Results from models containing increasing numbers of explanatory variables, using both unstandardised population genetic diversity measures (Beta) and standardized genetic diversity (Z) as the response.

Explanatory variables are as follows: S = Species, M = genetic marker, L = latitude, L2 = latitude squared, R = IMCRA region, n = sample per population. DIC is the deviance information criterion, and delta represents the difference of a model’s DIC from the best model. PPP is the p value from our posterior predictive tests ([60]) derived from a comparison of the observed data with data generated from the model. Extreme probability values (e.g. p 0.95) indicate a contradiction of the model by the observed data [61]. DICw represents DIC weight calculated according to [58]. The best model from each analysis is indicated with an asterisk.