Collaborative Research: Parasitism and Mutation in the Maintenance of Sex

交叉受精的持续和广泛发生被广泛认为是自然选择进化论面临的最有趣的挑战之一。一种有希望的理论是，通过创造遗传可变的后代，交叉受精被认为是一种降低寄生虫感染风险的方法，这种寄生虫进化成攻击常见宿主基因的寄生虫。在这里，我们检验了这一理论的一些重要预测和假设。具体目标有五个方面：(1)确定寄生虫是否可以在实验室条件下进化，感染单个宿主基因类型，以及这种反应是否需要权衡感染其他宿主基因类型的能力；(2)创造并实验感染杂交蜗牛，以确定感染的遗传基础；(3)延长一项为期7年的关于宿主基因类型的进化动力学及其在自然种群中被寄生虫感染的研究；(4)测量突变累积的速度，以检验另一种理论，即交叉受精有助于消除有害突变；以及(5)对寄生虫假说提供直接的实验测试。流行病学家、作物病理学家和保护生物学家对寄主遗传多样性和共同进化的寄生虫和病原体的影响之间的相互作用感兴趣。这一结果也将引起进化生物学家的广泛兴趣，他们对自然选择对动植物繁殖策略的影响感兴趣。

The persistence and widespread occurrence of cross-fertilization is widely recognized as one of the most interesting challenges for the theory of evolution by natural selection. One promising theory is that, by creating genetically variable progeny, cross-fertilization is favored as a way to reduce the risk of infection by parasites that evolve to attack common host genotypes. Here we test some important predictions and assumptions of this theory. The specific objectives are five fold: (1) to determine whether parasites can evolve under laboratory conditions to infect individual host genotypes, and whether such a response entails a trade-off in ability to infect other host genotypes; (2) to create and experimentally infect hybrid snails to determine the genetic basis of infection; (3) to extend a seven-year study of the evolutionary dynamics of host genotypes and their infection by parasites in a natural population; (4) to measure the rate of mutation accumulation as a test of an alternative theory that cross fertilization helps eliminate harmful mutations; and (5) to provide a direct experimental test of the parasite hypothesis. The results will be of interest to epidemiologists, crop plant pathologists, and conservation biologists interested in the interplay between host genetic diversity and the effects of coevolving parasites and pathogens. The results will also be of wide interest to evolutionary biologists interested in the effects of natural selection on the reproductive strategies of plants and animals.