Conditional reduction of predation risk associated with a facultative symbiont in an insect

Symbionts are widespread among eukaryotes and their impacts on the ecology and evolution of their hosts are meaningful. Most insects harbour obligate and facultative symbiotic bacteria that can influence their phenotype. In the pea aphid Acyrthosiphon pisum, an astounding symbiotic-mediated phenotype has been recently observed: when infected with the symbiotic bacteria Rickettsiella viridis, young red aphid larvae become greener at adulthood and even darker green when co-infected with Rickettsiella viridis and Hamiltonella defensa. As body colour affects the susceptibility towards natural enemies in aphids, the influence of the colour change due to these facultative symbionts on the host survival in presence of predators was tested. Our results suggested that the Rickettsiella viridis infection may impact positively host survival by reducing predation risk. Due to results from uninfected aphids (i.e., more green ones attacked), the main assumption is that this symbiotic infection would ...共生体在真核生物中广泛分布，其对宿主生态学与演化的影响意义深远。多数昆虫携带有专性与兼性共生细菌，这些细菌可调控宿主的表型。在豌豆蚜（Acyrthosiphon pisum）中，近期研究发现了一种由共生菌介导的惊人表型：当被共生菌绿色立克次体（Rickettsiella viridis）侵染时，幼年红色蚜幼虫在成虫阶段会变为绿色；若同时被绿色立克次体（Rickettsiella viridis）与汉密尔顿氏菌（Hamiltonella defensa）共同侵染，成虫体色甚至会更深绿。由于蚜虫的体色会影响其对天敌的易感性，本研究针对这些兼性共生菌引发的体色变化，在捕食者存在的条件下，探究其对宿主存活的影响。研究结果显示，绿色立克次体侵染可通过降低捕食风险，对宿主存活产生积极影响。结合未侵染蚜虫的实验结果（即更多绿色个体被攻击），本研究的核心假设为：该共生菌侵染可……