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，雨季的降雨及临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，季节周期性会影响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大核心生态学机制。本研究依托潘塔纳尔湿地强烈的季节周期性，以湖脂鲤（Astyanax lacustris，一种脂鲤（tetra fish））为研究对象，探究个体内部与个体间的食性差异如何与其种群的季节性生态位动态相关联。研究通过胃容物（gut contents）与稳定同位素（stable isotopes）分析量化食性生态位。结果显示，雨季中该脂鲤的胃饱满度更高、身体状况更佳，这表明旱季的种内竞争更为激烈。尽管旱季种内竞争可能更强，但雨季的种群生态位宽度更大，这源于个体间食性分化程度的提升。我们提出：旱季较低的生态机会会限制种内竞争的分化效应，进而制约种群生态位的扩张。本研究结果为季节周期性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的交互作用决定了季节性环境中的时间生态位变异。