Table 3 data

<br><b>• Background and Aims </b>Freshwater nitrogen inputs are increasing globally, altering the structure and function of wetland ecosystems adapted to low nutrient conditions. Carnivorous wetland plants of the genus <i>Utricularia </i>are hypothesized to reduce their reliance on carnivory and increase their assimilation of environmental nutrients when the supply of ambient nutrients increases. Despite success in using stable isotope approaches to quantify carnivory of terrestrial carnivorous plants, quantifying carnivory of aquatic <i>Utricularia </i>requires improvement.<b>• Methods </b>We developed stable isotope mixing models to quantify aquatic plant carnivory and used these models to measure dietary changes of three <i>Utricularia </i>species, <i>Utricularia australis</i>, <i>U. gibba </i>and <i>U. uliginosa</i>, in 11 wetlands across a 794-km gradient in eastern Australia. Diet was assessed using multiple models that compared variations in the natural-abundance nitrogen isotope composition (δ15N) of <i>Utricularia </i>spp. with that of non-carnivorous plants, and environmental and carnivorous nitrogen sources.<b>• Key Results </b>Carnivory supplied 40–100 % of plant nitrogen. The lowest carnivory rates coincided with the highest availability of ammonium and dissolved organic carbon.<b>• Conclusions </b>Our findings suggest that <i>Utricularia </i>populations may adapt to high nutrient environments by shifting away from energetically costly carnivory. This has implications for species conservation as anthropogenic impacts continue to affect global wetland ecosystems.

• <b>研究背景与研究目的</b>
全球范围内淡水氮输入持续增加，正改变适应低营养条件的湿地生态系统的结构与功能。学界提出假说：狸藻属（<i>Utricularia</i>）食肉湿地植物在环境营养供给提升时，会降低对食肉习性的依赖，并增加对环境营养的吸收。尽管利用稳定同位素方法量化陆生食肉植物食肉习性的研究已取得进展，但水生狸藻属植物食肉习性的量化方法仍有待完善。
• <b>研究方法</b>
本研究开发了稳定同位素混合模型（stable isotope mixing models）以量化水生植物的食肉习性，并借助该模型对澳大利亚东部沿794公里梯度分布的11处湿地中的3种狸藻属物种——南方狸藻（<i>Utricularia australis</i>）、圆叶狸藻（<i>U. gibba</i>）与湿地狸藻（<i>U. uliginosa</i>）的食性变化进行了测定。本研究通过多种模型开展食性评估，该类模型将狸藻属物种的自然丰度氮同位素组成（δ¹⁵N）与非食肉植物、环境氮源及食肉来源氮的同位素变异进行对比分析。
• <b>主要研究结果</b>
食肉习性可为狸藻属植物提供40%~100%的氮素来源。最低的食肉率与最高的铵态氮及溶解有机碳可利用性相吻合。
• <b>研究结论</b>
本研究结果表明，狸藻属种群可通过摒弃能量成本高昂的食肉习性，以适应高营养环境。随着人类活动持续影响全球湿地生态系统，该研究发现对物种保护工作具有重要指导意义。