Visual environment shapes the social dynamics of coloration and competition in an African cichlid fish

An animal's ability to adapt to a changing environment often requires the coordination of various traits. Across these traits, many covary with one another to generate a diversity of complex phenomes tuned to a given ecology. While many reports have documented trait covariation in populations, less is known about how plastic traits co-vary to facilitate adaptation in an individual. In African cichlids, morphology and behavior are two hallmarks driving the adaptive speciation of lineages within the East African Great Lakes. Here, we leveraged social rank and body coloration as plastic model traits to understand the interactions shaping male competition in the African cichlid Astatotilapia burtoni. Addressing the need to disentangle the influence of environmental adaptation on color morphology from that of social dynamics, we conducted experiments rearing cichlids in visually distinct environments using blue and yellow gravel substrates to induce blue/yellow color morphs. Our results demonstrate that the visual environment significantly influences the emergence of male color morphs: yellow territorial males were more prevalent on brown gravel, whereas blue males predominantly appeared in blue backgrounds. Contrary to previous reports, we found that blue males consistently outcompete yellow males in direct contests. Furthermore, behavioral patterns changed over time, with blue males adjusting their aggression strategies based on their visual environment, while yellow males exhibited a higher propensity to flee. These findings indicate that animal coloration and behavior are plastic traits that interact to shape male competition and behavioral ecology. This study provides new insights into the dynamics of phenotypic plasticity, adaptive strategies in fluctuating environments and trait covariation.