Quantitative genetic variation in, and environmental effects on, pathogen resistance and temperature-dependent disease severity in a wild trout

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 dem...

病原体（pathogen）接触后，个体的健康状态存在显著差异，这源于病原体载量（pathogen load，受抗性（resistance）调控）以及针对该载量的疾病严重程度（受耐受性（tolerance）调控）的不同。为解析病原体驱动的宿主演化（host evolution）进程，明确非遗传变异（nongenetic variation）与遗传变异（genetic variation）对宿主抗性和耐受性的相对贡献，以及二者如何随环境变化而改变，至关重要。我们对来自两条河流的鳟鱼（trout）同胞个体的病原体载量及与之相关的温度依赖性疾病（temperature-dependent disease）开展了定量分析。结果显示，在水温更低的河流中，病原体载量的遗传方差是另一河流的6.6倍。与之相反，在疾病表现更为严重的水温较高的河流中，疾病相关性状的遗传方差往往更大。在水温较高的河流中，疾病严重程度与病原体载量（即耐受性）之间的关系呈现出：低载量阶段存在平台期，高载量阶段斜率显著陡增。本研究[原文未完结]