Bérénos C, Schmid-Hempel P, Wegner K Mathias
Experimental Ecology, Institute of Integrative Biology, ETH Zürich, 8092 Zürich, Switzerland.
J Evol Biol. 2009 Oct;22(10):2049-56. doi: 10.1111/j.1420-9101.2009.01821.x. Epub 2009 Sep 1.
Standard epidemiological theory predicts that parasites, which continuously release propagules during infection, face a trade-off between virulence and transmission. However, little is known how host resistance and parasite virulence change during coevolution with obligate killers. To address this question we have set up a coevolution experiment evolving Nosema whitei on eight distinct lines of Tribolium castaneum. After 11 generations we conducted a time-shift experiment infecting both the coevolved and the replicate control host lines with the original parasite source, and coevolved parasites from generation 8 and 11. We found higher survival in the coevolved host lines than in the matching control lines. In the parasite populations, virulence measured as host mortality decreased during coevolution, while sporeload stayed constant. Both patterns are compatible with adaptive evolution by selection for resistance in the host and by trade-offs between virulence and transmission potential in the parasite.
标准流行病学理论预测，在感染过程中持续释放繁殖体的寄生虫，在毒力和传播之间面临权衡。然而，对于在与专性杀手的协同进化过程中宿主抗性和寄生虫毒力如何变化，我们知之甚少。为了解决这个问题，我们进行了一项协同进化实验，让白僵菌在八株不同品系的赤拟谷盗上进化。11代后，我们进行了一项时间转移实验，用原始寄生虫来源以及第8代和第11代的协同进化寄生虫感染协同进化的宿主品系和复制对照宿主品系。我们发现，协同进化的宿主品系的存活率高于匹配的对照品系。在寄生虫种群中，以宿主死亡率衡量的毒力在协同进化过程中下降，而孢子负荷保持不变。这两种模式都与通过选择宿主抗性以及寄生虫毒力与传播潜力之间的权衡进行适应性进化相一致。
