Any deep account of how individual organisms and species come to be distributed across landscapes must also consider the organization and dynamics of interactions among taxa. Such interactions provide the biotic framework for the flow of energy and resources within and across ecosystems. Ecological interactions and flows are particularly important for understanding how diversity is generated and maintained, as well as understanding the fate of species and ecosystems in response to natural and anthropogenic perturbations, such as climate change, habitat loss, and invasions.

SFI Visiting Professor Jennifer Dunne, External Professor Mercedes Pascual and colleagues at the Pacific Ecoinformatics and Computational Ecology Lab study the emergence, organization and dynamics of complex networks of interacting species. Whereas quantitative analysis of food-web structure has a three-decade history in ecology, it is only recently, partly through the efforts of SFI researchers, that this work has been drawn into the broader context of network research. This has led to new insights about characteristics, generalities, and scale-dependencies of ecological network structure, and has also identified limits to prior claims about the ubiquity of network patterns such as power-law degree distributions. Dunne in collaboration with SFI Professor Doug Erwin is now extending the study of ecological networks through deep time, as well as their role in niche construction. Initial findings suggest that the fundamental network structure of modern and ancient food webs is very similar, that such structure scales with species and link richness, and that observed structures are well-described by a simple niche model of food webs. Ongoing and future work is focused on compilation and analysis of multiple food webs across the Phanerozoic, including more focused work to look at whether and how network structure responds to major environmental shifts, trophic habit innovations, and major extinctions.

In addition to studying ecological networks, SFI researchers are engaged in modeling ecological processes. SFI Postdoctoral Fellow Michael Gastner is extending the well-known Contact Process model for colonization-extinction processes in space to population dynamic processes. SFI Postdoctoral Fellow Lauren Buckley has been developing dynamic bioenergetic models to predict species’ distributions and range shifts. The models are among the first to produce dynamic range predictions based on first principles of morphology and physiology. Future work by Buckley will extend and empirically validate these models, in particular comparing the ecologies of endotherms and ectotherms, and will include the first analysis of environmental and historical constraints on global patterns of amphibian richness, a widely recognized but poorly understood indicator of the biodiversity implications of environment change. Postdoctoral Fellow Joshua Ladau is developing null models to test for the effects of competitive interaction on community composition. These methods are robust and account well for much of the variability observed in real ecosystems. Ladau is currently extending these methods to treat multiple hierarchical levels of community structure, and developing a public-domain computer application to standardize tests for effects of interspecific interactions in ecological communities. In addition to being useful for testing for the effects of competitive interactions, the methods appear to be one element in a simple, general theory of community assembly. SFI Professor Geoffrey West, External Professor Jim Brown , and SFI Postdoctoral Fellow Chen Hou are integrating ecological principles with results on the thermodynamic organization of metabolism, an extension of very successful SFI research on allometric scaling (see Physics of Complex Systems).