Insect bacterial symbionts and short term adaptation of aphids to abiotic and biotic stress

现代进化理论认为，动物和植物的微生物共生体是帮助宿主适应资源、天敌和气候条件快速生态变化的关键媒介。我们将在对照实验中使用一种叫做蚜虫的小昆虫和它们的寄生黄蜂，来验证蚜虫严重依赖于它们的细菌共生体的快速进化潜力来生存的假设，这种生态压力是它们日常生活的一部分，它们以维管植物为食物和栖息地。一个众所周知的物种，豌豆蚜虫，将暴露在不同的生态压力制度下的实验进化中，这些生态压力要么是剧毒的寄生虫，要么是在不同的宿主植物物种之间转换，要么是在炎热的夏天，它们每天都要面对的高温压力，同时以空中植物的部分为食。在这些蚜虫中，最著名的是母系遗传的四种蚜虫细菌共生体将在连续几代的应激过程中使用分子技术进行密切监测，以记录在特定应激制度下蚜虫细菌群落的适应性变化。我们的研究结果应该有助于了解蚜虫在逆境下是否通过调节其细菌组的大小和组成对特定的生态威胁做出快速和适应性的反应，这是可以预期的，因为与昆虫相比，细菌的繁殖速度更快。我们的研究系统的独特之处在于对自然陆生食物网的四个层次进行了仔细研究，我们将对植物、小型食草昆虫、它们的共生细菌群体以及作为天敌攻击它们的寄生蜂进行实验。

Modern theories of evolution consider microbial symbionts of animals and plants as key mediators helping their host to adapt to rapid ecological change in their resources, natural enemies, and climatic conditions. We will use small insects called aphids and their parasitic wasps in controlled experiments, to test the hypothesis that aphids critically depend on the rapid evolutionary potential of their bacterial symbionts to survive to ecological stress that they face as part of their daily life on vascular plants used as their food and habitat. A well known species, the pea aphid, will be exposed to experimental evolution in distinct regimes of ecological stress imposed on them either as more or less virulent parasites, shifts between differently hospitable host plant species, or as a high temperature stress which they often face daily in hot summer while feeding on aerial plant parts. Four species of aphid bacterial symbionts among the best known to be maternally inherited in these aphids will be monitored closely using molecular techniques during the course of successive generations of stress, to document adaptive changes in the aphid bacterial community under particular stress regimes. Our findings should help to understand if aphids under stress respond quickly and adaptively to specific ecological threats, by modulating the size and composition of their bacteriome, which can be expected because of the fast rate of multiplication of bacteria compared to insects. Our study system is unique in bringing under scrutiny four levels of a natural terrestrial food web, where we will experiment with plants, small insect herbivores, their consortia of symbiotic bacteria, and parasitic wasps attacking them as natural enemies.