Departamento de Oceanografía Biológica, Centro de Investigación Científica y de Educación Superior de Ensenada, Ensenada, Baja California, México.
Moss Landing Marine Laboratories, San Jose State University, Moss Landing, CA, USA.
J Anim Ecol. 2021 Jun;90(6):1583-1595. doi: 10.1111/1365-2656.13478. Epub 2021 May 5.
Understanding the effect of stage-specific traits on species feeding habits can reveal how natural selection shapes life strategies. Amino acid (AA) nitrogen stable isotopes (δ N) provide multiple proxies of habitat baseline values and diet that can improve our understanding of species feeding strategies relative to their animal metabolism. We evaluated the effect of body length as a proxy for life stage and sex on the feeding habits of the common dolphin Delphinus delphis delphis using δ C and δ N in bulk tissue and AAs δ N from skin samples collected for almost two decades. For bulk δ C and δ N data, we used SIBER analysis to compare isotopic niches by sex and life stage. For AA δ N data, we developed a hierarchical Bayesian model (HBM) to estimate indices of trophic status (Δ N and trophic position). The model reflected the natural hierarchical structure of AA data by partitioning variability into three sources: between laboratory replicates, within dolphins and among dolphins. Estimates of Δ N based on all trophic and source AAs were more precise for each dolphin, less variable among dolphins and on average 2.4‰ higher than indices based on single trophic (Glx) and source (Phe) AAs. Precision was further increased when information was shared among individuals through random effects or regression models. Estimates of trophic position showed similar patterns. Both Δ N and δ N isotopic niches showed no difference by sex, suggesting that males and females have similar feeding habits and may not segregate. However, lower Δ N values for weaning calves and smaller juveniles discriminate them from adults, whereas δ N bulk isotopic niches do not. A trophic discrimination factor (TDF ) of 3.1‰ was required for reasonable estimates of trophic position for these dolphins. Together, the lack of δ N differences between sexes, low variation between juveniles and adults and knowledge of common dolphins' social organization support intraspecific feeding cooperation as an important strategy to feed in the highly dynamic marine environment. Our study also presents an efficient way to analyse complex AA δ N data using HBM to investigate foraging behaviour in long-lived marine species difficult to study in the wild.
了解阶段特异性特征对物种食性的影响，可以揭示自然选择如何塑造生活策略。氨基酸（AA）氮稳定同位素（δ N）提供了多个栖息地基线值和饮食的替代指标，可以提高我们对物种食性策略的理解，相对于其动物代谢。我们评估了体长作为代表生命阶段和性别的代理对普通海豚 Delphinus delphis delphis 食性的影响，使用了近二十年收集的皮肤样本中的总组织δ C 和δ N 以及 AA 的δ N。对于总δ C 和δ N 数据，我们使用 SIBER 分析来比较性别和生命阶段的同位素生态位。对于 AA 的δ N 数据，我们开发了一个分层贝叶斯模型（HBM）来估计营养状态指数（Δ N 和营养位置）。该模型通过将变异性分为三个来源来反映 AA 数据的自然层次结构：实验室重复之间、海豚内部和海豚之间。基于所有营养和来源 AA 的Δ N 估计值对于每个海豚来说更准确，海豚之间的变异性更小，平均比基于单个营养（Glx）和来源（Phe）AA 的指数高 2.4‰。当通过随机效应或回归模型在个体之间共享信息时，精度进一步提高。营养位置的估计值也显示出类似的模式。Δ N 和δ N 同位素生态位在性别上没有差异，这表明雄性和雌性具有相似的食性，并且可能没有分离。然而，断奶幼海豚和较小的幼海豚的Δ N 值较低，将它们与成年海豚区分开来，而δ N 总同位素生态位则没有。对于这些海豚，需要 3.1‰的营养分辨因子（TDF）才能合理估计营养位置。缺乏性别之间的δ N 差异、青少年和成年人之间的低变异性以及对普通海豚社会组织的了解，支持种内摄食合作作为在高度动态的海洋环境中觅食的重要策略。我们的研究还提出了一种使用 HBM 分析复杂 AA δ N 数据的有效方法，以研究在野外难以研究的长寿海洋物种的觅食行为。
