Stutz William E, Calhoun Dana M, Johnson Pieter T J
Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO, 80309, USA.
Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO, 80309, USA.
Exp Parasitol. 2019 Apr;199:80-91. doi: 10.1016/j.exppara.2019.03.001. Epub 2019 Mar 9.
Hosts have two general strategies for mitigating the fitness costs of parasite exposure and infection: resistance and tolerance. The resistance-tolerance framework has been well developed in plant systems, but only recently has it been applied to animal-parasite interactions. However, difficulties associated with estimating fitness, controlling parasite exposure, and quantifying parasite burden have limited application of this framework to animal systems. Here, we used an experimental approach to quantify the relative influence of variation among host individuals and genetic families in determining resistance and tolerance within an amphibian-trematode system. Importantly, we used multiple, alternative metrics to assess each strategy, and employed a Bayesian analytical framework to compare among responses while incorporating uncertainty. Relative to unexposed hosts, exposure to the pathogenic trematode (Ribeiroia ondatrae) reduced the survival and growth of California newts (Taricha torosa) (survival: 93% vs. 74%; growth: 0.29 vs. -0.5 vs mm day ). Similarly, parasite infection success (the inverse of resistance) ranged from 8% to 100%. Yet despite this broad variation in host resistance and tolerance among individual newts, we found no evidence for transmissable, among-family variation in any of the resistance or tolerance metrics. This suggests that opportunities for evolution of these traits is limited, likely requiring significant increases in mutation, gene flow, or environmental heterogeneity. Our study provides a quantitative framework for evaluating the importance of alternative metrics of resistance and tolerance across multiple time points in the study of host-parasite interactions in animal systems.
抗性和耐受性。抗性 - 耐受性框架在植物系统中已得到充分发展，但直到最近才应用于动物 - 寄生虫相互作用。然而，与估计适应性、控制寄生虫暴露和量化寄生虫负荷相关的困难限制了该框架在动物系统中的应用。在这里，我们采用实验方法来量化宿主个体和遗传家族间的变异在确定两栖动物 - 吸虫系统中的抗性和耐受性方面的相对影响。重要的是，我们使用多种替代指标来评估每种策略，并采用贝叶斯分析框架在纳入不确定性的同时比较不同反应。相对于未暴露的宿主，暴露于致病性吸虫（Ribeiroia ondatrae）会降低加州蝾螈（Taricha torosa）的生存和生长（生存：93% 对 74%；生长：0.29 对 -0.5 毫米/天）。同样，寄生虫感染成功率（抗性的倒数）从 8% 到 100% 不等。然而，尽管个体蝾螈之间的宿主抗性和耐受性存在广泛差异，但我们没有发现任何抗性或耐受性指标在家族间存在可传播变异的证据。这表明这些性状的进化机会有限，可能需要突变、基因流或环境异质性显著增加。我们的研究提供了一个定量框架，用于评估在动物系统宿主 - 寄生虫相互作用研究中多个时间点上抗性和耐受性替代指标的重要性。
