Artificial Selection Optimizes Clonality in Chaya (Cnidoscolus Aconitifolius)

Abstract In angiosperms, clonality is a derived trait and is present in several wild and cultivated plant species. Therefore, over time, natural and artificial selection have optimized the novel function of being a propagule in organs whose previous function was exclusively vegetative. Although increased resource storage and resistance to desiccation have been suggested as the main adaptations for clonality in crops, there is little empirical evidence to support this assertion. Here, I assessed the changes that the stems of chaya (Cnidoscolus aconitifolius), a clonal crop, have undergone through domestication and evaluated their performance as propagules. To infer which traits have been optimized by artificial selection, I compared stem traits and their performance in root development and clone survival between wild and domesticated plants. I found that, relative to their wild ancestors, the stems of domesticated chaya have a greater storage capacity for water and starch. Additionally, the stems of domesticated plants produced more roots, shoots and leaves, and their clones lived longer. My results strongly suggest that artificial selection has optimized water and starch storage by stems in chaya. Because these traits also confer greater fitness, they could be considered adaptations to clonal propagation.