Morphological divergence between wild and cultivated chaya (Cnidoscolus aconitifolius) (Mill.) IM Johnst

Chaya (Cnidoscolus aconitifolius) (Mill.) I.M. Johnst is a neglected and underutilized crop, cultivated clonally by the Maya from pre-Hispanic times to the present in their home gardens for their own consumption. Like other crops in the early stages of domestication, cultivated chaya co-occurs with its wild relatives, however, the degree of domestication of chaya is unclear. Wild and cultivated chaya exhibit some morphological differences, however, no study has assessed quantitatively the degree of divergence between these varieties. The main objective of this study was to assess the domestication degree of chaya, by measuring morphological divergence in vegetative traits (leaf number, area, toughness, trichome number, as well as plant size, number of branches and trunk width) in wild and cultivated plants. Our results show that cultivated and wild plants had only a minor degree of overlap in the multivariate morphological space. The cultivated variety had more branches and leaves, and their leaves were softer and had fewer trichomes than the wild variety. This divergence is probably reinforced by the fact that desirable traits (number of branches and leaves) are negatively correlated with undesired traits (number of trichomes and toughness). Despite significant divergences between the two varieties, a few cultivated plants fell within phenotypic range of variation for wild plants, which could be due to recent artificial selection.