Virulence-transmission trade-offs and population divergence in virulence in a naturally occuring butterfly parasite
Virulence-transmission trade-offs and population divergence in virulence in a naturally occuring butterfly parasite
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DOI：
10.1073/pnas.0710909105
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发表时间：
2008-05-27
影响因子：
11.1
通讯作者：
Altizer, Sonia
中科院分区：
文献类型：
--
作者：
de Roode, Jacobus C.;Yates, Andrew J.;Altizer, Sonia
为什么寄生虫会伤害宿主？传统观点认为，因为寄生虫。它们的生存和传播依赖于宿主，它们应该进化成良性的，然而许多寄生虫会造成伤害。理论预测，寄生虫可以通过平衡寄生虫复制的传播利益与宿主死亡的代价来进化出毒力（即寄生虫诱导的宿主适应性降低）。这一观点使研究人员预测人类干预（如疫苗）如何改变毒力进化，但缺乏经验支持。我们研究了黑脉金斑蝶的一种原生动物寄生虫，发现较高水平的宿主内复制会导致更高的毒力和更大的传播，从而支持寄生虫传播的选择倾向于导致实质性伤害的寄生虫基因型的观点。寄生虫的适应性在寄生虫复制的中间水平达到最大，超过这个水平，宿主死亡率增加的代价超过了传播增加的好处。一项单独的实验证实了寄生虫复制与毒力之间的遗传关系，并表明来自两个黑脉金斑蝶种群的寄生虫基因型导致不同的毒力。这些结果表明，寄生虫传播的选择可以解释为什么寄生虫对宿主有害，并表明宿主生态施加的约束可能导致寄生虫毒力的种群差异。
Why do parasites harm their hosts? Conventional wisdom holds that because parasites. depend on their hosts for survival and transmission, they should evolve to become benign, yet many parasites cause harm. Theory predicts that parasites could evolve virulence (i.e., parasite-induced reductions in host fitness) by balancing the transmission benefits of parasite replication with the costs of host death. This idea has led researchers to predict how human interventions-such as vaccines-may alter virulence evolution, yet empirical support is critically lacking.. We studied a protozoan parasite of monarch butterflies and found that higher levels of within-host replication resulted in both higher virulence and greater transmission, thus lending support to the idea that selection for parasite transmission can favor parasite genotypes that cause substantial harm. Parasite fitness was maximized at an intermediate level of parasite replication, beyond which the cost of increased host mortality outweighed the benefit of increased transmission. A separate experiment confirmed genetic relationships between parasite replication and virulence, and showed that parasite genotypes from two monarch populations caused different virulence. These results show that selection on parasite transmission can explain why parasites harm their hosts, and suggest that constraints imposed by host ecology can lead to population divergence in parasite virulence.