Ecology, evolution, and genetics of parasitism and symbiosis in insects

病原体和寄生虫感染是所有生物体面临的最强大威胁之一，也是创新和快速进化的主要驱动力。事实上，生物体已经进化出多种防御措施来应对感染，包括复杂的免疫系统和病原体回避行为。我的实验室研究宿主-寄生虫相互作用的进化和生态学，使用昆虫作为模型宿主，在这个提议中，我将研究两个普遍但神秘的角色-防御性共生体和自私的遗传元素。最近，我们开始意识到许多生物体都含有有益的微生物，可以保护它们免受有害感染。然而，我们对共生体介导的保护在野外有多重要，或者它如何与其他防御模式（如免疫系统）相互作用没有很好的理解。我们也没有很好的理解天敌如何对抗共生体。我们最近发现，常见的林地苍蝇，果蝇neotestacea，窝藏一株细菌共生体螺原体，保护它免受致命的寄生线虫。共生体带来的好处是如此之大，以至于感染共生体的苍蝇正在N.我们将确定这是如何影响寄生虫和它感染的各种苍蝇物种的。线虫进化出对共生体的抵抗力了吗？螺原体还保护宿主免受寄生蜂的侵害，同时，我们将确定这种情况是否发生，以及在该领域是否重要。我们还发现，寄生线虫本身窝藏专性细菌内共生体，我们将确定其在苍蝇线虫相互作用的作用。生物体通常也窝藏基因组寄生虫-也被称为自私的遗传因素。为了获得传播优势，这些行为打破了孟德尔遗传的基本规则，通常会带来负面的适应性后果。自私的遗传元件是宿主基因组上普遍存在的负担，但它们的研究要少得多，因为它们是隐蔽的，经常被基因组的其他部分抑制。自私的遗传因素中最引人注目的一种是自私的X染色体，携带自私的X染色体的雄性产生一种基因产物，破坏携带Y染色体的精子，几乎只生女儿。这种性别比例的扭曲可能会对人口产生严重的影响。自私的X染色体是如何在进化过程中持续存在的？它们有其他健身后果吗？基因组的其余部分是如何抑制它们的？自私和抵制自私的行动方式是什么？我们最近在D. testacea（D. neotestacea），我们将回答这些问题，使用生态学和基因组学的方法。

Infection by pathogens and parasites is one of the most powerful threats that all organisms face, and is a major driver of innovation and rapid evolution. Indeed, organisms have evolved diverse defenses to deal with infection, including sophisticated immune systems and pathogen avoidance behaviours. My lab studies the evolution and ecology of host-parasite interactions, using insects as model hosts, and in this proposal, I will study the role of two pervasive but cryptic players - defensive symbionts and selfish genetic elements. Recently, we have come to appreciate that many organisms harbour beneficial microbes that protect them against harmful infections. Yet we do not have a good understanding of how important symbiont-mediated protection is in the wild, or how it interacts with other modes of defense, such as the immune system. Nor do we have a good understanding of how natural enemies counter-resist symbionts. We recently found that the common woodland fly, Drosophila neotestacea, harbours a strain of the bacterial symbiont Spiroplasma, that protects it against a virulent parasitic nematode. The benefit conferred by the symbiont is so great that symbiont-infected flies are rapidly spreading across N. America, and we will determine how this has affected the parasite and the various fly species it infects. Have nematodes evolved resistance to symbionts? Spiroplasma also protects hosts against parasitic wasps, and in parallel, we will determine whether this occurs and is important in the field. We have also discovered that the parasitic nematode itself harbours an obligate bacterial endosymbiont and we will determine its role in the fly-nematode interaction. Organisms also commonly harbour genomic parasites - also known as selfish genetic elements. These break the basic rules of Mendelian inheritance in order to gain a transmission advantage, often with negative fitness consequences. Selfish genetic elements are pervasive burdens on host genomes but they are much less studied because they are cryptic and often suppressed by the rest of the genome. One of the most striking types of selfish genetic elements are selfish X chromosomes, whereby males that carry a selfish X chromosome produce a gene product that destroys Y-bearing sperm, siring almost exclusively daughters. This sex ratio distortion can have drastic population consequences. How do selfish X chromosomes persist over evolutionary time? Do they have other fitness consequences? How does the rest of the genome suppress them? What is the mode of action of selfishness and resistance to it? We recently discovered a selfish X chromosome, as well as an autosomal gene that suppresses it, in D. testacea (the sister species of D. neotestacea) and we will answer these questions, using both ecological and genomic approaches.