Table 1 . Comparison between the results of linear mixed models and of hierarchical partitioning in explaining the alien species richness of plants and birds. The variables incorporated in the model were the same as Dawson et al. (2017), but islands have been excluded from the analyses here. Significant P values (P < 0.05) are bolded. *** indicates P < 0.001. See the results for the other taxonomic groups in the Supporting information. The marginal and conditional R 2for mixed models are given in parentheses; the equivalent “total” for hierarchical partitioning is also given. GDPc: Gross Domestic Product per capita, and HPD: Human Population Density.