Department of Genetics, University of Cambridge, Cambridge, United Kingdom; School of Biological Sciences, University of East Anglia, Norwich, United Kingdom
Jonathan P Day
Department of Genetics, University of Cambridge, Cambridge, United Kingdom
Davide Maria Vespasiani
Department of Genetics, University of Cambridge, Cambridge, United Kingdom
Yannik Thüringer
Department of Genetics, University of Cambridge, Cambridge, United Kingdom
Department of Genetics, University of Cambridge, Cambridge, United Kingdom; Centre for Ecology and Conservation, Biosciences, University of Exeter (Penryn Campus), Cornwall, United Kingdom
It is common to find considerable genetic variation in susceptibility to infection in natural populations. We have investigated whether natural selection increases this variation by testing whether host populations show more genetic variation in susceptibility to pathogens that they naturally encounter than novel pathogens. In a large cross-infection experiment involving four species of Drosophila and four host-specific viruses, we always found greater genetic variation in susceptibility to viruses that had coevolved with their host. We went on to examine the genetic architecture of resistance in one host species, finding that there are more major-effect genetic variants in coevolved host-pathogen interactions. We conclude that selection by pathogens has increased genetic variation in host susceptibility, and much of this effect is caused by the occurrence of major-effect resistance polymorphisms within populations.
