Beaver dams shift desert fish assemblages toward dominance by non‐native species (Verde River, Arizona, USA)

Gibson, Polly P.; Olden, Julian D.; O’Neill, Matthew

doi:10.1111/eff.12150

Cited by 26 publications

(22 citation statements)

References 61 publications

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“…In our study, only the green sunfish Lepomis cyanellus benefitted from the anomalous droughts that were negatively associated with native abundances, and no non‐natives were reduced in abundance by the floods that were positively associated with native abundance. Whereas the positive response of green sunfish to anomalous droughts is in agreement with its high preference for slow current conditions and lacustrine habitats (Frimpong & Angermeier, ; Gibson et al ., ; Pool & Olden, ), non‐natives not responding to anomalous floods is a more intriguing outcome. We offer two explanations for the observed lack of response by non‐natives: (i) catastrophic floods (4 events during the studied period and 6 preceding it) were perhaps not intense enough to influence the non‐native assemblage; or (ii) non‐natives indeed responded (negatively) to flow variation on the short‐term but recolonized quickly, so that analyses of long‐term trajectories would not reflect such responses.…”

Section: Discussionmentioning

confidence: 99%

Anomalous droughts, not invasion, decrease persistence of native fishes in a desert river

Ruhí

Holmes

Rinne

et al. 2014

Global Change Biology

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Changing climate extremes and invasion by non-native species are two of the most prominent threats to native faunas. Predicting the relationships between global change and native faunas requires a quantitative toolkit that effectively links the timing and magnitude of extreme events to variation in species abundances. Here, we examine how discharge anomalies--unexpected floods and droughts--determine covariation in abundance of native and non-native fish species in a highly variable desert river in Arizona. We quantified stochastic variation in discharge using Fourier analyses on >15,000 daily observations. We subsequently coupled maximum annual spectral anomalies with a 15-year time series of fish abundances (1994-2008), using Multivariate Autoregressive State-Space (MARSS) models. Abiotic drivers (discharge anomalies) were paramount in determining long-term fish abundances, whereas biotic drivers (species interactions) played only a secondary role. As predicted, anomalous droughts reduced the abundances of native species, while floods increased them. However, in contrast to previous studies, we observed that the non-native assemblage was surprisingly unresponsive to extreme events. Biological trait analyses showed that functional uniqueness was higher in native than in non-native fishes. We also found that discharge anomalies influenced diversity patterns at the meta-community level, with nestedness increasing after anomalous droughts due to the differential impairment of native species. Overall, our results advance the notion that discharge variation is key in determining community trajectories in the long term, predicting the persistence of native fauna even in the face of invasion. We suggest this variation, rather than biotic interactions, may commonly underlie covariation between native and non-native faunas, especially in highly variable environments. If droughts become increasingly severe due to climate change, and floods increasingly muted due to regulation, fish assemblages in desert rivers may become taxonomically and functionally impoverished and dominated by non-native taxa.

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Section: Discussionmentioning

confidence: 99%

Anomalous droughts, not invasion, decrease persistence of native fishes in a desert river

Ruhí

Holmes

Rinne

et al. 2014

Global Change Biology

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“…We examined the seven most common fish species in the upper Verde River, collectively representing, on average, 87% of stream reach biomass (Gibson et al. ). Native fishes included desert sucker ( Catostomus clarki ), Sonora sucker ( Catosotmus insignis ), and roundtail chub ( Gila robusta ); species that are endemic to the Colorado River Basin.…”

Section: Methodsmentioning

confidence: 99%

Increasing drought favors nonnative fishes in a dryland river: evidence from a multispecies demographic model

et al. 2019

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Understanding how novel biological assemblages are structured in relation to dynamic environmental regimes remains a central challenge in ecology. Demographic approaches to modeling species assemblages show promise because they seek to represent fundamental relationships between population dynamics and environmental conditions. In dryland rivers, rapidly changing climate conditions have shifted drought and flooding regimes with implications for fish communities. Our goals were to (1) develop a mechanistic multispecies demographic model that links native and nonnative species with river flow regimes, and (2) evaluate demographic responses in population and community structure to changing flow regimes. Each fish species was represented by a stage‐structured matrix, and species were coupled together into a multispecies framework through density‐dependent relationships in reproduction. Then, community dynamics were simulated through time using annual flow events classified from gaged streamflow data. We parameterized the model with vital rates and flow–response relationships for a community of native and nonnative fishes using literature‐derived values. We applied the simulation model to the Verde River (Arizona, USA), a major tributary within the Colorado River Basin, for the past half century (1964–2017). Model validation revealed a match between model projections and relative abundance trends observed in a long‐term fish monitoring dataset (1994–2008). At the beginning of the validation period (1994), model and survey observations showed that native species comprised approximately 80% of total abundance. Model projections beyond the survey data (2008–2017) predicted a shift from a native dominant to a nonnative dominant assemblage, coinciding with increasing drought frequency. Trade‐offs between native and nonnative species dominance emerged from differences in mortality in response to the changing sequence of major flow events including spring floods, summer high flows, and droughts. In conclusion, the demographic approach presented here provides a flexible modeling framework that is readily applied to other stream systems and species by adjusting or transferring, when appropriate, species vital rates and flow‐event thresholds.

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“…In May-June 2012, fish communities were sampled in 25 stream sites in the upper Verde watershed (Figure 1; Gibson, Olden, & O'Neill, 2015). At each designated site, a~100 m reach with 1-2 pool-riffle-run sequences was enclosed with block nets, and the fish community was surveyed using 2-pass depletion backpack electrofishing.…”

Section: Fish Community Samplingmentioning

confidence: 99%

“…Suites of candidate models were specified that included either F I G U R E 1 Locations of fish community sampling efforts (Gibson et al, 2015; grey circles) and per capita nutrient recycling measurements (this study; black crosses) in streams of the upper Verde River watershed in central Arizona, USA no random effects (i.e. Suites of candidate models were specified that included either F I G U R E 1 Locations of fish community sampling efforts (Gibson et al, 2015; grey circles) and per capita nutrient recycling measurements (this study; black crosses) in streams of the upper Verde River watershed in central Arizona, USA no random effects (i.e.…”

Section: Modelling Per Capita Recycling Ratesmentioning

confidence: 99%

Estimating the effects of non‐native species on nutrient recycling using species‐specific and general allometric models

Fritschie

Olden

2018

Freshwater Biology

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Non‐native species are now common in community assemblages, but the influence of multiple introductions on ecosystem functioning remains poorly understood. In highly invaded systems, one promising approach is to use functional traits to scale measured individuals’ effects on ecosystem function up to the community level. This approach assumes that functional traits provide a common currency among species to relate individuals to ecosystem functioning. The goals of this study were to (i) test whether the relationship between body size and ecosystem functioning (per capita nutrient recycling) was best described by general or species‐specific scaling models; (ii) relate community structure (total biomass, average body size, non‐native dominance) to aggregated, community‐level nutrient recycling rates and ratios; and (iii) determine whether conclusions regarding the relationships between community structure and aggregate ecosystem functioning differed between species‐specific and general scaling approaches. By combining experimental incubations and field surveys, we compare consumer‐mediated nutrient recycling of fish communities along a non‐native dominance gradient in the Verde River watershed of central Arizona, USA. Data from ˜340 field‐sampled freshwater fish demonstrated support for general allometric relationships predicted by the metabolic theory of ecology (NH4‐N scaling coefficient = 0.72 [0.64–0.80]; PO4‐P = 0.67 [0.47–0.86]). However, the best‐fit models for N and P included species‐specific random effects for both allometric slopes and intercepts. According to species‐specific models, stream fish communities recycled 1–12 mmol NH4‐N/hr (median = 2.8 mmol/hr) and 0.02–0.74 mmol PO4‐P/hr (median = 0.07 mmol/hr) at N:P ratios between 13.3 and 83.5 (median = 28.8). General models generated similar estimates for NH4‐N recycling but less accurate estimates for PO4‐P. Stochastic simulations that incorporated error around allometric parameter estimates led to qualitatively similar but larger differences between general and species‐specific results. Community structure influenced aggregate nutrient recycling, but specific conclusions depended on the scaling approach. Total biomass explained much of the among‐community variation in aggregate NH4‐N and PO4‐P for both model types, whereas non‐native dominance alone best predicted variation in aggregate N:P. Surprisingly, species‐specific and general models both reached significant yet quantitatively opposing conclusions regarding the relationship between N:P supply and non‐native dominance. Study results indicate that shifting fish community structure can substantially alter ecosystem functioning in this river system. However, some inferred relationships between community structure and aggregate nutrient recycling varied depending on whether general or species‐specific scaling approaches were taken. Although trait‐based approaches to link environmental change, community structure and ecosystem function hold much promise, it will be important to consider wh...

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Beaver dams shift desert fish assemblages toward dominance by non‐native species (Verde River, Arizona, USA)

Cited by 26 publications

References 61 publications

Anomalous droughts, not invasion, decrease persistence of native fishes in a desert river

Anomalous droughts, not invasion, decrease persistence of native fishes in a desert river

Increasing drought favors nonnative fishes in a dryland river: evidence from a multispecies demographic model

Estimating the effects of non‐native species on nutrient recycling using species‐specific and general allometric models

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