Genetics and evolutionary dynamics of male-killer suppression in the lacewing, Mallada desjardinsi

历史上，进化一直被认为是一个缓慢的过程，发生在地质时期。然而，我们现在知道，当代的进化实际上可以非常快，新的遗传类型(突变)在自然种群中迅速传播。进化特别快的一个例子是昆虫种群对杀死雄性的细菌的反应。许多昆虫物种携带这种微生物--正如它们的名字所示--只杀死雄性携带者(而不伤害雌性)。它们从雌性昆虫(母亲)传给儿子和女儿，并杀死儿子。当然，自然选择促进了昆虫的突变，从而拯救了这些雄性昆虫。这些抢救突变目前在四个不同的案例中已知。2007年，我们有幸观察到其中一种救援基因在自然界中通过蝴蝶种群传播。在拯救突变传播之前，杀死雄性的细菌是如此普遍和有效，以至于每只雄性蝴蝶对应100只雌性蝴蝶。在救援元素扩散后，男性和女性同样常见。这种拯救突变在不到一年的时间里在整个种群中传播--10代蝴蝶。进一步的研究也告诉我们救援是如何进行的--这种突变使雄性蝴蝶以一种不同的方式阻止它们被杀死。一个日本研究小组最近的研究发现，在世界不同地区的不同细菌/昆虫相互作用中，发生了相同类型的进化事件。在这里，这种昆虫是一种草鱼，雄性救援突变花了4-5年的时间才建立起来--即使不是那么快，也是非常快的。我们将这些独立但相似的事件称为趋同进化的案例--它们让我们有一个极好的机会来理解自然选择是否采取相同的路线来‘解决’相同的问题--以及针对这些寄生虫的进化是否击中了宿主生物学的一个方面--还是许多方面。这项研究将检验这一研究体系，以确定表面上相似的事件(拯救雄性的进化)是否具有相同的目标，或者这些进化事件实际上是否涉及男性/女性发育的许多不同方面。我们将使用最先进的基因组技术来确定拯救雄性花纹蝶的基因变化是否与拯救雄性蝴蝶的基因变化是相同的。此外，我们可以问，这些超快进化事件的动力学在不同的情况下是否相同--或者它是否取决于特定共生体的属性。我们预测在这种情况下情况会有所不同，因为共生体对宿主的影响在一些重要方面有所不同。最后，我们询问拯救突变是否会影响雄性和雌性成虫的生育力和繁殖力。如果是这样的话，这意味着雄性和雌性的差异不仅仅是性选择的结果--竞争配偶或选择后代--也是为了避免特定性别的寄生而进行的选择。该团队将互补的技能结合在一起。这个日本团队带来了研究系统的专业知识，以及重要的历史样本和数据，使我们能够直接推断进化。这家英国集团带来了进化变化的基因分析方面的专业知识。在一起，他们可以解开一个长期存在的谜题。

Evolution has historically been thought of as a slow process, happening over geological time periods. However, we now know that contemporary evolution can in fact be very fast, with new genetic types (mutations) spreading rapidly through natural populations. One case where evolution is particularly quick is the response of insect populations to male-killing bacteria. Many insect species carry these microbes - which do exactly what their name suggests -kill only male carriers (and leave females unharmed). They pass from a female (mother) insect into sons and daughters - and kill the sons.Natural selection, of course, promotes mutations in insects that rescues these males. These rescue mutations are known in four different cases now. In 2007, we were fortunate enough to observe one of these rescue genes spread in nature through a population of butterflies. Before the rescue mutation spread, male-killing bacteria were so common and effective there were 100 females to every male butterfly. After the spread of the rescue element, males and females equally common. The rescue mutation spread through the population in under a year - 10 butterfly generations. Further research has also told us how rescue works - the mutation makes male butterflies in a different way that stops them being killed.Recent work by a Japanese group observed the same type of evolutionary event in a different bacteria/insect interaction in a different part of the world. Here, the insect was a lacewing, and the male rescue mutation took 4-5 years to establish - very fast even if not quite as quick. We call these independent but similar events cases of convergent evolution - and they allow us a wonderful opportunity into understanding whether natural selection takes the same route to 'solve' the same problem - and whether evolution in response to these parasites hits a single aspect of host biology - or many.This study will examine this study system in order to determine if the outwardly similar event (evolution to rescue males) has the same target or whether these evolutionary events actually involve many different aspects of male/female development. We will use state of the art genomic technology to determine whether the gene changes that rescue male lacewings are of the same kind that rescue male butterflies. Further, we can ask if the dynamics of these super fast evolutionary events is the same in different cases - or whether it depends on the properties of the particular symbiont. We predict it will be different in this case, as the symbionts affect on the host differ in some important ways.Finally, we ask if the rescue mutation affects the fertility and fecundity of male and female adults. If it does, then this implies that how male and females are is not simply a product of sexual selection - of competition for mates or selection to produce offspring - but also selection to avoid sex specific parasitism.The team brings together complementary skills. The Japanese group brings expertise of the study system, and vital historical samples and data that allow us to infer evolution directly. The UK group brings expertise in the genetic analysis of evolutionary change. Together, they can solve a long standing puzzle.