Oliver Kerry M, Russell Jacob A, Moran Nancy A, Hunter Martha S
Department of Entomology, University of Arizona, Tucson, AZ 85721, USA.
Proc Natl Acad Sci U S A. 2003 Feb 18;100(4):1803-7. doi: 10.1073/pnas.0335320100. Epub 2003 Jan 31.
Symbiotic relationships between animals and microorganisms are common in nature, yet the factors controlling the abundance and distributions of symbionts are mostly unknown. Aphids have an obligate association with the bacterium Buchnera aphidicola (the primary symbiont) that has been shown to contribute directly to aphid fitness. In addition, aphids sometimes harbor other vertically transmitted bacteria (secondary symbionts), for which few benefits of infection have been previously documented. We carried out experiments to determine the consequences of these facultative symbioses in Acyrthosiphon pisum (the pea aphid) for vulnerability of the aphid host to a hymenopteran parasitoid, Aphidius ervi, a major natural enemy in field populations. Our results show that, in a controlled genetic background, infection confers resistance to parasitoid attack by causing high mortality of developing parasitoid larvae. Compared with uninfected controls, experimentally infected aphids were as likely to be attacked by ovipositing parasitoids but less likely to support parasitoid development. This strong interaction between a symbiotic bacterium and a host natural enemy provides a mechanism for the persistence and spread of symbiotic bacteria.
动物与微生物之间的共生关系在自然界中很常见，但控制共生体丰度和分布的因素大多未知。蚜虫与蚜虫内共生菌（主要共生体）存在专性共生关系，研究表明这种共生关系直接影响蚜虫的适应性。此外，蚜虫有时还携带其他垂直传播的细菌（次要共生体），此前几乎没有文献记载感染这些细菌有什么益处。我们进行了实验，以确定豌豆蚜体内这些兼性共生关系对蚜虫宿主易受膜翅目寄生蜂——田间种群的主要天敌豌豆蚜茧蜂攻击的影响。我们的结果表明，在受控的遗传背景下，感染会导致发育中的寄生蜂幼虫高死亡率，从而使宿主对寄生蜂的攻击产生抗性。与未感染的对照组相比，经实验感染蚜虫被产卵寄生蜂攻击的可能性相同，但支持寄生蜂发育的可能性较小。共生细菌与宿主天敌之间的这种强烈相互作用为共生细菌的持续存在和传播提供了一种机制。
