Cooperation or conflict in coexisting aphid symbionts?

许多昆虫携带从母亲传给后代的细菌共生体。这些共生体在宿主的生活史中扮演着不同的角色。最著名的共生体是细菌，它们为宿主提供宿主无法从食物中获得的营养。这些类型的细菌通常发生在以非常不平衡的食物类型为食的昆虫中，例如植物汁液，纤维素或血液，并且通常在昆虫物种的每个个体中发现。第二类共生体的分布变化更大;在一个昆虫种群中，它们通常存在于一些个体中，而不是其他个体中。然而，这些类型的细菌，称为次级共生体，可以为其宿主提供重要的益处，并经常帮助昆虫科普环境挑战。例如，它们可以保护昆虫免受诸如病毒和其他病原体等天敌的攻击，或减少高温的有害影响。许多携带这种共生体的昆虫是农业害虫或人类疾病的媒介。因此，了解这些相互作用的生物学是重要的，并可能导致新的控制策略。例如，有人尝试使用共生细菌来抑制引起诸如疟疾、登革热病毒或恰加斯病等疾病的昆虫传播病原体的传播。蚜虫是温带地区最重要的农业害虫之一。它们以植物汁液为食，同时经常传播植物病毒，从而损害植物。所有蚜虫都有一个营养共生体，许多蚜虫还携带一个或多个次级共生体。拟议的项目旨在了解这种共生体动物园中的相互作用。通常在一个宿主个体中发现几个次级共生体物种。我们对这些共生体本身的许多影响有很好的了解，但对它们如何协同作用知之甚少。例如，其中一种共生体增加了蚜虫对寄生蜂的抵抗力，而另一种则增加了对病原真菌的抵抗力。当它们同时发生时，很可能这两个物种在昆虫内部相互竞争，我们试图调查这种竞争是否限制了它们对宿主有益的能力。与此同时，这两种共生体可能会在许多代中共存，因为它们是从母亲传给后代的。因此，它们与宿主有共同的兴趣，应该被选择，以便昆虫适应性最大化。拟议的工作旨在了解这些相互作用的过程。一种预测是，当共存了很长时间的共生体相互作用时，竞争的负面影响最小化，但当共生体形成新的协会时，竞争更加严重，可能会给宿主带来更高的成本。这项工作将推进我们对生态群落如何进化的理解，并可能通过更好地了解蚜虫生物学为新的害虫控制策略提供途径。

Many insects carry bacterial symbionts that are transmitted from mother to offspring. These symbionts have diverse roles in their hosts' life-histories. The best-known group of symbionts are bacteria that provide nutrients to their hosts, which the host cannot obtain from its diet. These types of bacteria typically occur in insects that feed on very imbalanced types of food such as plant saps, cellulose or blood and are usually found in every individual of the insect species. A second group of symbionts has a much more variable distribution; within a population of insects they are usually found in some individuals but not others. However, these types of bacteria, called secondary symbionts, can provide important benefits to their hosts and often help the insect to cope with environmental challenges. They can, for example, protect the insect from attack by natural enemies such as viruses and other pathogens or reduce the detrimental effects of high temperatures.Many of the insects that carry such symbionts are agricultural pests or vectors of human diseases. Understanding the biology of these interactions is therefore important and might lead to novel control strategies. For example, there are attempts of using symbiotic bacteria to inhibit the transmission of insect-borne pathogens that cause diseases such as malaria, dengue virus or Chagas disease. Aphids are one of the most important agricultural pests in temperate regions. They damage plants by feeding on plant sap and simultaneously often transmit plant viruses. All aphids host a nutritional symbiont and many also carry one or more secondary symbionts.The proposed project seeks to understand the interactions in this menagerie of symbionts. Often several secondary symbiont species are found in one host individual. We have a good understanding of many of the effects of these symbionts on their own, but know very little of how they act in concert. For example, one of the symbiont species increases the aphid's resistance to parasitic wasps, while another increases resistance to pathogenic fungi. When they co-occur, it is likely that the two species compete with each other inside the insect and we seek to investigate whether this competition limits their ability to benefit the host. At the same time, the two symbionts are likely to coexist over many generations since they are transmitted from mother to offspring. They therefore share interests with their host and should be selected so that the insect fitness is maximised. The proposed work aims at understanding these interacting processes. One prediction is that the negative effects of competition are minimised when symbionts that have coexisted for a long time interact, but that competition is more severe and might carry higher costs for the host when symbionts form novel associations. This work will advance our understanding how ecological communities evolve and might through a better understanding of aphid biology provide avenues towards new pest control strategies.