Data from: The role of the environment in the evolution of tolerance and resistance to a pathogen

Defense against parasites can be divided into resistance, which limits parasite burden, and tolerance, which reduces pathogenesis at a given parasite burden. Distinguishing between the two and understanding which defense is favored by evolution in different ecological settings are important, as they lead to fundamentally different evolutionary trajectories of host-parasite interactions. We let the mosquito Aedes aegypti evolve under different food levels and with either no parasite, a constant parasite, or a coevolving parasite (the microsporidian Vavraia culicis). We then tested tolerance and resistance of the evolved lines on a population level at the two food levels. Exposure to parasites during evolution increased resistance and tolerance, but there were no differences between the lines evolved with coevolving or constant parasites. Mosquitoes that had evolved with food restriction had higher resistance than those evolved with high food but similar tolerance. The mosquitoes that had restricted food when being tested had lower tolerance than those with normal food, but there was no difference in resistance. Our results emphasize the complexity and dependence on environmental conditions of the evolution and expression of resistance and tolerance and help to evaluate some of the predictions about the evolution of host defense against parasites.宿主对抗寄生虫的防御策略可分为两类：一类是抗性（resistance），即限制寄生虫负荷；另一类是耐受性（tolerance），即在既定寄生虫负荷下降低发病程度。区分这两类防御策略，并明确不同生态环境中演化更青睐哪一种防御机制，具有重要意义——二者会导致宿主-寄生虫互作演化轨迹产生根本性差异。我们让埃及伊蚊（Aedes aegypti）在不同食物水平下进行演化，同时分别施加无寄生虫、恒定寄生虫或共演化寄生虫（即微孢子虫Vavraia culicis）三种处理。随后，我们在两种食物水平下，从种群层面检测了各演化株系的耐受性与抗性。演化过程中接触寄生虫可提升宿主的抗性与耐受性，但经共演化寄生虫处理与经恒定寄生虫处理的株系之间并未出现显著差异。经食物限制处理演化的埃及伊蚊，其抗性高于经高食物水平处理演化的蚊株，但二者耐受性并无差异。在检测阶段接受食物限制的蚊株，其耐受性低于正常进食的蚊株，但抗性水平并无显著差异。本研究结果凸显了抗性与耐受性的演化及其表达的复杂性，以及其对环境条件的依赖性，同时有助于验证关于宿主抗寄生虫防御演化的部分预测假说。