Data and R codes for Competition induces higher intraspecific trait variability in inferior than in superior tree species.

Theory suggests that intraspecific trait variability may promote species coexistence when competitively inferior species have higher intraspecific trait variability than their superior competitors. Here, we provide empirical evidence for this phenomenon in tree seedlings. We evaluate intraspecific variability and plastic response of ten traits in 6750 seedlings of ten species in a three-year greenhouse experiment. While we observe no relationship between intraspecific trait variability and species competitiveness in competition-free homogeneous environments, an inverse relationship emerges under interspecific competition and in spatially heterogeneous environments. We show that this relationship is driven by the plastic response of the competitively inferior species: compared to their competitively superior counterparts, they exhibit a greater increase in trait variability, particularly in fine-root traits, in response to competition, environmental heterogeneity and their combination. Our findings contribute to understanding how interspecific competition and intraspecific trait variability together structure plant communities.