Cytoplasmic Imcompatibility in Flour Beetles: A Model of Host-Parasite Coevolution

寄生虫无处不在，可以对宿主进行长期的强大选择。宿主与寄生虫的相互作用可能促进物种多样性，改变宿主行为，促进物种形成，也许还会促进和维持性行为。我的研究使用一种常见的节肢动物寄生虫来研究宿主-寄生虫的共同进化。这种寄生虫是一种细胞质传播的细菌，会导致生殖不相容。受感染的雄性和未受感染的雌性杂交是不育的。通过“绝育”不传播寄生虫的雌性，受感染的雄性增加了感染的频率，寄生虫应该传播，直到所有个体都被感染。讨论了关于宿主-寄生虫共同进化的两个问题。寄生虫诱导的对宿主繁殖成功的影响是否存在遗传变异？一项基因分析测量了寄生虫对宿主繁殖成功影响的遗传性。对选择(R)的响应取决于选择(S)和遗传力（h2）， R=S*h2。因此，该实验阐明了宿主-寄生虫系统进化的潜力。第二个问题是：寄生虫的毒力是如何进化的？新的寄生虫菌株将被引入不同的宿主遗传背景。寄生虫对宿主的影响将在长期和短期内进行测量。本实验是寄生虫毒力模型的重要试验。总之，这些实验提供了宿主-寄生虫共同进化的重要信息。

Parasites are ubiquitous and can exert powerful long-term selection on hosts. Host-parasite interactions may promote species diversity, alter host behavior, contribute to speciation and perhaps foster and maintain sex. My research uses a common arthropod parasite to investigate host-parasite coevolution. The parasite is a cytoplasmically transmitted bacterium that causes reproductive incompatability. Crosses between infected males and uninfected females are sterile. By "sterilizing" females not transmitting the parasite, infected males increase the frequency of infection and the parasite should spread until all individuals are infected. Two questions about host-parasite coevolution are addressed. Is there genetic variation for parasite-induced affects on host reproductive success? A genetic analysis measures the heritability of the parasite's effect on the host reproductive success. The response to selection (R) depends on selection (S) and heritability (h2), R=S*h2. Thus this experiment elucidates the potential of the host-parasite system to evolve. The second question is: How does parasite virulence evolve? Novel parasite strains will be introduced into different host genetic backgrounds. The parasite's effects on the host will be measured over long and short term. This experiment is an important test of models of parasite virulance. Together, these experiments provide important information on host-parasite coevolution.