Based on GPS coordinates, we estimated the potential distribution of the species in Europe using the hypervolume package in R (R Development Core Team 2008; Blonder et al. 2014; Blonder 2015). We used 19 gridded bioclimatic variables with a spatial resolution of 2.5 arc min (approximately 4 km within Europe) representing average climate conditions between 1950 and 2000 from the WorldClim database (Hijmans et al. 2005). These 19 variables were transformed into four principal components with eigenvalues >1, which were used as orthogonal niche axes to compute the hypervolumes (for factor loadings, see Fig. S2).