Relating food web structure to resilience, keystone status and uncertainty in ecological responses

Abstract

Abstract. Food webs often include substructures that occur in much higher numbers than would be expected in random networks. These are referred to in the literature as network motifs. Here we explore how feedbacks within the most common food web motifs influence their responses to external factors such as environmental change or harvesting of species. We have used qualitative modelling approaches to demonstrate that simple three-and four-member motifs that include a closed feedback loop can exhibit a diverse range of qualitative responses, some of which are non-intuitive. The same outcomes are demonstrated to be emergent behaviors of larger food webs represented in complex ecosystem models. The sensitivity of ecological responses to small differences in food web motifs underlines the broader importance of structural uncertainty in ecological models. It is also argued that the resilience of species and their keystone status may be strongly influenced by their ecological role within particular motifs. Examples are provided from fisheries off southeastern Australian, where the slow recovery rates of some species have not previously been explained.

Climate change alters stability and species potential interactions in a large marine ecosystem

“…Importantly, this method accounts for the degree of asymmetry in the overlaps. We identified potential structural keystone species that we know also have a functional relationship with the other species we measured and are known to be ecologically important in the ecosystem (Condie, Johnson, Fulton, & Bulman, ).…”

Sequential boundary eigenvalue destabilisation (SeBEDes): An expert method for parameter screening and estimation in complex ecosystem models

“…The shift of biomass from the top trophic level to the bottom with the increased resilience of the system is an interesting phenomena in the context of current theory on the structure and stability of food webs (Gunderson, 2000;McCann, 2012). The distribution of biomass observed in the "steady state" fact solutions for these parameter sets in the context of the very broad functional groupings we have used to represent populations suggests a fundamental "wasp-waisted" food web structure (Bakun, 2006) that is sometime associated with resilience (Condie et al, 2014;Madigan et al, 2012).…”