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Abstract The Trophic Disruption Hypothesis (TDH) predicts that invasive species may cause native species to undergo trophic dispersion (change in trophic‐niche area) and trophic displacement (diet switching), predictably altering food‐web structure and biodiversity. In Everglades National Park, Florida, USA, African Jewelfish (Rubricatochromis letourneuxi) density has recently (2012–2017) undergone a boom‐bust cycle, linked to declines of native taxa and altered aquatic‐community composition that persist after the bust. Everglades restoration efforts seek to restore historic hydrologic conditions that may contribute to food‐web changes unfolding coincidentally with the jewelfish boom. We used complementary datasets of stomach contents and stable isotopes (δ15N and δ13C) to quantify pre‐ and post‐invasion consumer diets, trophic positions, trophic niches, basal energy use (autotrophic vs. heterotrophic), and energy fluxes to test assumptions of the TDH. The direction of change for these metrics from dry season to wet‐season post‐invasion (i.e., effect of adding water) was used as a proxy for the direction of effects from restored water delivery. For trophic shifts attributable to jewelfish invasion, we tested assumptions of the TDH. Comparing pre‐ versus post‐invasion for native consumers, we observed trophic displacement in 42% of species size classes (based on stomach contents), trophic dispersion for 57% of species (based on stable isotopes) and 54% of species size classes (based on stomach contents), and overall greater reliance on autotrophic energy. Altered trophic dynamics were more frequent pre‐ versus post‐invasion than among habitats or between seasons, and the direction of those responses was in the opposite direction of dry‐season to wet‐season differences and/or occurred at a higher frequency. Post‐invasion food‐web structure and function revealed increased relative abundance of mesopredators (including African Jewelfish) and reduced biomass and energy fluxes into and out of small fishes (e.g., Cyprinodontiformes). Our results show that African Jewelfish invasion is linked to altered spatiotemporal trophic dynamics and energy fluxes through declines in native fishes and invertebrates, which indirectly affected trophic relationships at the regional scale in the Everglades. As a result, we suggest extending the TDH to explicitly include the potential for invasive species to alter basal energy use, spatiotemporal trophic dynamics, and energy fluxes.
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This content will become publicly available on June 1, 2026
Invasive species invoke a lifetime of trophic change in native stream fishes
Abstract Trophic interactions operate across the lifetime of an individual organism, yet our understanding of these processes is largely limited to a single life stage or moment in time. Management and conservation implications of this knowledge gap are particularly important, given the mounting number, spread, and ecological impacts of invasive species. Biotracers, such as carbon and nitrogen stable isotopes of animal muscle, are commonly used to characterize the trophic ecology of an individual but fail to capture intraindividual variation and ontogenetic dietary shifts. However, recent work suggests that eye lenses may facilitate the reconstruction of individual lifetime trophic trajectories for fishes, including the chronology of past trophic positions of and carbon flow to consumers. By combining stable isotope analysis of fish eye lens tissue with aging techniques (otolith growth measurements), this study is the first to ask how the lifetime trophic niches of individuals vary within different community contexts. The results provide evidence for asymmetric competition causing differing trajectories in lifetime trophic niches for native and nonnative fishes along an invasion gradient in Burro Creek, Arizona, USA. Native roundtail chub, Sonora sucker, and desert sucker all displayed a coordinated displacement of lifetime trophic trajectories to a lower trophic level and reliance on aquatic, rather than terrestrial, resources as indicated by a shift to lower δ13C and δ15N in mixed, relative to native‐only, communities. By contrast, the trophic trajectories of nonnative green sunfish and bullhead species remained consistent between native and nonnative dominated communities. The presence of nonnative species led to a significantly greater decrease in δ13C through ontogeny for roundtail chub, a species of conservation concern in Arizona. These results demonstrate the prolonged trophic impact of nonnative fishes on native fishes beyond a single life stage. Displacement of ontogenetic dietary shifts by native fishes through interactions with nonnative species may lead to reduced fish growth and fitness, with implications at the population and ecosystem levels. Stable isotope analysis of fish eye lens tissue offers new opportunities to study the lifetime chronology of individual feeding habits and allows for exploration of the impacts of invasive species and environmental change throughout ontogeny.
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- Award ID(s):
- 1922004
- PAR ID:
- 10629661
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Ecosphere
- Volume:
- 16
- Issue:
- 6
- ISSN:
- 2150-8925
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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