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<p>Niche theory predicts that species with similar traits can coexist by reducing overlap through spatial, temporal, or dietary segregation. Because such partitioning usually develops over evolutionary timescales, closely related invasive fishes are expected to have limited potential for stable coexistence. In the upper Paraná River floodplain, two non-native cichlids, <i>Satanoperca pappaterra</i> and <i>Geophagus sveni</i>, share similar traits and now coexist, but their trophic interactions remain poorly understood. Here, we used stable carbon and nitrogen isotopes to examine trophic niche overlap and assess temporal variations in the abundance of these two non-native fish species. Our findings revealed low isotopic niche overlap between <i>S. pappaterra</i> and <i>G. sveni</i>. Although the population size of the more recent invader (<i>G. sveni</i>) increased, the population size of the older invader (<i>S. pappaterra</i>) declined over the same period. Contrary to expectations, our results suggest that differences in trophic niche use, rather than direct competition for feeding resources, are associated with these population dynamics. Instead, trophic segregation characterized their feeding interactions across seasons. These insights contribute to our understanding of trophic interactions and the mechanisms underlying the coexistence of recently introduced and resident fish species.</p>

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Stable isotopes reveal food resource partitioning between two invasive sympatric cichlids in a Neotropical floodplain

  • 期刊论文

  • 发表日期：

    2026年2月26日

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  • Gustavo H. Zaia Alves,
  • Driele Delanira-Santos,
  • Bruno R. S. Figueiredo,
  • Vinícius Andrade Urbano,
  • Evanilde Benedito

摘要

Niche theory predicts that species with similar traits can coexist by reducing overlap through spatial, temporal, or dietary segregation. Because such partitioning usually develops over evolutionary timescales, closely related invasive fishes are expected to have limited potential for stable coexistence. In the upper Paraná River floodplain, two non-native cichlids, Satanoperca pappaterra and Geophagus sveni, share similar traits and now coexist, but their trophic interactions remain poorly understood. Here, we used stable carbon and nitrogen isotopes to examine trophic niche overlap and assess temporal variations in the abundance of these two non-native fish species. Our findings revealed low isotopic niche overlap between S. pappaterra and G. sveni. Although the population size of the more recent invader (G. sveni) increased, the population size of the older invader (S. pappaterra) declined over the same period. Contrary to expectations, our results suggest that differences in trophic niche use, rather than direct competition for feeding resources, are associated with these population dynamics. Instead, trophic segregation characterized their feeding interactions across seasons. These insights contribute to our understanding of trophic interactions and the mechanisms underlying the coexistence of recently introduced and resident fish species.