Duncan Alison B, Little Tom J
Institute of Evolutionary Biology, School of Biology, University of Edinburgh, Kings Buildings, West Mains Road, Edinburgh, EH9 3JT, United Kingdom.
Evolution. 2007 Apr;61(4):796-803. doi: 10.1111/j.1558-5646.2007.00072.x.
A substantial body of theory indicates that parasites may mould the population genetic structure of their hosts, but few empirical studies have directly linked parasitism to genetic dynamics. We used molecular markers (allozymes) to investigate genotype frequency changes in a natural population of the crustacean Daphnia magna in relation to an epidemic of the bacterial pathogen Pasteuria ramosa. The population experienced a severe epidemic during the study period in which parasite prevalence reached 100% of the adult portion of the population. The parasite epidemic was associated with genetic change in the host population. Clonal diversity was observed to decrease as parasite prevalence increased in the population, and tests for differences in the clonal composition of the population before, during, and after the epidemic indicated that significant change had occurred. A laboratory infection experiment showed that the genotypes which were more common following the peak of the parasite epidemic were also the most resistant to parasite infection. Thus, this study provides an illustration of parasite-mediated selection in the wild.
大量理论表明，寄生虫可能会塑造其宿主的种群遗传结构，但很少有实证研究直接将寄生现象与遗传动态联系起来。我们使用分子标记（等位酶）来研究甲壳动物大型溞自然种群中的基因型频率变化，该变化与细菌性病原菌罗氏巴斯德氏菌的一次流行有关。在研究期间，该种群经历了一次严重的流行病，其中寄生虫在成年种群中的患病率达到了100%。寄生虫流行与宿主种群的遗传变化相关。随着种群中寄生虫患病率的增加，观察到克隆多样性降低，并且对流行病之前、期间和之后种群克隆组成差异的测试表明发生了显著变化。一项实验室感染实验表明，在寄生虫流行高峰之后更常见的基因型也是对寄生虫感染最具抗性的。因此，本研究例证了野外寄生虫介导的选择。
