Global gradients in intraspecific variation in vegetative and floral traits are partially associated with climate and species richness

Aim Intraspecific trait variation (ITV) can be large within natural plant communities, influencing local ecological processes and dynamics. Here, we shed light on how ITV in vegetative and floral traits responds to large-scale abiotic and biotic gradients (i.e. climate and species richness). Specifically, we tested if associations of ITV with temperature, precipitation and species richness reflect the predicted patterns of four hypotheses relating to stress-tolerance and competition. Furthermore, we estimate the degree of correlation between ITV in vegetative and floral traits and how it varies along the gradients. Location Global. Time period 1975-2016. Major taxa studied Herbaceous and woody plants. Methods We compiled a dataset of 18,112 measurements of the absolute extent of ITV (measured as coefficient of variation) in nine vegetative and seven floral traits from 2,774 herbaceous and woody species at 2,306 locations. Results Large-scale associations between the absolute extent of ITV and climate were trait-specific and more prominent for vegetative traits, especially leaf morphology, than for floral traits. Climate showed pronounced associations with ITV, with lower ITV values in colder areas and higher values in drier areas. The associations of species richness with ITV were inconsistent across traits. Species-specific associations across gradients were often idiosyncratic and covariation in ITV was weaker between vegetative and floral traits than within the two trait groups. Main conclusions Our results show that, depending on the traits considered, ITV either increased or decreased with climate stress and species richness, suggesting that both factors can constrain or enhance ITV, which might foster plant populations’ persistence under stressful conditions. Given the species-specific responses and covariation in ITV, associations can be hard to predict for traits and species not yet studied. We conclude that considering ITV can improve our understanding of how plants cope with stressful conditions and environmental change across spatial and biological scales.