Burrowing Behavior and Species Recognition Predict Color Pattern Evolution in Freshwater Crayfishes

Color patterns are the spatial arrangements of contrasting colors on an organism's body and can have several non-mutually exclusive functions, including crypsis, species recognition, or as a warning display. Here, I test how color patterns correspond to ecological and morphological factors across 393 freshwater crayfish species. Using a time-calibrated phylogeny and phylogenetic logistic regression, I examined whether body size, congeneric sympatry, or burrowing behavior predict the presence of color patterning. The best-supported model included additive effects of burrowing ecology and congeneric sympatry, but not body size. Patterned coloration was 7.3 times more likely in aquatic species compared to semi-terrestrial species, consistent with the hypothesis that increased exposure to visually oriented predators correlates to the presence of cryptic color patterns. Patterning also increased with the number of sympatric congeners, suggesting a role in species recognition. The best fit model exhibited weak phylogenetic signal, indicating that the relationship between patterning and the ecological predictors were not strongly influenced by shared ancestry. Together, these results suggest that predation pressure and social interactions jointly drive the diversification of color patterns in crayfishes.