Farmer-mediated shifts in drought tolerance traits across an aridity gradient in an indigenous food security crop

Increased drought stress resulting from climate change poses a significant threat to global food security, requiring crop adaptations. Indigenous knowledge and sustainable practices in drought-prone agricultural systems may offer climate adaptation strategies. This study investigates the functional traits that may be associated with reported drought tolerance in enset (Ensete ventricosum), an indigenous Ethiopian staple crop that supports more than 20 million people. Through field surveys and farmer interviews along three aridity gradients in southwest Ethiopia, we determine how domestication and current farmer cultivation choices have shaped enset trait and landrace diversity. We measured 13 morphological and physiological traits of 430 cultivated enset plants on farms and a subset of traits of 30 wild enset plants. We demonstrate for the first time that domestication led to a reduced trait variance and altered trait means in cultivated enset and to lower landrace diversity in arid environments. Farmers in arid areas chose landraces with drought tolerance traits, resulting in trait differentiation between wetter and drier farms. Cultivated enset exhibited a lower stomatal density and a narrower aridity niche compared to wild enset, suggesting an adaptation to reduce water loss and improve water use efficiency. We also found significantly increased leaf wax coverage, leaf number, leaf temperature differential and plant height growth rate and significantly reduced stomatal conductance on drier compared to wetter farms. Field interviews revealed farmers’ knowledge of climatic history and drought tolerance traits, which guided their selection of drought tolerant landraces. Overall, our study underscores the impact of domestication and environmental filtering on drought tolerance traits, illustrating the climate adaptation mechanisms of indigenous farming systems.