Dissertation Research: Local adaptation and gene flow: The legume-rhizobia mutualism and edaphic heterogeneity

虽然细菌对大型生物体的负面影响是众所周知的，但它们对宿主的积极影响更为神秘。一个典型的例子是豆科植物，如豆类和三叶草，从植物根部的固氮细菌根瘤菌中获得的好处。植物用富含能量的光合作用糖与根瘤中的细菌交换细菌获得的氮，氮是植物生长的限制性营养素。这种共生关系已被证明是一种非常有效的策略，豆类可以在各种各样的栖息地中持续存在。豆科植物在任何特定环境中的表现都取决于植物和根瘤菌对特定环境的适应程度，因为这两个伙伴是高度相互依赖的。然而，很少有人知道的相对重要性，宿主植物与根瘤菌的适应生存的任何合作伙伴。本计画探讨原生豆科植物与入侵豆科植物与根瘤菌共生体之间的交互作用，在蛇形露头上与外的差异。 这些露出地面的岩石中保存着加州原生植物多样性的残余部分，这些植物在严酷的土壤条件下免受大多数入侵植物的侵害。原生或入侵的豆科植物可能能够在没有特定根瘤菌的帮助下适应这种恶劣的环境，或者它们可能依赖于具有专门针对该特定环境的共生体。了解蛇形土壤上和蛇形土壤外豆科植物根瘤菌共生的性质是管理和保护这些受威胁植物群落的重要第一步。本科生将参与这项研究，结果将通过现有的网页公布。

While the negative effects of bacteria on larger organisms are familiar, more mysterious are the multitudes of positive effects they can have on their hosts. One model case is the benefit leguminous plants, like beans and clovers, receive from nitrogen-fixing bacteria called rhizobia that live in the plant's roots. Plants trade energy-rich photosynthetic sugars to bacteria housed in root nodules for bacterially-obtained nitrogen, a limiting nutrient for plant growth. This symbiosis has proven to be a highly effective strategy, and legumes can persist in a wide variety of habitats. The performance of a legume in any particular environment can depend on how well adapted both the plant and rhizobia are to the particular aspects of a site, since both partners are highly interdependent. However, very little is known about the relative importance of host plant versus rhizobia adaptations to the survival of either partner. This project addresses how interactions between a native and an invasive legume and their rhizobial partners differ on and off serpentine outcrops. These outcrops harbor remnant pockets of California's native floral diversity, protected from most invasive plants by harsh soil conditions. Native or invasive legumes may be able to adapt to this harsh environment without the aid of specific rhizobia, or they may depend on having symbionts that are specialized for that particular environment. Understanding the nature of legume-rhizobia symbioses on and off serpentine soils is an essential first step toward managing and conserving these threatened plant communities. Undergraduate students will be involved in this research, and results will be made public via an existing webpage.