Isotopic niche reflects stress-induced variability in physiological status

The isotopic niche has become an established concept in trophic ecology. However, the assumptions behind this approach have rarely been evaluated. The evidence is accumulating that physiological stress can affect both magnitude and inter-individual variability of the isotopic signature in consumers via alterations in metabolic pathways. We hypothesized that stress factors (inadequate nutrition, parasite infestations, and exposure to toxic substances or varying oxygen conditions) might lead to suboptimal physiological performance and altered stable isotope signatures. The latter can be misinterpreted as alterations in isotopic niche. This hypothesis was tested by inducing physiological stress in the deposit-feeding amphipod Monoporeia affinis exposed to either different feeding regimes or contaminated sediments. In the amphipods, we measured body condition indices or reproductive output to assess growth status and δ13C and δ15N values to derive isotope niche metrics. As hypothesized, gre...

同位素生态位（isotopic niche）已成为营养生态学（trophic ecology）中一个公认的概念。然而，该方法背后的假设却鲜有评估。越来越多的证据表明，生理压力（physiological stress）可通过改变代谢途径（metabolic pathways），影响消费者同位素特征的大小及其个体间变异性。我们假设，压力因素（营养不足、寄生虫感染、接触有毒物质或不同氧气条件）可能导致次优生理表现及稳定同位素特征（stable isotope signatures）改变，而后者可能被误判为同位素生态位的变化。通过对底栖摄食端足类（deposit-feeding amphipod）Monoporeia affinis施加生理压力，使其暴露于不同喂食制度或污染沉积物中，对该假设进行了验证。在这些端足类中，我们测量了身体状况指数或繁殖输出以评估生长状态，并测定了δ13C和δ15N值以推导同位素生态位指标。正如假设所示，gre...