Intraindividual variation in light-related functional traits: magnitude and structure of leaf trait variability across global scales in Olea europaea trees

Abstract

Intraspecific variation in leaf functional traits can play a crucial role at multiple ecological scales. However, our understanding of leaf functional trait variation (FV) across spatial scales is limited. Moreover, the influence of FV in specific responses to the environment remains poorly assessed. We investigated FV across multiple nested ecological scales in a set of leaf traits related to light interception and photosynthetic performance in eight populations of Olea europaea trees distributed over a wide latitudinal gradient (~60°). Specifically, we measured SLA, leaf shape, leaf’s spatial position (leaf angles) and leaf’s potential exposure to direct sunlight (silhouette area of the leaf blade and silhouette to area ratio of the leaf blade). The variability in leaf traits revealed two main patterns depending on the considered trait. Differences among sites absorbed >50% of the trait variation related to leaf shape and structure. Conversely, traits related to leaf position and exposure to direct light varied mostly within individuals among crown positions. The variation within trees for multiple traits ranged from 4 to 14%. Trees of equatorial populations had wider, thinner and more exposed leaves to direct light than trees of the remaining populations. The FV for multiple leaf traits at the tree scale was spatially structured within the tree crown and was higher for populations at the equator than for populations located in other latitudes. The differences among traits and scales in the magnitude of FV revealed a complex structure that could be linked to local adaptation.