Wolbachia increases the susceptibility of a parasitoid wasp to hyperparasitism

The success of maternally transmitted endosymbiotic bacteria, such as Wolbachia, is directly linked to their host reproduction but in direct conflict with other parasites that kill the host before it reaches reproductive maturity. Therefore, symbionts that have evolved strategies to increase their host’s ability to evade lethal parasites may have high penetrance, while detrimental symbionts would be selected against, leading to lower penetrance or extinction from the host population. In a natural population of the parasitoid wasp Hyposoter horticola in the Åland Islands (Finland), the Wolbachia strain wHho persists at an intermediate prevalence (∼50%). Additionally, there is a negative correlation between the prevalence of Wolbachia and a hyperparasitoid wasp, Mesochorus cf. stigmaticus, in the landscape. Using a manipulative field experiment, we addressed the persistence of Wolbachia at this intermediate level, and tested whether the observed negative correlation could be due to Wolbac...

母系传播的内共生细菌（maternally transmitted endosymbiotic bacteria）如沃尔巴克氏体（Wolbachia），其存续状态直接与宿主繁殖过程紧密关联，却与其他会在宿主达到繁殖成熟前将其致死的寄生虫形成直接冲突。因此，那些演化出策略以提升宿主躲避致死寄生虫能力的共生体，往往具有较高的外显率（penetrance）；而有害共生体则会被自然选择淘汰，进而在宿主种群中呈现更低的外显率甚至彻底灭绝。在芬兰奥兰群岛（Åland Islands）的园艺赫塞恩寄生蜂（Hyposoter horticola）自然种群中，沃尔巴克氏体菌株wHho以约50%的中间感染率持续存在。此外，在该区域景观尺度上，沃尔巴克氏体的感染率与重寄生蜂疑似斑痣长距茧蜂（Mesochorus cf. stigmaticus）的种群丰度呈负相关。本研究通过控制性野外实验，探究了沃尔巴克氏体以该中间感染率持续存续的机制，并检验了观测到的负相关关系是否由沃尔巴克氏体所致。