Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Casillla 653, Santiago, Chile.
J Comp Physiol B. 2013 Apr;183(3):419-30. doi: 10.1007/s00360-012-0711-6. Epub 2012 Sep 27.
We analyzed the carbon and nitrogen isotopic values of the muscle, liver, and crop contents ("diet") of 132 individuals of 16 species of Chilean birds. The nitrogen content of diet was tightly correlated with the fraction of gut contents represented by insects relative to plant material. The carbon and nitrogen isotopic values of diet, liver, and muscle were all linearly correlated, implying high temporal consistency in the isotopic value of the diet of these birds. However, δ(15)N was not significantly related with the percentage of insects in diet. These results cast doubt on the applicability of the use of (15)N enrichment to diagnose trophic level in, at least some, terrestrial ecosystems. However, the residuals of the relationship relating the isotopic value of bird tissues with those of their diet were weakly negatively correlated with insect intake. We hypothesize that this negative correlation stems from the higher quality of protein found in insects relative to that of plant materials. Finally, our data corroborated a perplexing and controversial negative relationship between tissue to diet isotopic discrimination and the isotopic value of diet. We suggest that this relationship is an example of the commonly observed regression to the mean effect that plagues many scientific studies.
我们分析了 132 只 16 种智利鸟类个体的肌肉、肝脏和嗉囊内容物（“饮食”）的碳和氮同位素值。饮食中的氮含量与昆虫相对于植物物质在肠道内容物中所占的比例密切相关。饮食、肝脏和肌肉的碳和氮同位素值都呈线性相关，这意味着这些鸟类饮食的同位素值在时间上具有高度一致性。然而，δ(15)N 与饮食中昆虫的比例没有显著关系。这些结果对使用（15）N 富集来诊断至少一些陆地生态系统中的营养水平的适用性提出了质疑。然而，鸟类组织与饮食之间同位素值关系的残差与昆虫摄入量呈弱负相关。我们假设这种负相关关系源于昆虫中蛋白质的质量相对高于植物材料。最后，我们的数据证实了组织与饮食之间同位素判别与饮食同位素值之间存在令人费解和有争议的负相关关系。我们认为，这种关系是许多科学研究中普遍存在的回归平均值效应的一个例子。
