Using δ13C stable isotopes to quantify individual-level diet variation
Using δ13C stable isotopes to quantify individual-level diet variation
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DOI：
10.1007/s00442-007-0687-1
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发表时间：
2007-07-01
期刊：
影响因子：
2.7
通讯作者：
dos Reis, Sergio F.
中科院分区：
文献类型：
--
作者：
Araujo, Marcio S.;Bolnick, Daniel I.;dos Reis, Sergio F.
通过肠道内容物分析可以轻松量化个体饮食差异。然而，由于肠道内容物是个体饮食习惯的“快照”，此类横截面数据可能会受到抽样误差的影响，并导致人们高估饮食变化的水平。相反，稳定同位素反映了个体的长期饮食，因此个体之间的同位素变化可以解释为饮食变化。然而，仅种群同位素方差不能直接在种群之间进行比较，因为它们取决于饮食变化水平和猎物同位素比率的变化。我们开发了一种方法，将群体同位素差异转换为个体专业化的标准化指数（WIC/TNW），可以在群体之间进行比较，或者转化为肠道内容物的变化。我们将此方法应用于巴西大草原四种青蛙的饮食和碳同位素数据。同位素表明，肠道内容物可以可靠地衡量三个人群的饮食变化，但大大高估了另一个人群的饮食变化。我们的方法对猎物的不完整采样和个体间的分割差异很敏感。因此，需要对猎物进行彻底采样并估计分级方差。除此之外，该方法很简单，并提供了一种结合肠道内容物和同位素数据来量化自然群体中个体水平饮食变化的新工具。
Individual-level diet variation can be easily quantified by gut-content analysis. However, because gut contents are a 'snapshot' of individuals' feeding habits, such cross-sectional data can be subject to sampling error and lead one to overestimate levels of diet variation. In contrast, stable isotopes reflect an individual's long-term diet, so isotope variation among individuals can be interpreted as diet variation. Nevertheless, population isotope variances alone cannot be directly compared among populations, because they depend on both the level of diet variation and the variance of prey isotope ratios. We developed a method to convert population isotope variances into a standardized index of individual specialization (WIC/TNW) that can be compared among populations, or to gut-content variation. We applied this method to diet and carbon isotope data of four species of frogs of the Brazilian savannah. Isotopes showed that gut contents provided a reliable measure of diet variation in three populations, but greatly overestimated diet variation in another population. Our method is sensitive to incomplete sampling of the prey and to among-individual variance in fractionation. Therefore, thorough sampling of prey and estimates of fractionation variance are desirable. Otherwise, the method is straightforward and provides a new tool for quantifying individual-level diet variation in natural populations that combines both gut-content and isotope data.