Investigating an ongoing selective sweep: the dynamics and consequences of the spread of male-killer suppression in the butterfly Hypolimnas bolina

自然选择最广为人知的是生物体对人为变化的反应——工业化后胡椒蛾的黑化，喷洒滴滴涕后对杀虫剂的抗性，细菌对抗生素的耐药性。当然，自然选择也发生在对自然环境变化的反应中，尽管反应的速度没有得到很好的研究。在这项研究中，我们将研究对自然存在的寄生虫的持续选择性反应。这种寄生虫生活在蝴蝶宿主体内，只杀死雄性宿主（它是一种“雄性杀手”）。在最近的过去，出现了一种抑制这种寄生虫活性的因子，它可以“拯救”雄性宿主。在这项研究中，我们将研究这种抑制因子的传播及其对宿主的影响。在传播方面，我们将研究抑制因子出现的时间有多近，以及它从地理上的源头传播了多远——该系统可能显示出迄今为止观察到的一些最快的动态。在对宿主的影响方面，我们将研究这个新突变的传播如何影响基因组中的其他基因。基因排列在染色体上，就像链上的珠子。当这些小珠中的一个被强烈选择时（就像我们的抑制子一样），那么共享这条链的基因变体也可能受到与原始选择突变相关的影响。这个过程被称为搭便车，因为一个人带着另一个没有被直接选中的人一起移动。因为在这种情况下选择是快速的，很可能许多其他基因也受到影响。我们将检查这种情况发生的程度。从长远来看，人们希望这项研究也能帮助确定抑制基因的特征。这有可能a)帮助我们理解细菌毒素活性可能被阻断的方式，在医学生物学中具有潜在的实用性；b)识别这种细菌产生的毒素，这将代表一种新型杀虫剂，在害虫和病媒控制中具有潜在的实用性。

Natural selection is best known from the response of organisms to anthropogenic change-melanization of peppered moths after industrialization, resistance to insecticides after spraying with DDT, antibiotic resistance in bacteria. Natural selection, of course, happens in response to natural environmental change as well, although the tempo of the response is less well worked out. In this study, we will examine an ongoing selective response to a naturally occurring parasite. This parasite lives in butterfly hosts, where it kills male hosts only (it is a 'male-killer'). In the recent past, a suppressor of the activity of this parasite arose that 'rescues' male hosts. In this study, we will examine the spread of this suppressor, and its effects on the host. In terms of spread, we will examine how recently the suppressor arose, and how far it has spread from its source geographically-potentially the system displays some of the fastest dynamics observed to date. In terms of effect on the host, we will examine how the spread of this one new mutation affects other genes in the genome. Genes are grouped on chromosomes, like beads on a chain. When one of these beads is strongly selected (as is our supressor), so variants of genes that share the chain may also be affected by association with the orginal selected mutation. This process is termed hitch-hiking, as the movement of one carries along another that is not directly being selected. Because the selection is rapid in this case, it is likely that many other genes are also affected. We will examine the degree to which this is has occurred. In the long term, it is hoped the research will also help characterize the suppressor gene. This has the potential a) to help our understanding in the ways in which bacterial toxin activity might be blocked, with potential utility in medical biology b) to identify the toxin produced by this bacterium, which will represent a novel insecticidal agent of potential utility in pest and vector control.