Consumer diversity drives stronger predation in tropical marine communities

Abstract

Biotic interactions are predicted to be stronger in the tropics compared to higher latitudes, contributing to observed patterns of global biodiversity. While increased consumer diversity and more complex food webs are expected in tropical communities, the trophic dynamics underlying strong regional effects of predation are not well understood. To identify drivers of variation in consumer effects, we first experimentally tested how predators impact prey community structure across latitude. We then explored the community-level characteristics of interacting predators that explain observed changes in prey community structure at low latitudes. Using a standardized experiment paired with underwater videography in four coastal regions spanning 47° of latitude in the eastern Pacific Ocean, we quantified species-specific feeding rates on sessile marine invertebrate communities and tested whether predation pressure led to changes in prey community structure. We applied a multivariate model-based framework to identify elements of the predator community that best explain compositional change in prey communities in the tropics. We found that mid- and high-latitude prey communities experienced low predation pressure, with no discernable effect of predators on community structure, whereas low-latitude communities experienced strong predation pressure by a diverse assemblage of predators resulting in significant changes in community structure. While tropical predator communities were consistently more diverse than those at higher latitudes, our results show that predator–prey interactions can be context-dependent. Predator diversity was the best predictor of prey compositional change in early assembly prey communities. At later stages of prey assembly, however, a lower diversity of predators was observed, and the presence of key predator taxa became the best predictor of prey change. Our findings suggest that both the standing diversity of predator communities and the identity of predators sampled from a diverse species pool are important drivers of strong regional interaction effects.