Leaf shape of quinoa’s wild ancestor <i>Chenopodium hircinum</i> (Amaranthaceae) in a geographic context

Abstract Intraspecific variation in plant traits, such as leaf morphology, offers insights into local adaptation and the ecological niche breadth of species. Chenopodium hircinum, the wild ancestor of quinoa, is widely distributed across various ecoregions in Argentina. A detailed comparative analysis of leaf morphology across 23 populations covering its entire known distribution was conducted to understand patterns of intraspecific variation along geographic gradients. A total of 104 leaves from these populations were analysed using shape, landmarks, and Fourier descriptors. Significant variability in leaf shapes was observed across all ecoregions, with notable admixture among populations. Although landmark-based and Fourier analyses differentiated populations, shape descriptors added intricacy to identification. Leaf morphology ranged from rounded and toothed to sharply lobed, with lobes primarily located at the base or middle of the leaf. Key environmental factors influencing leaf shape were mean annual temperature (MAT) and altitude. The study suggests that leaf shape variability in C. hircinum extends beyond a simple lobed vs. entire dichotomy. Leaf morphology and margin traits are primarily governed by the relative position of the lobes, which correlate strongly with MAT at the population’s origin. This convergence across ecoregions highlights the need to explore the functional significance of this variation further.