Current project

Urban evolution of seasonal plasticity in Lepidoptera

Cities dramatically change many different aspects of the environment, and thus they have become an ideal setting for studying rapid evolution. Seasonality is no exception, and in this context, urbanization makes two important changes: the urban heat island effect increases temperature, and light pollution increases daylength.

Many organisms use daylength as a cue to predict future seasonal conditions and produce an appropriate plastic phenotype for the upcoming season. Thus, when cities change either daylength or temperature, this can cause the plastic response which evolved under natural conditions to make mistakes. Evolution, however, could alter the response to photoperiod allowing adaptation to the new urban conditions.

To test how seasonal plasticity is evolving in cities, we are studying Pieris napi (green-veined white butterflies) and their winter diapause. In previous research, I compared populations of butterflies from Stockholm, Helsinki, and their surrounding rural environments and found that urban butterflies wait until shorter daylengths to enter diapause. This change corresponds to the predicted evolutionary response to the urban heat island.

We are currently extending this research to consider how the urban evolution of diapause varies across Europe, testing the hypothesis that light pollution will have a greater influence at low latitudes. We are also collaborating with colleagues at the University of Helsinki and University of Oulu to conduct interdisciplinary education research in which we will work with school classes to test what benefits (if any) P. napi’s urban evolution provides under “natural” urban conditions.