Dissertation Research: The Effect of Breeding System on the Level and Pattern of Molecular Variation in Plant Populations

这项研究将检验最近的理论，即高度自交的物种应该在中性变异中消失。从理论上讲，植物种群遗传变异的模式和数量在很大程度上受交配系统的影响，而交配系统又受自花受精率的强烈影响。核苷酸序列变异将在一组已知的自花受精率差异的植物中进行量化（Leavenworthia；芸苔科）。所得到的数据将允许在核苷酸水平上比较具有不同繁殖系统的分类群之间的中性和适应性相关变异水平。了解近亲繁殖对中性位点和适合度相关位点遗传变异的影响，以及群体间每种遗传多样性差异的原因，对植物遗传学的各个方面都具有重要意义。自然种群遗传变异的研究结果也将对植物遗传保护具有重要价值。保护生物学家认为，近亲繁殖的分类群对环境退化非常敏感，因为它们影响适应性的性状的遗传变异性较低。这项资助的研究通过量化这种高度近亲繁殖群体的健康相关遗传变异来解决这一假设的有效性。核苷酸序列数据可以进一步用于推断所研究群体的系统发育。反过来，这将为理解育种系统特征和生活史特征的进化史提供一个有价值的框架。

9532071 CHARLESWORTH This research will test recent theories that highly selfing species should be depauperate in neutral variation. Theoretically, the pattern and amount of genetic variation in plant populations are greatly influenced by the mating system which, in turn, is strongly influenced by the self-fertilization rate. Nucleotide sequence variation will be quantified in a group of plants with known differences in self-fertilization rates (Leavenworthia ; Brassicaceae). The resulting data will allow the comparison of levels of neutral and fitness-related variation at the nucleotide level among taxa with diverse breeding systems. Understanding the influence of inbreeding on genetic variability at neutral and fitness related loci, and the causes of differences in each kind of genetic diversity among populations, is important in relation to all aspects of plant genetics. Findings on genetic variation from natural populations will also be of value for plant genetic conservation. Conservation biologists assume that inbreeding taxa are highly susceptible to environmental degradation, because of their low reservoir of genetic variability in traits affecting fitness. The funded research addresses the validity of this assumption by quantifying fitness-related genetic variation for such highly inbred populations. The nucleotide sequence data can be further utilized for inferring the phylogeny of the group studied. This will, in turn, ppovide a valuable framework for understanding the evolutionary history of breeding system traits and life history characters in the genus.