Brockhurst Michael A, Buckling Angus, Poullain Virginie, Hochberg Michael E
School of Biological Sciences, Biosciences Building, University of Liverpool, Crown Street, Liverpool L69 7ZB, United Kingdom.
Evolution. 2007 May;61(5):1238-43. doi: 10.1111/j.1558-5646.2007.00087.x.
Natural populations of hosts and parasites are often subdivided and patchily distributed such that some regions of a host species' range will be free from a given parasite. Host migration from parasite-free to parasite-containing patches is expected to alter coevolutionary dynamics by changing the evolutionary potential of antagonists. Specifically, host immigration can favor parasites by increasing transmission opportunities, or hosts by introducing genetic variation. We tested these predictions in coevolving populations of Pseudomonas fluorescens and phage Phi2 that received immigrants from phage-free populations. We observed a negative quadratic relationship between sympatric resistance to phage and host immigration rate (highest at intermediate immigration) but a positive quadratic relationship between coevolution rate and host immigration rate (lowest at intermediate immigration). These results indicate that for a wide range of rates, host immigration from parasite-free patches can increase the evolutionary potential of parasites, and increase the coevolutionary rate if parasite adaptation is limiting in the absence of immigration.
宿主和寄生虫的自然种群通常是细分且分布不均的，以至于宿主物种分布范围内的某些区域不会受到特定寄生虫的影响。预计宿主从无寄生虫斑块迁移到有寄生虫斑块会通过改变拮抗者的进化潜力来改变协同进化动态。具体而言，宿主迁入可以通过增加传播机会来有利于寄生虫，或者通过引入遗传变异来有利于宿主。我们在荧光假单胞菌和噬菌体Phi2的协同进化种群中测试了这些预测，这些种群接收了来自无噬菌体种群的移民。我们观察到对噬菌体的同域抗性与宿主迁入率之间呈负二次关系（在中等迁入率时最高），但协同进化率与宿主迁入率之间呈正二次关系（在中等迁入率时最低）。这些结果表明，在广泛的迁入率范围内，来自无寄生虫斑块的宿主迁入可以增加寄生虫的进化潜力，并且如果在没有迁入的情况下寄生虫适应受到限制，则可以提高协同进化率。
