COS 141-5
The effect of species interactions on community stability varies with diversity and dispersal rate
The variation in community composition over time can result from a variety of processes, including environmental variation, species interactions, dispersal, and stochastic events. In most communities these processes occur simultaneously, making it difficult to identify the relative importance of any single process on its own. Here, we ask whether the influence of species interactions and stochasticity on community stability, measured by the change in community composition over time, varies with diversity and dispersal rate. To isolate these processes we performed a laboratory experiment in which ten regions, each with six local communities, were allowed to assemble in a constant laboratory environment. After 3 months of assembly, a high and low dispersal treatment was applied, in which either 5 or 50 percent of each local community in a region was removed, mixed, and reintroduced back into each local community in the region. The communities were sampled before and after this dispersal treatment, and a null model was applied to assess whether the relative importance of stochasticity and species interactions varied with diversity or dispersal.
Results/Conclusions
Diversity affected the relative importance of species interactions and stochasticity on community stability, but this effect depended on the dispersal rate. When only 5 percent of a community was removed, mixed with other communities in the region, and then dispersed back into local communities, diversity was negatively related to the importance of species interactions. This result occured due to higher than expected colonization rates in species poor regions. This trend disappeared, however, in the high dispersal treatment, due to increased extinction in the most diverse regions and communities.