LAUSR

BACKGROUND AND AIMS Intraspecific variability in leaf water-related traits remains little explored despite its possible importance in the context of increasing drought frequency and severity. Studies comparing intra- and inter-specific variability of leaf traits often rely on unappropriate sampling designs that result in non-robust estimates, mainly due to an excess of the species/individual ratio in community ecology, or on the contrary to an excess of the individual/species ratio in population ecology. METHODS We virtually tested three strategies to compare intra- and interspecific trait variability. Guided by the results of our simulations, we carried out a field sampling. We measured 9 traits related to leaf water and carbon acquisition in 100 individuals from 10 neotropical tree species. We also assessed trait variation among leaves within individuals and among measurements within leaves to control for sources of intraspecific trait variability. KEY RESULTS The most robust sampling based on the same number of species and individuals per species revealed higher intraspecific variability than previously recognized, higher for carbon related traits (47-92% & 4-33% of relative and absolute variation resp.) than for water related traits (47-60% & 14-44% of relative and absolute variation resp.), which remained non negligible. Nevertheless, part of the intraspecific trait variability was explained by leaves variation within individuals (12-100% of relative variation) or measurements variations within leaf (0-19% of relative variation) and not only by individual ontogenetic stages and environmental conditions. CONCLUSIONS We conclude that robust samplings based on the same number of species and individuals per species are needed to explore global or local variation in leaf water and carbon related traits within and among tree species, since our study revealed higher intraspecific variation than previously recognized.