Analyses of literature and own data
We analyzed the decrease and regrowth values of braincase height, brain mass, and body mass from all populations of S. araneus collected from the literature and the two new populations (Gugny and Žofín). To explore geographical trends in the decrease and/or regrowth of braincase height we fit two sets of four linear models using percentage of decrease (in the first set of models) or regrowth (in the second set) as response variable and a single dependent variable: longitude, latitude, altitude, or the interaction latitude X longitude. We fit the same sets of linear models for brain mass and body mass. Additionally, we used this same approach to analyze the geographical variation in overall size (braincase height, brain mass and body mass) in each of the age stages (juveniles, winter subadults and adults). Similarly, we fit linear models for these response variables with each of the climate variables.