Phenotypic Plasticity in Arabidopsis thaliana Is Fitness‐Neutral, and Costs Are Lacking Across Experimental Environments

ABSTRACT Phenotypic plasticity produces multiple phenotypes depending on the environment, and its evolutionary trajectory is determined by the fitness consequences of those phenotypes. Adaptive plasticity in traits would reduce plasticity in fitness across the range of environments experienced by a species. However, it is unclear how often plasticity is adaptive, neutral, or maladaptive. Here, we quantified plasticity in Arabidopsis thaliana across multiple environments, asking whether accessions with high plasticity across eight traits have low plasticity in seed output. In addition, we examine if phenotypic plasticity is adaptive, neutral, or maladaptive and test for costs of plasticity. We found no significant relationships between trait plasticity and either seed output or plasticity in seed output, indicating that plasticity is neutral for the traits and environments examined. We also found no evidence of costs of plasticity. We found that plants that exhibit plasticity in the number of rosette leaves when fertilized had higher seed output under control conditions. Given that phenotypic plasticity in the number of rosette leaves is present in accessions with high seed output, phenotypic plasticity in this trait may be affiliated with other traits under strong selection rather than under direct selection itself. Results of this study contribute to our understanding of the frequency of neutral plasticity.