title: Host allometry influences the evolution of parasite host-generalism: theory and meta-analysis.
abstract: Parasites vary widely in the diversity of hosts they infect: some parasite species are specialists-infecting just a single host species, while others are generalists, capable of infecting many. Understanding the factors that drive parasite host-generalism is of basic biological interest, but also directly relevant to predicting disease emergence in new host species, identifying parasites that are likely to have unidentified additional hosts, and assessing transmission risk. Here, we use mathematical models to investigate how variation in host body size and environmental temperature affect the evolution of parasite host-generalism. We predict that parasites are more likely to evolve a generalist strategy when hosts are large-bodied, when variation in host body size is large, and in cooler environments. We then explore these predictions using a newly updated database of over 20 000 fish-macroparasite associations. Within the database we see some evidence supporting these predictions, but also highlight mismatches between theory and data. By combining these two approaches, we establish a theoretical basis for interpreting empirical data on parasites' host specificity and identify key areas for future work that will help untangle the drivers of parasite host-generalism.This article is part of the themed issue 'Opening the black box: re-examining the ecology and evolution of parasite transmission'.
authors.affiliation: School of Biological Sciences, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TQ, UK.|School of Social and Community Medicine, University of Bristol, Oakfield House, Oakfield Grove, Bristol BS8 2BN, UK.
authors.forename: Josephine G
authors.identifier: http://orcid.org/0000-0002-9732-5738
authors.initials: JG
authors.lastname: Walker
authors.affiliation: Department of Biology, Memorial University of Newfoundland, St John's, Newfoundland, Canada A1B 3X9.|Department of Mathematics and Statistics, Memorial University of Newfoundland, St John's, Newfoundland, Canada A1C 5S7.
authors.forename: Amy
authors.initials: A
authors.lastname: Hurford
authors.affiliation: School of Biosciences, Cardiff University, Cardiff CF10 3AX, UK.
authors.forename: Jo
authors.identifier: http://orcid.org/0000-0002-8510-7055
authors.initials: J
authors.lastname: Cable
authors.affiliation: School of Biosciences, Cardiff University, Cardiff CF10 3AX, UK.
authors.forename: Amy R
authors.initials: AR
authors.lastname: Ellison
authors.affiliation: UCL Genetics Institute, Gower Street, London WC1E 6BT, UK.
authors.forename: Stephen J
authors.identifier: http://orcid.org/0000-0001-6983-6250
authors.initials: SJ
authors.lastname: Price
authors.affiliation: School of Biological Sciences, University of Nebraska-Lincoln, 424 Manter Hall, 1104 T St, Lincoln, NE 68588-0118, USA ccressler2@unl.edu.
authors.forename: Clayton E
authors.identifier: http://orcid.org/0000-0002-6281-2798
authors.initials: CE
authors.lastname: Cressler
mesh_terms: D000818:Animals; D005075:Biological Evolution; D049628:Body Size; D005399:Fishes / Q000469:parasitology*; D058507:Host Specificity; D006790:Host-Parasite Interactions; D008954:Models, Biological; D013696:Temperature
keywords: fish parasites; host range; invasion analysis; specialism; transmission