REU: Genetic Variability in Bryophyte Populations

性别的进化意义是进化生态学的一个核心问题。已经有大量的模型预测有性生殖与无性生殖的相对优势，但很少有经验检验存在。这项研究的目的就是提供这样一个测试，使用森林苔藓植物，透明四叶草。苔藓植物是检验不同环境下有性或无性生殖有效性假设的理想系统，因为它们具有高度的生境特异性和广泛的生殖模式。已经证明，一些无性物种的遗传变异水平与有性物种的遗传变异水平相当。无性繁殖并不一定会减少遗传变异，特别是在那些生殖系没有从体细胞突变中分离出来的生物体中。传统观点认为，性通过创造遗传多样性来增强适应性，这在苔藓植物中可能是不合适的。本研究的长期目标是研究体细胞非生殖细胞突变的可能性，作为遗传变异的一个来源，可能等于或超过苔藓植物的性重组。在进行这种调查之前，需要提供某些背景资料。这项研究计划补助金将允许Kimmerer博士完成初步研究并开发支持长期目标的方法。这里提出的活动是为一项重大研究工作所作的必要准备。

The evolutionary significance of sex is a central problem in evolutionary ecology. There has been a proliferation of models which predict the relative benefits of sexual vs. asexual reproduction but few empirical tests exist. The goal of this research is to provide just such a test, using the forest bryophyte, Tetraphis pellucida. Bryophytes are ideal systems in which to test hypotheses concerning the effectiveness of sexual or asexual reproduction in different environments since they exhibit a high degree of habitat specificity and wide array of reproductive modes. It has been demonstrated that levels of genetic variability in some asexual species are equivalent to those of sexual species. Asexual reproduction does not necessarily yield reduced genetic variability, especially in those organisms in which the germ line is not isolated from somatic mutation. The traditional view that sex enhances fitness through the creation of genetic diversity may be inappropriate in bryophytes. The long-term goal of this research is to examine the possibility that somatic non-germ cell mutation, as a source of genetic variability, may equal or exceed that of sexual recombination in mosses. Certain background information is required prior to such an investigation. This Research Planning Grant would permit Dr. Kimmerer to complete preliminary studies and to develop methods which would support the long-term goal. The activities proposed here constitute essential preparation for a major research effort.