Host competence, defined as the likelihood that a host will transmit infection, may be affected by an individual's resistance to infection and its ability to withstand damage caused by infection (tolerance). Host competence may therefore be one of the most important factors to impact host–parasite dynamics, yet the relationships among resistance, tolerance and competence are poorly understood. The objective of the present study was to determine whether individual host resistance (ability to resist or minimize infection) and/or tolerance (ability to withstand or minimize reduction in fitness due to infection) contributed to the competence (ability to spread infection) of hosts using guppies infected with the ectoparasite, Gyrodactylus turnbulli. This individual-fish level analysis used data collected from a previous metapopulation experiment that had tracked host–parasite dynamics at the metapopulation scale using individually marked guppies that were moved among experimental tanks within replicate metapopulations. Fish tolerance was measured as the residual from a fish's expected survival post-infection for a given parasite burden. Fish resistance was measured as the peak parasite load (– log-transformed). Host competence was measured as the incidence (number of new infections over two days after the arrival of a fish to a tank) weighted by the density of available uninfected fish in the tank. In contrast to the assumption of a trade-off between resistance and tolerance, individual fish tolerance and resistance were both negatively associated with competence. Connectivity (the number of fish with which an individual came into contact) was not associated with competence. Our results indicate that resistance and tolerance are both important to disease spread. These findings highlight the importance of understanding how individual defence against parasites may contribute to its competence as a host, and therefore impact metapopulation-level dynamics.

中文翻译：

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寄生虫在实验性复合种群中的传播：抗性、耐受性和宿主能力

宿主能力，定义为宿主传播感染的可能性，可能受个体对感染的抵抗力及其抵御感染造成的损害的能力（耐受性）的影响。因此，宿主能力可能是影响宿主 - 寄生虫动态的最重要因素之一，但对抵抗力、耐受性和能力之间的关系知之甚少。本研究的目的是确定个体宿主的抵抗力（抵抗或最小化感染的能力）和/或耐受性（抵抗或最小化因感染引起的适应性降低的能力）是否有助于宿主的能力（传播感染的能力）使用感染了外寄生虫Gyrodactylus turnbulli 的孔雀鱼. 这种个体鱼类水平分析使用从先前的集合种群实验中收集的数据，该实验使用单独标记的孔雀鱼在重复的集合种群内的实验池之间移动，在集合种群规模上跟踪宿主 - 寄生虫动态。鱼的耐受性被测量为在给定的寄生虫负荷下鱼在感染后的预期存活率。鱼的抵抗力被测量为峰值寄生虫负载（– 对数转换）。宿主能力的衡量标准是发生率（鱼到达鱼缸后两天内新感染的数量）由鱼缸中可用未感染鱼的密度加权。与抗性和耐受性之间权衡的假设相反，个体鱼的耐受性和抗性都与能力呈负相关。连通性（个人接触的鱼的数量）与能力无关。我们的结果表明抗性和耐受性对疾病传播都很重要。这些发现强调了了解个体对寄生虫的防御如何有助于其作为宿主的能力，从而影响元种群水平动态的重要性。