Department of Zoology, University of Oxford, Oxford OX1 3PS, UK.
Ecol Lett. 2011 Jul;14(7):635-42. doi: 10.1111/j.1461-0248.2011.01624.x. Epub 2011 Apr 27.
Host-parasite coevolution is a key driver of biological diversity and parasite virulence, but its effects depend on the nature of coevolutionary dynamics over time. We used phenotypic data from coevolving populations of the bacterium Pseudomonas fluorescens SBW25 and parasitic phage SBW25Φ2, and genetic data from the phage tail fibre gene (implicated in infectivity evolution) to show that arms race dynamics, typical of short-term studies, decelerate over time. We attribute this effect to increasing costs of generalism for phages and bacteria with increasing infectivity and resistance. By contrast, fluctuating selection on individual host and parasite genotypes was maintained over time, becoming increasingly important for the phenotypic properties of parasite and host populations. Given that costs of generalism are reported for many other systems, arms races may generally give way to fluctuating selection in antagonistically coevolving populations.
寄生虫与宿主的共同进化是生物多样性和寄生虫毒力的关键驱动因素，但它的影响取决于随着时间的推移共同进化动态的性质。我们使用了从共同进化的荧光假单胞菌 SBW25 种群和寄生噬菌体 SBW25Φ2 中获得的表型数据，以及与感染性进化有关的噬菌体尾部纤维基因的遗传数据，表明典型的短期研究中的军备竞赛动态会随着时间的推移而减缓。我们将这种效应归因于随着感染性和抗性的增加，噬菌体和细菌的广义性成本增加。相比之下，随着时间的推移，对单个宿主和寄生虫基因型的波动选择得以维持，对于寄生虫和宿主种群的表型特性变得越来越重要。鉴于许多其他系统都报告了广义性成本，因此在拮抗共同进化的种群中，军备竞赛可能通常会让位于波动选择。
