Institute for Evolution and Biodiversity, Westphalian Wilhelms-University Muenster, 48149 Muenster, Germany.
Proc Natl Acad Sci U S A. 2010 Apr 20;107(16):7359-64. doi: 10.1073/pnas.1003113107. Epub 2010 Apr 5.
The coevolution between hosts and parasites is predicted to have complex evolutionary consequences for both antagonists, often within short time periods. To date, conclusive experimental support for the predictions is available mainly for microbial host systems, but for only a few multicellular host taxa. We here introduce a model system of experimental coevolution that consists of the multicellular nematode host Caenorhabditis elegans and the microbial parasite Bacillus thuringiensis. We demonstrate that 48 host generations of experimental coevolution under controlled laboratory conditions led to multiple changes in both parasite and host. These changes included increases in the traits of direct relevance to the interaction such as parasite virulence (i.e., host killing rate) and host resistance (i.e., the ability to survive pathogens). Importantly, our results provide evidence of reciprocal effects for several other central predictions of the coevolutionary dynamics, including (i) possible adaptation costs (i.e., reductions in traits related to the reproductive rate, measured in the absence of the antagonist), (ii) rapid genetic changes, and (iii) an overall increase in genetic diversity across time. Possible underlying mechanisms for the genetic effects were found to include increased rates of genetic exchange in the parasite and elevated mutation rates in the host. Taken together, our data provide comprehensive experimental evidence of the consequences of host-parasite coevolution, and thus emphasize the pace and complexity of reciprocal adaptations associated with these antagonistic interactions.
宿主和寄生虫之间的共同进化预计会对两者都产生复杂的进化后果，通常在短时间内发生。迄今为止，主要针对微生物宿主系统提供了确凿的实验支持，但仅针对少数多细胞宿主分类群。在这里，我们引入了一个实验共同进化的模型系统，该系统由多细胞线虫宿主秀丽隐杆线虫和微生物寄生虫苏云金芽孢杆菌组成。我们证明，在受控实验室条件下进行的 48 代宿主共同进化实验导致了寄生虫和宿主的多种变化。这些变化包括与相互作用直接相关的特征的增加，例如寄生虫的毒力（即宿主致死率）和宿主的抗性（即抵抗病原体的能力）。重要的是，我们的结果为共同进化动态的其他几个中心预测提供了证据，包括（i）可能的适应成本（即，在没有拮抗剂的情况下，与繁殖率相关的特征减少），（ii）快速的遗传变化，以及（iii）随着时间的推移遗传多样性的整体增加。发现遗传效应的潜在机制包括寄生虫中遗传交换率的增加和宿主中突变率的升高。总之，我们的数据提供了宿主-寄生虫共同进化后果的综合实验证据，因此强调了与这些拮抗相互作用相关的相互适应的速度和复杂性。
