Evolution under domestication triggers widespread deviation to the coat versus kernel mass allometry in seeds

Abstract

This study investigates the impacts of domestication and crop improvement on seed coat and kernel mass allocation. I ask if and how evolution under cultivation deviates seeds from the allometric allocation of mass between the coat and the kernel observed in wild plants. Using data from 20 crops, including their wild relatives, early domesticates, and improved varieties, I analyzed changes in seed traits across different stages of crop evolution. Results revealed that domestication generally leads to very flat kernel-to-coat allometric slopes. This means that, as crop seeds get larger in size during domestication, kernels enlarge more rapidly than coats, and this imbalance happens more disproportionately than in wild plants. This indicates that selection during domestication can override natural allometric constraints. Crop improvement also affects seed coat allocation but with more variability and generally weaker effects than domestication. These results highlight the evolutionary flexibility of seed traits under cultivation. More broadly, this study provides new insights into how domestication and improvement have expanded the evolutionary pathways available to crops beyond those observed in wild plants.