Understanding the processes that shape ecological communities is one of the main goals of ecology. Multiple dynamic models of ecological communities have been developed, but they are typically tested by examining static patterns such as Species Abundance Distributions. Much less is known about the ability of these theories to explain the actual dynamics that are observed in ecological communities.

I focused on the two most minimalistic models of community dynamics, the Neutral Theory of Biodiversity (NTB) and Dynamic Equilibrium theory (DE). For both theories, I asked: 1) can the model explain observed patterns of community dynamics? 2) if not, what processes need to be added to explain community dynamics?

I have found that the magnitude of changes in abundances and species composition in the Barro Colorado Island forest community is considerably larger than expected under NTB. However, incorporating environmental fluctuations into the theory allows explaining patterns of richness, commonness and rarity, and dynamics in that forest. In my work on DE, I have used a novel methodology to show that both the assumptions and the predictions of the theory are violated in thousands of communities worldwide. I have found that there are larger temporal changes in species richness than expected, which are associated with a positive covariance between species, representing the shared response to environmental changes.

Overall, while most previous work in community ecology has emphasized the role of competition in shaping ecological communities, my results demonstrate the crucial role of environmental changes as a driver of community assembly.