Figure 1. Predictions of how ant diversity could be influenced by environmental filtering and habitat connectivity. (a) The scenario in which environmental filtering is the dominant driver shaping beta diversity of ant assemblages across vertical and horizontal dimensions. In the vertical dimension, microclimate tends to change linearly with vertical height, and such changes are predicted to result in a linear relationship between vertical distance and beta diversity. In contrast, microclimate can vary non-linearly across horizontal space, in which case there should be no relationship between distance and beta diversity. (b) The scenario when habitat connectivity is the dominant factor in shaping beta diversity of ants across horizontal and vertical dimensions. Vertically, the habitat connectivity is high regardless of vertical distance, thus there is no effect of vertical distance on beta diversity, which remains low. Horizontally, habitat connectivity is likely to be low across trees and remain low across all distances, resulting in a lack of relationship between horizontal distance and beta diversity. However, due to lower habitat connectivity horizontally than vertically at comparable distances, the beta diversity of ants should be higher horizontally than vertically.