DISSERTATION RESEARCH: Genetic and Ecophysiological Causes of Differential Fitness in a Natural Plant Hybrid Zone

自然杂交是许多植物物种进化过程中的一个重要过程。为了了解杂交结果不同的可能性，有必要确定选择如何针对不同的杂交基因类型起作用。本研究利用一种模式自然杂交系统来研究杂交种间适合度差异的潜在原因，以及在限制和促进杂交过程中哪些过程是重要的。通过田间和温室实验，本研究考察了：(1)天然杂交群体中核型和细胞质基因型的分布；(2)核和胞核互作对杂交种适合度的影响，以及这些互作是否与环境有关；(3)杂交种和亲本之间的生态生理差异可能会影响杂交区环境条件下的相对表现。这项工作使用了一种综合的方法，检查了可能影响自然杂交结果的遗传和生态因素。了解这些因素如何影响差异杂交适合度，对于理解杂交的进化后果，以及最终物种之间的基因流动是必要的。这些关于杂交区动态的信息对于评估本地物种和外来物种或转基因物种之间杂交的潜在影响具有广泛的意义。

Natural hybridization is an important process in the evolution of many plant species. Determining how selection acts against different hybrid genotypes is necessary for understanding the likelihood of different outcomes of hybridization. This study uses a model natural hybrid system between Ipomopsis aggregata and I. tenuituba to examine potential causes of fitness differences among hybrids, and thus what processes are important in limiting and promoting hybridization. Using field and greenhouse experiments, this study examines: (1) the distribution of nuclear and cytoplasmic genotypes in a natural hybrid population; (2) the influence of nuclear and cytonuclear interactions on fitness of hybrid genotypes, and if these interactions are environment-dependent; (3) ecophysiological variation among hybrid and parental genotypes that may affect relative performance across environmental conditions in a hybrid zone. This work uses an integrated approach that examines both genetic and ecological factors that may influence the outcome of natural hybridization. Understanding how these factors affect differential hybrid fitness is necessary for understanding the evolutionary consequences of hybridization, and ultimately gene flow between species. Such information about hybrid zone dynamics has broad implications for evaluating the potential impacts of hybridization between native and exotic or genetically modified species.