Climate links leaf shape variation and functional strategies in quinoa's wild ancestor.

Understanding how leaf morphology mediates plant responses to environmental variability is critical for predicting species adaptability under climate change. This study examines whether intraspecific variation in leaf shape among Chenopodium hircinum populations is linked to physiological and functional trait differences and whether such variation reflects adaptive responses to source climate. We cultivated 11 populations of C. hircinum from diverse climatic origins in a common garden experiment. Leaf shape was quantified using descriptors (aspect ratio, circularity, solidity), landmarks, and Elliptical Fourier Descriptors. Physiological traits (stomatal conductance, leaf temperature, chlorophyll content) and functional traits (leaf area, leaf dry weight and leaf mass per area) were measured and analysed in relation to shape and environmental data. Leaf morphology varied significantly among populations and was associated with climatic conditions at origin, especially mean summer temperature. Functional and physiological traits were not directly correlated with environmental variables but showed strong associations with leaf shape. Landmark-based PC2 (lobed vs. rounded forms) and aspect ratio emerged as key predictors of trait variation. Most trait variation occurred at the individual level rather than among populations. Our findings highlight leaf shape as a central mediator linking environmental heterogeneity to physiological function. This suggests that morphology-driven trait integration may enhance adaptability in C. hircinum. Intraspecific diversity in shape and associated traits could serve as a reservoir of resilience under climate change, reinforcing the evolutionary and applied significance of wild relatives in crop improvement.