Collaborative Research: Parasitism and Mutation in the Maintenance of Sex

异种受精的持续存在和广泛发生被广泛认为是对自然选择进化理论最有趣的挑战之一。一个很有前景的理论是，通过创造基因可变的后代，异卵受精被认为是一种降低寄生虫感染风险的方法，寄生虫会进化成攻击普通宿主的基因型。在这里，我们测试了该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以感染单个宿主基因型，以及这种反应是否需要在感染其他宿主基因型的能力方面进行权衡；(2)建立并实验感染杂交钉螺，确定感染的遗传基础；(3)延续一项为期7年的宿主基因型进化动态及其在自然种群中被寄生虫感染的研究；(4)测量突变积累速率，以检验杂交受精有助于消除有害突变的另一种理论；(5)为寄生虫假说提供了直接的实验检验。研究结果将对研究寄主遗传多样性与共同进化的寄生虫和病原体之间相互作用的流行病学家、作物病理学家和保护生物学家产生重要意义。这些结果也将引起对自然选择对动植物繁殖策略影响感兴趣的进化生物学家的广泛兴趣。

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.