title: When condition trumps location: seed consumption by fruit-eating birds removes pathogens and predator attractants.
abstract: Seed ingestion by frugivorous vertebrates commonly benefits plants by moving seeds to locations with fewer predators and pathogens than under the parent. For plants with high local population densities, however, movement from the parent plant is unlikely to result in 'escape' from predators and pathogens. Changes to seed condition caused by gut passage may also provide benefits, yet are rarely evaluated as an alternative. Here, we use a common bird-dispersed chilli pepper (Capsicum chacoense) to conduct the first experimental comparison of escape-related benefits to condition-related benefits of animal-mediated seed dispersal. Within chilli populations, seeds dispersed far from parent plants gained no advantage from escape alone, but seed consumption by birds increased seed survival by 370% - regardless of dispersal distance - due to removal during gut passage of fungal pathogens and chemical attractants to granivores. These results call into question the pre-eminence of escape as the primary advantage of dispersal within populations and document two overlooked mechanisms by which frugivores can benefit fruiting plants.
authors.affiliation: Department of Biology, University of Washington, Seattle, WA 98195, USA. ecfricke@u.washington.edu
authors.forename: Evan C
authors.initials: EC
authors.lastname: Fricke
authors.forename: Melissa J
authors.initials: MJ
authors.lastname: Simon
authors.forename: Karen M
authors.initials: KM
authors.lastname: Reagan
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: Levey
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Riffell
authors.forename: Tomás A
authors.initials: TA
authors.lastname: Carlo
authors.forename: Joshua J
authors.initials: JJ
authors.lastname: Tewksbury
mesh_terms: D000818:Animals; D001717:Birds / Q000502:physiology*; D001838:Bolivia; D002212:Capsicum / Q000737:chemistry* / Q000254:growth & development / Q000382:microbiology / Q000502:physiology*; D005247:Feeding Behavior; D020387:Food Chain; D005670:Fusarium / Q000502:physiology*; D058614:Seed Dispersal; D012639:Seeds / Q000737:chemistry / Q000254:growth & development / Q000382:microbiology / Q000502:physiology
keywords: Endozoochory; Janzen-Connell hypothesis; frugivory; fungal pathogens; interaction modification; negative density dependence; seed dispersal