Data pre-treatment and choice of resemblance metric affect how fatty acid profiles depict known dietary origins

Austin Happel, Sergiusz Czesny, Jacques Rinchard, S. Dale Hanson

Research output: Contribution to journalArticlepeer-review

Abstract

Fatty acids (FA) are increasingly being used in ecology to qualitatively infer diets of consumers. Analysis of FA data requires standardization to express FAs either in mg g−1 lipids, mg g−1 tissue, or as percentages of the total mass of FAs. Additionally, various transformations [square root, arcsin, log(X + 1), log-ratio, etc.] are often used to differentially weight the contribution of less abundant FAs. The choice of standardization unit and transformation can affect interpretations of results and ultimately our understanding of trophic relationships. Data from published feeding experiments were analyzed with visualization (i.e., nMDS) and multivariate rank-based methods (i.e. Mantel Tests) to evaluate how choice of standardization, transformation, and resemblance metric (i.e., Euclidean distance, Bray–Curtis similarities, etc.) reflects known dietary treatment groups. Our results indicate that diet interpretations were best inferred from data standardized to the total mass of FAs quantified. We found transforming data provided only weak advantages for discriminating among diet groups. Euclidean distances between FA proportions represented the known dietary differences to a high degree, are relatively easily interpretable, are applicable to a wide variety of statistical techniques, and are thus a reasonable choice of metric when analyzing FA proportions.

Original languageEnglish (US)
Pages (from-to)757-767
Number of pages11
JournalEcological Research
Volume32
Issue number5
DOIs
StatePublished - Sep 1 2017

Keywords

  • Biochemical tracers
  • Ecological data
  • Multivariate analysis
  • Transformation
  • Trophic connections

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics

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