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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. 

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. 

Abstract A narrative in ecology is that prey modify traits to reduce predation risk, and the trait modification has costs large enough to cause ensuing demographic, trophic and ecosystem consequences, with implications for conservation, management and agriculture. But ecology has a long history of emphasising that quantifying the importance of an ecological process ultimately requires evidence linking a process to unmanipulated field patterns. We suspected that such process‐linked‐to‐pattern (PLP) studies were poorly represented in the predation risk literature, which conflicts with the confidence often given to the importance of risk effects. We reviewed 29 years of the ecological literature which revealed that there are well over 4000 articles on risk effects. Of those, 349 studies examined risk effects on prey fitness measures or abundance (i.e., non‐consumptive effects) of which only 26 were PLP studies, while 275 studies examined effects on other interacting species (i.e., trait‐mediated indirect effects) of which only 35 were PLP studies. PLP studies were narrowly focused taxonomically and included only three that examined unmanipulated patterns of prey abundance. Before concluding a widespread and influential role of predation‐risk effects, more attention must be given to linking the process of risk effects to unmanipulated patterns observed across diverse ecosystems.