Adaptive parental effects: the importance of estimating environmental predictability and offspring fitness appropriately

Anticipatory parental effects (APE's) occur when parents adjust the phenotype of their offspring to match the local environment, so as to increase the fitness of both parents and offspring. APE's, as in the evolution of adaptive phenotypic plasticity more generally, are predicated on the idea that the parental environment is a reliable predictor of the offspring environment. Most studies on APE's fail to explicitly consider environmental predictability so risk searching for APE's under circumstances where they are unlikely to occur. This failure is perhaps one of the major reasons for mixed evidence for APE's in a recent meta-analysis. Here, we highlight some often-overlooked assumptions in studies of APE's and provide a framework for identifying and testing APE's. Our review highlights the importance of measuring environmental predictability, outlines the minimal requirements for experimental designs, explains the important differences between relative and absolute measures of offspring fitness, and highlights some potential issues in assigning components of offspring fitness to parental fitness. Our recommendations should result in more targeted and effective tests of APE's.