The 102nd annual meeting’s theme is focused on “how biodiversity is the foundation for many ecosystem services, how ecosystem functioning can translate into ecosystem services, and the role different dimensions of biodiversity play in developing such understanding.” Our proposed symposium is aimed at addressing the role that an important, yet often overlooked, dimension of biodiversity – species dominance – plays in determining ecosystem function and services. A fundamental pattern in ecology is that species vary in their abundances, with even the most diverse communities containing only a few, common (dominant) species and many rare species. Theory predicts this pattern has important implications for ecosystem functioning and services. Indeed, the mass ratio hypothesis predicts that dominant species, as a consequence of their high abundance, will have large impacts ecosystem functions and services, and there is growing empirical support for this hypothesis in a number of ecosystems. Yet, much of the research to date has focused on another aspect of biodiversity – species richness – with much debate surrounding the importance of this aspect of biodiversity in driving ecosystem functioning and services in natural ecosystems. The proposed session will provide an overview of current state of understanding of the role of dominant species in determining ecosystem functioning and services from the genetic to landscapes scales, contrast dominant species with another, highly recognized dimension of biodiversity – species richness, and explore how dominant species are a key way to link biodiversity to ecosystem functioning and services across scales.