Phenotypic plasticity can lead to rapid and important changes of trait distributions depending on environmental conditions, with important consequences for population dynamics, species interactions and adaptation. To better understand the evolution and importance of plasticity, we need to improve our ability to quantify and compare phenotypic plasticity among organisms, and estimate the evolutionary potential of plastic capacity. Plasticity is classically quantified through regression slopes, with units of traits per environment that by definition vary across organisms, traits and studies, and makes complex the comparison of how does plasticity vary across biological units, especially when linear versus quadratic reaction norms are considered. A clear methodology to quantify phenotypic plasticity in a way that allow for comparison across traits, organisms and environments is lacking.

In this contribution, Pierre de Villemereuil and Luis-Miguel Chevin clarify key concepts about variability and evolutionary potential of plasticity, and propose an efficient method to partition phenotypic variance between genotype and environment. Expanding from the classical (too) simple regression slope approach, and directly integrating the genetic variability of plasticity, they provide a clear framework to quantify the part of phenotypic variance resulting from phenotypic plasticity, integrate the role of the shape of reaction norms, and estimate the heritable variation of trait plasticity. They integrate this method in a R package named Reacnorm, with step by step decision tree, that should greatly help the applicability of this framework.

The authors here propose a contribution that simultaneously clarify key concepts and challenges about plasticity and reaction norms, being very interesting on the theoretical side, and is directly and quite simply applicable to any trait and organism. This should help and stimulate comparative studies of how does plasticity vary across traits, organisms and environmental contexts, both using already published datasets and through new experiments.

References

Pierre de Villemereuil, Luis-Miguel Chevin (2025) Partitioning the phenotypic and genetic variances of reaction norms. EcoEvorxiv, ver.4 peer-reviewed and recommended by PCI Evol Biol https://doi.org/10.32942/X2NC8B