators enter to access the nectar – correlated positively with bumblebee size. These results suggest that urbanization, by changing pollinator communities, drives evolutionary changes in flower morphology.