title: When experimental selection for virulence leads to loss of virulence.
abstract: Information on virulence evolution is critical for understanding disease dynamics. Theory predicts that under certain evolutionary conditions virulence should increase; for example, during host-parasite coevolution. Although these theoretical predictions are supported by natural observations, tests of these hypotheses using experimental evolution have yielded confounding and contradictory results, with discrepancies often being seen among experiments. Here we provide a critical overview of experimental tests of hypotheses regarding virulence evolution and provide potential explanations for the contradictory results. We emphasise the key role of parasite transmission mechanisms that can explain many of the observed discrepancies among evolution experiments. Finally, we make suggestions for how evolution experiments could be conducted in the future to avoid potentially confounding factors.
authors.affiliation: Department of Zoology, University of Oxford, The Tinbergen Building, South Parks Road, Oxford OX1 3PS, UK; Evolutionary Ecology and Genetics, Zoologisches Institut, CAU Kiel, Am Botanischen Garten 1-9, 24119 Kiel, Germany; Institute for Phytopathology and Applied Zoology, University of Giessen, Heinrich-Buff-Ring 26-32, 35392 Gießen, Germany. Electronic address: charlotte.rafaluk@gmail.com.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Rafaluk
authors.affiliation: Evolutionary Ecology and Genetics, Zoologisches Institut, CAU Kiel, Am Botanischen Garten 1-9, 24119 Kiel, Germany.
authors.forename: Gunther
authors.initials: G
authors.lastname: Jansen
authors.affiliation: Evolutionary Ecology and Genetics, Zoologisches Institut, CAU Kiel, Am Botanischen Garten 1-9, 24119 Kiel, Germany.
authors.forename: Hinrich
authors.initials: H
authors.lastname: Schulenburg
authors.affiliation: Institute for Phytopathology and Applied Zoology, University of Giessen, Heinrich-Buff-Ring 26-32, 35392 Gießen, Germany.
authors.forename: Gerrit
authors.initials: G
authors.lastname: Joop
mesh_terms: D000818:Animals; D005075:Biological Evolution; D006790:Host-Parasite Interactions / Q000235:genetics / Q000502:physiology*; D008962:Models, Theoretical; D010271:Parasites / Q000472:pathogenicity*; D010272:Parasitic Diseases / Q000469:parasitology / Q000635:transmission*; D014774:Virulence / Q000502:physiology*
keywords: coevolution; experimental evolution; serial passage; trade-off hypothesis; transmission; virulence