Colour pattern variation can inform about extinction risk in moths

Theory posits that species with inter-individual variation in colour patterns should be less vulnerable to extinction, compared with species that do not vary in colour. To evaluate this prediction, we explored whether differences in colour pattern diversity was associated with extinction risk, using red-list status for more than 350 species of noctuid moths in Sweden. We also evaluated six other species characteristics that have been proposed to influence extinction risk namely: host plant niche breadth, habitat type, area of occupancy, body size, overwintering life-history stage and length of flight activity period. We found that species with variable colour patterns had reduced extinction risk overall compared with species having non-variable colour patterns, and that this difference was pronounced more strongly among species having smaller areas of occupancy. There were also significant associations with host plant niche breadth and habitat type, extinction risk being lower on average in polyphagous species and in generalist species that occupied different habitat types. These findings represent the first evidence for insects that variable colouration is associated with reduced extinction risks. Information on colour pattern variation is readily available for many taxa and may be used as a cost-effective proxy for endangerment in the work of halting national and global biodiversity loss.