New Metrics to Quantify Food Web Structure
The Virgin Islands
In species-rich, complex food webs, many traditional approaches to elucidate food web structure are difficult to employ. As such, new approaches to understand food web structure are increasingly needed - especially in light of widespread and on-going impacts to ecosystems globally. I have proposed a novel application of stable isotope ratios that provides a quantitative, community-wide measure of characteristics of food web structure. Since stable isotope ratios in proteins of consumers reflect those of their diets in such a predictable manner, they provide a powerful tool to infer diet and trophic relationships. Standard application of stable isotope ratios involves plotting species (or individuals) in d13C and d15N bi-plot space, and inferring ecological relationships, e.g., consumer trophic position and percent contribution of different prey to those consumers. Such applications focus on particular energy flow pathways leading to one (or a few) consumers of interest, and typically do not characterize trophic structure at the level of the entire web (i.e., the overall distribution and spacing of species within existing niche space). By applying the metrics to analyze stable isotope characterization of species niches at a community-wide level, we hope to provide a very different approach to the study of food web dynamics. For more details see:
Layman, C.A., Arrington, D.A., Montaņa, C.G., and Post, D.M. In press. Can stable isotope ratios provide for community-wide measures of trophic structure? Ecology.
Our on-going research focuses on applying this approach to examine human impacts on food web structure. For example, we are examining how food webs in Bahamian tidal creeks are altered by fragmentation by road construction. We are also using the metrics to track changes following restoration of tidal flow to previously degraded systems. In tropical floodplain rivers, we are examining mechanisms of community assembly in littoral patch habitats. Our lab is especially interested to collaborate with others to apply rigorous statistical or null modeling approaches to the extensive and growing community-level isotopic databases that we currently are working with.