Background: Domestication-driven shifts to a relatively more acquisitive strategy and increased biomass allocation in plant organs have been demonstrated in some major crops. However, the extent to which this pattern is influenced by the relatively more resource-rich conditions prevailing in agroecosystems is less clear. Although soil is the main source of nutrients for plants, it remains unknown if the effect of domestication on resource-use strategy and biomass allocation patterns is contingent upon soil origin. Hypothesis: The effects of domestication and soil origin on the resource-use strategy and biomass allocation are not additive. Studied species Chaya (Cnidoscolus aconitifolius I.M. Johnst.). Methods: The effects of domestication (wild vs. domesticated plants) and soil origin (forest, homegardens, and intensive orchards) on leaf traits associated with the leaf economic spectrum and biomass allocation to above- and below-ground organs were assessed experimentally. Results: A domestication-driven shift to a relatively more acquisitive strategy was found. This effect was contingent upon soil origin. Domesticated plants reverted to a more conservative strategy when they were grown in forest soil. Increased biomass allocation and decoupling among different organs were observed in domesticated plants. Leaf production and the root:shoot ratio were also contingent upon soil origin, with greater values observed when domesticated chaya was grown in orchard soil. Conclusions: This study supports the existence of an intraspecific leaf economic spectrum in chaya. While domestication, as a main effect, tends to shift the resource-use strategy to the acquisitive side of the spectrum, this effect is clearly contingent upon the soil origin.

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.