Experimenting with domestication: Understanding macro- and micro-phenotypes and developmental plasticity in teosinte in its ancestral pleistocene and early holocene environments
Living representatives of the wild progenitors of domesticated species constitute a significant basis for morphological and genetic study of once ancestral plants and their early domesticated forms. However, plants, in part through phenotypic (developmental) plasticity, are well-known to directly respond to environmental changes creating phenotypic variability and new morphologies. Therefore, how the wild progenitors of domesticated species and their proto-crops may have responded to Late Pleistocene (LP) and early Holocene (EH) climatic conditions are important, yet little-studied issues. We grew the wild ancestor of maize, Zea mays ssp. parviglumis (Iltis&Doebley), and maize in the lower atmospheric CO2 and temperature characteristic of their ancestral LP and EH environments and studied key macro- and micro-traits important in the domestication process. Teosinte responded with some remarkable phenotypic changes including in key morphological traits in plant architecture, inflorescence sexuality, seed dormancy, and grain nakedness previously thought to be a result of domestication. An artificial selection experiment carried out on plastic maize-like traits in teosinte demonstrated their stability across generations that would have enabled early cultivators to cement the traits in all environments, as in modern maize. Our results arguably provide more faithful replicas of what the first teosinte collectors and cultivators exploited, and point to an alternative pathway to maize domestication not heretofore demonstrated in a crop plant. They demonstrate how experimental research informs current questions in domestication research and evolutionary biology more generally, while raising others that had not previously drawn attention.
