<scp>frair</scp>: an R package for fitting and comparing consumer functional responses

Pritchard, Daniel W.; Paterson, Rachel A.; Bovy, Helene C.; Barrios‐O'Neill, Daniel

doi:10.1111/2041-210x.12784

Cited by 203 publications

(231 citation statements)

References 45 publications

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“…Where results were ambiguous, fits for different FR types were compared using Akaike's Information Criterion (AIC) (Pritchard et al 2017). Based on these analyses, all FRs were modelled as Type II curves.…”

Section: Methodsmentioning

confidence: 99%

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Predatory impacts of alien decapod Crustacea are predicted by functional responses and explained by differences in metabolic rate

Taylor

Dunn

2018

Biol Invasions

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Alien predators can have large impacts on prey. It is important that we understand, and ideally predict, these impacts. Here, we compare predatory impacts of size-matched decapod crustaceans-invasive alien Eriocheir sinensis and Pacifastacus leniusculus, and native European Austropotamobius pallipes-and use this case study to inform methods for impact prediction. We quantify functional responses (FRs) on three macroinvertebrate prey species, examine switching behaviour, and measure metabolic rates as a possible mechanistic explanation for differences in predation. FRs show a consistent pattern: attack coefficients and maximum feeding rates are ordered E. sinensis≥P. leniusculus≥A. pallipes for all prey species. Attack coefficients of E. sinensis are up to 6.7 times greater than those of size-matched crayfish and maximum feeding rates up to 3.0 times greater. FR parameters also differ between the invasive and native crayfish, but only up to 2.6 times. We find no evidence of switching behaviour in crayfish but suggestions of negative switching in E. sinensis. Differences in FR parameters are mirrored by differences in routine, but not standard, metabolic rate. Overall, our data predict strong predatory impacts of E. sinensis, even relative to alien P. leniusculus. Strong impacts of P. leniusculus relative to A. pallipes may be driven more by body size or abundance than per capita effect. FRs vary between prey types in line with existing knowledge of impacts, supporting the use of FRs in quantitative, prey-specific impact predictions. MRs could offer a general mechanistic explanation for differences in predatory behaviour and impacts.

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Section: Methodsmentioning

confidence: 99%

“…Based on these analyses, all FRs were modelled as Type II curves. Maximum likelihood model fitting and parameter estimation were performed within the R package frair (frair::frair_fit; Pritchard et al 2017) and used Rogers' random predator equation (Eq. 2; Rogers 1972) which modifies Holling's disk equation (Eq.…”

Section: Methodsmentioning

confidence: 99%

Predatory impacts of alien decapod Crustacea are predicted by functional responses and explained by differences in metabolic rate

Taylor

Dunn

2018

Biol Invasions

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“…The R package 'frair' (Pritchard 2014;Pritchard et al 2017) was used to model the functional response Type of Scyliorhinus canicula preying on Echinogammarus marinus. Functional response Type (I, II, III) was determined using a logistic regression of the proportion of prey consumed against prey density.…”

Section: Statistical Analysesmentioning

confidence: 99%

“…Therefore, when non-significant terms were encountered, a scatterplot with locally weighted scatterplot smoothing (LOWESS) lines, with a smoothing factor of 9/10, were fitted to assess the direction of proportional consumption. This was used to assess the shape of proportional consumption of prey at different prey densities (Pritchard et al 2017).…”

Section: Statistical Analysesmentioning

confidence: 99%

Effects of acute and chronic temperature changes on the functional responses of the dogfish Scyliorhinus canicula (Linnaeus, 1758) towards amphipod prey Echinogammarus marinus (Leach, 1815)

South

Dick

2017

Environ Biol Fish

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Predation is a strong driver of population dynamics and community structure and it is essential to reliably quantify and predict predation impacts on prey populations in a changing thermal landscape. Here, we used comparative functional response analyses to assess how predator-prey interactions between dogfish and invertebrate prey change under different warming scenarios. The Functional Response Type, attack rate, handling time and maximum feeding rate estimates were calculated for Scyliorhinus canicula preying upon Echinogammarus marinus under temperatures of 11.3°C and 16.3°C, which represent both the potential daily variation and predicted higher summer temperatures within Strangford Lough, N. Ireland. A two x two design of BPredator Acclimated^, BPrey Acclimated^, BBoth Acclimated^, and BBoth Unacclimated^was implemented to test functional responses to temperature rise. Attack rate was higher at 11.3°C than at 16.3°C, but handling time was lower and maximum feeding rates were higher at 16.3°C. Non-acclimated predators had similar maximum feeding rate towards nonacclimated and acclimated prey, whereas acclimated predators had significantly higher maximum feeding rates towards acclimated prey as compared to nonacclimated prey. Results suggests that the predator attack rate is decreased by increasing temperature but when both predator and prey are acclimated the shorter handling times considerably increase predator impact. The functional response of the fish changed from Type II to Type III with an increase in temperature, except when only the prey were acclimated. This change from population destabilizing Type II to more stabilizing Type III could confer protection to prey at low densities but increase the maximum feeding rate by Scyliorhinus canicula in the future. However, predator movement between different thermal regimes may maintain a Type II response, albeit with a lower maximum feeding rate. This has implications for the way the increasing population Scyliorhinus canicula in the Irish Sea may exploit valuable fisheries stocks in the future.

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“…Differences in a and h between the invader and native species can then be tested for their statistical significance (Dick et al, , 2017aBarrios-O'Neill et al, 2016;Guo et al, 2017;Laverty et al, 2017). This testing can be completed in specific R packages, such as 'Functional responses in R' (Frair; Pritchard, 2014;Pritchard, Paterson, Bovy & Barrios-O'Neill, 2017). ' The utility of the approach for testing high impact invaders was revealed by Alexander et al (2014), who compared FRs of the largemouth bass Micropterus salmoides, a globally invasive piscivorous fish with reported impacts on native prey communities (e.g.…”

Section: Comparative Behavioural Functional Responsesmentioning

confidence: 99%

Untitled

Britton¹

2019

Turk. J. Fish. Aquat. Sci.

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Predicting the ecological impacts of invasive fishes is crucial for understanding their risks in the environment. Experimental approaches that provide empirical data on invasion impacts provide both theoretical insights and data of high management utility for prioritising high-risk invaders. Here, a synthesis of some experimental approaches that predict invasion impacts of non-native fish is presented, where the focus is on impacts relating to the trophic impacts of the invader on either native trophically analogous fishes or prey populations. Experiments in tank aquaria are advantageous in providing homogenous and controlled conditions that also enable high replication. Competition-based studies can determine invasion impacts via exposure of fish to fixed food rations, although these experiments tend to produce results in intensely competitive conditions that might not occur in the wild. Comparative functional response experiments in tank aquaria have been successfully applied to determining the relative impacts of invaders compared with native species on prey populations, and have revealed high resource efficiency in globally invasive piscivorous fishes. Experiments completed in mesocosms and small ponds have the advantage of providing replicated systems in semi-natural conditions. They have been successful in revealing that rather than competing with native fishes, many invasive fishes show strong patterns of trophic niche partitioning. These patterns are also evident in these fishes when in natural invaded communities. Thus, whilst it is often suggested invasion impacts from non-native fishes result from inter-specific competition, evidence for this from experimental and field-based predictions is equivocal.

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frair: an R package for fitting and comparing consumer functional responses

Cited by 203 publications

References 45 publications

Predatory impacts of alien decapod Crustacea are predicted by functional responses and explained by differences in metabolic rate

Predatory impacts of alien decapod Crustacea are predicted by functional responses and explained by differences in metabolic rate

Effects of acute and chronic temperature changes on the functional responses of the dogfish Scyliorhinus canicula (Linnaeus, 1758) towards amphipod prey Echinogammarus marinus (Leach, 1815)

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