Bromaghin Jeffrey F, Rode Karyn D, Budge Suzanne M, Thiemann Gregory W
U.S. Geological Survey, Alaska Science Center 4210 University Drive, Anchorage, Alaska, 99508.
Process Engineering and Applied Science, Dalhousie University Halifax, Nova Scotia, B3H 4R2, Canada.
Ecol Evol. 2015 Mar;5(6):1249-62. doi: 10.1002/ece3.1429. Epub 2015 Feb 24.
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.
定量脂肪酸特征分析已成为生态学尤其是海洋生态学中饮食估计的一种重要方法。已对来自不同分类群的几个物种进行了对照饲养试验，以验证该方法并估计考虑个体脂肪酸差异代谢所需的校准系数。然而，对估计方法潜在改进的研究一直很有限。我们比较了估计饮食组成的原始方法与基于猎物和捕食者脂肪酸特征空间之间不同距离度量和校准系数转换组合的五个变体的性能。使用先前用于估计北极熊（Ursus maritimus）和灰海豹（Halichoerus grypus）饮食的两个猎物数据集的已知饮食混合物构建了拟捕食者的脂肪酸特征，然后使用所有六个变体估计它们的饮食。此外，使用所有六种方法重新估计了楚科奇海北极熊先前公布的饮食。我们的研究结果表明，估计方法的选择会对饮食组成的估计产生重大影响。在允许评估偏差和精度的拟捕食者结果中，估计器性能的差异很少很大，而且没有一种估计器普遍受到青睐，尽管基于艾奇逊距离度量的估计器与基于库尔贝克 - 莱布勒距离度量的估计器相比往往具有适度优越的特性。然而，在估计的北极熊饮食中观察到了更大的差异，这很可能是由于估计器对假设违反的敏感性不同。我们的结果，特别是北极熊的例子，表明有必要对估计器性能和模型诊断进行更多研究。
