Chapter 8 - Valuing Biodiversity and Ecosystem Services in a Complex Marine Ecosystem

Abstract

The distribution of consumer trophic roles in complex food webs is crucial for community organization and functional diversity. Although aspects such as the position and width of the trophic niche of consumers are conceptually robust in theory, they are difficult to quantify in natural systems. Here, we present a new approach for characterizing the trophic niche of consumers that is based on three resource species traits that can be obtained for real systems: prey size, prey trophic position, and prey mobility. Using these traits we construct two three-dimensional measures termed trophic flexibility, and trophic uniqueness, which describe consumer trophic niche width and distance to neighboring niches of other consumers. We illustrate the use of these metrics with data from a real community of high trophic complexity: the marine food web of the Lough Hyne ecosystem. High trophic flexibility combined with low trophic uniqueness of most consumer species typifies this exceptional system. Our new metrics should be useful for describing the distribution of trophic roles of consumers in ecological communities and provide a tool for analyzing differences in trophic structure between ecosystems. They can complement topological and dynamical analyses of community robustness and we suggest that they could be useful for predicting the response of food webs to perturbations such as species loss.