One of the fundamental goals of ecology is to uncover the processes controlling the patterns of diversity and abundance that we observe in nature. How does diversity emerge, and how is it maintained? The EECRG seeks to develop empirical approaches that test and quantify the relative importance of different potentially important processes, such as dispersal and other neutral processes versus niche processes. Important insights can be gained from looking across traditionally distinct disciplines; today we are, for example, seeing convergent discussions on these issues in macroecology, metacommunity theory, and microbial biogeography. We approach these fundamental questions at a broad range of spatial and temporal scales, from centimetres to continents and from snapshots to millennia.