Inferring diet-switches from stable isotope analyses of multiple tissues - CANCELLED

Background/Question/Methods Stable isotope analysis has become an important tool for inferring dietary food utilization, trophic position in animals and understanding physiological processes and migratory history. When organisms feed on two isotopically distinct resources, ecologists have used stable carbon isotopes to partition dietary intake between the two diets. Although stable carbon isotopes can partition the cumulative intake of sources with different isotopic signatures, a traditional mixing model cannot distinguish the case when organisms simultaneously feed on both sources (diet mixing) from the case when they feed on the sources sequentially (diet switching). Sampling multiple tissues at a single time point can discriminate between these two scenarios if carbon turns over at different rates in different tissues, even when researchers do not know the rates at which tissues turnover. Deterministic models illustrate the role of differences in tissue turnover rates, fractionation and diet end-member signatures on the application of this technique. Results/Conclusions For both one-time and repeated diet switches, the most important factor in being able to detect diet switches is having a suitably large difference between tissues' turnover rates. While halving the difference in turnover rates halved the time diet switches were detectable, halving the potential range of one tissue's signatures only led to a twenty percent reduction in detection time. This technique for inferring past diet switches from a single sample point will allow researchers to study the dietary histories of small, mobile, or otherwise hard to repeatedly capture organisms.