Phenotypic Plasticity Beyond Domestication: Trait- and Accession-Dependent Responses to Light in Capsicum annuum

Domestication may modify phenotypic plasticity by shifting plants from heterogeneous natural habitats to more uniform agricultural environments, potentially reducing environmental responsiveness. However, whether domestication consistently alters plasticity across traits, populations, and varieties remains unresolved. Here, we evaluated phenotypic plasticity to light availability in a crop–wild system of Capsicum annuum by comparing three wild populations and three domesticated accessions grown under full, moderate, and low light conditions (~1000, 565, and 160 µmol m−2 s−1, respectively). We quantified vegetative, physiological, and reproductive traits and assessed plasticity using hierarchical models, reaction norm slopes, and multivariate ordination. Light availability strongly influenced plant phenotype, but the effects of domestication were weak and not uniform across varieties and traits. Vegetative traits including leaf area, specific leaf area, leaf number, and leaf mass showed pronounced responses to light availability, whereas flowering-related traits were less consistently responsive. Low light induced the clearest multivariate phenotypic shift, characterized by larger and thinner leaves. However, these vegetative adjustments did not maintain reproductive performance. Fruit production remained relatively stable under medium light but declined sharply under severe shade. Together, our results show that domestication does not lead to a uniform reduction in phenotypic plasticity. Instead, plasticity in chili depends on the trait and on the population or variety evaluated and is expressed more strongly in vegetative than in reproductive components. These findings indicate that the biological consequences of plastic responses should be evaluated in relation to reproductive performance, not only vegetative adjustment.