<b>Unveiling diversity-function relationships from the traits of individuals</b>

Niche theory challenges the idea that locally, species-rich communities always exhibit the highest functional diversity. As species richness increases, the traits of individuals can pack closer in the functional space, decoupling individual-level functional diversity from species richness. Hence, diversity–function relationships at species and individual levels may differ significantly. However, as the diversity among individuals in communities is overlooked, testing of these ideas remains lacking. Studying invertebrate detritivore communities in forested streams at an individual trait resolution, we observed a decoupling between functional richness at interspecific and individual levels. Individual-based functional richness enhanced litter shredding rate, whereas species-based richness did not. Trait packing increased with species richness, probably increasing competition or reducing complementarity. With a trait-based simulation, we corroborated our empirical results. Diversity at the individual level must be taken into account in order to better understand the links between diversity and ecosystem processes and the possibilities for their conservation.