The ecology and adaptive function of clownfish color patterns

Abstract

Anti-predator coloration strategies vary widely from conspicuous to cryptic, and everything between. Coloration serves multiple functions, and determining the selective pressures that drive this diversity is a long-standing mystery. Clownfishes display enormous inter- and intra-specific variation in coloration without the influence of sexual selection, providing an excellent system in which to explore these drivers in closely related and sympatric species. Across clownfishes, three color-pattern phenotypes have evolved convergently with host anemone use, implying adaptive functions linked to the hosts physical and chemical properties. Here we conducted a comprehensive study to infer the ultimate functions of clownfish color patterns. By integrating multiple levels of biological organization, including behavior, visual ecology, dietary niche, and microbiome, our data overwhelmingly indicate that specialist and generalist clownfish color patterns have different underlying ecologies and adaptive functions. Specialist clownfishes background match their anemones, remain near hosts, and have specialized diets and microbiomes. Generalists are highly contrasting with their anemones, remain far from hosts, and have variable diets and microbiomes. Taken together, specialist color patterns align with functional expectations of camouflage while generalists align with aposematic or disruptive coloration. Our study provides novel insights into how ecological conditions shape the evolution of multiple anti-predator coloration strategies.