title: Why fruit rots: theoretical support for Janzen's theory of microbe-macrobe competition.
abstract: We present a formal model of Janzen's influential theory that competition for resources between microbes and vertebrates causes microbes to be selected to make these resources unpalatable to vertebrates. That is, fruit rots, seeds mould and meat spoils, in part, because microbes gain a selective advantage if they can alter the properties of these resources to avoid losing the resources to vertebrate consumers. A previous model had failed to find circumstances in which such a costly spoilage trait could flourish; here, we present a simple analytic model of a general situation where costly microbial spoilage is selected and persists. We argue that the key difference between the two models lies in their treatments of microbial dispersal. If microbial dispersal is sufficiently spatially constrained that different resource items can have differing microbial communities, then spoilage will be selected; however, if microbial dispersal has a strong homogenizing effect on the microbial community then spoilage will not be selected. We suspect that both regimes will exist in the natural world, and suggest how future empirical studies could explore the influence of microbial dispersal on spoilage.
authors.affiliation: School of Biology, University of St Andrews, , St Andrews KY16 9TH, UK, Biology and Earth sciences, Liverpool John Moores University, , Liverpool L3 3AF, UK, Department of Evolutionary Biology and Animal Ecology, Faculty of Biology, University of Freiburg, , Hauptstrasse 1, Freiburg 79104, Germany, Department of Biology, Carleton University, , Ottawa, Ontario, Canada , K1S 5B6.
authors.forename: Graeme D
authors.initials: GD
authors.lastname: Ruxton
authors.forename: David M
authors.initials: DM
authors.lastname: Wilkinson
authors.forename: H Martin
authors.initials: HM
authors.lastname: Schaefer
authors.forename: Thomas N
authors.initials: TN
authors.lastname: Sherratt
mesh_terms: D000818:Animals; D002755:Choice Behavior; D017753:Ecosystem; D005247:Feeding Behavior / Q000502:physiology*; D005638:Fruit / Q000382:microbiology*; D064307:Microbiota; D008954:Models, Biological; D014714:Vertebrates
keywords: carrion; competition; frugivory; fungus; metapopulations; yeast