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.