README_DataSet Vejrik et al.xlsx

<strong>Trophic position of the species and site trophic state affect the foraging behavior: from apex predator to herbivore</strong> The impact of trophic position of the species and site trophic state on the (i) total niche width (TNW), (ii) individual niche width (INW), and (iii) individual specialization (IS) was studied using an innovative approach. Stable isotopes (<em>δ</em>13C, <em>δ</em>15N) of four body tissues differing in isotopic turnover rates were used from four freshwater fish representing the entire food web: European catfish (<em>Silurus glanis</em>), Northern pike (<em>Esox lucius</em>), Eurasian perch (<em>Perca fluviatilis</em>), and rudd (<em>Scardinius erythrophthalmus</em>). TNW was largest and narrowest for the apex predator (European catfish) and obligate predator (Northern pike), respectively. INW exhibited a polynomial trend for European catfish, Northern pike and Eurasian perch (representing mesopredator), it decreased with body mass, but then increased after exceeding a certain species dependent body mass threshold. Thus, for ectothermic species, apex predator status is not strictly linked to the species but to the size of individuals. In herbivores (rudd), INW increased with body mass. IS of predators negatively correlated with site trophic state. Thus, human-induced eutrophication can significantly change the foraging behaviors. The trends can be generalized to other species at similar trophic positions in either aquatic or terrestrial systems.

物种营养级与生境营养状态对觅食行为的影响：从顶级捕食者到植食性物种

本研究采用创新研究范式，探讨了物种营养级与生境营养状态对（i）总生态位宽度（total niche width, TNW）、（ii）个体生态位宽度（individual niche width, INW）以及（iii）个体特化程度（individual specialization, IS）的调控作用。研究采集了同位素周转速率存在差异的四种身体组织的稳定同位素（δ¹³C、δ¹⁵N）样本，供试对象为覆盖完整淡水食物网的四种鱼类：欧鲶（*Silurus glanis*）、白斑狗鱼（*Esox lucius*）、河鲈（*Perca fluviatilis*）以及赤眼鳊（*Scardinius erythrophthalmus*）。

总生态位宽度在顶级捕食者欧鲶处达到最大值，在专性捕食者白斑狗鱼处则为最小值。个体生态位宽度在欧鲶、白斑狗鱼以及作为中型捕食者代表的河鲈中呈现多项式变化趋势：其随体质量增加而下降，但在超过物种特异性体质量阈值后又会回升。由此可见，对于变温物种而言，顶级捕食者的生态位并非严格由物种属性决定，而是取决于个体的体型大小。在植食性物种赤眼鳊中，个体生态位宽度则随体质量增长而持续上升。

捕食者的个体特化程度与生境营养状态呈显著负相关。据此可知，人为诱导的富营养化可显著改变物种的觅食行为。上述研究趋势可推广至水生或陆生生态系统中处于相似营养级的其他物种。