Data from: Experimental evolution with a multicellular host causes diversification within and between microbial parasite populations – differences in emerging phenotypes of two different parasite strains

Host-parasite coevolution is predicted to have complex evolutionary consequences, potentially leading to the emergence of genetic and phenotypic diversity for both antagonists. However, little is known about variation in phenotypic responses to coevolution between different parasite strains exposed to the same experimental conditions. We infected Caenorhabditis elegans with one of two strains of Bacillus thuringiensis and either allowed the host and the parasite to experimentally coevolve (coevolution treatment) or allowed only the parasite to adapt to the host (one-sided parasite adaptation). By isolating single parasite clones from evolved populations, we found phenotypic diversification of the ancestral strain into distinct clones, which varied in virulence towards ancestral hosts and competitive ability against other parasite genotypes. Parasite phenotypes differed remarkably not only between the two strains, but also between and within different replicate populations, indicating diversification of the clonal population caused by selection. This study highlights that the evolutionary selection pressure mediated by a multicellular host causes phenotypic diversification, but not necessarily with the same phenotypic outcome for different parasite strains.宿主-寄生虫协同进化（Host-parasite coevolution）被预测会产生复杂的进化效应，有望促成两类拮抗生物各自形成遗传与表型多样性。然而，目前对于同一实验条件下的不同寄生虫菌株，其针对协同进化的表型响应差异仍知之甚少。本研究将秀丽隐杆线虫（Caenorhabditis elegans）分别感染两种苏云金芽孢杆菌（Bacillus thuringiensis）菌株中的一种，并设置两种实验处理：允许宿主与寄生虫进行实验性协同进化（coevolution treatment），或仅允许寄生虫适配宿主（one-sided parasite adaptation）。通过从进化后的种群中分离单个寄生虫克隆，我们发现祖先菌株的表型发生了分化，形成多个不同的克隆类群，这些类群在对祖先宿主的毒力以及与其他寄生虫基因型的竞争能力上均存在差异。寄生虫的表型不仅在两种原始菌株间存在显著差异，在不同重复种群之间以及种群内部也存在显著分化，这表明选择作用可引发克隆种群的表型多样化。本研究表明，由多细胞宿主介导的进化选择压力能够引发表型分化，但不同寄生虫菌株的表型演化结果未必一致。