OOS 43-3 - The dynamics of food web assembly: Structure, stability, and trophic cascades

Thursday, August 10, 2017: 2:10 PM
Portland Blrm 258, Oregon Convention Center
Ashkaan K. Fahimipour, Biology and the Built Environment Center, University of Oregon, Eugene, OR

Food webs — ecological networks describing who-eats-whom in an ecosystem — form through a dynamic assembly process. New species colonize habitats, initiating interactions with species that are already present while others are extirpated, leading to changes of network structure through the addition and subtraction of nodes and edges. At the same time assembly involves changes on networks that occur as interacting populations grow, shrink and adapt, modulating flows of energy and materials along network edges. This talk will synthesize results from gradient-based laboratory and field experiments, and analytical and computational models to examine how assembly processes shape the formation of webs, subsequent community responses to perturbations and the strengths of interspecific indirect effects.


I will combine models and data to demonstrate that food webs follow repeatable assembly trajectories that are influenced by species’ colonization dynamics. I will also show how these trajectories subsequently influence foraging strategies of consumers in situ, and determine emergent community features like resilience and the strength of trophic cascade. Finally, I will discuss how issues of scale together with insufficient data combine to make the development of a predictive theory of web assembly a difficult problem, and discuss how gradient-based approaches can address this challenge.