Predation and landscape characteristics independently affect reef fish community organization

Background/Question/Methods

Trophic island biogeography theory predicts that the effect of predators on prey diversity are context-dependent and should shift across heterogeneous landscapes. However, experimental tests of the predicted context dependency in top-down control remain limited. Using a factorial field experiment we quantify the effects of predation and patch characteristics (size, fragmentation) on coral reef fish communities. 

Results/Conclusions

We found independent effects of predation and patch characteristics on prey communities. Predators reduced prey abundance by 50% and gamma diversity by 45%, with a disproportionately strong effect on rare species relative to common species (60% and 16% reduction, respectively – an oddity effect). Larger patches contained more fishes, but a doubling of patch size led to a modest (36%) increase in prey abundance. Fragmented patches had 50% higher species richness and modified species composition relative to unfragmented patches. Our findings suggest two different pathways (i.e., habitat or predator shifts) by which natural and/or anthropogenic processes can drive variation in fish biodiversity.