Structure, dynamics and fragility of ecological networks

Darwin used the metaphor of the tangled bank to illustrate the idea and importance of a complex network of interactions among species to understand ecology and evolution. Biodiversity research typically focus on species richness often neglecting species interactions, or addressing only the interactions between a pair of species or a few species at a time. We now know species interactions and their reciprocal evolutionary change –i.e. coevolution- determines both species evolution and how biodiversity is organized and sustained in ecosystems. Although great strides have been made in understanding the evolution and ecology of two-species interactions, little is known about evolution in a broader community context. Over the last decade new studies on the patterns of species interactions in large networks, in particular food webs –who eats whom- and mutualistic networks of free-living species – as those describing plants and their pollinators- have shown universal patterns in the way species interact across different habitat types (e.g. Montoya et al. 2006, Ings et al. 2009). Some of these patterns challenged prevailing wisdom about the outcome of coevolution based on pairwise interactions. For instance, reciprocal specializations that occur when a consumer specializes on a particular resource -illustrated most famously by the Malagasy orchid and the moth Darwin predicted would pollinate it - are extremely rare when the whole interaction network is considered (Joppa et al. 2009). These patterns are not only interesting in themselves, but they also determine how fast populations recover from perturbations, and the consequences of species extinctions on the remaining species within the interaction network (Solé & Montoya 2001, Montoya et al. 2009).

Lake Victoria food web

We investigate the patterns in the way species interact across different habitats, how these patterns have emerged using mathematical and simulation models (Montoya & Solé 2003), and the consequences of these patterns for ecosystem persistence and the effects of species extinctions within these networks. We also use some species traits -e.g. metabolism, body size-, and ecological theories -e.g. metabolic and food web theory- to reduce ecosystem complexity and gain predictive power into network patterns and dynamics (e.g. Woodward et al. 2005).

I have a large network of collaborators on this topic, including Guy Woodward (Queen Mary University of London), Mark Emmerson (Queen´s University Belfast), Stuart Pimm (Duke University), Lucas Joppa (Microsoft Research), Ricard Solé (Universitat Pompeu Fabra), Jordi Moyá-Laraño (CSIC). I belong to an european network focused on this topic (SIZEMIC).