UV-B radiation limits tropical colour diversity in ants

Summary This repository contains the data and the codes used to analyse global patterns of colour diversity in ants in this research paper "XX et al., 2026 - UV-B radiation limits tropical colour diversity in ants. in prep" Abstract The long-standing hypothesis that life is more colourful in the tropics is well supported in birds but remains largely untested in other taxa. Using 34,331 images of 10,400 ant species, we quantified assemblage-level colour diversity across the colour space of ants. Contrary to expectations, colour diversity did not peak in the tropics. Rather, it was highest outside the equatorial zone, after controlling for species richness and phylogeny. Decomposing ant colour variation into two axes, we found that higher UV-B was associated with reduced colour diversity, compressing the phenotypic range, darkening the palest and darkest species and fading red extremes. In contrast, maximum temperature and elevation increased redness, intensifying the colour of the reddest species. These results suggest that UV-B exposure constrains ant colour diversity, preventing a tropical peak, consistent with protective cuticle darkening and the loss of phototoxic red phenotypes under high UV-B, and revealing clade-specific latitudinal patterns.