Ecomorphological convergence in planktivorous surgeonfishes

Morphological convergence plays a central role in the study of evolution. Often induced by shared ecological specialization, homoplasy hints at underlying selective pressures and adaptive constraints that deterministically shape the diversification of life. Though midwater zooplanktivory has arisen in adult surgeonfishes (family Acanthuridae) at least four independent times, it represents a clearly specialized state, requiring the capacity to swiftly swim in midwater locating and sucking small prey items. While this diet has commonly been associated with specific functional adaptations in fishes, acanthurids present an interesting case study as all other species feed by grazing on benthic algae and detritus, requiring a vastly different functional morphology that emphasizes biting behaviors. We examined the feeding morphology in 30 acanthurid species and, combined with a pre-existing phylogenetic tree, compared the fit of evolutionary models across two diet regimes: zooplanktivores and ...