Latitudinal gradients in predation in a marine ecosystem: frontiers in experimental macroecology

Background/Question/Methods

Latitude is the largest global gradient upon which many ecological patterns and processes hinge. Classic theory predicts stronger interactions at lower latitudes, but we are still at the early stages of understanding the generality of this pattern and its ecological implications. Further, global change continues to modify natural systems through climate warming, changing disturbance regimes, invasive species, and habitat loss. Understanding large-scale patterns of trophic interactions and their impacts on ecological communities in a changing world requires an integration of community ecology and macroecology. Experimental macroecology, and the use of replicated distributed experiments, facilitates this integration, allowing the study of local processes operating across biogeographic scales. I will present an overview of recent research exploring latitudinal patterns in predation in nearshore marine communities that leverages standardized, replicated experiments that span contiguous coastlines of the Americas. Focal communities are composed of vertebrate and invertebrate predators (e.g., fish, crabs) and a broad diversity of invertebrate prey, creating exceptionally diverse but experimentally tractable communities with which to understand large-scale changes in trophic dynamics.

Results/Conclusions

The strength of trophic interactions can indeed change across latitudinal gradients, with important consequences for patterns of biodiversity and ecosystem functioning. Results show higher predation intensity (i.e., consumption rates) as well as greater impacts on prey communities (i.e., biomass, composition) at warm, tropical latitudes in comparison to cooler temperate and subpolar latitudes. While many factors change across latitude, temperature is a strong predictor of these patterns, highlighting the potential for climate change to further modify temperature-regulated predator-prey interactions across the globe. Further, patterns of biological invasions are also shaped by these trophic interactions, with implications for both local abundances, regional distributions, and forecasts of future change. In addition to these recent advances, I will discuss the strengths and limitations of experimental macroecology for understanding trophic interactions in a changing world.