Abstract Disentangling mechanisms shaping species richness is fundamental to understanding how biodiversity is structured across geography. The latitudinal diversity gradient (LDG) is a classic pattern in which the tropics harbour the greatest number of species. Patterns deviating from the classic LDG, such as an inverse gradient in which diversity is higher towards the poles, have been considered exceptions and attributed to taxon-specific causes rather than to general processes. Here, we evalu