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重要过程。 确定选择如何作用于不同的杂交基因型是必要的理解不同的杂交结果的可能性。本研究以一个典型的自然杂交系统--Ipomopsis aggregata和I. tenuituba研究杂种之间的适应性差异的潜在原因，从而什么过程是重要的限制和促进杂交。本研究利用田间和温室试验，研究了：（1）天然杂种群体中细胞核和细胞质基因型的分布，（2）细胞核和细胞核互作对杂种基因型适合度的影响，以及这些互作是否依赖于环境;（3）杂种和亲本基因型之间的生理生态差异，这些差异可能影响杂种区不同环境条件下的相对表现。 这项工作使用了一种综合的方法，检查遗传和生态因素，可能会影响自然杂交的结果。 了解这些因素如何影响差异杂交适合度是必要的理解杂交的进化后果，并最终在物种之间的基因流。 这种信息杂交区动态具有广泛的影响，评估本地和外来或转基因物种之间的杂交的潜在影响。

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.