关于适应性的传统观点是，它在生物个体层面上发挥作用，但关于在具有空间结构的种群中（在这种种群中扩散是有限的）感染蛾子和细菌的病毒毒性之演化的最新观测结果，却被解释为群体选择的例子。
Wild等人在此用数学方法对以前的模型进行了延伸，发现扩散对寄生虫毒性的影响，可以完全在亲缘选择理论的范畴内被理解为寄生虫在个体层面上的一种适应行为。（生物谷Bioon.com）
生物谷推荐原始出处：
Nature 459, 983-986 (18 June 2009) | doi:10.1038/nature08071
Adaptation and the evolution of parasite virulence in a connected world
Geoff Wild1, Andy Gardner2 & Stuart A. West3
1 Department of Applied Mathematics, University of Western Ontario, London, Ontario N6A 5B7, Canada
2 Institute of Evolutionary Biology, University of Edinburgh, King's Buildings, Edinburgh EH9 3JT, UK
3 Department of Zoology, University of Oxford, Oxford OX1 3PS, UK
Adaptation is conventionally regarded as occurring at the level of the individual organism, where it functions to maximize the individual's inclusive fitness1, 2, 3. However, it has recently been argued that empirical studies on the evolution of parasite virulence in spatial populations show otherwise4, 5, 6, 7. In particular, it has been claimed that the evolution of lower virulence in response to limited parasite dispersal8, 9 provides proof of Wynne-Edwards's10 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 given6, 8, 11, 12, 13, 14, 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 generally16.
