title: Partitioning the net effect of host diversity on an emerging amphibian pathogen.
abstract: The 'dilution effect' (DE) hypothesis predicts that diverse host communities will show reduced disease. The underlying causes of pathogen dilution are complex, because they involve non-additive (driven by host interactions and differential habitat use) and additive (controlled by host species composition) mechanisms. Here, we used measures of complementarity and selection traditionally employed in the field of biodiversity-ecosystem function (BEF) to quantify the net effect of host diversity on disease dynamics of the amphibian-killing fungus Batrachochytrium dendrobatidis (Bd). Complementarity occurs when average infection load in diverse host assemblages departs from that of each component species in uniform populations. Selection measures the disproportionate impact of a particular species in diverse assemblages compared with its performance in uniform populations, and therefore has strong additive and non-additive properties. We experimentally infected tropical amphibian species of varying life histories, in single- and multi-host treatments, and measured individual Bd infection loads. Host diversity reduced Bd infection in amphibians through a mechanism analogous to complementarity (sensu BEF), potentially by reducing shared habitat use and transmission among hosts. Additionally, the selection component indicated that one particular terrestrial species showed reduced infection loads in diverse assemblages at the expense of neighbouring aquatic hosts becoming heavily infected. By partitioning components of diversity, our findings underscore the importance of additive and non-additive mechanisms underlying the DE.
authors.affiliation: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA cgb58@cornell.edu.
authors.forename: C Guilherme
authors.initials: CG
authors.lastname: Becker
authors.affiliation: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA Department of Agriculture, Texas State University, San Marcos, TX 78666, USA.
authors.forename: David
authors.initials: D
authors.lastname: Rodriguez
authors.affiliation: Departamento de Biologia Animal, Universidade Estadual de Campinas, Campinas, São Paulo 13083-970, Brazil.
authors.forename: L Felipe
authors.initials: LF
authors.lastname: Toledo
authors.affiliation: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Ana V
authors.initials: AV
authors.lastname: Longo
authors.affiliation: Departamento de Biologia Animal, Universidade Estadual de Campinas, Campinas, São Paulo 13083-970, Brazil.
authors.forename: Carolina
authors.initials: C
authors.lastname: Lambertini
authors.affiliation: Departamento de Biologia Animal, Universidade Estadual de Campinas, Campinas, São Paulo 13083-970, Brazil Department of Integrative Biology, The University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Décio T
authors.initials: DT
authors.lastname: Corrêa
authors.affiliation: Departamento de Genética, Evolução e Bioagentes, Universidade Estadual de Campinas, Campinas, São Paulo 13083-970, Brazil.
authors.forename: Domingos S
authors.initials: DS
authors.lastname: Leite
authors.affiliation: Departamento de Zoologia, Universidade Estadual Paulista, Rio Claro, São Paulo 13506-900, Brazil.
authors.forename: Célio F B
authors.initials: CF
authors.lastname: Haddad
authors.affiliation: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Kelly R
authors.initials: KR
authors.lastname: Zamudio
mesh_terms: D000818:Animals; D001001:Anura; D044822:Biodiversity; D001938:Brazil; D008411:Chytridiomycota / Q000502:physiology*; D003247:Conservation of Natural Resources; D054884:Host-Pathogen Interactions; D009181:Mycoses / Q000382:microbiology / Q000662:veterinary*
keywords: Batrachochytrium dendrobatidis; biodiversity; dilution effect; diversity–disease relationship