Predator‐induced phenotypic plasticity in tadpoles: extension or innovation?

Abstract Phenotypic plasticity, the ability of a trait to change as a function of the environment, is central to many ideas in evolutionary biology. A special case of phenotypic plasticity observed in many organisms is mediated by their natural predators. Here, we used a predator–prey system of dragonfly larvae and tadpoles to determine if predator‐mediated phenotypic plasticity provides a novel way of surviving in the presence of predators (an innovation) or if it represents a simple extension of the way noninduced tadpoles survive predation. Tadpoles of Limnodynastes peronii were raised in the presence and absence of predation, which then entered a survival experiment. Induced morphological traits, primarily tail height and tail muscle height, were found to be under selection, indicating that predator‐mediated phenotypic plasticity may be adaptive. Although predator‐induced animals survived better, the multivariate linear selection gradients were similar between the two tadpole groups, suggesting that predator‐mediated phenotypic plasticity is an extension of existing survival strategies. In addition, nonlinear selection gradients indicated a cost of predator‐induced plasticity that may limit the ability of phenotypic plasticity to enhance survival in the presence of predators.