title: Parasite transmission in a natural multihost-multiparasite community.
abstract: Understanding the transmission and dynamics of infectious diseases in natural communities requires understanding the extent to which the ecology, evolution and epidemiology of those diseases are shaped by alternative hosts. We performed laboratory experiments to test how parasite spillover affected traits associated with transmission in two co-occurring parasites: the bacteriumPasteuria ramosaand the fungusMetschnikowia bicuspidataBoth parasites were capable of transmission from the reservoir host (Daphnia dentifera) to the spillover host (Ceriodaphnia dubia), but this occurred at a much higher rate for the fungus than the bacterium. We quantified transmission potential by combining information on parasite transmission and growth rate, and used this to compare parasite fitness in the two host species. For both parasites, transmission potential was lower in the spillover host. For the bacterium, virulence was higher in the spillover host. Transmission back to the original host was high for both parasites, with spillover influencing transmission rate of the fungus but not the bacterium. Thus, while inferior, the spillover host is not a dead-end for either parasite. Overall, our results demonstrate that the presence of multiple hosts in a community can have important consequences for disease transmission, and host and parasite fitness.This article is part of the themed issue 'Opening the black box: re-examining the ecology and evolution of parasite transmission'.
authors.affiliation: Biological and Environmental Sciences, University of Stirling, Stirling FK9 4LA, UK s.k.auld@stir.ac.uk.
authors.forename: Stuart K J R
authors.identifier: http://orcid.org/0000-0001-6691-7442
authors.initials: SK
authors.lastname: Auld
authors.affiliation: Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Catherine L
authors.identifier: http://orcid.org/0000-0002-6607-2299
authors.initials: CL
authors.lastname: Searle
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109-1048, USA.
authors.forename: Meghan A
authors.identifier: http://orcid.org/0000-0002-8142-0802
authors.initials: MA
authors.lastname: Duffy
mesh_terms: D000818:Animals; D005075:Biological Evolution; D033361:Cladocera / Q000382:microbiology*; D003621:Daphnia / Q000382:microbiology; D005260:Female; D058507:Host Specificity; D054884:Host-Pathogen Interactions; D055163:Metschnikowia / Q000502:physiology*; D058676:Pasteuria / Q000502:physiology*
keywords: epidemics; host–parasite interactions; spillback; spillover; virulence evolution