Department of Biology, University of Maryland, College Park, Maryland 20742, USA.
Evolution. 2010 Jun;64(6):1825-35. doi: 10.1111/j.1558-5646.2009.00928.x. Epub 2009 Dec 17.
Mutations are the ultimate source of genetic diversity and their contributions to evolutionary process depend critically on their rate and their effects on traits, notably fitness. Mutation rate and mutation effect can be measured simultaneously through the use of mutation accumulation lines, and previous mutation accumulation studies measuring these parameters have been performed in laboratory conditions. However, estimation of mutation parameters for fitness in wild populations requires assays in environments where mutations are exposed to natural selection and natural environmental variation. Here we quantify mutation parameters in both the wild and greenhouse environments using 100 25th generation Arabidopsis thaliana mutation accumulation lines. We found significantly greater mutational variance and a higher mutation rate for fitness under field conditions relative to greenhouse conditions. However, our field estimates were low when scaled to natural environmental variation. Many of the mutation accumulation lines have increased fitness, counter to the expectation that nearly all mutations decrease fitness. A high mutation rate and a low mutational contribution to phenotypic variation may explain observed levels of natural genetic variation. Our findings indicate that mutation parameters are not fixed, but are variables whose values may reflect the specific environment in which mutations are tested.
突变是遗传多样性的最终来源，其对进化过程的贡献取决于突变率及其对性状（尤其是适应性）的影响。通过使用突变积累系，可以同时测量突变率和突变效应，以前在实验室条件下进行的测量这些参数的突变积累研究就是如此。然而，要在野生种群中估计适应性的突变参数，则需要在突变受到自然选择和自然环境变化影响的环境中进行测定。在这里，我们使用 100 个第 25 代拟南芥突变积累系，在野外和温室环境中量化了突变参数。我们发现，与温室条件相比，野外条件下的适应性突变方差和突变率显著更高。然而，当我们将野外估计值与自然环境变化的幅度进行比较时，结果却很低。许多突变积累系的适应性增强，这与几乎所有突变都会降低适应性的预期相反。高突变率和对表型变异的低突变贡献可能解释了观察到的自然遗传变异水平。我们的研究结果表明，突变参数不是固定的，而是可以变化的，其值可能反映了测试突变的特定环境。
