Both inter- and intra-specific diversity can have significant ecological and evolutionary effects on population, community, and ecosystem processes. While the majority of empirical studies manipulate the number of species within a community or the number of genotypes within a population, recent research suggests that the phylogenetic relatedness of species and the genetic relatedness of genotypes may be important predictors of population dynamics, community interactions, and ecosystem function. Building on the interesting parallels between these metrics of diversity and their effects on ecological and evolutionary dynamics, the proposed symposium will highlight important commonalities between genetic and phylogenetic relatedness, as well as identify key differences between the mechanisms underlying their effects at the intra- and inter-specific levels. To facilitate synthesis, we will include speakers studying species with diverse life history strategies from a wide range of aquatic and terrestrial systems. Phenotypic and functional trait variation will also be considered within the context of genetic and phylogenetic relatedness, exploring a potentially valuable mechanistic link between ecological and evolutionary processes operating at the intra- and inter-specific levels in diverse ecosystems.