Ecology and evolution of mimicry in coral reef fishes

This review examines the literature on mimicry in coral reef fishes and evaluates the prevalence of mimicry in different taxa, its ecological consequences and postulated modes of evolution. Mimicry appears to be a widespread and common phenomenon in coral reef fishes, with approximately 60 reported cases. Although many are largely anecdotal accounts based on colour resemblance, recent quantitative comparisons and experimental manipulations have confirmed that many do represent mimic-model relationships. The distribution of mimics and models among reef fish families appears largely serendipitous. Mimics are most common in the families Blenniidae, Serranidae and Apogonidae and models in the families Pomacentridae, Blenniidae and Labridae. Mimics and model species usually represent less than 10% of species within families, although imperfect forms of mimicry are likely to have been underestimated. Mimicry appears to be particularly important during juvenile stages, with 28% of mimic species losing their mimic colouration when they outgrow their models. All cases of mimicry support predictions that mimics are rare relative to their models. Furthermore, the abundance of mimics in different areas may increase in proportion to model abundance. The spatial distribution of mimics appears to be limited by that of their model species, although some change models in different habitats or in different parts of their range. Many mimics live in close association with their models, and both foraging advantages and predator avoidance have been experimentally demonstrated. Aggressive mimicry appears to be the most prevalent type of mimicry overall in coral reef fishes, constituting 48% of all cases reported to date, followed by Batesian (40%) and social mimicry (12%). Mullerian mimicry seems to be rare, although it may contribute to the mimetic complexes involving members of the blenniid tribe Nemophini. However, these traditional classifications are too simplistic for reef fishes because both foraging advantages and predator avoidance can apply in a single mimetic relationship, and their relative importance has not been evaluated. Preliminary data suggest a high degree of phenotypic plasticity in mimetic colouration and little genetic differentiation among different mimics of the same species. Overall, the review highlights the many significant steps that need to be taken towards a more complete understanding of the ecological and evolutionary significance of mimicry in coral reef fishes.