STABLE ISOTOPES IN ANIMAL ECOLOGY: ASSUMPTIONS, CAVEATS, AND A CALL FOR MORE LABORATORY EXPERIMENTS

TLDR

Stable isotope ratios have long been used by plant ecologists to disentangle ecological and physiological processes, and the method holds promise for animal ecology, but its application relies on assumptions that are rarely tested and not widely recognized. The authors aim to identify the assumptions underlying stable isotope analyses in animal ecology, delineate when they fail, and propose laboratory experiments to test them. They propose comparative laboratory experiments to evaluate the validity of the assumptions that underpin stable isotope interpretations. The rapid accumulation of animal isotopic data, facilitated by easy sampling and the method’s popularity, underscores the need to scrutinize its assumptions.

Abstract

For decades, plant ecologists have used naturally occurring stable isotope ratios to disentangle ecological and physiological processes. The methodology can also become a very powerful tool in animal ecology. However, the application of the technique relies on assumptions that are not widely recognized and that have been rarely tested. The purpose of this communication is to identify these assumptions, to characterize the conditions in which they are not met, and to suggest the laboratory experiments that are needed to validate them. The ease with which isotopic data can be gathered and the growing popularity of the method are generating a large amount of data on the isotopic ecology of animals. The proper interpretation of these data demands that we identify the assumptions on which these inferences are based, and that we conduct comparative laboratory experiments to assess their validity.