Data from: Seasonal population and individual niche dynamics in a tetra fish in the Pantanal wetlands

In seasonal tropical regions, rainfall and/or temporary floods during the wet season generally increase the abundance and diversity of food resources to many consumers as compared to the dry season. Therefore, seasonality can affect intraspecific competition and ecological opportunity, which are two important ecological mechanisms underlying population and individual niche variations. Here, we took advantage of the strong seasonality in the Pantanal wetlands to investigate how within- and between-individual diet variations relate to seasonal population niche dynamics of the tetra fish Astyanax lacustris. We quantified dietary niche using gut contents and stable isotopes. Tetras had higher gut fullness and better body condition in the wet season, suggesting that competition is more intense in the dry season. The population niche was broader in the wet season due to an increase in diet divergence between individuals, in spite of potential stronger competition in the dry season. We posit that low ecological opportunity in the dry season limits the diversifying effect of intraspecific competition, constraining population niche expansion. Our results add new insights on how seasonality affects population and individual diets, indicating that intraspecific competition and ecological opportunity interact to determine temporal niche variations in seasonal environments.在季节性热带区域，相较于旱季，湿季的降雨及暂时性洪水通常可提升多数消费者可获取的食物资源丰度与多样性。因此，季节性变化会作用于种内竞争与生态机会——这二者是驱动种群与个体生态位变异的两类核心生态学机制。本研究依托潘塔纳尔湿地（Pantanal wetlands）显著的季节性特征，以脂鲤科鱼类河溪丽脂鲤（Astyanax lacustris）为研究对象，探究个体内部与个体间的食性差异如何与种群季节性生态位动态相关联。本研究通过胃含物分析与稳定同位素技术量化食性生态位，结果显示该脂鲤在湿季的胃饱满度更高、躯体状况更佳，表明旱季的种内竞争更为激烈。尽管旱季潜在竞争更强，但湿季的种群生态位更宽，这源于个体间食性分化程度的提升。我们提出假说：旱季较低的生态机会限制了种内竞争的分化效应，进而制约了种群生态位的扩张。本研究结果为解析季节性变化如何影响种群与个体食性提供了新视角，表明种内竞争与生态机会共同作用，决定了季节性环境中的时间生态位变异。