Distance measures and optimization spaces in quantitative fatty acid signature analysis

Ecology and Evolution

Jeffrey F. Bromaghin²  Karyn D. Rode²  Suzanne M. Budge¹ 

[1] Process Engineering and Applied Science, Dalhousie University, Halifax, Nova Scotia, Canada;U.S. Geological Survey, Alaska Science Center, Anchorage, Alaska

关键词: Aitchison;    Chukchi Sea;    diet composition;    gray seal;    Halichoerus grypus;    Kullback–Leibler;    polar bear;    QFASA;    Ursus maritimus;   

DOI  :  10.1002/ece3.1429

来源: Wiley

【 摘 要 】

Abstract

Quantitative fatty acid signature analysis has become an important method of diet estimation in ecology, especially marine ecology. Controlled feeding trials to validate the method and estimate the calibration coefficients necessary to account for differential metabolism of individual fatty acids have been conducted with several species from diverse taxa. However, research into potential refinements of the estimation method has been limited. We compared the performance of the original method of estimating diet composition with that of five variants based on different combinations of distance measures and calibration-coefficient transformations between prey and predator fatty acid signature spaces. Fatty acid signatures of pseudopredators were constructed using known diet mixtures of two prey data sets previously used to estimate the diets of polar bears Ursus maritimus and gray seals Halichoerus grypus, and their diets were then estimated using all six variants. In addition, previously published diets of Chukchi Sea polar bears were re-estimated using all six methods. Our findings reveal that the selection of an estimation method can meaningfully influence estimates of diet composition. Among the pseudopredator results, which allowed evaluation of bias and precision, differences in estimator performance were rarely large, and no one estimator was universally preferred, although estimators based on the Aitchison distance measure tended to have modestly superior properties compared to estimators based on the Kullback–Leibler distance measure. However, greater differences were observed among estimated polar bear diets, most likely due to differential estimator sensitivity to assumption violations. Our results, particularly the polar bear example, suggest that additional research into estimator performance and model diagnostics is warranted.

【 授权许可】

CC BY   
© 2015 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.

Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.