Effects of The Rate of Environmental Change on Mutational Patterns and Evolutionary Constraints

项目摘要 人口必须能够适应环境条件， （在一代人之内）或逐渐（在多代人之间）。理论模型预测， 这些环境变化速度的差异将从根本上影响 和效应大小的突变，但很少有研究已经机械地检查了遗传学 适应随着时间的推移变得越来越紧张的环境。此外，理论上 模型并不总是解释引入进化约束的公知现象， 例如基因型与环境（GxE）相互作用和多效性。本研究的目的是 比较基因组进化模式和突变在RNA病毒中的影响， 或逐渐的环境变化，并使用这些数据来评估理论模型， 适应以不同速度变化的环境。该项目采用耐温 模型噬菌体106囊病毒的群体，其先前通过 进化实验中，病毒种群暴露于热休克温度， 逐渐增加（逐渐种群）或突然增加（突然种群）。在这里， 我们建议使用这些群体来检查突变固定的模式，并表征 GxE相互作用和多效性在以不同速率变化的环境中的作用。 具体来说，我们将1）评估突变的数量，固定的时间和单体型 突变和渐变群体的多样性; 2）测量连续突变的影响 从选择的谱系对病毒热稳定性和生长速率的影响，并将这些影响与 世系所经历的环境变化的速度。我们的研究将解决中央 进化生物学中关于选择的强度和克里思的变化如何影响 适应，并将阐明适应的机械基础，在不同的速度， 环境变化确定在变革中起作用的选择性压力和限制 环境将给我们提供预测或控制病毒进化的工具。

PROJECT SUMMARY Populations must be able to adapt in environmental conditions that may change either suddenly (within one generation) or gradually (over multiple generations). Theoretical models predict that these differences in the rate of environmental change will fundamentally influence the number and effect sizes of mutations that fix, but few studies have mechanistically examined the genetics of adaptation in environments that become more stressful over time. Moreover, the theoretical models do not always account for well-known phenomena that introduce evolutionary constraints, such as genotype by environment (GxE) interactions and pleiotropy. The goal of this research is to compare patterns of genome evolution and effects of mutations in RNA viruses under sudden or gradual environmental change, and to use these data to evaluate theoretical models of adaptation in environments that change at different rates. The project uses temperature-resistant populations of the model bacteriophage ɸ6 Cystovirus that were previously generated through an evolution experiment in which viral populations were exposed to a heat shock temperature that was increased either gradually (Gradual populations) or suddenly (Sudden populations). Here, we propose to use these populations to examine patterns of mutation fixation and to characterize the role of GxE interactions and pleiotropy in environments that change at different rates. Specifically, we will 1) evaluate the number of mutations, their times to fixation, and haplotype diversity of Sudden and Gradual populations; and 2) measure the effects of sequential mutations from select lineages on both viral thermostability and growth rate, and correlate those effects with the rate of environmental change experienced by the lineage. Our study will address the central question in evolutionary biology of how changes to the strength and tempo of selection influence adaptation, and will illuminate the mechanistic underpinnings of adaptation in different rates of environmental change. Establishing the selective pressures and constraints at play in changing environments will give us tools to predict or control viral evolution.