Growth and trait covariations across 100 olive (Olea europaea L.) varieties: phenotypic structure depends more on the identity of varieties than on their genetic and geographic origins

Understanding how traits covary and influence growth is key to understanding adaptation in perennial species. In the Mediterranean olive tree (Olea europaea L.), both genetic background and geographical origin may shape trait variability, covariation patterns, and growth strategies, however these relationships remain largely unexplored. We analysed 100 olive varieties, representing four genetic groups and two geographical origins (North vs. South Mediterranean), by measuring eleven morpho-anatomical and physiological traits, and two growth indicators. We combined multivariate analyses, correlation networks, and regression models to explore trait covariation and its impact on growth. Our findings show that trait variation was primarily structured at the varietal level, while both genetic groups and geographic origin significantly shaped covariation patterns and functional integration, with southern-origin varieties tending to exhibit thicker and denser leaves. Trait networks revealed a robust coordination between leaf and stem structural traits, with modularity and connectivity varying across groups. The South group exhibited a more modular network, suggesting more constrained trait integration under arid conditions. At both stem and whole-plant levels, growth was positively associated with leaf area. In contrast, LDMC showed a positive relationship with stem diameter growth but a negative relationship with whole-plant growth, suggesting that different mechanisms underlie short-term stem expansion and long term cumulative growth. Overall, genetic factors, environmental context, and trait coordination jointly structure olive phenotypic diversity. These findings provide a functional framework for guiding the selection and conservation of olive varieties with growth strategies suited to current and future Mediterranean climates.