Antagonistic selection from predators and pathogens alters food-web structure

Selection can alter predator-prey interactions. However, whether and how complex food-webs respond to selection remain largely unknown. We show in the field that antagonistic selection from predators and pathogens on prey body-size can be a primary driver of food-web functioning. In Windermere, U.K....

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Bibliographic Details
Published in:	Proceedings of the National Academy of Sciences - PNAS 2008-12, Vol.105 (50), p.19792-19796
Main Authors:	Edeline, Eric, Ari, Tamara Ben, Vøllestad, L. Asbjørn, Winfield, Ian J, Fletcher, Janice M, James, J. Ben, Stenseth, Nils C
Format:	Article
Language:	eng
Subjects:	Animals Biodiversity and Ecology Biological Sciences Body length Body temperature Communities Ecological competition Ecological genetics Ecology Ecology, environment Environmental Monitoring Environmental Sciences Esocidae - physiology Esox lucius Evolution Female Fish Fish Diseases Food Chain Food chains Food Preferences Life Sciences Male Pathogens Perca fluviatilis Perches - growth & development Perches - physiology Population Predation Predators Trophic relationships
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Summary:	Selection can alter predator-prey interactions. However, whether and how complex food-webs respond to selection remain largely unknown. We show in the field that antagonistic selection from predators and pathogens on prey body-size can be a primary driver of food-web functioning. In Windermere, U.K., pike (Esox lucius, the predator) selected against small perch (Perca fluviatilis, the prey), while a perch-specific pathogen selected against large perch. The strongest selective force drove perch trait change and ultimately determined the structure of trophic interactions. Before 1976, the strength of pike-induced selection overrode the strength of pathogen-induced selection and drove a change to larger, faster growing perch. Predation-driven increase in the proportion of large, infection-vulnerable perch presumably favored the pathogen since a peak in the predation pressure in 1976 coincided with pathogen expansion and a massive perch kill. After 1976, the strength of pathogen-induced selection overrode the strength of predator-induced selection and drove a rapid change to smaller, slower growing perch. These changes made perch easier prey for pike and weaker competitors against juvenile pike, ultimately increasing juvenile pike survival and total pike numbers. Therefore, although predators and pathogens exploited the same prey in Windermere, they did not operate competitively but synergistically by driving rapid prey trait change in opposite directions. Our study empirically demonstrates that a consideration of the relative strengths and directions of multiple selective pressures is needed to fully understand community functioning in nature.
ISSN:	0027-8424 1091-6490