Newsome Seth D, Tinker M Tim, Gill Verena A, Hoyt Zachary N, Doroff Angela, Nichol Linda, Bodkin James L
Biology Department, University of New Mexico, Albuquerque, NM, 87131, USA,
Oecologia. 2015 May;178(1):45-59. doi: 10.1007/s00442-015-3223-8. Epub 2015 Feb 3.
The quantification of individuality is a common research theme in the fields of population, community, and evolutionary ecology. The potential for individuality to arise is likely context-dependent, and the influence of habitat characteristics on its prevalence has received less attention than intraspecific competition. We examined individual diet specialization in 16 sea otter (Enhydra lutris) populations from southern California to the Aleutian Islands in Alaska. Because population histories, relative densities, and habitat characteristics vary widely among sites, we could examine the effects of intraspecific competition and habitat on the prevalence of individual diet specialization. Using observed diet data, we classified half of our sites as rocky substrate habitats and the other half containing a mixture of rocky and unconsolidated (soft) sediment substrates. We used stable isotope data to quantify population- and individual-level diet variation. Among rocky substrate sites, the slope [±standard error (SE)] of the positive significant relationship between the within-individual component (WIC) and total isotopic niche width (TINW) was shallow (0.23 ± 0.07) and negatively correlated with sea otter density. In contrast, the slope of the positive WIC/TINW relationship for populations inhabiting mixed substrate habitats was much higher (0.53 ± 0.14), suggesting a low degree of individuality, irrespective of intraspecific competition. Our results show that the potential for individuality to occur as a result of increasing intraspecific competition is context-dependent and that habitat characteristics, which ultimately influence prey diversity, relative abundance, and the range of skillsets required for efficient prey procurement, are important in determining when and where individual diet specialization occurs in nature.
个体性的量化是种群、群落和进化生态学领域的一个常见研究主题。个体性出现的可能性可能取决于环境，并且栖息地特征对其普遍程度的影响比起种内竞争受到的关注更少。我们研究了从南加利福尼亚到阿拉斯加阿留申群岛的16个海獭（Enhydra lutris）种群的个体饮食特化情况。由于各地点的种群历史、相对密度和栖息地特征差异很大，我们能够检验种内竞争和栖息地对个体饮食特化普遍程度的影响。利用观察到的饮食数据，我们将一半的地点归类为岩石基质栖息地，另一半则包含岩石和非固结（软）沉积物基质的混合物。我们使用稳定同位素数据来量化种群和个体水平的饮食差异。在岩石基质地点中，个体内成分（WIC）与总同位素生态位宽度（TINW）之间显著正相关关系的斜率[±标准误差（SE）]较浅（0.23±0.07），并且与海獭密度呈负相关。相比之下，栖息在混合基质栖息地的种群的WIC/TINW正相关关系的斜率要高得多（0.53±0.14），这表明个体性程度较低，无论种内竞争如何。我们的结果表明，由于种内竞争加剧而出现个体性的可能性取决于环境，并且栖息地特征最终会影响猎物多样性、相对丰度以及有效获取猎物所需的技能范围，在确定自然界中个体饮食特化何时何地发生时很重要。
