Adaptation and the evolution of parasite virulence in a connected world
Adaptation and the evolution of parasite virulence in a connected world
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DOI：
10.1038/nature08071
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发表时间：
2009-06-18
期刊：
影响因子：
64.8
通讯作者：
West, Stuart A.
中科院分区：
文献类型：
--
作者：
Wild, Geoff;Gardner, Andy;West, Stuart A.
适应通常被认为发生在个体层面，它的作用是最大限度地提高个体的适应性（1-3）。然而，最近有人认为，对空间种群中寄生虫毒力进化的实证研究表明情况并非如此（4-7）。特别是，有人声称，为了应对有限的寄生虫传播，进化出了较低的毒力（8,9），这证明了Wynne-Edwards（10）在群体水平上的适应思想。尽管先前的理论工作表明，有限的扩散有利于降低毒性，但并没有阐明原因，给出了五种不同的建议（6,8,11-15）。在这里，我们表明传播对寄生虫毒力的影响可以完全在包容适应度理论的框架内理解。有限的寄生虫传播有利于降低寄生虫的生长速度，从而降低毒性，因为它(1)降低了产生后代的直接利益（分散者比非分散者更有价值，因为它们可以去没有或更少寄生虫的斑块），(2)增加了对宿主的竞争，焦点个体（“自我遮蔽”）和它们的亲属（“亲属遮蔽”）都经历了宿主的竞争。这表明，降低毒力可以被理解为寄生虫为最大化其包容性适应度而进行的个体水平的适应，并更广泛地阐明了与毒力理论的联系（16）。
Adaptation is conventionally regarded as occurring at the level of the individual organism, where it functions to maximize the individual's inclusive fitness(1-3). However, it has recently been argued that empirical studies on the evolution of parasite virulence in spatial populations show otherwise(4-7). In particular, it has been claimed that the evolution of lower virulence in response to limited parasite dispersal(8,9) provides proof of Wynne-Edwards's(10) idea of adaptation at the group level. Although previous theoretical work has shown that limited dispersal can favour lower virulence, it has not clarified why, with five different suggestions having been given(6,8,11-15). Here we show that the effect of dispersal on parasite virulence can be understood entirely within the framework of inclusive fitness theory. Limited parasite dispersal favours lower parasite growth rates and, hence, reduced virulence because it (1) decreases the direct benefit of producing offspring(dispersers are worth more than non-dispersers, because they can go to patches with no or fewer parasites), and (2) increases the competition for hosts experienced by both the focal individual ('self-shading') and their relatives ('kin shading'). This demonstrates that reduced virulence can be understood as an individual-level adaptation by the parasite to maximize its inclusive fitness, and clarifies the links with virulence theory more generally(16).