Intraspecific Variability in Leaf Functional Traits Reveals Divergent Resource-Use Strategies and Geographic Adaptation in Mediterranean Olive Cultivars from Worldwide Olive Germplasm Bank of Marrakech

Abstract

Understanding intraspecific functional trait variability (ITV) is crucial for elucidating plant functional strategies under environmental change. This study investigates the functional responses of 129 Mediterranean olive (<i>Olea europaea</i> L.) cultivars conserved in the Worldwide Olive Germplasm Bank of Marrakech (WOGBM), focusing on three key leaf traits: specific leaf area (SLA), specific leaf water content (SLWC), and leaf area (LA). Substantial ITV was observed, with variability predominantly driven by cultivar differences and geographic origin. LA accounted for the highest within-cultivar variability (43.60%), followed by SLWC (31.67%) and SLA (17.92%). Geographic origin significantly influenced trait expression, with eastern Mediterranean cultivars exhibiting conservative resource-use strategies (high SLWC, low SLA, and LA), while western cultivars displayed acquisitive strategies (high SLA and LA, low SLWC). Principal component analysis further differentiated eastern and western cultivars, reflecting biogeographical and evolutionary influences. The relationship between LA and climatic variables suggests climate-driven selection, where cultivars from wetter regions develop larger leaves to optimize light capture and carbon assimilation, whereas those from drier environments exhibit smaller leaves to reduce water loss. These findings highlight a trade-off between resource acquisition and conservation, supporting the leaf economic spectrum at the intraspecific level. This study underscores the importance of ITV in olive diversification and adaptation, providing insights for breeding, conservation, and climate resilience. A trait-based approach proves valuable for exploring domestication processes and plant responses to environmental gradients.