DISSERTATION RESEARCH: Genomic signatures of pathogen-mediated selection in diachronic populations of the House Finch

这项研究将研究家雀是如何进化出对一种新病原体的抗性和耐受性的。新的病原体是许多物种面临的挑战，了解物种可能如何反应对于为保护全球生物多样性的保护工作提供信息是不可或缺的。考虑到全球旅行的便利，人类将病原体引入新环境的做法在今天很常见。1994年，一种历史上与家禽有关的细菌--鸡毒霉，感染了家雀，估计导致2.25亿人死亡(占东部人口的60%)。这种病原体是家禽业最重要的疾病之一的原因，因此在这个House Finch被确定为进化目标的任何基因也可能适用于提高家禽的抵抗力和耐受性。该项目将使用全基因组重新测序和免疫基因的基因分型，如MHC和TLRs，以解开两种重要免疫反应-抗药性和耐受性的遗传基础。从美国各地野生种群在接触病原体之前和之后的多个时间段收集的数据将显示家雀是如何进化的。研究人员将测试MHC和TLR个体内的等位基因多样性是否因强烈的选择而增加，或者特定的等位基因是否通过随着时间的推移增加或减少频率而赋予对病原体的抗性或敏感性。对来自历史上未接触过病毒的人群的实验感染个体进行基因分型，将测试假定选择的等位基因是否与病原体负载或结膜肿胀等疾病表型有关。

This study will examine how the House Finch has evolved resistance and tolerance to a novel pathogen. Novel pathogens are a challenge faced by many species, and understanding how species might respond is integral for informing conservation efforts to protect global biodiversity. Human-mediated introductions of pathogens into new environments are common today given the ease of global travel. In 1994, a species of bacteria, Mycoplamsa gallisepticum, historically associated with poultry, infected the House Finch and killed an estimated 225 million individuals (60% of the eastern population). This pathogen is the cause of one of the most significant diseases of the poultry industry, so any genes identified as targets of evolution in this House Finchmay also be applicable to improving resistance and tolerance in poultry.The project will use whole genome resequencing and genotyping of immune genes such as MHC and TLRs to disentangle the genetic underpinnings of two important immunological responses, resistance and tolerance. Data collected from wild populations around the U.S. in multiple time periods before and after exposure to the pathogen will show how the House Finch has evolved. The researchers will test whether MHC and TLR intra-individual allelic diversity has increased in response to strong selection, or if specific alleles confer resistance or susceptibility to the pathogen by increasing or decreasing in frequency over time. Genotyping of experimentally infected individuals from a historically unexposed population will test whether putatively selected alleles are associated with disease phenotypes such as pathogen load or conjunctival swelling.