Predator diet breadth influences prey metacommunity assembly

Background/Question/Methods

One central question in metacommunity ecology is how local communities assemble from the regional species pool. Predation is among the most important biotic factors affecting many natural communities, yet we have a rather incomplete understanding of its role in modulating metacommunity assembly. Several experiments have shown that predation operates to promote the importance of deterministic processes relative to stochastic processes, resulting in low beta diversity. However, only one type of predators was used in these studies, making it difficult to generalize their results to other systems. Here we hypothesize that generalist and specialist predators may differentially affect metacommunity assembly due to their potentially different effects on deterministic and stochastic processes. We tested this hypothesis using protist microcosm metacommunities that varied in predator diet breadth (generalist vs. specialist predators), dispersal among local communities (no dispersal vs. dispersal), and the history of species colonization into local communities.

Results/Conclusions

Generalist predation reduced alpha diversity and increased beta diversity, as it resulted in the extinction of different prey species in different local communities. This increase in the importance of stochastic assembly in response to generalist predation is robust to species dispersal among local communities. Similar results, however, did not occur in the presence of specialist predators. Rather, species dispersal induced source-sink dynamics in the specialist predation treatments, resulting in increased alpha diversity and reduced beta diversity. These results provide strong evidence that predator diet breadth can impose important influences on the assembly of their prey metacommunities.