COMPARATIVE MUTATION ACCUMULATION IN RHABDITID NEMATODES

突变是进化变化的基本动因，有害突变被认为是多种重要生物现象的因果动因。最近的发展使人们对在表型和分子水平上关于新突变的发生率和平均影响的普遍看法产生了怀疑。不幸的是，关于突变特性的良好数据只存在于两个物种，即黑腹果蝇（Drosophila melanogaster）和秀丽隐杆线虫（Caenorhabditis elegans），这两个物种在系统发育上距离较远，在生活史上差异很大。在相当小的进化距离内，突变特性是如何变化的，我们几乎一无所知。本文拟对三种横纹肌线虫的突变特性进行研究。突变将允许在最初基因相同的种群中积累超过100代。标准方法将用于估计对表型具有可检测影响的新突变的比率和平均效应，并将变异划分为种内和种间成分。分子方法也将用于在DNA序列水平上直接估计突变率。由此产生的数据将允许在动态进化的背景下，即在密切相关的物种内部和之间，解释广泛分离的分类群之间的突变特性的差异和/或相似性。

Mutation is the fundamental agent of evolutionary change, and deleterious mutations have been implicated as the causal agent responsible for a variety of important biological phenomena. Recent developments have cast doubt on the prevailing wisdom regarding rates and average effects of new mutations at both the phenotypic and the molecular levels. Unfortunately, good data on mutational properties exist for only two species, Drosophila melanogaster and Caenorhabditis elegans, species that are phylogenetically distant and that differ substantially in life history. Almost nothing is known about how mutational properties vary over fairly small evolutionary distances. Herein I propose to investigate the mutational properties of three species of Rhabditid nematode. Mutations will be allowed to accumulate in initially genetically identical stocks for upwards of 100 generations. Standard methods will be used to estimate the rate and average effect of new mutations with detectable effects on the phenotype, and to partition the variance into within- and among-species components. Molecular methods will also be used to directly estimate the mutation rate at the level of the DNA sequence. The resulting data will allow the interpretation of differences and/or similarities in mutational properties among widely separated taxa in the context of dynamic evolution, that is, within and among closely related species.