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

本研究将研究家雀如何进化出对一种新型病原体的抗性和耐受性。新型病原体是许多物种面临的挑战，了解物种如何应对对于保护全球生物多样性的保护工作至关重要。鉴于全球旅行的便利性，人类介导的病原体引入新环境在今天很常见。1994年，一种历史上与家禽有关的鸡败支原体细菌感染了家雀，估计造成2.25亿人死亡（占东部人口的60%）。这种病原体是家禽业中最重要的疾病之一的原因，因此任何被确定为这种家雀进化目标的基因也可能适用于提高家禽的抗性和耐受性。该项目将使用免疫基因的全基因组重测序和基因分型，如MHC和tlr，以解开两种重要免疫反应的遗传基础，抗性和耐受性。在接触病原体之前和之后的多个时间段内，从美国各地的野生种群中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个体内等位基因多样性是否因强选择而增加，或者特定等位基因是否随时间增加或减少频率而赋予对病原体的抗性或易感性。从历史上未暴露人群中对实验感染个体进行基因分型，将测试假设选择的等位基因是否与疾病表型（如病原体负荷或结膜肿胀）相关。

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.