| Summary: | Health after pathogen contact varies among individuals because of differences in pathogen load (which is limited by resistance) and disease severity in response to pathogen load (which is limited by tolerance). To understand pathogen-induced host evolution, it is critical to know not only the relative contributions of nongenetic and genetic variation to resistance and tolerance but also how they change environmentally. We quantified nongenetic and genetic variation in parasite load and the associated temperature-dependent disease among trout siblings from two rivers. We detected a genetic variance for parasite load 6.6 times as large in the colder river. By contrast, genetic variance for disease traits tended to be larger in the warmer river, where the disease was manifested more severely. The relationships between disease severity and pathogen load (tolerance) exhibited plateaus at low pathogen load and stronger steepening slopes at high pathogen load in the warmer river. Our study demonstrates the environmental influence on disease severity, nongenetic and genetic variance for health-damage-limiting host abilities, and the shape of tolerance curves. Environmental variability is predicted to govern the presence and intensity of selection, change the relative contributions of nongenetic and genetic variance, and therefore hamper evolution toward more resistant and tolerant hosts. Genotypes_Altja STR genotypes for Salmo trutta individuals from River Altja Genotypes_Mustoja STR genotypes for Salmo trutta individuals from River Mustoja MarkerTypeErrorRate STR genotyping error file used in parental reconstruction analysis using the program Colony MinerData.All.Ecorr qPCR quantification cycle as inferred by the online tool 'Real-time PCR Miner' http://miner.ewindup.info/ given per plate and well, including amplification efficiencies and efficiency-corrected quantification cycle PhenotypeData Phenotype and sampling information for Salmo trutta individuals from rivers Altja and Mustoja. PKD.NegativeData Phenotype ...
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