DISSERTATION RESEARCH: Experimental Evolution in an RNA Bacteriophage

为了回答适应遗传学中的几个重要问题，有必要对种群如何适应新环境有更丰富的理解。不幸的是，在自然种群中很难获得进一步这项工作所需的数据；例如，只有少数情况下我们可以确定适应性替代。然而，在微生物实验进化系统中，关于适应性进化的数据要容易得多。例如，在我们正在使用的噬菌体系统中，适应性替换的特性、年代学和适应性效应都是已知的。在我的论文工作中，我正在使一种RNA噬菌体的几条线适应新的环境，并研究核苷酸替代。在这里，我建议通过两个新项目来扩展这项工作。第一个是与我的论文研究直接相关的：我想通过测量每个噬菌体基因型的生长速度来直接测量每个适应性替代的适应度效应。第二个项目提出了一个关于适应的新问题：进化是否受到顺序上位性的限制，即，晚期替换的同一性是否取决于早期替换的同一性？总而言之，这些项目将为适应的遗传学提供亟需的信息。

A richer understanding of how populations adapt to new environments is necessary to answer several important questions in the genetics of adaptation. Unfortunately, the data necessary to further this work are difficult to come by in natural populations; for example, there are only a handful of cases in which we can identify an adaptive substitution. In microbial experimental evolution systems, however, data on adaptive evolution are much more easily obtained. In the bacteriophage system we are using, for example, the identity, chronology, and fitness effects of adaptive substitutions are all known. In my dissertation work, I am adapting several lines of an RNA bacteriophage to a new environment and studying the nucleotide substitutions. Here, I propose to extend this work with two new projects. The first is directly related to my dissertation research: I would like to directly measure the fitness effects of each adaptive substitution by measuring the growth rate of each phage genotype. The second project asks a novel question about adaptation: is evolution constrained by sequential epistasis, i.e., is the identity of late substitutions dependent on the identity of early substitutions? Together, these projects will shed much needed light on the genetics of adaptation.