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Functional immunogenetic variation, rather than local adaptation, predicts ectoparasite infection intensity in a model fish species
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  • Karl Phillips,
  • Joanne Cable,
  • Ryan Mohammed,
  • Sebastian Chmielewski,
  • Karolina Przesmycka,
  • Cock Van Oosterhout,
  • Jacek Radwan
Karl Phillips
University College Cork National University of Ireland University College Cork Boole Library
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Joanne Cable
Cardiff University
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Ryan Mohammed
The University of the West Indies at Saint Augustine
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Sebastian Chmielewski
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Karolina Przesmycka
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Cock Van Oosterhout
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Jacek Radwan
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Abstract

Natural host populations differ in their susceptibility to infection by parasites, and these intra-population differences are still an incompletely understood component of host-parasite dynamics. In this study, we used controlled infection experiments with wild-caught guppies (Poecilia reticulata) and their ectoparasite Gyrodactylus turnbulli to investigate the roles of local adaptation and host genetic composition (immunogenetic and neutral) in explaining differences in susceptibility to infection. We found differences between our four study host populations that were consistent between two parasite source populations, with no indication of local adaptation by either host or parasite at two tested spatial scales. Greater host population genetic variability metrics broadly aligned with lower population mean infection intensity, with the best alignments associated with Major Histocompatibility Complex (MHC) ‘supertypes’. Controlling for intra-population differences and potential inbreeding variance, we found a significant negative relationship between individual-level functional MHC variability and infection: fish carrying more MHC supertypes experienced infections of lower severity, with limited evidence for supertype-specific effects. We conclude that population-level differences in host infection susceptibility likely reflect variation in parasite selective pressure and/or host evolutionary potential, underpinned by functional immunogenetic variation.

Peer review status:IN REVISION

21 Apr 2021Submitted to Molecular Ecology
22 Apr 2021Assigned to Editor
22 Apr 2021Submission Checks Completed
30 Apr 2021Reviewer(s) Assigned
07 Jun 2021Review(s) Completed, Editorial Evaluation Pending
10 Jun 2021Editorial Decision: Revise Minor