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Individuals matter more than replicates: distribution of sampling effort in isotopic niche estimation

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Abstract

The number of individuals to be sampled is a key element in the sampling design of any study as it directly affects the estimations and inferences made. Additionally, in cases where several replicates per individual can be taken, it is important to define how the sampling effort will be distributed between the intraindividual and interindividual components (within and between individuals, respectively). Determining how samples should be distributed among these components can help optimize the available resources and reduce bias in the estimations. To study population trophic diversity, the total niche width (TNW) is usually estimated, which is an approximation of resource diversity at the population level. TNW is the sum of the resource diversity consumed at the intraindividual (replicates) and interindividual (individuals) level. In this study, the effect of prioritizing the number of individuals or the number of replicates on the accuracy and precision of TNW estimations was tested. Multiple isotopic (δ13C and δ15N) values per individual in populations with different degree of individual specialization were simulated. Then, isotopic data from natural populations within the same species (available published studies) were used to assess the results obtained with simulated data. It was found that TNW estimations were more accurate and precise when prioritizing the number of individuals over the replicates, along the entire individual gradient of trophic specialization. Therefore, it is advisable to prioritizing the number of individuals. This methodological contribution should be considered in future studies that use repeated measures of isotopic data to estimate TNW.

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Data availability

The datasets analyzed during the current study are available in Dryad repository (https://doi.org/https://doi.org/10.5061/dryad.k231g) and in the Australian data center (https://data.aad.gov.au/metadata/records/ASAC_2940).

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Acknowledgements

The authors thank National Agency for Research and Innovation, Uruguay (ANII) and Postgraduate Academic Commission—UdelaR (CAP) for the MSc scholarship awarded to FHG. VFT and DEN were supported by a Clemente Estable fund 2019-156387 (ANII, National Agency or Research and Innovation, Uruguay). They also thank two anonymous reviewers for their constructive comments to a first draft of the manuscript. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Funding

This work was supported by the MSc scholarship number #POS_NAC_2022_1_173718 awarded to FHG by the Agencia Nacional de Investigación e Innovación (ANII) and by the Comisión Académica de Posgrado (CAP). VFT was supported by a Clemente Estable fund 2019-156387 (ANII).

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Authors and Affiliations

  1. Departamento de Ecología y Evolución, Facultad de Ciencias, Programa de Desarrollo de Las Ciencias Básicas (PEDECIBA), Universidad de La República, Iguá 4225, 11400, Montevideo, Uruguay

    Federico Garrido-de León, Daniel E. Naya & Valentina Franco-Trecu

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  1. Federico Garrido-de León
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  2. Daniel E. Naya
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  3. Valentina Franco-Trecu
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Contributions

The idea and designed methodology were conceived by FGDL, VFT, and DEN; VFT collected the samples; FGDL, VFT, and DEN analyzed the samples and data. All authors contributed critically to the drafts and gave final approval for publication.

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Correspondence to Federico Garrido-de León.

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Databases of natural populations that were already available in online repositories were used. Therefore, no ethical approval is required.

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Garrido-de León, F., Naya, D.E. & Franco-Trecu, V. Individuals matter more than replicates: distribution of sampling effort in isotopic niche estimation. Mar Biol 171, 97 (2024). https://doi.org/10.1007/s00227-024-04410-9

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