Domestication Enhances the Plastic Response of Root Economic Traits to Soil Variation in the Perennial Crop Cnidoscolus aconitifolius

Domestication-driven shifts toward resource acquisition are well-documented above ground, but how it impacts belowground strategies remains controversial. Furthermore, the role of environmental variation and phenotypic plasticity in shaping root economic space traits has been largely neglected. Here, the effects of domestication, soil origin, and their interaction on four root economic traits (average root diameter, specific root length, root tissue density, and root nitrogen content) were experimentally assessed using wild and domesticated chaya (Cnidoscolus aconitifolius) grown in forest, home garden, and intensive orchard soils. Domestication did not trigger a unidirectional shift to more acquisitive roots, but significantly enhanced phenotypic plasticity across soils. Significant interactions for average root diameter and nitrogen content showed that domesticated plants exhibited variable, decoupled responses in agroecosystem soils, while domesticated and wild plants remained very similar in forest soils. Wild plants remained phenotypically canalized. Multivariate analysis revealed that expected trade-offs among traits and orthogonality between conservation and collaboration gradients were only partially met. In conclusion, belowground strategies in this perennial crop are reconfigured by domestication through increased phenotypic plasticity, allowing independent modulation of key root traits, particularly under nutrient-rich environments.