One of the important goals in plant ecology is to form a mechanistic link between the underlying processes driving the dynamics and structure of communities and the observed demography (i.e., growth, survival, and recruitment) and assembly (i.e., distribution of species) in a community via traits. Although the importance of traits to performance is evident, their direct links to demography and the resulting assembly in tree communities are often found to be fairly weak probably because a single "mean" trait value for a species is not enough to capture complex life histories. In this paper, we review how traits at the organ‐level and at the whole plant level, demography, and assembly change with size in diverse tropical forests and summarize what know so far. We argue the importance of trait‐based life‐history strategies revealing trait‐environment‐demography linkages across ontogenetic stages to achieve the ultimate goal of forming a mechanistic link between the underlying processes driving the dynamics and structure of communities and the observed demography and assembly. [ABSTRACT FROM AUTHOR]