Data from: 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 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.

宿主接触病原体后的健康状态存在个体差异，这源于病原体载量（受宿主抗性调控）以及宿主对病原体载量的疾病反应严重程度（受宿主耐受调控）的差异。为阐明病原体驱动的宿主演化机制，我们不仅需要明确非遗传变异与遗传变异对宿主抗性和耐受的相对贡献，还需厘清这些变异如何随环境变化而改变。本研究针对两条河流中的鳟鱼同胞个体，量化了其病原体载量以及与之相关的温度依赖性疾病的非遗传与遗传变异。研究发现，在水温更低的河流中，病原体载量相关的遗传变异是另一条河流的6.6倍；与之相反，疾病相关性状的遗传变异在水温更高的河流中更为显著，该环境下疾病的表现也更为严重。在水温更高的河流中，疾病严重程度与病原体载量（即宿主耐受）之间的关系呈现出低载量下的平台期，以及高载量下斜率显著增大的特征。本研究证实了环境因素对疾病严重程度、限制宿主健康损伤的相关能力（即抗性与耐受）的非遗传与遗传变异，以及耐受曲线形态的调控作用。环境异质性被认为会调控选择作用的存在与强度，改变非遗传与遗传变异的相对贡献，进而阻碍宿主向更高抗性与耐受能力的方向演化。