Predicted number of bumblebee species, derived from the sum of each species presence maps. Presence was defined for each species using an individual threshold applied to the predicted probability of occurrence (see main text for details). Values above the threshold were set to 'presence' (1) and values below it to 'absence' (0). The sum of 'presences' indicate, for each locality on the map, the number of bumblebee species potentially present, i.e. the potential species richness.