Climatic variables
We used nine climatic niche variables for each species in our analysis. We obtained the mean, minimum, and maximum annual temperature (°C), and annual precipitation sum (mm) from an open dataset CLIMBER (Climatic niche characteristics of the butterflies in Europe) and averaged each variable across each species’ distribution (data from 1971 to 2000) (Schweiger et al. 2014). The other five climatic variables, namely solar irradiation (kJ m-2 day-1), isothermality, temperature seasonality, precipitation seasonality, and water vapour pressure (kPa) were compiled for every 50 km using WorldClim data (Fick & Hijmans 2017) (data from 1970 to 2000) and averaged over all years and across species’ range.