Dissertation Research: Mechanisms Defining Ecological Range Limits in a Plant Hybrid Zone

不同的物种通常在生殖上彼此隔离。 然而，在某些情况下，杂交区形成的物种交叉受精，并产生可行的后代。 这个项目的重点是如何生理和传粉者的差异保持独立的海拔范围的两个植物物种，从而物种的差异，尽管一些杂交。 该研究系统由两种生长在内华达州山脉不同海拔的五蕊花属野花组成。 以前的实验表明，无论是完全分离的传粉者或遗传障碍，防止杂交，这表明环境因素的重要性。 在拟进行的试验中，将在三个海拔高度的普通园林中测定纯系亲本和杂种的存活率和生长率。 将测量生理性状（光合速率和水分利用），以确定它们是否负责确定纯亲本和杂交种的海拔范围。传粉者将进行研究，以确定是否杂交是有限的传粉者的行为选择。 该项目将阐明不同物种和杂交种形成海拔范围的机制。 它将有助于了解新物种的产生和维持，这是进化生物学的一个基本问题。 它还将为保护受杂交威胁的稀有植物物种以及转基因作物与本地物种杂交的风险提供有用的信息。 该项目每年将为一名研究生和几名本科生提供培训。

Different species are usually reproductively isolated from one another. However, in some cases hybrid zones form where species cross-fertilize and produce viable offspring. This project focuses on how physiological and pollinator differences maintain separate elevational ranges of two plant species, and thereby the species differences, despite some hybridization. The study system consists of two species of Penstemon wildflowers that grow at different elevations in the Sierra Nevada Mountains. Previous experiments indicated that neither complete separation of pollinators nor genetic barriers prevent hybridization, suggesting the importance of environmental factors. In the proposed experiment, survival and growth rate of pure parents and hybrids will be measured in common gardens at three elevations. Physiological traits (photosynthetic rate and water use) will be measured to determine whether they are responsible for determining the elevational ranges of pure parents and hybrids. Pollinators will be studied to determine whether hybridization is limited by behavioral choices of pollinators. This project will clarify mechanisms responsible for shaping elevational ranges of different species and hybrids. It will contribute to knowledge about the production and maintenance of new species, a fundamental issue in evolutionary biology. It will also provide useful information for conservation of rare plant species threatened by hybridization, and about risks of hybridization between genetically modified crops and native species. This project will provide training to one graduate student and several undergraduates per year of funding.