Natural selection on a measure of parasite resistance varies across ages and environmental conditions in a wild mammal
Date
2011
Authors
Hayward, Adam D.
Wilson, Alastair J.
Pilkington, Jill G.
Clutton-Brock, Tim H
Pemberton, Josephine M
Kruuk, Loeske
Journal Title
Journal ISSN
Volume Title
Publisher
Blackwell Publishing Ltd
Abstract
Parasites detrimentally affect host fitness, leading to expectations of positive selection on host parasite resistance. However, as immunity is costly, host fitness may be maximized at low, but nonzero, parasite infection intensities. These hypotheses are rarely tested on natural variation in free-living populations. We investigated selection on a measure of host parasite resistance in a naturally regulated Soay sheep population using a longitudinal data set and found negative correlations between parasite infection intensity and annual fitness in lambs, male yearlings and adult females. However, having accounted for confounding effects of body weight, the effect was only significant in lambs. Associations between fitness and parasite resistance were environment-dependent, being strong during low-mortality winters, but negligible during harsher high-mortality winters. There was no evidence for stabilizing selection. Our findings reveal processes that may shape variation in parasite resistance in natural populations and illustrate the importance of accounting for correlated traits in selection analysis.
Description
Keywords
Keywords: data set; egg; fitness; host-parasite interaction; immunity; life history trait; mortality; natural selection; parasite infestation; parasitic disease; sheep; wild population; age; animal; animal disease; article; body size; feces; female; genetic selecti Faecal egg count; Parasite burden; Soay sheep; Strongyles; Teladorsagia; Trichostrongylus
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Source
Journal of Evolutionary Biology
Type
Journal article
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Restricted until
2037-12-31