Eyespot function in butterflyfishes (Chaetodontidae): comparing evidence for aposematism, automimicry, and predator mimicry

Abstract Many species of butterflyfish display false eyespots, but factors underlying eyespot diversity remain poorly understood. Eyespots are thought to function in predator avoidance, but there are multiple ways in which this might occur. An eyespot can function as deflection when distracting predators away from the true eye of the fish by mimicking it elsewhere on the body (automimicry). It can also function as intimidation, either by mimicking the appearance of predator eyes (predator mimicry) or by serving as a conspicuous warning to predators that the fish is spiny (warning coloration). Colour patterns that conceal the eye are common among butterflyfishes. Eye concealment is predicted under automimicry and can also occur in predator mimicry but is not predicted under warning coloration. Long median fin spines and deep bodies can make many species of butterflyfishes unpalatable, as predicted under intimidation. We adopt a comparative approach to examine relationships between eyespot presence, conspicuousness, and position on the body with eye coverage and physical defences, in order to evaluate evidence under the deflection vs. intimidation hypotheses within different trait complexes. Our results suggest that eyespots and eye coverage have evolved in conjunction with traits that facilitate predator evasion. We did not find evidence to support eyespots functioning as warning coloration for physical defences.