How do sex ratio distorting symbionts affect the evolution of their host?

动物的生物学在某种程度上是与它们相互作用的微生物的功能。例如，在消化过程中，食物会被消化系统分泌的酶和肠道内微生物分泌的酶分解。在许多昆虫中，微生物与宿主的相互作用甚至更为发达。细菌共生体生活在昆虫体内的细胞中，这些共生体通过卵子从雌性传给后代：可遗传的共生体。我们对这些共生体如何影响被它们感染的个体有很多了解。一个特别有趣的影响是杀死雄性，细菌从雌性转移到她的卵子，杀死那些发育成雄性的。我们知道杀死雄性的细菌很常见：它们存在于许多物种中，而且，它们存在的地方，可以存在于大多数个体中——这就产生了雄性很少的昆虫种群。然而，我们对这些细菌如何影响昆虫的生态或进化知之甚少。许多研究人员认为，这些共生体可能会改变雄性和雌性昆虫在发育和性别决定过程中的形成方式。这个假设很简单——当共生体只以雄性为目标时，自然选择通过偏爱新的方法来制造雄性，从而避免雄性被杀死，从而抵消了这一点。这项研究将检验这一理论，为最近的一个蓝月亮蝴蝶进化的案例，以避免雄性杀死细菌沃尔巴克氏体的作用。我们已经记录了一种突变的传播，这种突变将雄性蓝月亮蝴蝶从沃尔巴克氏体引起的死亡中拯救出来。这个项目将确定这种突变是什么，它是否涉及一种被称为“双性”的基因的变化，这种基因定义了昆虫的雄性和雌性特征。男性杀手的第二个方面是，他们可能会推动非常强烈的自然选择来拯救男性。选择的强度如此之大，以至于为拯救雄性而发生的变化可能在其他方面是有害的。该项目的第二个目标是确定这是否属实，以及这种突变（除了拯救男性之外）是否会降低男性和女性的功能。在完成这个项目后，我们将首次直接测试使男性/女性不同的过程可以由微生物驱动的理论。这是一种神秘的联系，它将使昆虫和微生物进化的相互依存关系变得清晰。

The biology of animals is in part a function of the microbes they interact with. During digestion, for instance, food is broken down both by enzymes secreted by our digestive system and those secreted by the microbes that live within the gut. In many insects, microbe-host interactions are even more developed. Bacterial symbionts live inside the cells of the insect body, and these are passed from a female to her offspring via her eggs: heritable symbiosis. We know a lot about how these symbionts affect the individual they infect. One particularly interesting impact is male-killing, where the bacterium passes from a female to her eggs, and kills those which develop as males. We know male-killing bacteria are common: they are present in many species, and, where they are present, can be present in the majority of individuals - this produces insect populations where males are rare. However, we know little about how these bacteria affect insect ecology or evolution. A variety of researchers believe these symbionts may drive changes in the way male and female insects are formed during development, sex determination. The hypothesis is simple - where symbionts target males only, natural selection counteracts this by favouring new ways of making a male that escape male-killing. This study will examine this theory for a recent case of evolution of the blue moon butterfly to avoid the action of male-killing bacterium called Wolbachia. We have documented the spread of a mutation that rescues male blue moon butterflies from Wolbachia-induced death. This project will establish what this mutation is, whether it involves changes in a gene called 'doublesex', which defines male and female characteristics in insects. A second aspect of male-killers is that they may drive very strong natural selection to rescue males. The intensity of selection is such that the changes that occur to rescue males may be otherwise deleterious. A second aim of the project is to establish if this is true, and whether the mutation (beyond rescuing males) degrades male and female function. In completing this project, we will present the first direct test of the theory that the processes that make males/females different can be driven by microbes. This is an enigmatic link that would make clear the interdependence of insect and microbe evolution.