A Direct, Experimental Test of Resource vs. Consumer Dependence: Comment

Jensen, Christopher X. Jon; Jeschke, Jonathan M.; Ginzburg, Lev

doi:10.1890/05-1945

Cited by 16 publications

(18 citation statements)

References 27 publications

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“…We will argue that the direct method of Fussmann et al (2005) is better suited for quantifying the functional response per se, and Fussmann et al (2005) are correct in rejecting the ratio-dependence hypothesis. This is contradictory to the criticism by Jensen et al (2007) who claimed that functional response data should be obtained at a time interval that captures the consequences of consumption. However, the functional response is defined as the rate of prey consumption by an average predator (e.g., Abrams and Ginzburg 2000), and includes no requirement for dealing with the consequences of food capture.…”

Section: Discussionmentioning

confidence: 62%

“…However, the functional response is defined as the rate of prey consumption by an average predator (e.g., Abrams and Ginzburg 2000), and includes no requirement for dealing with the consequences of food capture. The additional criteria of Jensen et al (2007) can be interpreted as a modeler's wish to integrate behavior and reproductive timescales. Thus, the diverging conclusions due to different timescale of observations by Fussmann et al (2005) and the present study, illustrate the general problem of integrating behavioral and reproductive timescales.…”

Section: Discussionmentioning

confidence: 99%

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Prey–predator dynamics in rotifers: density‐dependent consequences of spatial heterogeneity due to surface attachment

Vadstein

Olsen

Andersen

2012

Ecology

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Abstract. Classical models of prey-predator interactions assume that per capita prey consumption is dependent on prey density alone and that prey consumption (functional response) and consumer proliferation (numerical response) operate on the same timescales and without time lags. Several modifications have been proposed for resolving this timescale discrepancy, including variants where the functional response depends on both prey and predator densities. A microcosm system with the rotifer Brachionus 'Nevada' feeding on the prasinophyte Tetraselmis sp. showed significant (P , 0.0005) increases in steady-state biomasses of both prey and predators with increasing carrying capacity (represented by total phosphorus of the growth medium), which is inconsistent with predictions based on the traditional prey-only-dependent functional response. We provide data indicating that surfaces where the predator can attach provide a high-quality habitat for rotifers, which can result in a predator-dependent functional response. We also show that partitioning between the attached and free-swimming habitats was fast compared to the timescale of the numerical response. When attached to surfaces, rotifers maximized net energy gain by avoiding the high cost of swimming and by increased food capture due to reduced viscous drag. A mathematical model with prey-dependent functional response and wall-attached and free-swimming fractions of the population describes our data adequately. We discuss the implications of this finding for extrapolating microcosm experiments to systems with other surface-to-volume ratios, and to what extent our findings may apply to other popular model organisms for prey-predator interaction.

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Section: Discussionmentioning

confidence: 62%

Section: Discussionmentioning

confidence: 99%

Prey–predator dynamics in rotifers: density‐dependent consequences of spatial heterogeneity due to surface attachment

Vadstein

Olsen

Andersen

2012

Ecology

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“…''Ratio-dependent'' models are a special case of predator dependence where predation rate does not depend on absolute numbers of either species but only on the prey to predator ratio (Arditi and Ginzburg 1989). Which models should be used for predicting predator-prey or food web dynamics remains controversial (Abrams and Ginzburg 2000;Fussmann et al 2005Fussmann et al , 2007Jensen et al 2007). …”

Section: Introductionmentioning

confidence: 99%

“…Feeding experiments that are nearly instantaneous relative to the generation times of model organisms are criticized for detecting only physical interference and failing to capture the interference caused by chemicals or inducible defenses (Arditi and Ginzburg 1989;Jensen et al 2007). Conversely, longer-term studies without prey replacement will give the appearance of predator dependence due to faster resource depletion in treatments with higher predator densities (Arditi and Saïah 1992;Abrams 1994).…”

Section: Introductionmentioning

confidence: 99%

Functional responses modified by predator density

et al. 2008

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Realistic functional responses are required for accurate model predictions at the community level. However, controversy remains regarding which types of dependencies need to be included in functional response models. Several studies have shown an effect of very high predator densities on per capita predation rates, but it is unclear whether this predator dependence is also important at low predator densities. We fit integrated functional response models to predation data from 4-h experiments where we had varied both predator and prey densities. Using an information theoretic approach we show that the best-fit model includes moderate predator dependence, which was equally strong even at low predator densities. The best fits of Beddington-DeAngelis and Arditi-Akçakaya functional responses were closely followed by the fit of the Arditi-Ginzburg model. A Holling type III functional response did not describe the data well. In addition, independent behavioral observations revealed high encounter rates between predators. We quantified the number of encounters between predators and the time the focal predator spent interacting with other individuals per encounter. This time "wasted" on conspecifics reduced the total time available for foraging and may therefore account for lower predation rates at higher predator densities. Our findings imply that ecological theory needs to take realistic levels of predator dependence into account.

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“…They suggested that, under certain conditions, certain functional responses are preferable. However, it still remains controversial as to which functional response should be used in predicting prey-predator dynamics [14].…”

Section: Functional and Numerical Response In Prey-predator System Inmentioning

confidence: 99%