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的一个重要过程。确定选择如何对不同的杂交基因型起作用，对于理解杂交不同结果的可能性是必要的。本研究利用Ipomopsis aggregata和I. tenuituba之间的自然杂交系统模型来研究杂种之间适应度差异的潜在原因，从而了解哪些过程在限制和促进杂交中起重要作用。通过田间和温室试验，研究了天然杂交群体核型和细胞质基因型的分布；(2)核和细胞核相互作用对杂交基因型适应度的影响，以及这些相互作用是否依赖于环境；(3)杂交种和亲本基因型之间的生理生态差异可能影响杂交种区不同环境条件下的相对生产性能。这项工作使用了一种综合的方法来检查可能影响自然杂交结果的遗传和生态因素。了解这些因素是如何影响差异杂交适应度的，对于理解杂交的进化结果以及物种之间的基因流动是必要的。这些杂交带动态的信息对于评估本地物种和外来物种或转基因物种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.