Seeing Double:

Gilljam, David; Thierry, Aaron; Edwards, François; Figueroa, David; Ibbotson, A.T.; Jones, J. Iwan; Lauridsen, Rasmus B.; Petchey, Owen L.; Woodward, Guy; Ebenman, Bo

doi:10.1016/b978-0-12-386475-8.00003-4

Cited by 64 publications

(11 citation statements)

References 107 publications

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“…Furthermore, species which ultimately reach a larger body size usually pass through a larger range of sizes during their growth, particularly in freshwater systems (Werner & Gilliam, 1984). This which allows or necessitates that, over the course of their life time, they exploit a wider range of resources than smaller individuals (Gilljam et al, 2011;Woodward, Ebenman, et al, 2005). In this way, a species may collectively exhibit a higher level of omnivory than a particular individual of that species at any one point in time.…”

Section: Overview Of Omn Ivorymentioning

confidence: 99%

Omnivory and stability in freshwater habitats: Does theory match reality?

Wootton

2017

Freshwater Biology

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Abstract1. Omnivory, feeding at more than one trophic level, is a prevalent feature of freshwater ecosystems. Understanding where and when omnivory is important, its relevance for sustaining diversity, and the effect it may have on ecosystem responses to disturbances, are necessary for effective management of freshwater ecosystems.2. The many theoretical predictions of the effects of omnivory are often contradictory, and empirical studies aimed at understanding omnivory have been difficult and contingent on a number of factors. Here, I synthesise theoretical evidence to generate five predictions of where omnivory will be most important in freshwater ecosystems, how it is maintained and the effect it will have on communities.3. First, theory indicates that, while strong omnivorous interactions are destabilising, weak omnivorous interactions usually enhance stability. Therefore, mechanisms which decrease the strength of omnivorous interactions should favour their occurrence and increase stability of food webs. Secondly, omnivorous interactions which are theoretically unstable may be found in stable food webs due to stabilising features of the web as a whole. Thirdly, omnivory is likely to persist primarily at intermediate productivity levels and be more common in disturbed environments. Fourthly, omnivory is likely to decrease the strength of trophic cascades. Finally, omnivores should generally make more successful invaders.4. These predictions are important for effective freshwater management because actions which decrease the strength of omnivorous interactions, such as maintaining habitat refuges for consumers (e.g. woody debris and aquatic plants), may be essential for sustaining biodiversity. In addition, if omnivores make better invaders, effective invasion management may benefit from focussing resources on omnivorous invaders to limit their spread and impact.5. Overall, this synthesis of theoretical and empirical studies indicates that, while their predictions may be frequently at odds, with deeper investigation they are largely reconcilable and can be used to make practical suggestions for the careful management of omnivory in freshwater food webs. K E Y W O R D Shabitat refuge, intraguild predation, trophic cascade, trophic level, weak interactions

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Section: Overview Of Omn Ivorymentioning

confidence: 99%

Omnivory and stability in freshwater habitats: Does theory match reality?

Wootton

2017

Freshwater Biology

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“…Their reduced abundance or extinction has particularly important implications for aquatic food webs, which are often strongly size-structured [15][16][17][18][19][20][21]. For instance, changes in the mass and abundance of consumers and resources can trigger dramatic changes, including trophic cascades and secondary extinctions [4,10,17].…”

Section: Introductionmentioning

confidence: 99%

Climate change impacts in multispecies systems: drought alters food web size structure in a field experiment

Woodward

Brown

Edwards

et al. 2012

Phil. Trans. R. Soc. B

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Experimental data from intergenerational field manipulations of entire food webs are scarce, yet such approaches are essential for gauging impacts of environmental change in natural systems. We imposed 2 years of intermittent drought on stream channels in a replicated field trial, to measure food web responses to simulated climate change. Drought triggered widespread losses of species and links, with larger taxa and those that were rare for their size, many of which were predatory, being especially vulnerable. Many network properties, including size -scaling relationships within food chains, changed in response to drought. Other properties, such as connectance, were unaffected. These findings highlight the need for detailed experimental data from different organizational levels, from pairwise links to the entire food web. The loss of not only large species, but also those that were rare for their size, provides a newly refined way to gauge likely impacts that may be applied more generally to other systems and/or impacts.

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“…Individual body size is often the trait used to describe community state (Andersen, Jacobsen, et al, 2015) because this trait influences metabolic rates (West, Brown, & Enquist, 1997), prey size (Barnes, Maxwell, Reuman, & Jennings, 2010;Gilljam et al, 2011), swimming performance (Ware, 1978) and the biomass distribution of individuals (Sheldon & Parsons, 1967;Sheldon et al, 1972). The assumption that individual body size governs community processes can result in a model with a fixed number of parameters regardless of the number of species.…”

Section: Trait-based Models To Inform Ecosystembased Managementmentioning

confidence: 99%

Realizing the potential of trait‐based approaches to advance fisheries science

et al. 2019

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Analysing how fish populations and their ecological communities respond to perturbations such as fishing and environmental variation is crucial to fisheries science. Researchers often predict fish population dynamics using species‐level life‐history parameters that are treated as fixed over time, while ignoring the impact of intraspecific variation on ecosystem dynamics. However, there is increasing recognition of the need to include processes operating at ecosystem levels (changes in drivers of productivity) while also accounting for variation over space, time and among individuals. To address similar challenges, community ecologists studying plants, insects and other taxa increasingly measure phenotypic characteristics of individual animals that affect fitness or ecological function (termed “functional traits”). Here, we review the history of trait‐based methods in fish and other taxa, and argue that fisheries science could see benefits by integrating trait‐based approaches within existing fisheries analyses. We argue that measuring and modelling functional traits can improve estimates of population and community dynamics, and rapidly detect responses to fishing and environmental drivers. We support this claim using three concrete examples: how trait‐based approaches could account for time‐varying parameters in population models; improve fisheries management and harvest control rules; and inform size‐based models of marine communities. We then present a step‐by‐step primer for how trait‐based methods could be adapted to complement existing models and analyses in fisheries science. Finally, we call for the creation and expansion of publicly available trait databases to facilitate adapting trait‐based methods in fisheries science, to complement existing public databases of life‐history parameters for marine organisms.

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Seeing Double:

Cited by 64 publications

References 107 publications

Omnivory and stability in freshwater habitats: Does theory match reality?

Omnivory and stability in freshwater habitats: Does theory match reality?

Climate change impacts in multispecies systems: drought alters food web size structure in a field experiment

Realizing the potential of trait‐based approaches to advance fisheries science

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