Inferences to estimate consumer’s diet using stable isotopes: Insights from a dynamic mixing model

Stable isotope ratios are used to reconstruct animal diet in trophic ecology via mixing models. Several assumptions of stable isotope mixing models are critical, i.e., constant trophic discrimination factor and isotopic equilibrium between the consumer and its diet. The isotopic turnover rate (λ and its counterpart the half-life) affects the dynamics of isotopic incorporation for an organism and the isotopic equilibrium assumption: λ involves a time lag between the real assimilated diet and the diet estimated by mixing models at the individual scale. Current stable isotope mixing model studies consider neither this time lag nor even the dynamics of isotopic ratios in general. We developed a mechanistic framework using a dynamic mixing model (DMM) to assess the contribution of λ to the dynamics of isotopic incorporation and to estimate the bias induced by neglecting the time lag in diet reconstruction in conventional static mixing models (SMMs). The DMM includes isotope dynamics of sources (denoted δs), λ and frequency of diet-switch (ω). The results showed a significant bias generated by the SMM compared to the DMM (up to 50% of differences). This bias can be strongly reduced in SMMs by averaging the isotopic variations of the food sources over a time window equal to twice the isotopic half-life. However, the bias will persist (∼15%) for intermediate values of the ω/λ ratio. The inferences generated using a case study highlighted that DMM enhanced estimates of consumer’s diet, and this could avoid misinterpretation in ecosystem functioning, food-web structure analysis and underlying biological processes.

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S1 Appendix. Patterns of simulated isotope values of consumer for different scenarios of λ values remain valid for different Brownian trajectories of food sources signatures.
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S2 Appendix. Choice of integration window length for the integrated static mixing model.
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S3 Appendix. Exploring the bias estimates () for different combinations of ω and λ.
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How to cite
Ballutaud Marine, Travers-Trolet Morgane, Marchal Paul, Dubois Stanislas, Giraldo Carolina, Parnell Andrew C., Nuche-Pascual M. Teresa, Lefebvre Sebastien (2022). Inferences to estimate consumer’s diet using stable isotopes: Insights from a dynamic mixing model. Plos One. 17 (2). e0263454 (26p.).,

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