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Stage-specific predator species help each other to persist while competing for a single prey
Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O. Box 94084, 1090 GB Amsterdam, The Netherlands.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
2008 (English)In: Proceedings from the National Academy of Science of the United States of America, ISSN 0027-8424, EISSN 1091-6490, Vol. 105, no 37, 13930-13935 p.Article in journal (Refereed) Published
Abstract [en]

Prey in natural communities are usually shared by many predator species. How predators coexist while competing for the same prey is one of the fundamental questions in ecology. Here we show that competing predator species may not only coexist on a single prey but even help each other to persist, if they specialize on different life history stages of the prey. By changing the prey size distribution a predator species may in fact increase the amount of prey available for its competitor. Surprisingly, a predator may even not be able to persist at all unless its competitor is also present. The competitor thus increases significantly the range of conditions for which a particular predator can persist. This “emergent facilitation” is a long-term, population-level effect that results from asymmetric increases in the rate of prey maturation and reproduction when predation relaxes competition among prey. Emergent facilitation explains observations of correlated increases of predators on small and large conspecific prey as well as concordance in their distribution patterns. Our results suggest that emergent facilitation may promote the occurrence of complex, stable community food webs and that persistence of these communities could critically depend on diversity within predator guilds.

Place, publisher, year, edition, pages
Washington, USA: The National Academy of Sciences of the United States of America , 2008. Vol. 105, no 37, 13930-13935 p.
Keyword [en]
emergent facilitation, food-dependent prey developmentpredator coexistence, prey stage, stage-specific predation
URN: urn:nbn:se:umu:diva-11414DOI: 10.1073/pnas.0803834105OAI: diva2:151085
Published online before print September 8, 2008, doi: 10.1073/pnas.0803834105 Free via Open Access: OA This research was supported by grants from the Swedish Research Council and the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning to L.P. T.S. was supported by the Lake Ecosystem Response to Environmental Change (LEREC) project. Available from: 2009-01-08 Created: 2009-01-08 Last updated: 2010-05-03Bibliographically approved
In thesis
1. The effects of stage-specific differences in energetics on community structure
Open this publication in new window or tab >>The effects of stage-specific differences in energetics on community structure
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

When intraspecific individuals differ in resource intake, scramble competition occurs among inferior individuals growing food-dependently. Scramble can be released through predation mortality. As a consequence of this release, production rates in inferior individuals increase and biomass overcompensation in the subsequent life-stages may occur. When intraspecific individuals do not differ in their resource intakes biomass overcompensation does not occur. If an individual changes its resource intake over ontogeny, the balance of intake and losses, its energetics, will change over ontogeny. Furthermore, differences will arise between the energetics of different life-stages. The predominant volume of interspecific competition theory is based on studies assuming no stage-specific differences in energetics, neglecting the influence of ontogeny on community dynamics altogether. We study how an stage-specific differences in energetics affect expectations from conventional competition theory.

We use a stage-structured biomass model consistently translating individual life history processes, in particular food-dependent growth in body size, to the population level. The stage-structured population can be reduced to an unstructured population, if the energetics of all individuals are assumed to be equal.  The stage-structured model, however can also describe population dynamics when this equality is broken. We use the stage-structured biomass model to contrast the stage-specific differences resulting in a stage-structured population model, with an unstructured population model assuming no differences between stages.

We show that stage-specific differences in energetics can affect competition on various trophic levels. I: In stead of outcompeting each other, a predator can be facilitated by another preying a scrambling prey life-stage of the same prey population. II: In coexistence with their prey, omnivores with an ontogenetic diet shift, where juvenile omnivores feed on resource and adults on prey, affect community structure only as predators, not as competitors to their prey. We show coexistence of omnivore and prey is not possible if the dominating interaction is competition. Feeding on prey, however, alleviates competition with prey and facilitates the introduction of omnivores. III: An ontogenetic diet shift creates niche partitioning, where without it this would result in neutral coexistence of two consumers competing for two resources. IV: Furthermore, predators can change resource requirements of diet shifters such that diet shifters can reduce resources to lower equilibria and sustain higher predator biomass than consumers without stage-specific differences in energetics.

Place, publisher, year, edition, pages
Umeå: Department of Ecology and Environmental Science, Umeå University, 2010. 47 p.
ontogenetic diet shift, stage-structured biomass model, food-dependence, growth, development
National Category
Earth and Related Environmental Sciences Natural Sciences
Research subject
Earth Sciences with Specialization Environmental Analysis
urn:nbn:se:umu:diva-33444 (URN)978-91-7264-996-5 (ISBN)
Public defence
2010-05-24, KBC-huset , Lilla Hörsalen, KB3A9, Umeå universitet, Linneus väg 6, Umeå, 10:00 (English)
Available from: 2010-05-03 Created: 2010-04-24 Last updated: 2010-05-07Bibliographically approved

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