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1. Contrasting invasion histories and effects of three non-native fishes observed with long-term monitoring data

   https://doi.org/10.1007/s10530-023-03146-9  

   Pintar, Matthew R.; Dorn, Nathan J.; Kline, Jeffrey L.; Trexler, Joel C. (August 2023, Biological Invasions)

   Boom-bust population dynamics are long-recognized phenomena during species invasions, but few studies documented impacts of these dynamic changes. The Florida Everglades is the largest wetland in the United States, is undergoing a multi-decade hydro-restoration effort, and has been invaded by several tropical freshwater fishes. We used a 26-year dataset of small native marsh fishes and decapods to assess potential effects of African Jewelfish (Hemichromis letourneuxi) invasion and compared their effects to those of a more recently invading species, Asian Swamp Eels (Monopterus albus/javanensis), and a long-established non-native species, Mayan Cichlids (Mayaheros urophthalmus). Unlike boom-bust dynamics of jewelfish, swamp eel abundance increased and stabilized over the course of this study. After accounting for effects of hydrologic variation, the densities of several native species were more reduced by either jewelfish or swamp eels than by native fish predators, while effects of Mayan Cichlids were similar to those of native fish predators. Impacts of the jewelfish boom in Shark River Slough were smaller (density reductions ≤ 50%) and more temporally limited than those of swamp eels, which produced near-complete loss of four species in Taylor Slough. Following the jewelfish bust, the density of affected species approximated pre-invasion predictions based on hydrology, but their recovery is now threatened by the subsequent invasion of swamp eels in Shark River Slough. Long-term monitoring data provide opportunities to probe for population-level effects at field scales, and indicate that impacts of non-native species can be context-dependent and vary across ecosystems and temporal scales. 

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2. Stomach contents (1977-1981) and stable isotopes (1994) from the Everglades, Florida, USA from the publication "Fishes in a seasonally pulsed wetland show spatiotemporal shifts in diet and trophic niche but not shifts in trophic position"

   https://doi.org/10.6073/pasta/c65efbbec61cfe1e70de11fe511d6830  

   Flood, Peter J; Loftus, William F; Trexler, Joel C (January 2025, Environmental Data Initiative)

   {"Abstract":["Stomach contents of fishes (1977-1981) and stable isotopes of fishes, invertebrates, and basal resources (1994) were collected from spikerush marsh, sawgrass ridge, and alligator pond habitats in Shark River Slough, Everglades National Park, Florida, USA. These data were used to quantify diet, trophic niche area, trophic position, basal resource use and how these metrics vary among size classes, seasons, and habitats. Data collection is complete. These data support Flood et al. (2023). Associated R code will be made available through Peter Flood's GitHub: https://github.com/pjflood/historic_everglades_aquatic_food_web. \n References:\n Flood, Peter J., William F. Loftus, and Joel C. Trexler. "Fishes in a seasonally pulsed wetland show spatiotemporal shifts in diet and trophic niche but not shifts in trophic position." Food Webs 34 (2023): e00265. https://doi.org/10.1016/j.fooweb.2022.e00265"]} 

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3. Bioenergy landscapes drive trophic shifts in generalist ants

   https://doi.org/10.1111/1365-2656.13407  

   Helms, IV, Jackson A.; Roeder, Karl A.; Ijelu, Selassie E.; Ratcliff, Ian; Haddad, Nick M.; Shik, ed., Jonathan Zvi (December 2020, Journal of Animal Ecology)

   Abstract Changes in trophic niche—the pathways through which an organism obtains energy and nutrients—are a fundamental way in which organisms respond to environmental conditions. But the capacity for species to alter their trophic niches in response to global change, and the ways they do so when able, remain largely unknown.Here we examine food webs in three long‐term and large‐scale experiments to test how resource availability and nutritional requirements interact to determine an organism's trophic niche in the context of one of the largest global trends in land use—the rise in bioenergy production.We use carbon and nitrogen stable isotope analyses to characterize arthropod food webs across three biofuel crops representing a gradient in plant resource richness (corn monocultures, fields dominated by native switchgrass and restored prairie), and to quantify changes in the trophic niche of a widespread generalist ant species across habitats. In doing so, we measure the effects of basal resource richness on food chain length, niche breadth and trophic position. We frame our results in the context of two hypotheses that explain variation in trophic niche—the niche variation hypothesis which emphasizes the importance of resource diversity and ecological opportunity, and the optimal diet hypothesis which emphasizes dietary constraints and the availability of optimal resources.Increasing plant richness lengthened food chains by 10%–20% compared to monocultures. Niche breadths of generalist ants did not vary with resource richness, suggesting they were limited by optimal diet requirements and constraints rather than by ecological opportunity. The ants instead responded to changes in plant richness by shifting their estimated trophic position. In resource‐poor monocultures, the ants were top predators, sharing a trophic position with predatory spiders. In resource‐rich environments, in contrast, the ants were omnivores, relying on a mix of animal prey and plant‐based resources.In addition to highlighting novel ecosystem impacts of alternate bioenergy landscapes, our results suggest that niche breadth and trophic diversification depend more on the presence of optimal resources than on ecological opportunity alone. 

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4. Habitat engineering by an apex predator generates spatial trophic dynamics across a temporal environmental stress gradient

   https://doi.org/10.1111/1365-2656.14248  

   Flood, Peter_J; Strickland, Bradley_A; Kline, Jeffrey_L; Trexler, Joel_C (January 2025, Journal of Animal Ecology)

   Abstract Ecosystem engineering is a facilitative interaction that generates bottom‐up extrinsic variability that may increase species coexistence, particularly along a stress/disturbance gradient. American alligators (Alligator mississippiensis) create and maintain ‘alligator ponds’ that serve as dry‐season refuges for other animals. During seasonal water recession, these ponds present an opportunity to examine predictions of the stress‐gradient (SGH) and intermediate disturbance hypotheses (IDH).To test the assumption that engineering would facilitate species coexistence in ponds along a stress gradient (seasonal drying), we modelled fish catch‐per‐unit‐effort (CPUE) in ponds and marshes using a long‐term dataset (1997–2022). Stomach contents (n = 1677 from 46 species) and stable isotopes of carbon and nitrogen (n = 3978 representing 91 taxa) from 2018 to 2019 were used to evaluate effects of engineering on trophic dynamics. We quantified diets, trophic niche areas, trophic positions and basal‐resource use among habitats and between seasons. As environmental stress increases, we used seasonal changes in trophic niche areas as a proxy for competition to examine SGH and IDH.Across long‐term data, fish CPUE increased by a factor of 12 in alligator ponds as the marsh dried. This validates the assumption that ponds are an important dry‐season refuge. We found that 73% of diet shifts occurred during the dry season but that diets differed among habitats in only 11% of comparisons. From wet season to dry season, both stomach contents and stable isotopes revealed changes in niche areas. Direction of change depended on trophic guild but was opposite between stable‐isotope and stomach‐content niches, except for detritivores.Stomach‐content niches generally increased suggesting decreased competition in the dry season consistent with existing theory, but stable‐isotope niches yielded the opposite. This may result from a temporal mismatch with stomach contents reflecting diets over hours, while stable isotopes integrate diet over weeks. Consumptive effects may have a stronger effect than competition on niche areas over longer time intervals.Overall, our results demonstrated that alligators ameliorated dry‐season stress by engineering deep‐water habitats and altering food‐web dynamics. We propose that ecosystem engineers facilitate coexistence at intermediate values of stress/disturbance consistent with predictions of both the SGH and IDH. 

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5. Invasive swamp eels reduce aquatic animal diversity and disproportionately reduce prey for nesting wading birds

   https://doi.org/10.1038/s41598-025-02887-y  

   Pintar, Matthew R; Dorn, Nathan J (December 2025, Scientific Reports)

   Ecosystem restoration often aims to create environmental conditions that support communities of native organisms resembling those prior to alteration by humans. One focus of the multi-decade multi-billion-dollar Florida Everglades restoration effort is to recreate hydrologic conditions in Everglades National Park and associated pulses of aquatic animal prey to support the large colonies of seasonally nesting wading birds that are iconic predators in the ecosystem. Recent studies indicate that invasion of predatory Asian Swamp Eels (Monopterus albus/javanensis) has disrupted the hydrology-mediated production of crayfish and some small fishes in the drainage of first invasion (circa 2012). Here we used a complete community dataset of fish and decapods to report changes to the aquatic community diversity, composition, and biomass of prey produced for wading birds. After the establishment of swamp eels in Taylor Slough (Everglades National Park) average fish and decapod richness declined by 25% and communities shifted to a new state dominated by grass shrimp and a few species of small fishes. Swamp eels differentially reduced the production of primary wading bird resources; while there has been a 68% decline in total small fish and decapod biomass, the biomass of the most important prey species for nesting wading birds declined 80%. If similar impacts follow the spread of swamp eels into other major drainages of the Everglades, the invasion may precipitate an ecosystem collapse—fundamentally simplifying and restructuring the aquatic communities of this vast wetland ecosystem and limiting the trophic support for wading bird breeding aggregations that are important indicators for ecological restoration. 

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