Using stable isotopes to investigate individual diet specialization in California sea otters (Enhydra lutris nereis)
Using stable isotopes to investigate individual diet specialization in California sea otters (Enhydra lutris nereis)
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DOI：
10.1890/07-1812.1
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发表时间：
2009-04-01
期刊：
影响因子：
4.8
通讯作者：
Estes, James A.
中科院分区：
文献类型：
--
作者：
Newsome, Seth D.;Tinker, M. Tim;Estes, James A.
同种之间的饮食组成的差异（饮食专业化）已被记录在广泛的分类群体和栖息地，在个人水平上的这种变化越来越被认为是营养相互作用的多样性的重要组成部分。然而，准确识别个人的饮食专业化，需要纵向的饮食记录，这是劳动密集型和成本高昂，以获得许多物种。在这里，我们探讨了使用稳定同位素（δ C-13和δ N-15）作为一种有前途的技术，用于检测和量化个人饮食专业化的模式。南方海獭（Enhydra lutris nereis）为测试这种方法提供了一个独特的机会，因为（1）它们消耗各种各样的猎物，跨越多个营养级，栖息地和生态定义的功能组;（2）个体饮食专业化可以通过现有的观察数据进行验证。我们分析了海獭触须（n = 31）的同位素组成，以表征在蒙特雷湾，加州，美国海獭饮食的个体间和个体内的变化。在种群水平上，海獭在δ C-13和δ N-15值上都表现出很大的变化，占据了几乎所有由潜在猎物类群的同位素特征多样性所创造的“同位素空间”。海獭触须的变异大部分是由个体间的差异引起的，而个体内的变异则占很小的比例。大多数海獭（类似于80%）的同位素组成的时间变异性相对较小，这表明大多数人的饮食比例组成是相对恒定的，随着时间的推移;少数人（类似于20%）表现出高度的内触须同位素变异性，这表明饮食组成的季节性变化。这些结果和我们对它们的解释得到了来自同一种群（n = 23）的放射性标记海獭饮食的长期观察数据的支持。我们的研究结果表明，稳定同位素可以提供一个有效的工具，用于测量个人和人口水平的饮食广度，并可能是有用的研究人群中的纵向数据，否则个人将不可能获得。这对于研究消费者群体内部和之间饮食差异的原因和后果至关重要，从而提高我们对社区一级这些重要的生态和进化过程的理解。
Differences in diet composition among conspecifics (dietary specialization) have been documented across a broad range of taxonomic groups and habitats, and such variation at the individual level is increasingly recognized as an important component of diversity in trophic interactions. Accurate identification of individual dietary specialization, however, requires longitudinal dietary records that are labor-intensive and cost-prohibitive to obtain for many species. Here we explore the use of stable isotopes (delta C-13 and delta N-15) as a promising technique for detecting and quantifying patterns of individual dietary specialization. Southern sea otters (Enhydra lutris nereis) offer a unique opportunity for testing this approach because (1) they consume a wide variety of prey that span multiple trophic levels, habitats, and ecologically defined functional groups; and (2) individual diet specialization can be validated with existing observational data. We analyzed the isotopic composition of sea otter vibrissae (n = 31) in order to characterize inter- and intra-individual variation in sea otter diets at Monterey Bay, California, USA. At the population level, sea otters showed substantial variation in both delta C-13 and delta N-15 values, occupying nearly all of the "isotopic space'' created by the diversity of isotopic signatures of potential prey taxa. Most of the variation in sea otter vibrissae was accounted for by differences between individuals, with much less contributed by within-individual variation. A majority of sea otters (similar to 80%) showed relatively little temporal variability in isotopic composition, suggesting that the proportional composition of most individuals' diets is relatively constant over time; a few individuals (similar to 20%) exhibited a high degree of intra-vibrissa isotopic variability, suggesting seasonal shifts in diet composition. These results and our interpretation of them were supported by long-term observational data on the diets of radio-tagged sea otters from the same population (n = 23). Our results demonstrate that stable isotopes can provide an efficient tool for measuring individual-and population-level dietary breadth and may be useful for studying populations where longitudinal data on individuals would otherwise be impossible to acquire. This will be critical for examining the causes and consequences of dietary variation within and among consumer populations, thereby improving our understanding of these important ecological and evolutionary processes at the community level.