Seasonality and interspecific competition shape individual niche variation in co-occurring tetra fish in Neotropical streams

The drivers of intraspecific niche variation and its effects on
species interactions are still unclear, especially in species-rich
Neotropical environments. Here, we investigated how ecological opportunity
and interspecific competition affect the degree of individual trophic
specialization and the population niche breadth in tetra fish. We studied
the four ecologically similar species (Psalidodon aff. gymnodontus, P. aff.
paranae, P. bifasciatus, and Bryconamericus ikaa) in subtropical headwater
streams (three sites with two co-occurring species and three sites with
only one species). We sampled fish in two contrasting seasons (winter/dry
and summer/wet), and quantified their trophic niches using gut content
analysis. Psalidodon bifasciatus was the only species distributed over all
the sampled streams. We observed seasonal differences in population trophic
niche breadth of P. bifasciatus just when this species co-occurred with P.
aff. gymnodontus. These findings confirm the complex natu...