Statistical analyses
We used linear mixed models (LMM), as in Dawson et al. (2017), which
arguably is the commonest approach used in ecology and evolution (Table
S1). We used RF and HP as alternative techniques to estimate measures of
relative variable importance. The three techniques followed designs
similar to the mixed models in Dawson et al. (2017) to facilitate
comparisons among methods. For the HP and LMM (but not in RF because the
outcome is invariant to log transformation; Breiman, 2001), we
log-transformed the region area, and the relative and absolute measures
of economy and population, and we used a square-root transformation for
precipitation to satisfy assumptions of linearity, normality of
residuals and homoscedasticity and to have the same LMMs as in Dawson et
al. (2017).