Functional attributes as a tool for understanding the process of cereal and pulse domestication

This thesis has sought to identify the selective pressures, both natural and anthropogenic, that led to cereal and pulse domestication in the Early Neolithic using a functional ecological approach. This was achieved through the identification of functional traits, which enabled certain species to thrive in response to the ecological selection pressures attendant on the climatic constraints the Late Pleistocene/early Holocene transition and on those of the anthropogenic environment in which domestication arose. Those traits that would best capture plant responses to these selection pressures were chosen, and relate to resource acquisition (responses to fertility and disturbance) and water-use efficiency (drought tolerance). The traits used comprise leaf dry matter content, specific leaf area, leaf area:thickness, stomatal density and length, canopy height and diameter, and genome size. The analyses of plants grown in natural habitats and those grown under experimental conditions show that these traits are robust across varying environmental conditions.

The research presented here demonstrates that there are traits that consistently differentiate domesticated cereal and pea crops and their wild progenitors from other wild grasses and legumes that were not domesticated. This thesis also demonstrates that not all Neolithic crops have the same responses to fertile conditions and drought tolerance. Examination of the functional traits indicates that domesticated barley, einkorn, emmer and pea and their progenitors, were physiologically predisposed to have a competitive advantage over other wild grass and legume species under fertile and moist conditions. The climatic amelioration associated with the early Holocene, and the engineered habitats associated with early Neolithic settlements and cultivation, favoured the competitive wild progenitors of the Neolithic cereal and pea crops. This competitive advantage for resource acquisition under productive conditions may have continued to be a significant selection pressure in early crop evolution. Lentil and chickpea are less competitive, however, and chickpea is less sensitive to droughted conditions compared to the other Neolithic crops. Lentil and chickpea may have enabled less fertile areas to be productive under cultivation, and chickpea potentially provided a buffer against crop failure during episodes of drought, to which cereal and pea crops are more susceptible.